Véronique Fontaine

Research in Drug Development (RD3)

Microbiology, Bioorganic and Macromolecular Chemistry

Research activities

The study of microorganisms, their virulence factors and drugs able to target them. My two main axes of research are human papillomaviruses (HPV) and mycobacteria. In virology, we are currently studying the regulation of the HPV-16 early gene expression and viral genome integration by various endogenic and iatrogenic factors. In mycobacteriology, our goals are to better characterize proteins involved in the synthesis of the waxy cell wall and to identify compounds able to inhibit the synthesis of this wall in order to target multidrug resistant Mycobacterium tuberculosis.

Top ten recent articles

Articles dans des revues avec comité de lecture

2023

Telacebec Interferes with Virulence Lipid Biosynthesis Protein Expression and Sensitizes to Other Antibiotics

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a public health issue, particularly due to multi-drug-resistant Mtb. The bacillus is wrapped in a waxy envelope containing lipids acting as essential virulence factors, accounting for the natural antibiotic resistance of mycobacteria. Telacebec (previously known as Q203) is a promising new anti-TB agent inhibiting the cytochrome bc1 complex of a mycobacterial electron transport chain (ETC). Here, we show that the telacebec-challenged M. bovis BCG exhibited a reduced expression of proteins involved in the synthesis of phthiocerol dimycocerosates (PDIMs)/phenolic glycolipids (PGLs), lipid virulence factors associated with cell envelope impermeability. Consistently, telacebec, at concentrations lower than its MIC, downregulated the transcription of a PDIM/PGL-synthesizing operon, suggesting a metabolic vulnerability triggered by the drug. The drug was able to synergize on BCG with rifampicin or vancomycin, the latter being a drug exerting a marginal effect on PDIM-bearing bacilli. Telacebec at a concentration higher than its MIC had no detectable effect on cell wall PDIMs, as shown by TLC analysis, a finding potentially explained by the retaining of previously synthesized PDIMs due to the inhibition of growth. The study extends the potential of telacebec, demonstrating an effect on mycobacterial virulence lipids, allowing for the development of new anti-TB strategies.

Antimycobacterial Activities of Hydroxamic Acids and Their Iron(II/III), Nickel(II), Copper(II) and Zinc(II) Complexes.

Hydroxamic acid (HA) derivatives display antibacterial and antifungal activities. HA with various numbers of carbon atoms (C2, C6, C8, C10, C12 and C17), complexed with different metal ions, including Fe(II/III), Ni(II), Cu(II) and Zn(II), were evaluated for their antimycobacterial activities and their anti-biofilm activities. Some derivatives showed antimycobacterial activities, especially in biofilm growth conditions. For example, 20-100 µM of HA10Fe2, HA10FeCl, HA10Fe3, HA10Ni2 or HA10Cu2 inhibited Mycobacterium tuberculosis, Mycobacterium bovis BCG and Mycobacterium marinum biofilm development. HA10Fe2, HA12Fe2 and HA12FeCl could even attack pre-formed Pseudomonas aeruginosa biofilms at higher concentrations (around 300 µM). The phthiocerol dimycocerosate (PDIM)-deficient Mycobacterium tuberculosis H37Ra was more sensitive to the ion complexes of HA compared to other mycobacterial strains. Furthermore, HA10FeCl could increase the susceptibility of Mycobacterium bovis BCG to vancomycin. Proteomic profiles showed that the potential targets of HA10FeCl were mainly related to mycobacterial stress adaptation, involving cell wall lipid biosynthesis, drug resistance and tolerance and siderophore metabolism. This study provides new insights regarding the antimycobacterial activities of HA and their complexes, especially about their potential anti-biofilm activities.

Untargeted Metabolomics Approach Correlated Enniatin B Mycotoxin Presence in Cereals with Kashin-Beck Disease Endemic Regions of China.

Kashin-Beck disease (KBD) is a multifactorial endemic disease that only occurs in specific Asian areas. Mycotoxin contamination, especially from the Fusarium spp., has been considered as one of the environmental risk factors that could provoke chondrocyte and cartilage damage. This study aimed to investigate whether new mycotoxins could be identified in KBD-endemic regions as a potential KBD risk factor. This was investigated on 292 barley samples collected in Tibet during 2009-2016 and 19 wheat samples collected in Inner Mongolia in 2006, as control, from KBD-endemic and non-endemic areas. The LC-HRMS(/MS) data, obtained by a general mycotoxin extraction technic, were interpreted by both untargeted metabolomics and molecular networks, allowing us to identify a discriminating compound, enniatin B, a mycotoxin produced by some Fusarium spp. The presence of Fusarium spp. DNA was detected in KBD-endemic area barley samples. Further studies are required to investigate the role of this mycotoxin in KBD development in vivo.

Clarifying the Configuration of Pandamine by an Extensive Spectroscopic Reinvestigation of the Authentic 1964 Sample

Since its partial configurational assignment in 1964, pandamine has not been isolated or obtained by total synthesis. For decades, different works representing the structure of pandamine for illustrative purposes have lent different configurations to this molecule, causing tenacious confusion about the structure of this ansapeptide. A comprehensive spectroscopic analysis of the authentic pandamine sample led to the complete and unambiguous assignment of its configuration, 59 years after its isolation. In addition to ascertaining and completing the initial structural deductions by a state-of-the-art set of analytical techniques, the purpose of this study is also to clarify the literature in a context in which various erroneous structures have been attributed to pandamine for half a century. While fully in agreement with Goutarel's conclusions, the specific example of pandamine should serve as a cautionary tale to any chemist interested in natural products, encouraging access to initial structural assignments rather than relying solely on subsequent, possibly erroneous, structure depictions of a natural product.

Easy, Flexible and Standardizable Anti-Nascent Biofilm Activity Assay to Assess Implant Materials

Medical implants have improved the quality of life of many patients. However, surgical intervention may eventually lead to implant microbial contamination. The aims of this research were to develop an easy, robust, quantitative assay to assess surface antimicrobial activities, especially the anti-nascent biofilm activity, and to identify control surfaces, allowing for international comparisons. Using new antimicrobial assays to assess the inhibition of nascent biofilm during persistent contact or after transient contact with bacteria, we show that the 5 cent Euro coin or other metal-based antibacterial coins can be used as positive controls, as more than 4 log reduction on bacterial survival was observed when using either S. aureus or P. aeruginosa as targets. The methods and controls described here could be useful to develop an easy, flexible and standardizable assay to assess relevant antimicrobial activities of new implant materials developed by industries and academics.

The Mycobacterium bovis BCG GroEL1 Contributes to Isoniazid Tolerance in a Dormant-Like State Model

Due to the Mycobacterium tuberculosis complex, including M. tuberculosis and M. bovis, tuberculosis still causes 1.6 million deaths per year. Therefore, efforts to improve tuberculosis treatment are necessary. We previously showed that the GroEL1 protein is involved in antibiotic intrinsic resistance. Indeed, the M. bovis BCG cpn60.1 gene (encoding GroEL1)-disrupted strain (Δcpn60.1) exhibits higher rifampicin and vancomycin susceptibility due to defective cell wall integrity. Here, we show that during hypoxia-triggered growth stasis, in the Wayne dormancy model, the mutant exhibited comparable rifampicin and ethionamide susceptibility but higher isoniazid susceptibility compared to the wild-type strain. Although the Δcpn60.1 strain showed compromised induction of the DosR regulon, growth stasis was achieved, but an ATP burst and a higher reactive oxygen species (ROS) production were observed in the isoniazid-treated Δcpn60.1 strain. GroEL1 could contribute to INH tolerance by reducing ROS.

