Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body but is mainly an infection of the lungs. It is caused by micro-organisms of the Mycobacterium tuberculosis complex. It is the second greatest killer worldwide due to a single infectious agent, after the Human Immunodeficiency Virus (HIV). Without treatment, fatality is 50% in immune competent persons. TB remains the leading cause of death among HIV positive persons, causing one fifth of the deaths. The World Health Organization estimates that one third of the world population is infected by this micro-organism but only 5 to 10% develop TB disease. Nevertheless, this enormous reservoir leads to around 1.4 millions deaths annually. Standard curative treatment lasts at least 6 months and includes 4 different drugs. Toxicity of the drugs leading to (severe) adverse events and the long duration of the daily administration challenges patient’s compliance. Subinhibitory concentration of the drugs (due to poor adherence) can induce resistance of the mycobacteria to the provided drugs. Unlike most bacteria where resistance is acquired by plasmids, drug resistance of mycobacteria is obtained by genomic mutations. “Multi drug-resistant tuberculosis (MDR-TB)” is strictly defined as TB resistant to specifically isoniazid and rifampicin, the two main first line drugs. “Extensively drug resistance (XDR)” is defined as MDR-TB with additional resistance to any of the fluoroquinolones (such as ofloxacin or moxifloxacin) and to at least one of three injectable second-line drugs (amikacin, capreomycin or kanamycin). The increase of MDR-TB represents an enormous challenge to Public Health globally. This research examined different aspects of tuberculosis resistance performed in the Belgian National Reference Center, a clinical laboratory setting. <p><p>First of all, a profound analysis of the MDR-TB situation in Belgium was conducted. It is the first retrospective population-based survey of MDR-TB in Belgium, covering a 15-year period (1994-2008). It comprises 174 patients representing more than 80% of the culture positive MDR-TB patients reported to the Belgian register, thus this study is considered of national relevance. It includes bacteriological and molecular data on the isolates as well as clinical aspects of the patients and treatment results. Considering only the patient’s first MDR-TB isolate, an increase over time was observed in the number of isolates resistant to a second-line drug as well as the total number of drugs each isolate was resistant to. XDR-TB was detected since 2002 and panresistant TB (resistant to every available antituberculosis drug) since 2009. Overall, a successful treatment outcome was obtained for 67.8% of the MDR-TB cases. Drug susceptibility testing (DST) of Mycobacterium tuberculosis to first line drugs (isoniazid, rifampicin, ethambutol and pyrazinamide) in liquid culture medium has a turn around time of at least two weeks, after identification of the positive culture (obtained after 2 to 4 weeks) from the patient’s clinical isolate. In order to provide the clinician with valuable information about the isolated mycobacteria leading to patient adapted therapy before bacteriological DST results are available, resistance is predicted by detection of mutations in certain genes of the mycobacteria. It is common practice for rifampicin (rpoB gene) and isoniazid (katG gene and/or inhA promoter region). In this MDR-TB collection, rifampicin resistant related mutations were found in 97.1% (168/173) of the clinical isolates and isoniazid resistant related mutations in 94.1% (160/170). The pncA, embB and gyrA genes have been sequenced to identify possible mutations because of their possible involvement with resistance to pyrazinamide, ethambutol and the fluoroquinolones respectively. However, little is known about the resistance prediction value of the mutations in these genes.<p>The study is also the first study on the molecular epidemiology of MDR-TB in the country. DNA fingerprinting showed a large diversity of strains (67% of the patients were infected by a strain with a unique pattern) and further epidemiological examination revealed limited local transmission of MDR-TB in Belgium.