Safety and Efficacy Evaluations for Vaginal and Rectal Use of BufferGel in the Macaque Model

Next generation 3D-printed intravaginal ring for prevention of HIV and unintended pregnancy

Globally, there are 20 million adolescent girls and young women living with HIV who have limited access to long-acting, effective, women-controlled preventative methods. Additionally, although there are many contraceptive methods available, globally, half of all pregnancies remain unintended. Here we report the first 3D-printed multipurpose prevention technology (MPT) intravaginal ring (IVR) for HIV prevention and contraception. We utilized continuous liquid interface production (CLIP™) to fabricate MPT IVRs in a biocompatible silicone-based resin. Etonogestrel (ENG), ethinyl estradiol (EE), and islatravir (ISL) were loaded into the silicone poly(urethane) IVR in a controlled single step drug loading process driven by absorption. ENG/EE/ISL IVR promoted sustained release of drugs for 150 days in vitro and 14 days in sheep. There were no adverse MPT IVR-related findings of cervicovaginal toxicity or changes in vaginal biopsies or microbiome community profiles evaluated in sheep. Furthermore, ISL IVR in macaques promoted sustained release for 28 days with ISL-triphosphate levels above the established pharmacokinetic benchmark of 50-100 fmol/106 PBMCs. The ISL IVR was found to be safe and well tolerated in the macaques with no observed mucosal cytokine changes or alterations in peripheral CD4 T-cell populations. Collectively, the proposed MPT IVR has potential to expand preventative choices for young women and girls.

Impact of the griffithsin anti-HIV microbicide and placebo gels on the rectal mucosal proteome and microbiome in non-human primates

Topical microbicides are being explored as an HIV prevention method for individuals who practice receptive anal intercourse. In vivo studies of these microbicides are critical to confirm safety. Here, we evaluated the impact of a rectal microbicide containing the antiviral lectin, Griffithsin (GRFT), on the rectal mucosal proteome and microbiome. Using a randomized, crossover placebo-controlled design, six rhesus macaques received applications of hydroxyethylcellulose (HEC)- or carbopol-formulated 0.1% GRFT gels. Rectal mucosal samples were then evaluated by label-free tandem MS/MS and 16 S rRNA gene amplicon sequencing, for proteomics and microbiome analyses, respectively. Compared to placebo, GRFT gels were not associated with any significant changes to protein levels at any time point (FDR < 5%), but increased abundances of two common and beneficial microbial taxa after 24 hours were observed in HEC-GRFT gel (p < 2E-09). Compared to baseline, both placebo formulations were associated with alterations to proteins involved in proteolysis, activation of the immune response and inflammation after 2 hours (p < 0.0001), and increases in beneficial Faecalibacterium spp. after 24 hours in HEC placebo gel (p = 4.21E-15). This study supports the safety profile of 0.1% GRFT gel as an anti-HIV microbicide and demonstrates that current placebo formulations may associate with changes to rectal proteome and microbiota.

A Study of the Potential of the Pig as a Model for the Vaginal Irritancy of Benzalkonium Chloride in Comparison to the Nonirritant Microbicide PHI-443 and the Spermicide Vanadocene Dithiocarbamate

A porcine model was established to test the mucosal toxicity potential of a thiophene thiourea (PHI-443)-based anti-HIV microbicide and a vanadocene-based spermicide, vanadocene dithiocarbamate (VDDTC) in comparison to benzalkonium chloride (BZK). Nine domestic pigs (Duroc) in nonestrus stage received a single intravaginal application of 2% BZK, 2% PHI-443, or 0.1% VDDTC-containing gel. At various times after gel application, cell differentials and levels of inflammatory cytokines (IL-1 β, IL-4, IL-6, IL-8, IL-10, IL-18, IFN- γ, and TNF- α) in cervicovaginal lavage (CVL) fluid were monitored by flow cytometry and ELISA, respectively. Eight pigs were exposed intravaginally to a gel with and without BZK or VDDTC for 4 consecutive days and vaginal tissues were scored histologically for inflammation using a new scoring system. Only CVL fluid from pigs exposed to BZK showed a significant increase of IL-1 β, IL-8, and also IL-18 production when compared to the controls, PHI-443 or VDDTC-treated groups. Maximum levels of BZK-induced IL-1 β (100-fold), IL-8 (2,500-fold), IL-18 (80-fold), and IFN- γ(10-fold) were found at 24 hours. In the in vivo porcine vaginal irritation model, increased levels of vaginal IL-1 β, IL-8, and IL-18 were associated with histological changes consistent with vaginal inflammation. These results demonstrate that key cervicovaginal inflammatory cytokines are useful in vivo biomarkers for predicting the mucosal toxicity potential of vaginal products in the physiologically relevant and sensitive porcine model.