Synthesis and biological activity of iron(II), iron(III), nickel(II), copper(II) and zinc(II) complexes of aliphatic hydroxamic acids

Aliphatic hydroxamic acids (HA) with varying numbers of carbon atoms, C2, C6, C8, C10, C12 and C17, and corresponding Fe(II), Fe(III), Ni(II), Cu(II) and Zn(II) complexes have been synthesized and characterized by various methods, including structural determination by single crystal X-ray diffraction and theoretical calculations. The biological activities of HA and their complexes have been assessed on a panel of pathogens, including eight bacteria strains and one fungus. The C12 aliphatic HA displayed the lowest minimum inhibitory concentrations (MIC) towards several microbial strains and a selective antifungal activity. This antifungal selectivity was further improved considering the Ni(II), Cu(II) and Zn(II) complexes of C12 HA showed higher IC50 values, thus less impact on the SiHa human cell line viability. This work warrants further investigation to understand the underlying mechanism of action and potential biological applications of HA and the derived metal complexes.

2022

Design of Thermoplastic Polyurethanes with Conferred Antibacterial, Mechanical, and Cytotoxic Properties for Catheter Application

Thermoplastic polyurethanes (TPUs) are proposed as suitable solution for the fabrication of biocompatible catheters with appropriate mechanical parameters and confirmed antibacterial and cytocompatible properties. For this purpose, a series of quaternary ammonium salts (QASs) and quaternary phosphonium salts (QPSs) based monomers were prepared followed by the determination of their minimal inhibitory concentrations (MICs) against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa). A combination of the most active ammonium (QAS-C14) and phosphonium (QPS-TOP) salts led to a MIC down to 2.4 μg/mL against S. aureus and 9 μg/mL against P. aeruginosa, corroborating the existence of a synergistic effect. These quaternary onium salt (QOS) units were successfully incorporated along the polymer chain, as part of a two-step synthesis approach. The resulting TPU-QOS materials were subsequently characterized through thermal, mechanical, and surface analyses. TPU-Mix (combining the most active QAS-C14and QPS-TOP units) showed the highest antibacterial efficiency, confirming the synergistic effect between both QOS groups. Finally, an MTT assay on the SiHa cell line revealed the low cytotoxicity level of these polymeric films, making these materials suitable for biomedical application. To go one step further in the preindustrialization approach, proof of concept regarding the catheter prototype fabrication based on TPU-QAS/QPS was validated by extrusion. copy; 2022 American Chemical Society.

Assessing Barriers Encountered by Women in Cervical Cancer Screening and Follow-Up Care in Urban Bolivia, Cochabamba

Background: Timely detection of cervical cells infected with high-risk human papillomavirus (HPV) improves cervical cancer prevention. In Bolivia, actual screening coverage only reaches 33.3% of the target population aged between 25 and 64 years despite free cytology screening. Furthermore, 50% to 80% screened women are lost during follow-up. This study aimed at identifying factors explaining this lack of follow-up care. Method: During the first phase, face-to-face semi-structured interviews were conducted with HPV-positive women. Secondly, we explored the reasons for the non-adherence to the follow-up care: knowledge, perceptions and beliefs about HPV, as well as barriers to healthcare access, using a structured survey on Cochabamba women and healthcare professionals. Results: Barriers to effective follow-up of the targeted populations were associated with health system shortcomings, including poor service delivery at the front- and second-line, health providers shortage, inadequate training, waiting time, high direct and indirect costs of care seeking and care, complex procedures to obtain HPV screening results and poor patient-provider communication. The follow-up was perceived as extremely stressful by the participants. Conclusion: Improved communication on HPV and HPV-related cancers in terms of representation in the general population and among the health professional's population is vital to improve access for HPV infection follow-up care.

In vitro and in vivo local tolerability of a synergistic anti‐tuberculosis drug combination intended for pulmonary delivery

A drug combination, vancomycin (VAN) plus tetrahydrolipstatin (THL), has demon-strated an effective synergistic action in vitro againstMycobacterium tuberculosis(Mtb). The poor oral bioavailability of VAN and THL and the predominant tropism ofMtb infection to the lungs make their pulmonary administration very attractive. Toevaluate their local tolerability, bronchial cells, alveolar cells and monocytes wereexposed to concentrations around and above their minimal inhibitory concentration(MIC). The VAN had no inhibitory activity on the tested human cell lines, even at aconcentration 125 times higher than its MIC, whereas the THL, alone or in combina-tion with VAN, presented a cytostatic action. Monolayer epithelium showed no sig-nificant irreversible damage at concentrations up to 100 times the combination MIC.BALB/cAnNRj mice exposed to concentration of 50 times the combination MICdelivered endotracheally 3 times a week for 3 weeks showed no clinical signs or sig-nificant weight loss. The increase of proinflammatory biomarkers (i.e., IL-1, IL-6, TNF-αand proportion of inflammatory cells) and cytotoxicity in bronchoalveolar lavagefluid (BALF) were non-significant. Lung histopathology did not show significant tissuedamage. The VAN/THL combination at doses up to 50 times the combination MIC isfound to be thus well tolerated by pulmonary route. This study is a promising resultand encouraging further investigations of pulmonary administration of VAN/THLcombination as dry powder for anti-tuberculosis treatment.

In vitro and in vivo local tolerability of a synergistic anti-tuberculosis drug combination intended for pulmonary delivery

Pyrrovobasine, hybrid alkylated pyrraline monoterpene indole alkaloid pseudodimer discovered using a combination of mass spectral and NMR-based machine learning annotations

The MS 2 -guided phytochemical investigation of Voacanga africana stem bark resulted in the isolation of pyrrovobasine, the first pyrraline-containing MIA.

Thermoplastic polyurethanes for biomedical application: A synthetic, mechanical, antibacterial, and cytotoxic study

Thermoplastic polyurethanes (TPUs) bear tunable chemistry offering the possibility to develop a rich palette of physio-mechanical properties, making the materials suitable for various fields of application. The great variety in TPUs properties comes from the choices of the monomers and the reaction conditions. Herein, the mechanical properties of the developed TPUs are tailored, while fine-tuning the hard and soft segment molar ratio, as well as the reaction conditions. TPUs are synthesized from 4,4′-methylenebis(phenyl isocyanate), poly(tetrahydrofuran), and 1,4-butanediol, and their thermal and mechanical properties are fully characterized. The sample with the most appropriate mechanical properties that are suitable for catheter fabrication, is selected for the biomedical application. Quaternary ammonium salt is synthesized, and 0.5 mol% is incorporated in the TPU to confer antibacterial properties to the material while preserving its mechanical strength. The microbiological tests reveal the antibacterial effect of the developed materials against Staphylococcus aureus and Pseudomonas aeruginosa, as well as 80% SiHa cell viability, after 72 h of exposure, as part of the performed cytotoxicity studies. Finally, TPUs catheter prototypes fabrication is also proposed, applying an extrusion or injection molding approach for the production of biomedical devices with desirable mechanical properties.

2021

Voatriafricanines A and B, Trimeric Vobasine-Aspidosperma-Aspidosperma Alkaloids from Voacanga africana

Voatriafricanines A and B (1 and 2), the first examples of vobasine-aspidosperma-aspidosperma monoterpene trisindole alkaloids, were isolated from the stem barks of Voacanga africana, guided by a molecular networking strategy. Their structures, including absolute configurations, were elucidated by spectroscopic methods and ECD calculations. Compounds 1 and 2 possess intramolecular hydrogen bonding, sufficiently robust to transfer homonuclear and heteronuclear magnetizations. Compound 1 exhibited potent antimycobacterial activity with no discernible cytotoxic activity.

