Preclinical Testing of Candidate Topical Microbicides for Anti-Human Immunodeficiency Virus Type 1 Activity and Tissue Toxicity in a Human Cervical Explant Culture

Laboratory Branch, Division of HIV/AIDS Prevention, National Center for HIV, STD, and TB Prevention, Center for Disease Control and Prevention, Atlanta, GA 30333, USA.
Antimicrobial Agents and Chemotherapy (Impact Factor: 4.48). 06/2007; 51(5):1770-9. DOI: 10.1128/AAC.01129-06
Source: PubMed


A human cervical explant culture was utilized for the preclinical assessment of anti-human immunodeficiency virus type 1 (HIV-1) activity and tissue toxicity of formulated, candidate topical microbicides. Products tested included cellulose acetate 1,2-benzene dicarboxylate (CAP), a carrageenan-based product (PC-515), a naphthalene sulfonate polymer (PRO 2000), a lysine dendrimer (SPL7013), a nonnucleoside reverse transcriptase inhibitor (UC781), and an antimicrobial peptide (D2A21), along with their placebos. Cervical explants were cultured overnight with HIV-1 with or without product, washed, and monitored for signs of HIV-1 infection. HIV-1 infection was determined by p24gag levels in the basolateral medium and by immunohistochemical analysis of the explant. Product toxicity was measured by the MTT [1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan] assay and histology. CAP, PRO 2000, SPL7013, and UC781 consistently prevented HIV-1 infection in all explants tested. PC-515 and D2A21 prevented HIV-1 infection in 50% or fewer of the explants tested. Placebos did not prevent infection in any of the explants tested. With the exception of PRO 2000 (4%), the MTT assay and histological analysis of the other products and placebos showed minimal toxicity to the epithelium and submucosa. Collectively, these data suggest that this culture system can be used for evaluating the safety and efficacy of topical microbicides designed for vaginal use.

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    • "There are at least two important issues: (1) the microbicide should not have any effect on vaginal mucosa, and (2) the microbicide should not generate any proinflammatory response. To determine preclinical efficacy as well as safety of the candidate topical microbicides, human cervical and colorectal explant cultures have been developed.113,114 Further, a three-dimensional in vitro human vaginal epithelial cell model has been developed that mimics human stratified squamous epithelium with microvilli, tight junctions, micro-folds, and mucus.115 "
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    ABSTRACT: Microbicides, primarily used as topical pre-exposure prophylaxis, have been proposed to prevent sexual transmission of HIV. This review covers the trends and challenges in the development of safe and effective microbicides to prevent sexual transmission of HIV Initial phases of microbicide development used such surfactants as nonoxynol-9 (N-9), C13G, and sodium lauryl sulfate, aiming to inactivate the virus. Clinical trials of microbicides based on N-9 and C31G failed to inhibit sexual transmission of HIV. On the contrary, N-9 enhanced susceptibility to sexual transmission of HIV-1. Subsequently, microbicides based on polyanions and a variety of other compounds that inhibit the binding, fusion, or entry of virus to the host cells were evaluated for their efficacy in different clinical setups. Most of these trials failed to show either safety or efficacy for prevention of HIV transmission. The next phase of microbicide development involved antiretroviral drugs. Microbicide in the form of 1% tenofovir vaginal gel when tested in a Phase IIb trial (CAPRISA 004) in a coitally dependent manner revealed that tenofovir gel users were 39% less likely to become HIV-infected compared to placebo control. However, in another trial (VOICE MTN 003), tenofovir gel used once daily in a coitally independent mode failed to show any efficacy to prevent HIV infection. Tenofovir gel is currently in a Phase III safety and efficacy trial in South Africa (FACTS 001) employing a coitally dependent dosing regimen. Further, long-acting microbicide-delivery systems (vaginal ring) for slow release of such antiretroviral drugs as dapivirine are also undergoing clinical trials. Discovering new markers as correlates of protective efficacy, novel long-acting delivery systems with improved adherence in the use of microbicides, discovering new compounds effective against a broad spectrum of HIV strains, developing multipurpose technologies incorporating additional features of efficacy against other sexually transmitted infections, and contraception will help in moving the field of microbicide development forward.
    Full-text · Article · Oct 2013 · HIV/AIDS - Research and Palliative Care
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    • "The clinical failure of several microbicide candidates due to safety concerns has emphasized the importance of safety evaluation in preclinical testing. Several important evaluations have been taken into consideration by current approaches, including the integrity of the cell layer by measuring the drop of transepithelial electrical resistance in a transwell culture model,9 cell toxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay,4,10,11 influence on the bacterial microenvironment by semiquantitative vaginal culture assay,12,13 inflammatory irritation and colposcopic abnormalities in a rabbit vaginal irritation models,4 and inflammatory cytokine production at the topical sites in mouse models.14 However, there are still some limitations to these evaluation approaches,5,6,7,8 and researchers continue to explore more sensitive assays to improve the examination of the safety profiles of microbicide candidates. "
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    ABSTRACT: To explore early biomarkers for establishing more sensitive safety evaluation assays in preclinical settings that determine the potential risks during the application of microbicide candidates, three representative microbicide candidates (cellulose sulphate, nonoxynol-9 and tenofovir), whose safety profiles have been well established in clinical trials, were included to gauge the sensitivities of different assays. Both mouse models and cell lines were employed to determine the sensitivities. The recruitment of immune cells at topical mucosal sites and the upregulation of HIV receptor/coreceptors in vitro were identified as highly sensitive biomarkers of the impact of microbicide candidates. Our data suggest that different evaluations/assays have their inherent sensitivities, and at least one assay from each sensitivity level should be included in the safety evaluation algorithm.
    Full-text · Article · Jul 2013 · Emerging Microbes and Infections
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    • "Macaque ectocervical tissues (Tissue Banking and Distribution Program, University of Washington National Primate Research Center) were processed for polarized explant cultures in duplicate on the day of surgery as previously described [36]–[38]. Briefly, a circular tissue punch was inserted through the transwell membrane with the luminal side up. "
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    ABSTRACT: Multipurpose prevention technologies (MPTs) that simultaneously prevent sexually transmitted infections (STIs) and unintended pregnancy are a global health priority. Combining chemical and physical barriers offers the greatest potential to design effective MPTs, but integrating both functional modalities into a single device has been challenging. Here we show that drug-eluting fiber meshes designed for topical drug delivery can function as a combination chemical and physical barrier MPT. Using FDA-approved polymers, we fabricated nanofiber meshes with tunable fiber size and controlled degradation kinetics that facilitate simultaneous release of multiple agents against HIV-1, HSV-2, and sperm. We observed that drug-loaded meshes inhibited HIV-1 infection in vitro and physically obstructed sperm penetration. Furthermore, we report on a previously unknown activity of glycerol monolaurate (GML) to potently inhibit sperm motility and viability. The application of drug-eluting nanofibers for HIV-1 prevention and sperm inhibition may serve as an innovative platform technology for drug delivery to the lower female reproductive tract.
    Full-text · Article · Nov 2012 · PLoS ONE
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