Defense-in-depth by mucosally administered anti-HIV dimeric IgA2 and systemic IgG1 mAbs: complete protection of rhesus monkeys from mucosal SHIV challenge

Although IgA is the most abundantly produced immunoglobulin in humans, its role in preventing HIV-1 acquisition, which occurs mostly via mucosal routes, remains unclear. In our passive mucosal immunizations of rhesus macaques (RMs), the anti-HIV-1 neutralizing monoclonal antibody (nmAb) HGN194, given either as dimeric IgA1 (dIgA1) or dIgA2 intrarectally (i.r.), protected 83% or 17% of the RMs against i.r. simian-human immunodeficiency virus (SHIV) challenge, respectively. Data from the RV144 trial implied that vaccine-induced plasma IgA counteracted the protective effector mechanisms of IgG1 with the same epitope specificity. We thus hypothesized that mucosal dIgA2 might diminish the protection provided by IgG1 mAbs targeting the same epitope. To test our hypothesis, we administered HGN194 IgG1 intravenously (i.v.) either alone or combined with i.r. HGN194 dIgA2. We enrolled SHIV-exposed, persistently aviremic RMs protected by previously administered nmAbs; RM anti-human IgG responses were undetectable. However, low-level SIV Gag-specific proliferative T-cell responses were found. These animals resemble HIV-exposed, uninfected humans, in which local and systemic cellular immune responses have been observed. HGN194 IgG1 and dIgA2 used alone and the combination of the two neutralized the challenge virus equally well in vitro. All RMs given only i.v. HGN194 IgG1 became infected. In contrast, all RMs given HGN194 IgG1+dIgA2 were completely protected against high-dose i.r. SHIV-1157ipEL-p challenge. These data imply that combining suboptimal defenses at the mucosal and systemic levels can completely prevent virus acquisition. Consequently, active vaccination should focus on defense-in-depth, a strategy that seeks to build up defensive fall-back positions well behind the fortified frontline.

Nonhuman primate models for cell-associated simian immunodeficiency virus transmission: the need to better understand the complexity of HIV mucosal transmission

Nonhuman primates are extensively used to assess strategies to prevent infection from sexual exposure to human immunodeficiency virus (HIV) and to study mechanisms of mucosal transmission. However, although semen represents one of the most important vehicles for the virus, the vast majority of preclinical challenge studies have used cell-free simian immunodeficiency virus (SIV) or simian/human immunodeficiency virus (SHIV) viral particles inoculated as diluted culture supernatants. Semen is a complex body fluid containing many factors that may facilitate or decrease HIV infectiousness. The virus in semen is present in different forms: as free virus particles or as cell-associated virus (ie, within infected leukocytes). Although cell-to-cell transmission of HIV is highly efficient, the role of cell-associated virus in semen has been surprisingly poorly investigated in nonhuman primate models. Mucosal exposure of macaques to cell-associated SIV by using infected peripheral blood mononuclear cells or spleen cells has been shown to be an efficient means of infection; however, it has yet to be shown that SIV- or SHIV-infected seminal leukocytes can transmit infection in vivo. Improvement of animal models to better recapitulate the complex microenvironment at portals of HIV entry is needed for testing candidate antiretrovirals, microbicides, and vaccines.

Formulation and delivery of anti-HIV rectal microbicides: advances and challenges

Men and women engaged in unprotected receptive anal intercourse (RAI) are at higher risk of acquiring HIV from infected partners. The implementation of preventive strategies is urgent and rectal microbicides may be a useful tool in reducing the sexual transmission of HIV. However, pre-clinical and first clinical trials have been able to identify limitations of candidate products, mostly related with safety issues, which can in turn enhance viral infection. Indeed, the development of suitable formulations for the rectal delivery of promising antiretroviral drugs is not an easy task, and has been mostly based on products specifically intended for vaginal delivery, but these have been shown to provide sub-optimal outcomes when administered rectally. Research and development in the rectal microbicide field are now charting their own path and important information is now available. In particular, specific formulation requirements of rectal microbicide products that need to be met have just recently been acknowledged despite additional work being still required. Desirable rectal microbicide product features regarding characteristics such as pH, osmolality, excipients, dosage forms, volume to be administered and the need for applicator use have been studied and defined in recent years, and specific guidance is now possible. This review provides a synopsis of the field of rectal microbicides, namely past and ongoing clinical studies, and details on formulation and drug delivery issues regarding the specific development of rectal microbicide products. Also, future work, as required for the advancement of the field, is discussed.

HPTN 035 phase II/IIb randomised safety and effectiveness study of the vaginal microbicides BufferGel and 0.5% PRO 2000 for the prevention of sexually transmitted infections in women

OBJECTIVES

To estimate the effectiveness of candidate microbicides BufferGel and 0.5% PRO 2000 Gel (P) (PRO 2000) for prevention of non-ulcerative sexually transmitted infections (STIs).

METHODS

Between 2005 and 2007, 3099 women were enrolled in HIV Prevention Trials Network (HPTN) protocol 035, a phase II/IIb evaluation of the safety and effectiveness of BufferGel and PRO 2000 for prevention of STIs, including Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Trichomonas vaginalis (TV). Incidences of STIs were determined by study arm, and HRs of BufferGel and PRO 2000 versus placebo gel or no gel control groups were computed using discrete time Andersen-Gill proportional hazards model.

RESULTS

The overall incidence rates were 1.6/100 person-years at risk (PYAR) for NG, 3.9/100 PYAR for CT and 15.3/100 PYAR for TV. For BufferGel versus placebo gel, HRs were 0.99 (95% CI 0.49 to 2.00), 1.00 (95% CI 0.64 to 1.57) and 0.95 (95% CI 0.71 to 1.25) for prevention of NG, CT and TV, respectively. For PRO 2000, HRs were 1.66 (95% CI 0.90 to 3.06), 1.16 (95% CI 0.76 to 1.79) and 1.18 (95% CI 0.90 to 1.53) for prevention of NG, CT and TV, respectively.