Antibacterial Activities of Homemade Matrices Miming Essential Oils Compared to Commercial Ones

The increasing bacterial resistance to antibiotics is a worldwide concern. Essential oils are known to possess remarkable antibacterial properties, but their high chemical variability complicates their development into new antibacterial agents. Therefore, the main purpose of this study was to standardize their chemical composition. Several commercial essential oils of ajowan (Trachyspermum ammi L.) and thyme (chemotype thymol) (Thymus vulgaris L.) were bought on the market. GC-MS analysis revealed that thyme essential oils have a chemical composition far more consistent than ajowan essential oils. Sometimes thymol was not even the major compound. The most abundant compounds and the homemade mixtures were tested against two Staphylococcus aureus strains. The antibacterial property of β-caryophyllene presented no direct activity against S. aureus LMG 15975, but in association with thymol or carvacrol at equal percentages an MIC of 125 μg/mL was observed. The mixture of those three compounds at equivalent percentages also decreased by 16-fold the MIC of the penicillin V. Against S. aureus LMG 21674, β-caryophyllene presented an MIC of 31.3 μg/mL and decreased by 267-fold the MIC of the penicillin V. These observations led us to question the benefits of using a complex chemical mixture instead of one active compound to fight bacterial resistance.

2020

Antibacterial and Cytotoxic Activities of Ten Commercially Available Essential Oils

Interplays between copper and Mycobacterium tuberculosis GroEL1

The chaperone GroEL1 enhances copper tolerance during Mycobacterium bovis BCG biofilm formation. The binding of copper ions to the GroEL1 histidine-rich region protects the chaperone from destabilization and increases its ATPase activity.

Evaluation of the effectiveness of high-risk human papilloma self-sampling test for cervical cancer screening in Bolivia

Background: In Bolivia the incidence and mortality rates of uterine cervix cancer are the highest in America. The main factor contributing to this situation is the difficulty of establishing and maintaining quality prevention programs based on cytology. We aimed to evaluate the effectiveness of HR-HPV testing on self-collected samples to detect cervical intra-epithelial neoplasia and identify the best combination of screening tests. Methods: A total of 469 women, divided in two groups, were included in this study. The first group included 362 women that underwent three consecutively primary screening tests: Self-collected sampling for HR-HPV detection, conventional cervical cytology and visual inspection under acetic acid (VIA). The second group included 107 women referred with a positive HR-HPV test that underwent conventional cervical cytology and VIA. The presence of high grade intraepithelial lesion (CIN 2+) or invasive cancer was verified by colposcopy and biopsy. Result: In the screening group the sensitivity to detect high grade intraepithelial lesion (CIN 2+) or invasive cancer were 100, 76, 44% for the VIA, HR-HPV test and cytology, respectively. In the referred group, the sensitivity to detect high grade intraepithelial lesion (CIN 2+) or invasive cancer by VIA and cytology were 100 and 81%, respectively. Conclusions: VIA and HR-HPV self-sampling were the best combination to detect CIN2+ lesions. Cytology analysis gave the poorest performance.

Methyl arachidonyl fluorophosphonate inhibits Mycobacterium tuberculosis thioesterase TesA and globally affects vancomycin susceptibility.

Phthiocerol dimycocerosates and phenolic glycolipids (PGL) are considered as major virulence elements of Mycobacterium tuberculosis, in particular because of their involvement in cell wall impermeability and drug resistance. The biosynthesis of these waxy lipids involves multiple enzymes, including thioesterase A (TesA). We observed that purified recombinant M. tuberculosis TesA is able to dimerize in the presence of palmitoyl-CoA and our 3D structure model of TesA with this acyl-CoA suggests hydrophobic interaction requirement for dimerization. Furthermore, we identified that methyl arachidonyl fluorophosphonate, which inhibits TesA by covalently modifying the catalytic serine, also displays a synergistic antimicrobial activity with vancomycin further warranting the development of TesA inhibitors as valuable antituberculous drug candidates.

2019

Assessment of a new low-cost, PCR-based strategy for high-risk human papillomavirus DNA detection for cervical cancer prevention

Background: HPV test implementation as a primary screening tool has the potential to decrease cervical cancer incidence as shown by several studies around the world. However, in many low-resource settings, the HPV test introduction has been backed down mainly due to its price. In this study, we present a novel low-cost strategy involving simple devices and techniques for high-risk human papillomavirus (HR-HPV) detection. The analytical performance to detect HR-HPV infections of this novel strategy was assessed by comparing it with the Hybrid Capture 2 system (HC2), which is used as gold standard. Methods: Paired-cervical samples were collected from 541 women assisting to gynecological services in an outpatient clinic. One sample was transported in the Hybrid Capture Standard Transport Medium for HR-HPV detection by the HC2. The second sample was transported on glass slide for detection by PCR-based techniques (GP-EIA, BSGP-EIA and pU 1 M-L/2R). Results: The level of agreement between the PCR-based techniques and HC2 system was determined with the Cohen's kappa value. The kappa values between HC2 and GP-EIA, BSGP-EIA and pU 1 M-L/2R were 0.71 (CI 95% 0.63-0.78), 0.78 (CI 95% 0.71-0.84) and 0.63 (CI 95% 0.55-0.72), respectively. However, when the results from both BSGP-EIA and pU 1 M-L/2R were combined, the level of agreement with HC2 was increased to 0.82 (CI 95% 0.76-0.88), reflecting a very good agreement between the two HR-HPV detection strategies. Furthermore, the sensitivity of both techniques combined was also increased compared to the BSGP-EIA (88.7% vs 77.4%) and the pU (88.7 vs 60.9%) without penalizing the specificity obtained with the BSGP-EIA (95.1% vs 96.9%) and the pU (95.1% vs 96.5%). Conclusions: This novel strategy, combining two PCR-based techniques for HR-HPV detection, could be useful for cervical cancer screening in self-collected samples in low-income countries.

Isoniazid Bactericidal Activity Involves Electron Transport Chain Perturbation.

Accumulating evidence suggests that the bactericidal activity of some antibiotics may not be directly initiated by target inhibition. The activity of isoniazid (INH), a key first-line bactericidal antituberculosis drug currently known to inhibit mycolic acid synthesis, becomes extremely poor under stress conditions, such as hypoxia and starvation. This suggests that the target inhibition may not fully explain the bactericidal activity of the drug. Here, we report that INH rapidly increased Mycobacterium bovis BCG cellular ATP levels and enhanced oxygen consumption. The INH-triggered ATP increase and bactericidal activity were strongly compromised by Q203 and bedaquiline, which inhibit mycobacterial cytochrome bc1 and FoF1 ATP synthase, respectively. Moreover, the antioxidant N-acetylcysteine (NAC) but not 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) abrogated the INH-triggered ATP increase and killing. These results reveal a link between the energetic (ATP) perturbation and INH's killing. Furthermore, the INH-induced energetic perturbation and killing were also abrogated by chemical inhibition of NADH dehydrogenases (NDHs) and succinate dehydrogenases (SDHs), linking INH's bactericidal activity further to the electron transport chain (ETC) perturbation. This notion was also supported by the observation that INH dissipated mycobacterial membrane potential. Importantly, inhibition of cytochrome bd oxidase significantly reduced cell recovery during INH challenge in a culture settling model, suggesting that the respiratory reprogramming to the cytochrome bd oxidase contributes to the escape of INH killing. This study implicates mycobacterial ETC perturbation through NDHs, SDHs, cytochrome bc1, and FoF1 ATP synthase in INH's bactericidal activity and pinpoints the participation of the cytochrome bd oxidase in protection against this drug under stress conditions.