<p><p>The second part investigated the pncA gene and its association with pyrazinamide resistance in MDR-TB isolates from Belgium and in vitro cultured spontaneous mutants. The genetic analysis showed that 98.3% (59/60) of the Belgian clinical MDR pyrazinamide resistant (PZAR) isolates present a mutation in the pncA gene. We found 1.7% (1/60) of the PZAR MDR-isolates encoding wild type pncA and flank. A total (PZAR and PZAS) of 41 different amino acid changes, 3 protein truncations and 5 frameshifts were observed including eight novel mutations: 8Asp>Ala, 13Phe>Leu, 64Tyr>Ser, 107Glu>stop, 143Ala>Pro, 172Leu>Arg and frameshifts starting in codon 55 and 82. Analysis of all observed mutations (i.e. in clinical isolates as well as spontaneous mutants) revealed that they are not always associated with drug resistance and that they are not scattered randomly throughout the gene, but occur rather at preferential sites such as in codons with amino acids associated with either iron or substrate binding and catalytic active sites. The frequency of in vitro mutagenesis to pyrazinamide at pH 6.0 was determined and found to be relatively high at 10-5 CFU/ml.<p><p>Finally, the in vitro activity of tobramycin and clarithromycin (with unclear efficacy against M. tuberculosis) was evaluated on 25 M. tuberculosis clinical isolates with various resistance profiles. The effect of the drugs administered together was examined for possible synergistic effect. The median minimum inhibitory concentration (MIC) of 8 µg/ml obtained for both drugs in this study is rather high but are beyond the concentrations obtained in lung tissues. This suggests that both drugs should be investigated further as potential adjuncts to the treatment of resistant TB when other alternatives have failed; in particularly through new drug delivery systems such as the Dry Power Inhaler which allows local drug deposition with high drug concentrations in the lungs but low toxicity due to limited systemic absorption. In addition, for 36% of the tested isolates a decrease of the MIC of clarithromycin by a single or twofold dilution was observed in the presence of a subinhibitory concentration of tobramycin and no antagonistic effect was seen for the remaining isolates.<p><p>This research illustrates different (laboratory) aspects in the fight against drug resistant TB, all using the Belgian TB collection: characterisation of the Belgian MDR-TB situation on bacteriological, molecular and epidemiological level; profound analysis of genomic mutations and their possible association with drug resistance; and investigation of synergistic activity of drugs with low efficacy against M. tuberculosis.<p> / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

Magister Curationis - MCur / Multidrug resistant TB (MDR-TB) is a form of TB caused by bacteria (germs) that are resistant to the usual drugs that are used to treat "normal" TB. The duration of treatment for MDR-TB is a maximum of 22 months. People with MDR-TB are treated in specialized tertiary hospitals and in out-patient clinics in the PHC facilities. The treatment includes a six months injectable phase with a wide range of TB drugs. The adverse effects of MDR-TB drugs are among the worst side effects ever reported by patients. The aim of the current study was to explore the experiences of adverse effects of MDR-TB treatment amongst patients in a primary health care facility in the Western Cape. An explorative qualitative study design was used to explore the experiences of patient with the adverse effects of MDR-TB treatment in a primary health care facility in the Western Cape. In depth interviews were conducted with 12 MDR-TB patients. Data analysis was done by using the Tesch's method of content analysis. The study revealed that participating MDR-TB patients experienced various emotional, financial, physical and social challenges. Participants explained that the experience of being on MDR-TB treatment is emotionally draining; the pain and discomfort of the adverse effect of treatment makes a person to feel anxious and depressed. Financially they depended on social grants because they had to stop working after starting treatment. They could not function well physically because of the toxic nature of the adverse effects of treatment; which resulted in fatigue, dizziness and burning sensation on the feet and hands. They were faced with a lot of stigma from the community and even family members because of their illness. The study also revealed that in spite of the challenges and obstacles the participants were all motivated to complete their treatment and get cured. It is recommended that more support structures be made available for patients who are being treated for MDRT-TB such as; psychotherapy, social support and counselling on health education. Provision needs to be made for patients who are receiving daily injection; for it to be given in their homes. Health care providers treating MDR-TB patients need to do home visits together with MDR-TB adherence counsellors, to monitor the physical wellbeing of patients at home. This will also provide patients with the platform to discuss their health concerns in a more accommodative and relaxed environment. New drug regimen with fewer tablets and less treatment duration is needed for MDR-TB.