CONCLUSIONS

The incidence of STIs was high during HIV Prevention Trials Network 035 despite provision of free condoms and comprehensive risk-reduction counselling, highlighting the need for effective STI prevention programmes in this population. Unfortunately, candidate microbicides BufferGel and PRO2000 had no protective effect against gonorrhoea, chlamydia or trichomoniasis.

TRIAL REGISTRATION NUMBER

NCT00074425.

Development of a rectal sexually transmitted infection--HIV coinfection model utilizing Chlamydia trachomatis and SHIVSF162p3

BACKGROUND

Rectal sexually transmitted infections (STIs) may increase HIV susceptibility in men who have sex with men (MSM), and Chlamydia trachomatis is prevalent among HIV-positive MSM. To study STIs and HIV infection in MSM, we first evaluated whether cynomolgus macaques can sustain both C. trachomatis and SHIVSF162p3 infections.

METHODS

Four SHIVSF162p3 -positive male cynomolgus macaques were used (n = 3 rectally inoculated with 10(6) IFU; n = 1 control). Systemic and rectal SHIV RNA levels and cytokines were measured by real-time PCR and Luminex assays, respectively.

RESULTS

Macaques were successfully Chlamydia infected. Rectal SHIV shedding (P = 0.02 χ(2) ) and levels of G-CSF, IL-1ra, IL-6, IL-8, IFN-γ, and TNF-α (P ≤ 0.01, Mann-Whitney) in rectal secretions increased following infection.

CONCLUSIONS

These pilot data successfully demonstrate rectal C. trachomatis-SHIV coinfection in cynomolgus macaques and suggest the feasibility of a rectal C. trachomatis model for SHIV susceptibility and biomedical prevention studies in the context of rectal STIs.

Rectal microbicide development

The last few years have seen important progress in demonstrating the efficacy of oral pre-exposure prophylaxis, vaginal microbicides, and treatment as prevention as effective strategies for reducing the risk of acquiring or transmitting HIV infection. There has also been significant progress in the development of rectal microbicides. Preclinical non-human primate studies have demonstrated that antiretroviral microbicides can provide significant protection from rectal challenge with SIV or SHIV. Recent Phase 1 rectal microbicide studies have characterized the safety, acceptability, compartmental pharmacokinetics (PK), and pharmacodynamics (PD) of both UC781 and tenofovir gels. The tenofovir gel formulation used in vaginal studies was not well tolerated in the rectum and newer rectal-specific formulations have been developed and evaluated in Phase 1 studies. The PK/PD data generated in these Phase 1 studies may reduce the risk of advancing ineffective candidate rectal microbicides into late stage development. Tenofovir gel is currently poised to move into Phase 2 evaluation and it is possible that a Phase 2B/3 effectiveness study with this product could be initiated in the next 2-3 years.

Rectal pre-exposure prophylaxis (PrEP)

Rectal pre-exposure prophylaxis (PrEP) will be a critical component of HIV prevention products due to the prevalence of unprotected receptive anal intercourse among men who have sex with men and heterosexual couples. Given the biological considerations of this compartment and the complexity of HIV infection, design of a successful rectal microbicide product faces a number of challenges. Important information is being compiled to begin to address deficits in knowledge toward design of rectal PrEP products for men and women. Aspects of formulation development and preclinical and clinical evaluation of rectal products studied to date are summarized in this review. This article is based on a presentation at the "Product Development Workshop 2013: HIV and Multipurpose Prevention Technologies," held in Arlington, Virginia on February 21-22, 2013. It forms part of a special supplement to Antiviral Research.

Theaflavin-3,3'-digallate and lactic acid combinations reduce herpes simplex virus infectivity

The present study examined the efficacy of using multiple mechanisms as part of a topical microbicide to inactivate herpes simplex virus (HSV) by combining theaflavin-3,3'-digallate (TF-3) and lactic acid (LA) over the pH range of 4.0 to 5.7 to mimic conditions in the female reproductive tract. Six clinical isolates of HSV-2 and two clinical isolates of HSV-1 were almost completely inactivated when TF-3 (100 μM) was present with LA over the pH range of 4.5 to 5.7, whereas four additional HSV-1 clinical isolates required TF-3 concentrations of 250 to 500 μM for comparable virus titer reduction. LA (1%) alone at pH 4.0 reduced the titers of laboratory and clinical isolates of HSV-1 and HSV-2 by ≥ 5 log10, but most LA-dependent antiviral activity was lost at a pH of ≥ 4.5. When HSV-1 and HSV-2 were incubated at pH 4.0 without LA virus titers were not reduced. At pH 4.0, HSV-1 and HSV-2 titers were reduced 5 log(10) in 20 min by LA alone. TF-3 reduced HSV-2 titers by 5 log10 in 20 to 30 min at pH 4.5, whereas HSV-1 required 60 min for comparable inactivation. Mixtures of TF-3 and LA stored at 37 °C for 1 month at pH 4.0 to 5.7 maintained antiviral activity. Semen, but not cervical vaginal fluid, decreased LA-dependent antiviral activity at pH 4.0, but adding TF-3 to the mixture reduced HSV titers by 4 to 5 log10. These results indicate that a combination microbicide containing TF-3 and LA could reduce HSV transmission.