Isoniazid bactericidal activity involves electron transport chain perturbation

Evaluation of the self-sampling for cervical cancer screening in Bolivia

Background: Incidence and mortality rates of cervical cancer in Bolivia are the highest in Latin America. Vaginal cell self-sampling can improve screening coverage. Information on common reasons for low screening coverage and preferences for future screening are essential to reduce cervical cancer incidence. We aimed to evaluate the knowledge about human papillomavirus (HPV) and cervical cancer of Bolivian women from urban, peri-urban and rural areas of Cochabamba and to determine their degree of acceptability and confidence towards vaginal HPV self-sampling. In addition, we assessed the impact of self-sampling on cervical cancer screening coverage in a selected peri-urban area. Methods: We gathered information from women living in urban, peri-urban and rural areas of Cochabamba province in Bolivia using two different structured questionnaires. In Survey1, we collected information from 222 women about their knowledge on HPV and cervical cancer. In Survey 2, the acceptance and confidence towards vaginal HPV self-sampling compared to the physician-sampling was assessed in 221 women. A non-probabilistic stratified sampling by areas was carried out for the two questionnaires. In the third phase of the study, we determined the impact of HPV self-sampling collection on screening coverage in a peri-urban area of Cochabamba. Results: Bolivian women knew little or nothing about cervical cancer and HPV infection in all areas. They all found self-sampling collection easier to perform (86.9 to 93.2%) and more comfortable (79.4 to 83.3%) compared to physician sampling. Sampling accuracy to detect cervical cancer was probably higher in their point of view when it was taken by physician (35.1 to 63.5%). However in rural areas women preferred self-sampling. Accordingly, the campaign of vaginal HPV self-sampling in this peri-urban area increased screening coverage, reaching in three months the annual rate average. Conclusions: The knowledge about cervical cancer and HPV infection is poor in Bolivia. Despite greater acceptance of the vaginal HPV self-sampling in all areas, women kept greater confidence in the screening performed by the gynecologist although HPV self-sampling improved coverage rate.

Cpn60.1 (GroEL1) Contributes to Mycobacterial Crabtree Effect: Implications for Biofilm Formation.

Biofilm formation is a survival strategy for microorganisms facing a hostile environment. Under biofilm, bacteria are better protected against antibacterial drugs and the immune response, increasing treatment difficulty, as persistent populations recalcitrant to chemotherapy are promoted. Deciphering mechanisms leading to biofilms could, thus, be beneficial to obtain new antibacterial drug candidates. Here, we show that mycobacterial biofilm formation is linked to excess glycerol adaptation and the concomitant establishment of the Crabtree effect. This effect is characterized by respiratory reprogramming, ATP downregulation, and secretion of various metabolites including pyruvate, acetate, succinate, and glutamate. Interestingly, the Crabtree effect was abnormal in a mycobacterial strain deficient for Cpn60.1 (GroEL1). Indeed, this mutant strain had a compromised ability to downregulate ATP and secreted more pyruvate, acetate, succinate, and glutamate in the culture medium. Importantly, the mutant strain had higher intracellular pyruvate and produced more toxic methylglyoxal, suggesting a glycolytic stress leading to growth stasis and consequently biofilm failure. This study demonstrates, for the first time, the link between mycobacterial biofilm formation and the Crabtree effect.

2018

Aloe Emodin Reduces Phthiodiolone Dimycocerosate Potentiating Vancomycin Susceptibility on Mycobacteria

Treatment of tuberculosis still represent a major public health issue. The emergence of multi-and extensively-drug resistant (MDR and XDR) Mycobacterium tuberculosis clinical strains further pinpoint the urgent need for new anti-tuberculous drugs. We previously showed that vancomycin can target mycobacteria lacking cell wall integrity, especially those lacking related phthiocerol and phthiodolone dimycocerosates, PDIM A and PDIM B, respectively. As aloe emodin was previously hypothesized to be able to target the synthesis of mycobacterial cell wall lipids, we tested its ability to potentiate glycopeptides antimycobacterial activity. The aloe emodin with the vancomycin induced a combination effect beyond simple addition, close to synergism, at a concentration lower to reported IC50 cytotoxic value, on M. bovis BCG and on H37Rv M. tuberculosis. Interestingly, out of six MDR and pre-XDR clinical strains, one showed a strong synergic susceptibility to the drug combination. Mycobacterial cell wall lipid analyses highlighted a selective reduction of PDIM B by aloe emodin.

In vitro methods for the evaluation of antimicrobial surface designs.

Bacterial adhesion and subsequent biofilm formation on biomedical implants and devices are a major cause of their failure. As systemic antibiotic treatment is often ineffective, there is an urgent need for antimicrobial biomaterials and coatings. The term "antimicrobial" can encompass different mechanisms of action (here termed "antimicrobial surface designs"), such as antimicrobial-releasing, contact-killing or non-adhesivity. Biomaterials equipped with antimicrobial surface designs based on different mechanisms of action require different in vitro evaluation methods. Available industrial standard evaluation tests do not address the specific mechanisms of different antimicrobial surface designs and have therefore been modified over the past years, adding to the myriad of methods available in the literature to evaluate antimicrobial surface designs. The aim of this review is to categorize fourteen presently available methods including industrial standard tests for the in vitro evaluation of antimicrobial surface designs according to their suitability with respect to their antimicrobial mechanism of action. There is no single method or industrial test that allows to distinguish antimicrobial designs according to all three mechanisms identified here. However, critical consideration of each method clearly relates the different methods to a specific mechanism of antimicrobial action. It is anticipated that use of the provided table with the fourteen methods will avoid the use of wrong methods for evaluating new antimicrobial designs and therewith facilitate translation of novel antimicrobial biomaterials and coatings to clinical use. The need for more and better updated industrial standard tests is emphasized.

I3-Ag85 effect on phthiodiolone dimycocerosate synthesis

The multiplicity of drug resistant Mycobacterium tuberculosis (Mtb) strains is a growing health issue. New therapies are needed, acting on new targets. The I3-Ag85 was already reported to reduce the amount of trehalose dimycolate lipid of the mycobacterial cell wall. This inhibitor of Ag85C increased the mycobacterial wall permeability. We previously showed that M. tuberculosis strains, even multi-drug resistant and extensively-drug resistant strains, can be susceptible to vancomycin when concomitantly treated with a drug altering the cell envelope integrity. We investigated the effect of the I3-Ag85 on vancomycin susceptibility of M. tuberculosis. Although no synergy was observed, a new target of this drug was discovered: the production of phthiodiolone dimycocerosate (PDIM B).

2017

Self-sampling for human papillomavirus DNA detection: A preliminary study of compliance and feasibility in BOLIVIA

Background: Cervical cancer incidence and mortality rates in Bolivia are among the highest in Latin America. This investigation aims to evaluate the possibility of using simple devices, e.g. a cotton swab and a glass slide, for self-sampling in order to detect human papillomavirus (HPV) DNA by PCR in cervico-vaginal cells. Methods: In the first phase of our study we evaluated the use of a glass slide as a transport medium for cervical cells. A physician took paired-cervical samples from 235 women. One sample was transported in Easyfix® solution and the other sample was smeared over a glass slide. Both were further analyzed and compared for human DNA recovery and HPV detection. A kappa value was determined to evaluate the agreement between the HPV DNA detection rates. In the second phase of the study, 222 women from the urban, peri-urban and rural regions of Cochabamba were requested to perform self-sampling using the following devices: a cotton swab combined with a glass slide, and a vaginal tampon. Women gave their opinion about the self-sampling technique. Finally, the agreement for high risk-HPV detection between self- and physician-collected samples was performed in 201 samples in order to evaluate the self-sampling technique. Results: Firstly, the comparison between Easyfix® solution and the glass slide to transport clinical samples gave a good agreement for HPV DNA detection (Κ = 0.71, 95% CI 0.60-0.81). Secondly, self-sampling, especially with cotton swab combined with glass slide, would generally be preferred over clinician sampling for a screening program based on HPV detection. Finally, we showed a good agreement between self- and physician collected samples for high risk-HPV detection (Κ = 0.71, 95% CI 0.55-0.88). Conclusions: Simple devices such as a cotton swab and a glass slide can be used to perform self-sampling and HPV DNA detection. Furthermore, most Bolivian women preferred self-sampling over clinician-sampling for cervical cancer screening.