Background: Disabling hearing loss is a global burden. This burden is worsened by the emergence of multi-drug resistant tuberculosis (MDR-TB). Some of the medications used to treat MDR-TB are damaging to the cochlea and auditory nerve (ototoxic) and can lead to permanent hearing loss and/or balance disorders. Ototoxicity monitoring aims to reduce this burden by preventing or minimising the damage caused by ototoxic treatment as it can progress and worsen speech perception difficulties. However, the proposed test battery for ototoxicity monitoring is lengthy and demands active participation which is not ideal for ill patients (such as those on MDR-TB treatment). The Sensitive Range of Ototoxicity (SRO) technique is recommended to shorten the test time. The SRO consists of seven consecutive relatively high frequencies determined from the highest frequency the participant responded to. The SRO technique is time efficient. Although the SRO technique provides the prospect of a shortened test battery, there is still a global lack of audiologists. Automated audiometry is a vital application for testing especially when audiologists are not available to physically do the test. Automated audiometry has been previously validated. Clinically, automated audiometry is objective and allows for standardisation. Even though automated audiometry helps improve access to monitoring more patients, patient preference is an important factor when using automated audiometry to ensure patient-centred care is not compromised. Aims and Objectives: This study aimed to investigate the specificity and sensitivity of the SRO technique with automated audiometry compared to the gold standard (manual audiometry). This comparison was made by firstly, determining the testing time efficiency and the correlation of thresholds obtained with the different test methods and, secondly, testing the diagnostic value of automated audiometry using the SRO technique. The incidence of an ototoxicity-induced hearing loss was described by determining the time interval between starting ototoxic MDR-TB treatment and the onset of a significant threshold shift (STS) according to ASHA's criteria. Lastly, the test method preference of the participants with MDR-TB was described and compared using a short exit survey. Study Design: A prospective repeated-measures study design was used. Participants were chosen based on a risk factor (i.e. exposure to ototoxic medication) for an outcome of interest (i.e. the presence or absence of an STS). With a repeated measures study, multiple tests using different test methods can be compared with the same sample. Participants: Twenty-seven in-patients at Brooklyn Chest Hospital and DP Marais TB Hospital with normal hearing and on MDR-TB medication were included in the study. Their age range was from 19 to 51 years old with an average age of 33 years old. Non-probability convenience sampling was used as it was cost-effective, reduced data collection time and was relatively easy to execute. Data collection materials and procedures: The procedure for data collection included weekly follow-up testing for a maximum of four weeks. The test battery was as follows: an auditory symptom questionnaire, otoscopy examination, and manual and automated audiometry using the SRO technique with a fifteen-minute break in between. Participants were tested with the KUDUwave ™ in a non-sound treated room. The frequency range was determined with the SRO technique. If an STS was obtained, the patient was discharged from the study after completing an exit survey. Statistics: Analysis included descriptive statistics and inferential statistics. A Bonferroni corrected p-value (initially p ≤ 0.05) was used. Manual and automated audiometry thresholds were compared using the Pearson's Correlation Coefficient test. Manual and automated audiometry testing time and threshold means were compared using paired sample's t-tests. The diagnostic value of automated audiometry with the SRO technique was assessed with Receiver Operating Characteristics (ROC) Curves. Results: Manual audiometry was statistically more time-efficient compared to automated audiometry by an average of one minute and ten seconds (t (94) = -5.44; p< 0.003). There was a strong positive correlation for both left and right ears between the thresholds' obtained from manual and automated audiometry at 8kHz to 16 kHz (df> 28 = r > 0.70, p< 0.003). Automated audiometry was found