Longitudinal assessment of pigtailed macaque lower genital tract microbiota by pyrosequencing reveals dissimilarity to the genital microbiota of healthy humans

Vaginal bacterial communities play an important role in human health and have been shown to influence HIV infection. Pigtailed macaques (Macaca nemestrina) are used as an animal model of HIV vaginal infection of women. Since the bacterial microbiota could influence retrovirus infection of pigtailed macaques, the genital microbiota in 10 cycling macaques was determined by pyrosequencing. The microbiota of all macaques was polymicrobial with a median of 13 distinct genera. Strikingly, the genera Sneathia and Fusobacterium, both in the phylum Fusobacteria, accounted for 18.9% and 13.3% of sequences while the next most frequent were Prevotella (5.6%), Porphyromonas (4.1%), Atopobium (3.6%), and Parvimonas (2.6%). Sequences corresponding to Lactobacillus comprised only 2.2% of sequences on average and were essentially all L. amylovorus. Longitudinal sampling of the 10 macaques over an 8-week period, which spanned at least one full ovulatory cycle, showed a generally stable presence of the major types of bacteria with some exceptions. These studies show that the microbiota of the pigtailed macaques is substantially dissimilar to that found in most healthy humans, where the genital microbiota is usually dominated by Lactobacillus sp. The polymicrobial makeup of the macaque bacterial populations, the paucity of lactobacilli, and the specific types of bacteria present suggest that the pigtailed macaque microbiota could influence vaginal retrovirus infection.

The role of bacterial vaginosis and trichomonas in HIV transmission across the female genital tract

Bacterial vaginosis (BV) and Trichomonas vaginalis (TV) infections are both very common and are associated with increased risk of sexual transmission of HIV. There are several mechanisms by which BV and TV could affect susceptibility including inducing pro-inflammatory cytokines and disrupting mucosal barrier function. This review highlights recent advances in our understanding of how these genital conditions lead to an increased risk of HIV infection in women.

A comparison of lower genital tract glycogen and lactic acid levels in women and macaques: implications for HIV and SIV susceptibility

Understanding factors that affect heterosexual transmission of HIV in women is of great importance. Lactobacilli in the lower genital tract of women utilize glycogen in vaginal epithelial cells as an energy source and produce lactic acid. The resultant vaginal acidity is believed to provide protection against HIV infection. Conversely, bacterial vaginosis (BV) is characterized by less lactic acid and a higher pH, and is associated with increased susceptibility to HIV infection. Because vaginal infection of macaques with simian immunodeficiency virus (SIV) or simian-human immunodeficiency virus (SHIV) is used as a model to study HIV sexual transmission, and because previous studies have shown a paucity of lactobacilli in rhesus macaques' lower genital tract, we compared lactic acid and glycogen levels in the genital fluid of rhesus and pigtail macaques with levels found in humans. The levels of lactic acid were lower in both rhesus (median=1.2 mol lactate/mg protein) and pigtail macaques (median=0.7 mol/mg) compared to women with healthy genital microbiota (median=4.2 mol/mg). Glycogen levels were significantly lower in both rhesus (median=0.004 μg glycogen/μg protein) and pigtail macaques (median=0 μg/μg) than in women (median=0.2 μg/μg). No significant differences in glycogen or lactate levels were observed comparing longitudinally collected samples from cycling pigtail macaques. These data show that the previously reported scarcity of lactobacilli in macaques correlates with low glycogen and lactic acid levels. These findings have important implications for studies of vaginal infection of macaques with SIV or SHIV and further our understanding of how the bacterial microbiota influences HIV infection.

Pigtailed macaque model refinement: topical microbicide safety in the presence of coitus

BACKGROUND

Inclusion of sexual activity in the macaque model for topical microbicide safety evaluation would more closely mimic human use of topical microbicides and provide a more rigorous safety assessment.

METHODS

Initially, male-female partners were monitored in cohousing arrangements to determine whether macaques would copulate ad libitum. The logistics of performing vaginal examinations before and after coital visits were analyzed and optimized. Findings from cervicovaginal examinations conducted before and after sexual activity were compared.

RESULTS

Coital activity was reliably observed in the majority of cohousing sessions, representing all phases of the menstrual cycle. Female macaques were trained to be restrained while fully alert for pre-coital vaginal sampling. Post-coital examinations occur under general sedation. Post-coital examinations reveal alterations to tissues, microbiology, and pH compared with pre-coital visits.

CONCLUSIONS

This work clearly demonstrates that it is feasible to incorporate sexual activity in the macaque model for topical microbicide safety assessment.

The formulated microbicide RC-101 was safe and antivirally active following intravaginal application in pigtailed macaques

Background

RC-101 is a congener of the antiretroviral peptide retrocyclin, which we and others have reported is active against clinical HIV-1 isolates from all major clades, does not hemagglutinate, and is non-toxic and non-inflammatory in cervicovaginal cell culture. Herein, film-formulated RC-101 was assessed for its antiviral activity in vitro, safety in vivo, retention in the cervix and vagina, and ability to remain active against HIV-1 and SHIV after intravaginal application in macaques.