In vitro Study of Five Herbs Used Against Microbial Infections in Burundi

The emergence of antimicrobial resistant infectious diseases remains a major threat to worldwide public health, in developed and in developing countries. Therefore, new antimicrobial agents acting by new mechanisms of action are urgently needed. As plants used in traditional medicine may help to overcome these problems, Justicia subsessilis, Platostoma rotundifolium, Pavetta ternifolia, Stomatanthes africanus, and Virectaria major (plants highly cited to be used against microbial infections in traditional Burundian medicine) were studied to assess their traditional use efficacy. We conducted a preliminary phytochemical screening of the extracts, as well as their direct and indirect (effect on antibiotic resistance) antibacterial activity on four bacterial strains (Staphylococcus sp. and Escherichia coli) by broth microdilution methods. All five medicinal plants investigated in this work were found to have direct antibacterial activity against all tested bacterial strains (minimum inhibitory concentration = 62.5-1000 μg/mL) that may support the use of these species in traditional Burundian medicine. Extracts (with no direct antibacterial activity), tested at 200 μg/mL, decreased the MIC values of β-lactams and aminoglycoside antibiotics by a factor of 2 to 64-fold. These interactions between plant extracts and antibiotics could open an avenue of research against antibiotic resistance. Copyright © 2017 John Wiley & Sons, Ltd.

2016

Effects of Lipid-Lowering Drugs on Vancomycin Susceptibility of Mycobacteria.

Tuberculosis is still a cause of major concern, partly due to the emergence of multidrug-resistant strains. New drugs are therefore needed. Vancomycin can target mycobacteria with cell envelope deficiency. In this study, we used a vancomycin susceptibility assay to detect drugs hampering lipid synthesis in Mycobacterium bovis BCG and in Mycobacterium tuberculosis We tested three drugs already used to treat human obesity: tetrahydrolipstatin (THL), simvastatin, and fenofibrate. Only vancomycin and THL were able to synergize on M. bovis BCG and on M. tuberculosis, although mycobacteria could also be inhibited by simvastatin alone. Lipid analysis allowed us to identify several lipid modifications in M. tuberculosis H37Rv treated with those drugs. THL treatment mainly reduced the phthiocerol dimycocerosate (PDIM) content in the mycobacterial cell wall, providing an explanation for the synergy, since PDIM deficiency has been related to vancomycin susceptibility. Proteomic analysis suggested that bacteria treated with THL, in contrast to bacteria treated with simvastatin, tried to recover, inducing, among other reactions, lipid synthesis. The combination of THL and vancomycin should be considered a promising solution in developing new strategies to treat multidrug-resistant tuberculosis.

Extrachromosomal HPV-16 LCR transcriptional activation by HDACi opposed by cellular differentiation and DNA integration

Histone deacetylase inhibitors (HDACi) have been shown to render HPV-carrying cells susceptible to intrinsic and extrinsic apoptotic signals. As such, these epigenetic drugs have entered clinical trials in the effort to treat cervical cancer. Here, we studied the effect of common HDACi, with an emphasis on Trichostatin A (TSA), on the transcriptional activity of the HPV-16 Long Control Region (LCR) in order to better understand the impact of these agents in the context of the HPV life cycle and infection. HDACi strongly induced transcription of the firefly luciferase reporter gene under the control of the HPV-16 LCR in a variety of cell lines. In the HaCaT keratinocyte cell line undergoing differentiation induced by TSA, we observed a reduction in LCR-controlled transcription. Three major AP-1 binding sites in the HPV-16 LCR are involved in the regulation by TSA. However, whatever the status of differentiation of the HaCaT cells, TSA induced integration of extra-chromosomal transfected DNA into the cellular genome. Although these data suggest caution using HDACi in the treatment of HR HPV infection, further in vivo studies are necessary to better assess the risk.

Chemical constituents, cytotoxic, antifungal and antimicrobial properties of Centaurea diluta Ait. subsp. algeriensis (Coss &Dur.) Maire

Objective To investigate the chemical composition of a moderately polar extract (CHCl3 soluble part of the MeOH-H2O extract) obtained from the aerial parts (leaves and flowers) of Centaurea diluta Ait. subsp. algeriensis (Coss. & Dur.) Maire, a species endemic to Algeria and Morocco on which no reports are available to date. To evaluate in vitro the cytotoxic, antifungal and antimicrobial activities of this extract and the cytotoxic and antimicrobial activities of its isolated secondary metabolites. Methods The cytotoxic effects of the extract were investigated on 3 human cancer cell lines i.e. the A549 non-small-cell lung carcinoma (NSCLC), the MCF7 breast adenocarcinoma and the U373 glioblastoma using a MTT colorimetric assay. Biological data allowed to guide the fractionation of the extract by separation and purification on silica gel 60 (CC and TLC). The isolated compounds which were characterized by spectral analysis, mainly HR-ESIMS, HR-EIMS, UV and NMR experiments (1H, 13C, COSY, ROESY, HSQC and HMBC) and comparison of their spectroscopic data with those reported in the literature, were evaluated for cytotoxic activities on six cancer cell lines (A549, MCF7, U373, Hs683 human glioma, PC3 human prostate and B16-F10 murine melanoma). The direct and indirect antibacterial and antifungal activities were determined using microdilution methods for the raw extract and TLC-bioautography and microdilution methods against standard and clinical strains for the isolated compounds. Results The raw extract reduced cell viability with IC50s of 27, 25 and 21 μg/mL on A549, MCF7 and U373, respectively. Five secondary metabolites: two phenolic compounds (vanillin 1, paridol 3), a lignan [(−)-arctigenin 2] and two flavonoid aglycones (eupatilin 4 and jaceosidin 5), were then isolated from this extract. Moderate cytotoxic effects were observed for (−)-arctigenin 2 (IC50s: 28 and 33 μM on Hs683 and B16-F10, respectively), eupatilin 4 (IC50s: 33 and 47 μM on B16-F10 and PC3, respectively) and jaceosidin 5 (IC50s: 32 and 40 μM on PC3 and B16-F10, respectively). Conclusions All the isolated compounds were described for the first time from this species. Although inactive against 7 tested microorganisms (fungi, bacteria and yeast, human or plant pathogens), the raw extract was able to potentiate the effect of beta-lactam antibiotics on methicillin-resistant Staphylococcus aureus (MRSA), reducing the minimal inhibitory concentrations (MICs) by a factor of 2-32-fold. No synergy was found between the extract and streptomycin. From the five isolated compounds only jaseosidin 5 showed a moderate antimicrobial activity.

2015

Increased vancomycin susceptibility in mycobacteria: a new approach to identify synergistic activity against multi-drug resistant mycobacteria.

Mycobacterium tuberculosis is wrapped in complex waxes, impermeable to most antibiotics. Comparing M. bovis BCG and M. tuberculosis mutants, lacking phthiocerol dimycocerosates (PDIM) and/or phenolic glycolipids, with wild-type strains, we observed that glycopeptides strongly inhibited PDIM deprived mycobacteria. Vancomycin together with a drug targeting lipids synthesis inhibited multidrug-resistant (MDR) and extensively-drug resistant (XDR) clinical isolates. Our study puts glycopeptides in the pipeline of potential anti-TB agents and might provide a new antimycobacterial drug-screening strategy.

Biochemical Analysis of the NAD+-Dependent Malate Dehydrogenase, a Substrate of Several Serine/Threonine Protein Kinases of Mycobacterium tuberculosis.

PknD is one of the eleven eukaryotic-like serine/threonine protein kinases (STPKs) of Mycobacterium tuberculosis (Mtb). In vitro phosphorylation assays with the active recombinant PknD showed that the intracellular protein NAD+-dependent malate dehydrogenase (MDH) is a substrate of this kinase. MDH, an energy-supplying enzyme, catalyzes the interconversion of malate and oxaloacetate and plays crucial roles in several metabolic pathways including the citric acid cycle. The phosphorylation site was identified on threonine residues and the phosphorylation inhibited the MDH activity. In vitro, the recombinant MDH could also be phosphorylated by at least five other STPKs, PknA, PknE, PknH, PknJ, and PknG. Immunoprecipitation analysis revealed that MDH was hyperphosphorylated in the bacteria at the beginning of the stationary and under oxygen-limited conditions by STPKs other than PknD. On the contrary, when PknD-deficient mutant mycobacteria were grown in a phosphate-depleted medium, MDH was not detectably phosphorylated. These results suggest that although the MDH is a substrate of several mycobacterial STPKs, the activity of these kinases can depend on the environment, as we identified PknD as a key element in the MDH phosphorylation assay under phosphate-poor conditions.