to be a fair diagnostic test (area under the curve was 0.75; p= 0.002). Also, the ROC curve revealed that automated audiometry had a sensitivity of 61% and specificity of 90% when compared to manual audiometry (gold standard). Only participants that started data collection within 31 days after starting their MDR-TB treatment were included in the analysis of determining the incidence of an ototoxicity-induced hearing loss (n= 24 ears). This study found that 41.67% of ears (n= 10) had an ototoxicity-induced hearing loss. A box and whisker plot revealed that data was skewed to the right (i.e. more variation in data between the median and the maximum values) and that the median number of days for an ototoxicity-induced hearing loss to appear was 33 days. Secondly, 55.55% of participants (n=15 out of 27) reported auditory symptoms before data collection commencement. Aural fullness was the most reported symptom (n= eight out of 15). Ten out of 15 (66.66%) participants that reported auditory symptoms obtained an ototoxicity-induced hearing loss. Lastly, most participants (i.e. 13 out of 19; 68.42%) that completed the exit survey had no preference between manual or automated audiometry. The common rationale among these participants was “No difference noted.” Conclusion: This research study has revealed that manual audiometry was more time-efficient compared to automated audiometry in patients with MDR-TB. Also, automated audiometry was a fair diagnostic test. It may aid in reducing the disproportionate audiologist to patient ratio, especially in a developing country. However, manual audiometry (with the SRO technique) is more clinically appropriate in patients that are difficult-to-test. Secondly, audiometric settings can be changed to accommodate testing frequencies in 1/6 octaves so that the SRO technique can be clinically adopted. An ototoxicity-induced hearing loss seems to appear 33 days after ototoxic MDR-TB treatment commencement. Aural fullness was a commonly reported symptom among participants with MDRTB. Aural fullness is omnipresent in peripheral auditory pathologies. Therefore, auditory symptoms reported by patients' needs a comprehensive audiological investigation. Lastly, more research is needed on how patients (and clinicians) experience the advances in technology innovation especially in audiology where technology innovation is continuously evolving.

Indiana University-Purdue University Indianapolis (IUPUI) / Human BCRP is one of the major ATP-binding cassette transporters involved in the development of multidrug resistance in cancer chemotherapy. Overexpression of BCRP in the tumor cell plasma membrane and apical membrane of the gastrointestinal tract leads to decreased intracellular accumulation of various anticancer drugs as well as reduced drug bioavailability. BCRP has been shown to exist on the plasma membrane as higher forms of homo-oligomers. In addition, the oligomerization domain of BCRP has been mapped to the carboxyl-terminal TM5-ECL3-TM6 and this truncated domain, when co-expressed with the full-length BCRP, displays a dominant inhibitory activity on BCRP function. Thus, the oligomerization of BCRP could be a promising target in reversing multidrug resistance mediated by BCRP. To further dissect the oligomerization domains of human BCRP and test the hypothesis that TM5, ECL3, and TM6 each plays a role in BCRP oligomerization and function, we engineered a series of BCRP domain-swapping constructs with alterations at TM5-ECL3-TM6 and further generated HEK293 cells stably expressing wild-type or each domain-swapping construct of BCRP. Using co-immunoprecipitation and chemical cross-linking, we found that TM5, ECL3, and TM6 all appear to partially contribute to BCRP oligomerization, which are responsible for the formation of oligomeric BCRP. However, only TM5 appears to be a major contributor to the transport activity and drug resistance mediated by BCRP, while ECL3 or TM6 is insufficient for BCRP functions. Taken together, these findings suggest that homo-oligomeric human BCRP may be formed by the interactions among TM5, ECL3 and TM6, and TM5 is a crucial domain for BCRP functions and BCRP-mediated drug resistance. These findings may further be used to explore targets for therapeutic development to reverse BCRP-mediated drug resistance and increase the bioavailability of anti-cancer drugs for better treatment of multidrug resistant cancers.

No description available.