Methodology/Principal Findings

RC-101 was formulated as a quick-dissolving film (2000 µg/film), retained complete activity in vitro as compared to unformulated peptide, and was applied intravaginally in six pigtailed macaques daily for four days. At one and four days following the final application, the presence of RC-101 was assessed in peripheral blood, cervicovaginal lavage, cytobrushed cervicovaginal cells, and biopsied cervical and vaginal tissues by quantitative western blots. One day following the last film application, cervical biopsies from RC-101-exposed and placebo-controlled macaques were collected and were subjected to challenge with RT-SHIV in an ex vivo organ culture model. RC-101 peptide was detected primarily in the cytobrush and biopsied cervical and vaginal tissues, with little to no peptide detected in lavage samples, suggesting that the peptide was associated with the cervicovaginal epithelia. RC-101 remained in the tissues and cytobrush samples up to four days post-application, yet was not detected in any sera or plasma samples. RC-101, extracted from cytobrushes obtained one day post-application, remained active against HIV-1 BaL. Importantly, cervical biopsies from RC-101-treated animals reduced RT-SHIV replication in ex vivo organ culture as compared to placebo-treated animals.

Conclusions/Significance

Formulated RC-101 was stable in vivo and was retained in the mucosa. The presence of antivirally active RC-101 after five days in vivo suggests that RC-101 would be an important molecule to develop further as a topical microbicide to prevent HIV-1 transmission.

An acceptability and safety study of the Duet cervical barrier and gel delivery system in Zimbabwe

Background

Adherence problems with coitally dependent, female-initiated HIV prevention methods have contributed to several trials' failure to establish efficacy. Continuous use of a cervical barrier with once-daily cleaning and immediate reinsertion may simplify use for women and improve adherence. We assessed the acceptability and safety of precoital and continuous use of the Duet^®, a cervical barrier and gel delivery system, in Zimbabwean women.

Methods

Using a two-arm crossover design with a parallel observation group, we randomized 103 women in a 2:2:1 ratio: (1) to use the Duet continuously for 14 days, followed by a minimum of seven days of washout and then 14 days of precoital use; (2) to use the same Duet regimens in reverse order; or (3) for observation only. Women were aged 18 to 40 years; half were recruited from a pool of previous diaphragm study participants and the other half from the general community. Acceptability and adherence were assessed through an interviewer-administered questionnaire at each of two follow-up visits. Safety was monitored through pelvic speculum exams and report of adverse events.

Results

The proportion of women who reported consistent Duet use during sex was virtually identical during continuous and precoital regimens (88.6% vs. 88.9%). Partner refusal was the most common reason cited for non-use during sex in both use regimens. Not having the device handy was the most common reason cited for non-daily use (in the continuous regimen). Most women were "very comfortable" using it continuously (86.3%) and inserting it precoitally (92.8%). The most favoured Duet attribute was that it did not interfere with "natural" sex (55%). The least favoured Duet attribute was the concern that it might come out during sex (71.3%). No serious adverse events were reported during the study; 57 participants reported 90 adverse events classified as mild or moderate. There were no statistically significant differences in: (1) the proportion of women reporting adverse events; (2) the severity of events among those using the Duet and observational controls; or (3) event severity reported during each regimen use period.

Conclusions

In this study, the Duet was found to be acceptable and safe when inserted precoitally or used continuously for 14 days. Assignment to use of the Duet continuously did not increase adherence to the Duet during sex. Future HIV prevention trials should evaluate use of the Duet (precoitally and continuously) with promising microbicide candidates.

Identification of rhesus macaque genital microbiota by 16S pyrosequencing shows similarities to human bacterial vaginosis: implications for use as an animal model for HIV vaginal infection

The composition of the lower genital tract microbiota in women is believed to affect the risk of sexually acquiring HIV. Since macaque genital microbiota could similarly impact vaginal infection with SIV we identified microbiota in 11 rhesus macaques using multitag pyrosequencing of the 16S rRNA gene. The microbiota was polymicrobial with a median of nine distinct bacterial taxa per macaque (range 3-16 taxa, each constituting 1% or more of the sequences). Taxa frequently found included Peptoniphilus, Sneathia, Porphyromonas, Mobiluncus, Atopobacter, Dialister, Thioreductor, Prevotella, and Streptococcus, many of which are also frequently found in women with bacterial vaginosis. Lactobacillus sequences (mostly L. johnsonii) were found in only four macaques but were not predominant in any (median of 0% of sequences, range 0-39%). All macaques were resampled 6 months after the first time point to determine the stability of the microbiota. The microbiota remained polymicrobial with a median of 10 taxa (range 6-18). Microbial patterns remained similar for six of the macaques, changed substantially in two, and had a mixed pattern in three. Significant sialidase enzyme activity, a marker of bacteria vaginosis in women, was detected in genital fluid from 9/11 and 8/11 macaques from the first and second time points, respectively. These results show that the macaque lower genital microbiota resembled a bacteria vaginosis-type microbiota in women and suggest that the microbiota of macaques in captivity promote rather than protect against vaginal infection with SIV. These results also suggest macaques could be used as an animal model to study some aspects of bacterial vaginosis.

A summary of preclinical topical microbicide rectal safety and efficacy evaluations in a pigtailed macaque model

BACKGROUND

There is widespread recognition of the potential promise of vaginal microbicides as a tool to combat global human immunodeficiency virus/acquired immunodeficiency syndrome and sexually transmitted infections epidemics, and candidate product development has maintained a rapid pace in recent years; however, rectal microbicide development has received less attention. As it is likely that commercial products developed for vaginal use will also be used rectally, there is a clear need to assess the safety and efficacy of candidate microbicide products specifically in the rectal compartment.