2014

Antimicrobial effects of arial parts from Algerian Centaury

2013

Inter-laboratory variability in the presence of human papillomavirus in normal and abnormal cervical cytology samples.

Introduction: Treatment of cervical carcinoma is affected by the stage of the disease, being most likely curable with early detection. High-risk human papillomavirus (HPV) infection and persistency are necessary to the development of precancerous and cancerous lesions leaving the possibility to detect in time cells progressing in at risk behaviour. Methods: This study documents the proportion of HPV DNA positivity in 906 samples with cytological result negative for intraepithelial lesion and malignancy (NILM), 220 atypical squamous cells of undetermined significance (ASC-US) samples and 211 low grade intraepithelial lesions (LSIL) samples collected from various pathological laboratories in Brussels, Belgium. Results: The proportion of samples harbouring one or more HPV types was 10.8% (95% confidence interval, 95% CI: 8.8-12.8) in NILM, 34.5% (95% CI: 27.6-40.3) in ASC-US, 54.3% (95% CI: 47.5-61.1) in LSIL, with significant variability of HPV proportion in ASC-US and LSIL between laboratories. Conclusion: This study provides an on-site picture, confirming an added value of HPV DNA detection.

2011

Regulation of human papillomavirus type 16 early gene expression in trophoblastic and cervical cells.

We compared the outcome of different cellular and viral factors on the regulation of the HPV-16 early viral gene expression in trophoblastic and cervical cancer cells. A high variability of the long control (LCR) activity was observed, prompting us to evaluate the role of secreted factors in the control of the early gene expression in trophoblastic cell lines. Endogenous progesterone and exogenous dexamethasone were found to activate LCR driven transcriptional activity. Since host cells express HPV early proteins to regulate LCR activity, we investigated the effect of the combined HPV-16 early proteins on the LCR driven transcription and the possible involvement of E2. A physiological level of HPV-16 early proteins expression strongly induced the LCR driven reporter activity. According to mutational analysis, E1 and E2 proteins, indispensable for viral replication, were not involved in LCR extrachromosomal transcriptional regulation. This suggests that E5 and/or E6 and/or E7, consequently, activated viral transcription.

Evidence of human papillomavirus in the placenta.

Human papillomavirus (HPV) is an epitheliotropic virus typically infecting keratinocytes but also possibly epithelial trophoblastic placental cells. In the present study, we set out to investigate whether HPV can be recovered from transabdominally obtained placental cells to avoid any confounding contamination by HPV-infected cervical cells. Thirty-five placental samples from women undergoing transabdominal chorionic villous sampling were analyzed, and we detected HPV-16 and HPV-62 in 2 placentas. This study suggests that HPV infection of the placenta can occur early in pregnancy. The overall clinical implication of these results remains to be elucidated.

2010

Comparative evaluation of 3 selective media for primary isolation of Helicobacter pylori from gastric biopsies under routine conditions.

This study evaluates 3 selective media (Pylori agar [bioMérieux, France], BD Helicobacter agar, modified [Becton Dickinson, USA], and an in-house medium) designed for Helicobacter pylori isolation. Ninety-eight strains were isolated from 400 gastric biopsies. The media were equally efficient for Helicobacter pylori's growth. However, contaminations were only observed using commercial media.

Effects of HPV-16 E5, E6 and E7 proteins on survival, adhesion, migration and invasion of trophoblastic cells.

Among high-risk human papillomaviruses (HPV), HPV-16 infection is the most prevalent causative factor for cervical cancer. Beside other mucosal targets, HPV-16 was reported to infect the placenta and to replicate in trophoblastic cells. Since these cells share invasive properties of tumoral cells, they represent an ideal model to investigate several oncogenic processes. In the present work, we analyzed the impacts of HPV-16 E5, E6 and E7 oncoproteins on the trophoblastic model. Our results showed that E5 impaired the viability of trophoblastic and cervical cell lines but E6 and E7, favoring cell growth, neutralized the E5 cytotoxic effect. In addition, E5 decreased the adhesiveness of trophoblastic cells to the tissue culture plastic and to endometrial cells similarly as described previously for E6 and E7. E5 and E6 plus E7 increased also their migration and their invasive properties. Cells expressing HPV-16 early proteins under the control of the long control region endogenous promoter displayed growth advantage and were also more motile and invasive compared with control cells. Interestingly, the E-cadherin was downregulated in trophoblastic cells expressing E5, E6 and E7. Nuclear factor-kappaB and activator protein-1 activities were also enhanced. In conclusion, HPV-16 early proteins enhanced trophoblastic growth and intensify the malignant phenotype by impairing cell adhesion leading to increased cellular motile and invasive properties. HPV-16 E5 participated, with E6 and E7, in these changes by impairing E-cadherin expression, a hallmark of malignant progression.

2009

Effects of HPV-16 early proteins on trophoblastic cells

2007

Detection of human papillomavirus types 45 and 51 by type-specific polymerase chain reaction.

Human papillomavirus (HPV) types 45 and 51 are both considered as high risk types for the development of human cervical cancer. To optimize the detection of these two types in clinical samples, HPV-45 and HPV-51 specific primers were designed to amplify respectively a 141bp and a 266bp fragment from the L1 gene by polymerase chain reaction (PCR). The sensitivity and the specificity of these two PCR reactions were determined using varying amounts of HPV DNA containing plasmids and negative and positive controls. Overall, the sensitivity for the HPV-45 plasmid DNA is 10fg, while for HPV-51 the sensitivity is 1fg. This is equivalent to approximately 100 and 10 HPV genome copies per PCR reaction, respectively.

Evaluation of combined general primer-mediated PCR sequencing and type-specific PCR strategies for determination of human papillomavirus genotypes in cervical cell specimens.

A strategy combining human papillomavirus general primer (mainly the PGMY primers)-directed PCR sequencing and type-specific PCR is presented. DNA samples were first tested in general primer-mediated PCR. The amplified fragments of positive samples after ethidium bromide-stained DNA gel analysis were further sequenced, and corresponding DNA samples were further analyzed by PCR using type-specific primers for human papillomavirus (HPV) types 16, 18, 31, and 52. The comparison of the results of 157 samples analyzed by this strategy in parallel with the Hybrid Capture 2 tests and with the HPV INNO-LiPA (Innogenetics line probe assay) shows that this method is suitable for HPV detection and genotyping in cervical cell samples. Although the PCR sequencing method is as sensitive as the HPV INNO-LiPA for HPV detection, our method allows the identification of a broader range of HPV types. In contrast, the HPV INNO-LiPA was less time-consuming and better identified coinfections.

La PCR en temps réel

2005

Efficiency of an inexpensive liquid-based cytology performed by cytocentrifugations: a comparative study using the histology as reference standard.

Although liquid-based cytology (LBC) is now recommended for cervical cancer screening, it requires expensive automated devices and materials. To evaluate the efficiency of inexpensive LBC methods relying on an inexpensive fixative liquid, Easyfix, we compared the results obtained by the liquid-based cytology (LBC) diagnoses performed by cytocentrifugations (Papspin and Turbitec) with those obtained by histology. Furthermore, we evaluated the efficiency of the fixative liquid, Easyfix, to preserve HPV DNA in the collected samples.