Blood-brain barrier (BBB) is a unique membranous barrier, which segregates brain from the circulating blood. It works as a physical and metabolic barrier between the central nervous system (CNS) and periphery. In mammals, endothelial cells were shown to be of BBB and are characterized by the tight junctions along with efflux system which are responsible for the restriction of movement of molecules within the cells. Efflux system consists of multidrug resistance proteins such as P-glycoprotein (P-gp). P-gp removes substances out back from the brain to the blood before they reach to the brain. So the barrier is impermeable to many compounds such as amino acids, ions, small peptides and proteins, making it the most challenging factor for the development of new drugs for targeting CNS. Curcumin is a bioactive compound that has a number of health promoting benefits such as anti-inflammatory, anticancer, anti-oxidant agent; as well as a role in neurodegenerative diseases, but low oral bioavailability is the major limiting factor. Low water solubility and rapid metabolism are the two important factors responsible for poor bioavailability of curcumin. Galaxolide is a musk compound and previously known for the bioaccumulation of toxic components in the aquatic animals by interference with the activity of multidrug/multixenobiotic resistance efflux transporters (MDR/MXR). The bioavailability of curcumin can be enhanced when administered with galaxolide. This study was carried out to investigate the effect of galaxolide on the permeation of curcumin through the epithelial cell monolayers. MDCKII-MDR1 cell monolayer is used an in vitro blood-brain barrier model while Caco-2 monolayer is used as an in vitro intestinal model, which also expresses the P-glycoprotein. The curcumin and galaxolide were separately solubilised in the DMSO and used in combination to perform permeation study, to determine the effect of galaxolide on curcumin permeation through epithelial cell monolayers. The galaxolide shows an efflux protein inhibition activity and this activity was used to enhance permeation of curcumin through the Caco-2 monolayer. In summary, galaxolide is a novel permeation enhancer molecule, which can be used for the improvement of drug delivery of other bioactive compounds in future. / Department of Social Welfare, Govt. of Maharashtra (India)

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The prevalence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis has been increasing to alarming levels globally. This has been exacerbated by tuberculosis (TB) co-infection with HIV where the epidemic is endemic. South Africa as a developing country is hit hard by TB and efforts to develop TB drugs that are compatible with anti-retroviral medication and also effective against MDR/XDR, could help shorten the treatment duration of the current TB treatment regimens. This thesis presents the identification and characterisation of a novel furanone based compound (F1082) and its derivatives as leads for anti-TB drug development. Furanones are generally known for an array of biological activities ranging from antibacterial, antifungal and antitumor. F1082 has an aromatic benzene structure and was identified from screening synthetic compounds against M. tuberculosis. It is potent against M. tuberculosis at minimum inhibitory concentration (MIC) of 8 μg/ml. It is selective for mycobacteria since it did not inhibit the growth of Gram-positive and Gram-negative bacteria at concentrations five times the MIC for M. tuberculosis. F1082 is generally bacteriostatic around MIC concentrations in its effects against M. tuberculosis however; it may be bactericidal at higher concentrations. It is as effective against MDR, XDR and clinical isolates of M. tuberculosis at the same concentration as the M. tuberculosis H37Rv reference strain. This suggests that F1082 may have a different mechanism of action compared to current TB drugs. It has been shown to have no antagonistic effect with the first-line anti-TB drugs and it has been shown to synergize with rifampicin by reducing the