METHODS

We have developed a standardized protocol for preclinical rectal safety and (chlamydial) efficacy assessment of topical microbicide candidates in a nonhuman primate model. We evaluated a total of 12 test compounds for rectal safety (via rectal pH, microflora, and rectal lavage) and 1 compound for efficacy against rectal chlamydial infection.

RESULTS

In this article, we describe our methods in detail and summarize our results, particularly noting the ability of our model to distinguish products with deleterious effects on the rectal environment. We also outline the specific criteria used to recommend products move into preclinical rectal efficacy trials or be recommended for reformulation to the product developer. In summary, we observed significant adverse effects in 2 products. The single product that underwent efficacy evaluation was not observed to be protective against rectal chlamydial infection.

CONCLUSIONS

A preclinical safety and efficacy model is critical to promoting rectal microbicide development, which will ultimately offer a significant opportunity for intervention in the global HIV/AIDS epidemic.

Disruption of tight junctions by cellulose sulfate facilitates HIV infection: model of microbicide safety

BACKGROUND

The lack of biomarkers that are predictive of safety is a critical gap in the development of microbicides. The present experiments were designed to evaluate the predictive value of in vitro models of microbicide safety.

METHODS

Changes in the epithelial barrier were evaluated by measuring transepithelial electrical resistance (TER) after exposure of human epithelial cells to candidate microbicides in a dual-chamber system. The significance of observed changes was addressed by challenging cultures with human immunodeficiency virus (HIV) and measuring the ability of virus to cross the epithelium and infect target T cells cultured in the lower chamber.

RESULTS

Exposure to nonoxynol-9 (N-9) or cellulose sulfate (CS), but not 9-[2-(phosphonomethoxy)propyl]adenine (also referred to as tenofovir) or PRO2000, resulted in a rapid and sustained reduction in TER and a marked increase in HIV infection of T cells cultured in the lower chamber. Moreover, CS triggered nuclear factor kappaB activation in peripheral blood mononuclear cells and increased HIV replication in chronically infected U1 cells.

CONCLUSIONS

Epithelial barrier disruption and enhanced viral replication may have contributed to the increased risk of HIV acquisition observed in phase 3 trials of N-9 and CS. Expansion of in vitro safety testing to include these models would provide a more stringent preclinical assessment of microbicide safety and may prove to be more predictive of clinical outcomes.

Formulating a sulfonated antiviral dendrimer in a vaginal microbicidal gel having dual mechanisms of action

SPL7013 is the sodium salt of a sulfonated dendrimer that has potent antiviral properties. VivaGel, a topical gel containing 3% (wt/wt) SPL7013, is in development as a vaginal microbicide. BufferGel is a Carbopol-based acidic buffering gel that enhances the natural protective action of the vagina to produce a broad-spectrum microbicidal environment. The positive attributes of both gels were combined into a combination vaginal microbicidal gel having dual mechanisms of action. A 3% (wt/wt) SPL7013 combination gel, pH 3.7, was developed and fully characterized and was shown to have more than twofold greater acidic buffering capacity than BufferGel. Ultracentrifugation experiments demonstrated that SPL7013 was not sequestered or entropically trapped in the viscous gel, thereby confirming, along with viral challenge studies, that SPL7013 has sufficient mobility in the viscous gel to exert antiviral properties.

A summary of preclinical topical microbicide vaginal safety and chlamydial efficacy evaluations in a pigtailed macaque model

BACKGROUND

The development of topical microbicides represents a new and exciting field in the prevention of sexually transmitted diseases, and it is especially important that candidate products undergo rigorous preclinical safety and efficacy testing before advancing to clinical trials.

METHODS

We have developed a standardized protocol for preclinical vaginal safety and efficacy assessment of topical microbicide candidates in a nonhuman primate model. Over 7 years of funding under an NIH contract, we evaluated a total of 28 test compounds for vaginal safety (via colposcopy, vaginal pH, and microflora) and 9 compounds for efficacy against cervical chlamydial infection. In this article, we describe our methods in detail and summarize our results, particularly noting the ability of our model to distinguish products with deleterious effects on the cervicovaginal environment. We also outline the specific criteria used to determine which products should move into efficacy trials and which should be recommended for reformulation to the manufacturer.

RESULTS

Overall, we noted acceptable safety profiles for 24 of 28 candidate products. Common findings included a transient decrease in vaginal pH, petechiae, and mild erythema. Four products were associated with significant adverse colposcopic findings including blisters, epithelial abrasions, and friability; all 4 products were successfully reformulated and showed acceptable safety profiles at lower concentrations. No products showed complete protection against cervical chlamydial infection.

CONCLUSIONS

The macaque preclinical safety and efficacy model is critical to maintaining the pace of topical microbicide development, which could ultimately offer a significant opportunity for intervention in the global HIV/AIDS epidemic.