2001

Inhibition of human papillomavirus-16 long control region activity by interferon-gamma overcome by p300 overexpression

Although interferons (IFNs) are currently used in the treatment of various human papillomavirus (HPV)-associated lesions, their mechanisms of action are still unclear. In this study, we clearly demonstrated that IFN-gamma was a strong inhibitor of HPV-16 long control region (LCR) activity in two human cervical carcinoma cell lines. The effect of IFN-gamma was dose dependent. We investigated whether the effect of IFN-gamma on HPV-16 LCR could involve the inhibition of the CREB-binding protein (CBP)/p300 family of transcriptional coactivators. In support of this model, we demonstrated by transfection experiments that a 12S E1A mutant (RG2), which interacts poorly with p300 and CBP in comparison to wild-type E1A, was less able to repress human papillomavirus (HPV) 16 long control region (LCR) than wild-type E1A. More important, overexpression of p300 was able to increase the HPV-16 LCR activity and to overcome inhibition by IFN-gamma. Finally, we demonstrated that p300 could cooperate with c-jun to activate HPV-16 LCR. According to our results, IFN-gamma might inhibit HPV-16 LCR transcription by activating the signal transducer and activator of transcription 1alpha, which in turn might compete for p300/CBP binding with specific transcription factors involved in LCR activation.

2000

A functional NF-kappaB binding site in the human papillomavirus type 16 long control region.

By computer search, we identified one potential NF-kappaB binding site in the HPV16 long control region (LCR) at position 7554-7563 having two mismatches in comparison to the consensus NF-kappaB binding site of the Igkappa L promoter. Bandshift experiments with nuclear extracts from HeLa cells or purified glutathione S-transferase-p65 fusion protein clearly demonstrated that NF-kappaB is able to bind to this region of the LCR. However, in comparison to NF-kappaB binding on a consensus probe, the affinity of NF-kappaB for this site is about 250-fold reduced. When mutations were introduced into this NF-kappaB binding site, the activity of the LCR was increased, strongly suggesting that NF-kappaB was acting as a transcriptional repressor in the context of the HPV16 LCR. In addition, overexpression of NF-kappaB p65 repressed the activity of the HPV16 LCR, strengthening this conclusion.

Transcriptional regulation of human papillomavirus type 16 LCR by different C/EBPbeta isoforms

During genital human papillomavirus (HPV) infection several cytokines are released, such as interleukin-1 (IL-1), tumor necrosis factoralpha (TNFalpha), IL-6, and IL-8. These cytokines may play a role in the immune surveillance against viral infection. Two of these cytokines, IL-1 and TNFalpha, suppress the transcription of the HPV16 early genes. CAATT/ enhancer binding protein, (C/EBPbeta), which is activated by IL-1 and TNFalpha, has been suggested to act as a mediator of this transcriptional downregulation. C/EBPbeta contains three different translation initiation sites that can lead probably by leaky ribosome scanning to the generation of three isoforms of C/EBPbeta, namely full-length C/EBPbeta, liver enriched transcriptional activator protein (LAP), and liver enriched inhibitory protein (LIP). When transiently expressed in C33A and HeLa cells, the first two C/EBPbeta isoforms activate the HPV16 long control region (LCR). LIP, which acts as an antagonist of C/EBPbeta, represses the HPV16 LCR activity. Our observation that treatment of HeLa cells with IL-1 leads to induction of LIP supports the hypothesis that the LCR downregulation by IL-1 is mediated by LIP.

1999

Evolution of the human immunodeficiency virus type 1 long terminal repeat promoter by conversion of an NF-kappaB enhancer element into a GABP binding site.

Human immunodeficiency virus type 1 (HIV-1) transcription is regulated by the viral Tat protein and cellular factors, of which the concentration and activity may depend on the cell type. Viral long terminal repeat (LTR) promoter sequences are therefore optimized to suit the specific nuclear environment of the target host cell. In long-term cultures of a Tat-defective, poorly replicating HIV-1 mutant, we selected for a faster-replicating virus with a 1-nucleotide deletion in the upstream copy of two highly conserved NF-kappaB binding sites. The variant enhancer sequence demonstrated a severe loss of NF-kappaB binding in protein binding assays. Interestingly, we observed a new binding activity that is specific for the variant NF-kappaB sequence and is present in the nuclear extract of unstimulated cells that lack NF-kappaB. These results suggest that inactivation of the NF-kappaB site coincides with binding of another transcription factor. Fine mapping of the sequence requirements for binding of this factor revealed a core sequence similar to that of Ets binding sites, and supershift assays with antibodies demonstrated the involvement of the GABP transcription factor. Transient transfection experiments with LTR-chloramphenicol acetyltransferase constructs indicated that the variant LTR promoter is specifically inhibited by GABP in the absence of Tat, but this promoter was dramatically more responsive to Tat than the wild-type LTR. Introduction of this GABP site into the LAI virus yielded a specific gain of fitness in SupT1 cells, which contain little NF-kappaB protein. These results suggest that GABP potentiates Tat-mediated activation of LTR transcription and viral replication in some cell types. Conversion of an NF-kappaB into a GABP binding site is likely to have occurred also during the worldwide spread of HIV-1, as we noticed the same LTR modification in subtype E isolates from Thailand. This typical LTR promoter configuration may provide these viruses with unique biological properties.

1998

Interferon-gamma and interleukin-6 inhibit proliferation in human melanoma cells by different signalling pathways.

Interferon regulatory factor-1 (IRF-1) is a cell growth inhibitor, induced by cytokines, which transactivates downstream effector genes. The role of IRF-1 in the antiproliferative effect of interleukin-6 (IL-6) was investigated using the A375 human melanoma cell line. IL-6 is a stronger inhibitor of A375 proliferation compared with interferon-gamma (IFNgamma). However, in contrast to IFNgamma, IL-6 triggered lower IRF-1 DNA binding activity and induced barely detectable IRF-1-dependent transactivation activity. Furthermore, although IFNgamma induces only activation of signal transducer and activator of transcription (STAT) 1, IL-6 activates mainly STAT3. These data suggest that IRF-1 plays a minor role in the antiproliferative effect of IL-6, which uses alternative signalling events to induce growth inhibition in A375 melanoma cells.

1997

Analysis of the mechanism of action of anti-human interleukin-6 and anti-human interleukin-6 receptor-neutralising monoclonal antibodies

Anti-human interleukin-6 (human IL-6) and anti-human IL-6 receptor (IL-6R)-neutralising monoclonal antibodies (mAbs) are among the most promising human IL-6-specific inhibitors and have been shown to exert short-term beneficial effects in clinical trials. Simultaneous treatment with different anti-human IL-6 or anti-human IL-6R mAbs was recently suggested to be a potent way to inhibit the action of the cytokine in vivo. Although some of these mAbs are already used, their mechanisms of action and the location of their epitopes on the surface of human IL-6 and human IL-6R are still unknown. Here, we analysed the capacity of several anti-human IL-6 and anti-human IL-6R mAbs to inhibit the interaction between human IL-6, human IL-6R, and human glycoprotein 130 (gp130). We mapped the epitopes of several of these mAbs by studying their binding to human IL-6 and human IL-6R mutant proteins. Our results show that several anti-human IL-6 and anti-human IL-6R-neutralising mAbs block the binding between human IL-6 and human IL-6R, whereas others block the binding to gp130. We:provide evidence that some of the latter mAbs inhibit interaction with gp130β1, whereas others interfere with the binding to gp130β2. Our results suggest that residues included in the C'D' loop of human IL-6R interact with gp130β2.