MIC of rifampicin. A drawback of F1082 is that it is cytotoxic to human cell lines, but this is presently being addressed through the synthesis of analogues that have shown improved activity and less cytotoxicity. The synthesis of more than 40 analogues has led to identification of 4 compounds that have more than five times higher activity and more than 100 times less cytotoxicity against human cell-lines. Microarray analyses have identified possible metabolic pathway/s in M. tuberculosis that is/are affected by F1082. One subset of genes which showed the most prominent alteration encodes the siderophores, which are involved with iron homeostasis in the M. tuberculosis bacillus. Of these genes, 7 were of interest (mbtB, mbtC, mbtD, mbtE, mbtF, mbtH and bfrB) as they all fall in the same cluster and are involved in iron acquisition. Due to the involvement of iron we also show that F1082 generates oxidative stress that is metal (iron) dependent. From the results we conclude that F1082 is a promising antituberculosis lead compound with unique target properties and also specificity against mycobacteria. / AFRIKAANSE OPSOMMING: Die voorkoms van veelvuldige middelweerstandige M.tuberculosis (MDR) en uiters middelweerstandige M.tuberculosis (XDR) is besig om toe te neem teen ‘n kommerwekkende tempo wêreldwyd. Hierdie situasie word vererger met die ko-infektering van M.tuberculosis en HIV. Suid- Afrika, as ontwikkelende land, word sleg benadeel met tuberkulose siekte. Antituberkulose middels wat kan saamwerk met bestaande antiretrovirale middels en ook effektief is teen MDR en XDR stamme, kan alles meewerk om die behandelingstyd van tuberkulose te verkort. In hierdie tesis identifiseer en karakteriseer ons ‘n furanoon-gebaseerde verbinding (F1082) en derivate daarvan as voorloper-middels vir anti-tuberkulose middelontwikkeling. Furanone is algemeen bekend vir ‘n verskeidenheid van biologiese aktiwiteite insluitende antibakteriële-, antifungale- en antitumor aktiwiteite. F1082 bevat ‘n aromatiese benseenstruktuur en is oorspronklik geïdentifiseer gedurende die skandering van sintetiese middels teen M.tuberculosis. Dit het ‘n sterk werking teen M.tuberculosis met ‘n minimum inhibitoriese konsentrasie (MIC) van 8ug/ml. Dit is baie selektief vir mikobakterieë aangesien dit nie gram-positiewe of gram-negatiewe bakterieë teen 5 maal die MIC, soos vir M.tuberculosis, geïnhibeer het nie. F1082 is bevind om, by laer konsentrasies, bakteriostaties te wees in sy aktiwiteit teen M.tuberculosis maar by hoër konsentrasies word ‘n meer bakteriosidiese effek waargeneem. F1082 is effektief teen MDR, XDR en kliniese isolate van M.tuberculosis en teen dieselfde konsentrasie soos vir die M. tuberculosis H37Rv verwysingstam waargeneem is. Dit impliseer dat F1082 dalk ‘n alternatiewe meganisme van werking het in vergelyking met die van die huidige TB teenmiddels. F1082 toon geen antagonistiese werking in kombinasie met die voorste anti- TB middels nie, maar toon wel sinergistiese werking in kombinasie met rifampisien. F1082 toon nog sitotoksiese aktiwiteit teenoor menslike sellyne, maar die sintese van derivate van F1082 toon tot dusvêr groter anti-TB aktiwiteit en verminderde sitotoksisiteit. Die sintese van meer as 40 homoloë het gelei tot die identifisering van vier verbindings met vyf keer hoër anti-TB aktiwiteit en honderd keer verminderde sitotoksisiteit teen menslike sellyne as F1082 self. “Microarray” ontledings het ‘n aantal metabolise paaie geïdentifiseer waar F1082 ‘n effek kan uitoefen. Een stel gene wat die mees uitstaande effek toon kodeer vir siderofore wat betrokke is by yster homeostase in M.tuberculosis. Van hierdie gene was daar sewe van belang omdat hulle in dieselfde groep voorkom en almal betrokke is by ysteropname (mbtB, mbtC, mbtD, mbtE, mbtF, mbtH, bfrB). Weens die rol wat F1082 in ysterhomeostase speel, toon ons ook dat F1082 intrasellulêre oksidatiewe stres bevorder wat yster afhanklik is. Al ons resultate dui daarop dat F1082 ‘n belowende ant-TB voorloper verbinding is met spesifisiteit teen M.tb en unieke teikeneienskappe in M. tuberculosis.