Comparative evaluation of virus transmission inhibition by dual-acting pyrimidinedione microbicides using the microbicide transmission and sterilization assay

In the absence of a fully effective human immunodeficiency virus (HIV) vaccine, topical microbicides represent an important strategy for preventing the transmission of HIV through sexual intercourse, the predominant mode of HIV transmission worldwide. Although a comprehensive understanding of HIV transmission has not yet emerged in the microbicide field, it is likely the result of rapid infection of monocyte-derived cells in the vaginal mucosa by CCR5-tropic viruses. Inhibition of HIV transmission requires agents that prevent entry, fusion, reverse transcription, or other preintegrative replication events or agents which directly inactivate HIV or modulate the target cells to render them uninfectible. In vitro assays typically used to evaluate the ability of a microbicide to prevent virus transmission use epithelial or human osteosarcoma-derived cells or immune cells more relevant to the development of anti-HIV therapeutic agents and quantify virus production at short time intervals following infection. We have developed a microbicide transmission and sterilization assay (MTSA) to more sensitively and quantitatively evaluate virus transmission in cell culture in the presence of microbicidal compounds. Results obtained with the MTSA demonstrate that the inhibitory capacity of microbicides is often overestimated in short-term transmission inhibition assays, while some compounds yield equivalent inhibitory results, indicating a biological relevance for the MTSA-based evaluations to identify superior potent microbicides. The MTSA defines the concentration of the microbicide required to totally suppress the transmission of virus in cell culture and may thus help define the effective concentration of the microbicide required in a formulated microbicide product.

Preclinical evaluation of a dual-acting microbicidal prodrug WHI-07 in combination with vanadocene dithiocarbamate in the female reproductive tract of rabbit, pig, and cat

The mucosal safety of the combination antiretroviral spermicide,WHI-07 [5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-bromophenyl)-methoxy alaninyl phosphate] and vanadocene dithiocarbamate (VDDTC), was evaluated in 3 different animal models. Twenty-seven NZW rabbits in four subgroups were exposed intravaginally to a gel-microemulsion (GM) with and without three dose levels of WHI-07 plus VDDTC (0.5+0.06%, 1.0+0.12% and 2.0+0.25%) or 4% nonoxynol-9 (N-9; Conceptrol) for 14 consecutive days. Ten nonestrus gilts (Duroc) in three subgroups received either a single or daily intravaginal application of GM with and without 2.0% WHI-07 plus 0.25% VDDTC or 2.0% benzalkonium chloride (BZK)-containing gel for 6 and 4 consecutive days, respectively. Five cats received a single intravaginal application of GM incorporating 2.0% WHI-07 plus 0.25% VDDTC. Genital tract histopathology was performed in the pig and rabbit at the end of dosing period but after 18 weeks post-dosing in the cat. Porcine cervicovaginal lavage (CVL) fluid was obtained for up to 72 hours after a single exposure and changes in the levels of inflammatory cytokines (IL-1beta, IL-8, IFN-gamma, and TNF-alpha) were quantitated by a multiplexed chemiluminescence-based immunoassay. Rabbit vaginal tissues were evaluated for localized cellular inflammation and in situ apoptosis by immunohistochemical staining for CD45, nuclear factor (NF)-kappa B, and terminal deoxynucleotidyl transferase-mediated FITC-deoxyuridine triphosphate nick-end labeling (TUNEL) using confocal laser scanning microscopy (CLSM), respectively. Vanadium content in selected organs and body fluids from rabbits and pigs was determined by atomic absorption spectroscopy. When compared with 4% N-9 (total irritation score 13-14 out of a possible 16), none of the rabbits given WHI-07 plus VDDTC intravaginally, developed histological alterations such as epithelial erosion, edema, leukocyte influx or vascular congestion characteristic of inflammation (total irritation score 4-6). CD45 and NF-kappa B immunoreactivity was limited to cells within the vascular lumen of both control and WHI-07 plus VDDTC-treated vaginal tissues. TUNEL assay revealed lack of increased apoptotic cells in vaginal mucosa exposed to increasing concentrations of WHI-07 plus VDDTC. Basal levels of proinflammatory cytokines (IL-1beta, IL-8, IFN-gamma and TNF-alpha) in porcine CVL were unaffected by intravaginal exposure to WHI-07 plus VDDTC when compared with BZK used as a positive control. Endpoint histology of the reproductive tract from cats and pigs after a single or repeated intravaginal exposure to WHI-07 plus VDDTC, respectively, revealed lack of irritation/inflammation in the epithelium, subepithelium/lamina propria, vessels/perivascular tissues, and underlying/surrounding muscles. Vanadium was not preferentially incorporated into rabbit or porcine tissues and body fluids at levels above 1 microg/g. Based on comparative histologic data and surrogate markers for inflammation, repeated intravaginal administration of WHI-07 plus VDDTC via a gel-microemulsion did not result in vaginal irritation, mucosal toxicity, or systemic absorption of vanadium. Therefore, the combined use of WHI-07 and VDDTC via gel-microemulsion appears safe for topical use as a prophylactic anti-HIV microbicide.

Characterization of baseline intestinal mucosal indices of injury and inflammation in men for use in rectal microbicide trials (HIV Prevention Trials Network-056)

OBJECTIVES

The purpose of this study was to evaluate the biologic stability of mucosal parameters that might be used as endpoints in phase 1 rectal safety studies.

METHODS

Sixteen male participants were enrolled into 4 groups defined by HIV status, viral load, and sexual activity. Each participant underwent 3 flexible sigmoidoscopies at 2-week intervals with collection of blood, intestinal biopsies, and rectal secretions. Intestinal histology, phenotypic characterization of mucosal mononuclear cells, cytokine messenger RNA (mRNA) profiles (RANTES, interferon-gamma [IFNgamma], and interleukin-10), and immunoglobulin secretion were assessed. Intraclass correlation (ICC) was calculated to assess endpoint stability.