Analysis of the human interleukin-6/human interleukin-6 receptor binding interface at the amino acid level

The interaction between interleukin-6 (IL-6) and IL-6 receptor (IL-6R) is the initial and most specific step in the IL-6 signaling pathway. Understanding its mechanism at the amino acid level is the basis for developing small IL-6-inhibiting molecules. We studied the human IL-6 (hIL-6)/hIL-6R binding interface by a combination of molecular modelling and site-directed mutagenesis. Our model suggests that the center of the interface between the two molecules consists of hydrophobic contacts predicted to account for most of the binding-free energy. These contacts can be regarded as a hydrophobic core shielded by hydrophilic residues that are also needed for recognition. Following this hypothesis, we altered in hIL-6 and hIL-6R residues predicted to reside in the contact region and to interact with each other. We studied the capacity of these mutants to form an IL-6/IL-6R complex and their ability to transduce the signal. This combined approach has led to the identification of certain residue-clusters in the binding interface and to a rational explanation of their specific interactions, suggesting therein a likely mechanism of complex formation. The results confirm the predictive model and strongly support our hypothesis. Comparison with other cytokines and their alpha-subunit receptors suggests that the structural location of certain binding sites are conserved.

1996

Effect of succinic acid monomethyl ester on interleukin-1β cytotoxicity in tumoural pancreatic islet cells

The IL-6/IL-6R binding interface. proposed mechanism of interaction

1994

Mutagenesis of the human interleukin-6 fourth predicted alpha-helix: involvement of the Arg168 in the binding site.

Random substitutions of amino acid 161-184 of human interleukin-6 (hIL-6) have been generated at the cDNA level using oligonucleotide-directed mutagenesis. Among the majority of the mutant proteins showing a reduced biological activity on murine hybridoma cells, only those having a substitution of Met161, Arg168, Arg179 or Met184, retained a tertiary structure similar to the IL-6 folding. These residues are thus probably involved in the interaction with the IL-6 receptor. However, the contacts established by Arg168 and Arg179 seem far more important for the biological activity. According to Bazan's model of cytokine folding and the receptor binding site on the fourth alpha-helix, based on growth hormone similarity, we propose that Arg168 and Arg179 are located on the exposed surface of this presumed helix.

Development of a human interleukin-6 receptor antagonist.

Neutralizing monoclonal antibodies specific for human interleukin-6 (IL-6) bind two distinct sites on the IL-6 protein (sites I and II). Their interference with IL-6 receptor binding suggested that site I is a receptor-binding site of IL-6, whereas site II is important for signal transduction. Mutagenesis of site II could therefore result in the isolation of IL-6 receptor antagonists. To test this hypothesis, a panel of IL-6 mutant proteins was constructed that did not bind to a site II-specific monoclonal antibody. One such site II mutant protein (with double substitution of Gln-160 with Glu and Thr-163 with Pro) was found to be an antagonist of human IL-6. It was inactive on human CESS cells, weakly active on human HepG2 cells, but active on mouse B9 cells. It could specifically antagonize the activity of wild-type IL-6 on CESS and HepG2 cells. The binding affinity of this variant for the 80-kDa IL-6 receptor was similar to that of wild-type IL-6. High affinity binding to CESS cells, however, was abolished, suggesting that the mutant protein is inactive because the complex of the 80-kDa IL-6 receptor and the mutant protein cannot associate with the signal transducer gp130. The human IL-6 antagonist protein may be potentially useful as a therapeutic agent.

1993

Involvement of the Arg179 in the active site of human IL-6.

Three internal-amino acid deletions of amino acids 171-179 of human interleukin 6 (IL-6) were introduced at the cDNA level. While all deletion proteins were biologically inactive, immunoprecipitations with a set of conformation-specific anti-(IL-6) monoclonal antibodies showed that only mutant delta 177-179 does not present major alterations in folding. This finding, together with the observation that delta 177-179 is not able to compete with IL-6 for binding to the soluble human IL-6 receptor, suggested that some or all of these three residues participate to the composition of the receptor-binding site of human IL-6. A large number of single-amino-acid-substitution mutants were generated in residues 177, 178 and 179. Their detailed analysis revealed that Arg179 is crucial for activity in mouse cells, because all amino acid substitutions in this position cause a dramatic drop of biological activity on murine hybridoma cells without affecting the overall protein folding. The only substitution which preserved some residual activity was the conservative Arg to Lys change. This demonstrates the absolute requirement for a positive charge in position 179 for the interaction of human IL-6 with its receptor.

1991

Internal deletions of amino acids 29-42 of human interleukin-6 (IL-6) differentially affect bioactivity and folding.

Internal deletions of the human interleukin-6 (IL-6) cDNA have been generated in the region encoding residues 29 to 42. Mutant proteins were produced by in vitro transcription-translation or in Escherichia coli and tested for their biological activity using the hybridoma growth factor (HGF) assay or a transcriptional activation assay on human hepatoma cells. The folding of the mutants was also checked by immunoprecipitation with conformation-specific monoclonal antibodies. The results show that only residues 29 to 34 are crucial for IL-6 activity and that the first two amino acids are probably involved in the definition of the IL-6 active site.

Internal deletions in human interleukin-6: structure-function analysis.

By cDNA mutagenesis, we have constructed internal and C-terminal deletions (delta 21-51, delta 52-97, delta 97-104, delta 127-174, delta 97-184 and delta 134-184) in human interleukin-6 (hIL-6). All those deletion-carrying hIL-6 (delta hIL-6) proteins were then produced in Xenopus laevis oocytes and examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results show that, at least in frog oocytes, the first potential N-glycosylation site (Asn45) is utilized exclusively. The IL-6 conformation of these deletion-carrying proteins has been studied by immunoprecipitation with two kinds of monoclonal antibodies (mAb's): mAb's that show preference towards denatured hIL-6, or conformation-specific mAb's. The binding pattern of these two series of mAb's indicated that the IL-6 conformation has been largely destroyed for four of our delta-proteins. Proteins delta 21-51 and delta 127-174 have kept a part of the IL-6 tertiary structure since they are still recognized by some conformation-specific mAb's. All of these delta hIL-6 proteins were inactive in the IL-6 hybridoma growth factor (HGF) assay and unable to inhibit the HGF activity of the recombinant human wild-type IL-6 (wt hIL-6). Moreover, the oocyte-synthesized delta hIL-6 (delta 21-51, delta 127-174, delta 97-184, delta 134-184) did not bind to the IL-6 receptor. Finally, we have produced two proteins with aa 29-33 or 97-104 substituted by corresponding murine IL-6 (mIL-6) sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-step purification and structural characterization of human interleukin-6 produced in Escherichia coli from a T7 RNA polymerase expression vector.

Human interleukin-6 or B-cell stimulatory factor-2 is a cytokine involved in acute phase and immune response. Cloning of cDNA for human interleukin-6 in the pT7.7 expression plasmid under the control of a bacteriophage T7 RNA polymerase promoter system allows rapid production of the cytokine in Escherichia coli. Upon cell induction with isopropyl thiogalactopyranoside, recombinant human interleukin-6 is overexpressed and forms insoluble inclusion bodies. Solubilization of the protein with 6 M guanidine hydrochloride and refolding in the presence of a reduction/oxidation system results in a quantitative recovery of recombinant human interleukin-6. This material is already 70% pure and can be further purified to homogeneity with a single passage over a weak anionic-exchange column. Extended structural characterization of the purified protein by electrospray mass spectrometry, automated Edman degradation and peptide mapping by high-pressure liquid chromatography/fast-atom-bombardment mass spectrometry demonstrates that recombinant human interleukin-6 is identical to the natural protein both in amino acid sequence and S-S bridge content. However, it contains a minor component accounting for about 20% of the entire translated protein which exhibits a Met-Ala dipeptide extension at the N-terminus. Purified recombinant human interleukin-6 is biologically active because it is able to induce at least 70-fold the human C-reactive promoter transfected in human hepatoma Hep 3B cells and is stable for several months in 10% glycerol at 4 degrees C. The expression system described in the present work has the main advantage of producing a high yield of recombinant human interleukin-6 (about 25 mg/l) combined with a very simple purification scheme.

1989

Modulation of interleukin-6 receptors in human cells