Magister Public Health - MPH (Public Health) / The presence of highly effective medicines has made very little impact in reducing deaths as a result of tuberculosis (TB), a curable condition but when managed inappropriately, may result in Drug Resistant TB. TB accounts for about one in four deaths that occur in HIV positive people and HIV has been found to be a risk factor for complex unfavorable outcomes in MDR TB patients and a very strong predictor for death and default. The relationship between diabetes and TB has also been explored, with some authors identifying diabetes as a risk factor for TB, and with related poor clinical outcomes in both conditions when they co-exist. Exploring the clinical characteristics and treatment outcomes of MDR TB patients in the presence of these risk factors could present an opportunity to provide better care through increased case-detection activities, improved clinical management and better access to care for all these conditions. The aim of the study was to describe the clinical characteristics and treatment outcomes of MDR TB patients initiated on treatment at Nkqubela and Fort Grey Hospitals.

L'acquisition du phénotype de résistance des cancers est souvent corrélée à l'expression de transporteurs membranaires appartenant à la superfamille des transporteurs ABC (« ATP-Binding Cassette »). Un de ces transporteurs, MRP1 (« Multidrug Resistance Protein 1 »), permet l'efflux de nombreux substrats, de type anioniques, conjugués au GSH, glucuronates ou sulfates, ou en co-transport avec le GSH.<br />Dans un premier temps, ce travail a porté sur l'étude des domaines de fixation des nucléotides isolés. Une étude biochimique a montré leur caractère fonctionnel asymétrique concernant les nucléotides, prouvant que seul la séquence primaire de ces NBD est responsable de cette fonctionnalité différentielle. L'étude de la fixation de substrats sur les NBD, a montré que ceux-ci pourraient, de part leur proximité avec les domaines transmembranaires, avoir un rôle dans la fixation des substrats.<br />La deuxième étape de ce travail a concerné la caractérisation de l'activité des énantiomères du vérapamil. Les résultats ont montré que le S-vérapamil est l'isomère responsable de la stimulation du transport du GSH, conduisant à la mort des cellules surexprimant MRP1. Le R-vérapamil est caractérisé comme un inhibiteur de MRP1. Ces résultats ont des répercussions importantes en terme de thérapie.<br />Deux études préliminaires de relation structure/fonction ont été menées en ce qui concerne des dérivés du vérapamil et des dérivés de flavonoïdes, afin de trouver des molécules plus efficaces contre MRP1.

L'objet de ce travail est de présenter de facon détaillée des méthodes de modélisation appliquées à l'analyse des mécanismes de reconnaissance moléculaire et à la conception de nouveaux composés bioactifs selon deux approches : la conception basée sur la structure des récepteurs et la conception basée sur la structure des ligands.<br />Dans le cadre du premier axe, la méthode de construction de protéines par homologie de Blundell, implémentée dans le module COMPOSER de SYBYL et la méthode d'amarrage de Morris, implémentée dans le logiciel AUTODOCK3, sont décrites et appliquées à la modélisation et à l'étude des mécanismes de reconnaissance moléculaire d'un antigène polysaccharidique de la bactérie Shigella flexneri 5a et de mimes peptidiques immunogènes par un anticorps humain protecteur : IgA I3.<br />Dans le cadre du second axe, l'analyse statistique de descripteurs de champs d'interaction moléculaire de type CoMSIA et les méthodes de validation des modèles qu'elle génère sont présentées et appliquées à l'étude des relations structure activité en trois dimensions d'une série de 27 analogues de flavonoïdes modulateurs du transporteur ABCG2 (BCRP), impliqué dans le mécanisme de résistance multiple aux anticancéreux que développent les cellules tumorales. La production de modèles statistiquement fiables et performants a permis de concevoir de nouveaux composés biologiquement actifs.