RESULTS

Qualitative histology demonstrated minimal inflammation in >95% of biopsies and remained stable throughout the study period. ICC for the tissue cytokine mRNA measurements and several T-cell phenotypic markers was >0.7, indicating stability over time. Mucosal CD4 lymphopenia was seen in the HIV-positive participants and was more pronounced in those with higher viral loads. Modest differences were observed for cytokine expression (IFNgamma) and T-cell phenotype (CD3, CD4, CD8, CD19, CD4/CCR5, and CD4/CD38) between the tissue samples collected at 10 and 30 cm.

CONCLUSIONS

These data help to provide a rationale for the selection of endpoints for future phase 1 rectal safety studies.

C34, a membrane fusion inhibitor, blocks HIV infection of langerhans cells and viral transmission to T cells

Development of topical microbicides that prevent sexual transmission of HIV is an active area of investigation. The purpose of this study was to test the ability of the potent membrane fusion inhibitor C34, an HIV gp41 antagonist, to block HIV infection of human Langerhans cells (LCs) in an epithelial environment that mimics a major route of HIV infection. We incubated freshly isolated epidermal explants containing LCs with various doses of C34 before, during, and after exposing explants to HIV. Although C34 only partially blocked HIV infection of LCs when pre-incubated with skin, it displayed full, dose-dependent inhibition when present during and after viral exposure. The poor protection from HIV infectivity in pre-incubated samples is consistent with mechanism of C34 inhibition and starkly contrasts to the full protection provided by PSC-RANTES, an entry inhibitor that prevents HIV gp120 interaction with its co-receptor CCR5. Real-time PCR confirmed that C34 blocked HIV infection of LCs before reverse transcription and inhibited LC-mediated transfer of virus to T cells. We conclude that C34, if used topically at susceptible mucosal sites, and if continually present, has the potential to block sexual transmission of HIV.

Vaginal and Rectal Topical Microbicide Development: Safety and Efficacy of 1.0% Savvy (C31G) in the Pigtailed Macaque

BACKGROUND

A 1.0% gel formulation of C31G, a surfactant, has been shown to have in vitro antiviral and antibacterial activity.

GOAL

The goal of this study was to evaluate the safety and efficacy of vaginal and rectal applications of 1.0% Savvy (C31G) in the nonhuman primate model.

STUDY DESIGN

The safety of repeated 1.0% C31G application was evaluated by microflora, pH, vaginal biopsy, colposcopy, and rectal lavage. Efficacy in preventing chlamydial infection was documented by culture, nucleic acid amplification tests, and serology.

RESULTS

Repeated applications of Savvy (1.0% C31G) were not associated with significant changes in pH, microflora, or inflammatory infiltrates on tissues. No significant differences in epithelial desquamation were noted after rectal product use compared with placebo. Four of 6 animals were protected from chlamydial infection after pretreatment with Savvy. C31G was shown to be safe to both vaginal and rectal mucosal tissues and to the microflora with repeated daily use.

CONCLUSION

Savvy has an acceptable safety profile after repeated vaginal and rectal use. A single intravaginal application of 1.0% C31G provided partial protection from acquiring cervical chlamydial infection.

Ex vivo culture of human colorectal tissue for the evaluation of candidate microbicides

OBJECTIVES

Establishment of an in vitro model to evaluate rectal safety and the efficacy of microbicide candidates.

DESIGN

An investigation and characterization of human colorectal explant culture for screening candidate microbicides to prevent rectal transmission of HIV-1 infection.

METHODS

Human colorectal explants were cultured at the liquid-air interface on gelfoam rafts. Phenotypic characterization of HIV-1 target cells was performed by fluorescence-activated cell sorter analysis. HIV-1 infection was determined by the measurement of p24 antigen release, viral RNA, and proviral DNA accumulation.

RESULTS

Colorectal explant CD4 T cells expressed higher CCR5 and CXCR4 levels compared with blood. Minor differences between the rectal and sigmoid colon were observed with a trend for slightly higher CCR5 and HLA-DR expression in cells from the sigmoid colon. Favourable culture conditions were established for colorectal tissue. Although tissue structure degenerated with time, CD4: CD8 cell ratios remained constant, and tissue supported productive HIV-1 infection. The ability of candidate microbicides to inhibit R5 HIV-1 infection was evaluated. Polyanion candidates, PRO2000 and dextrin sulphate, provided 99% protection at 1 microg/ml and 1 mg/ml, respectively, equivalent to 1/5000 and 1/40 of the vaginal formulations. The nucleotide reverse transcriptase inhibitor (NRTI) 9-[2-(phosphonomethoxy)propyl]adenine (PMPA) provided protection at concentrations 1000-fold lower (10 microg/ml) than the proposed vaginal formulation (1%). Furthermore, non-NRTI UC-781 and TMC-120 provided greater than 99% inhibition at 3.3 or 0.33 microg/ml, respectively. No products demonstrated toxicity to rectal mucosa at inhibitory concentrations.

CONCLUSION

Colorectal explant culture was shown to be a useful tool for the preclinical evaluation of potential microbicides. The data suggest that rectally applied microbicides might provide protection from HIV-1 transmission.

Lactobacilli-expressed single-chain variable fragment (scFv) specific for intercellular adhesion molecule 1 (ICAM-1) blocks cell-associated HIV-1 transmission across a cervical epithelial monolayer

The vaginal and cervical epithelia provide an initial barrier to sexually acquired HIV-1 infection in women. To study the interactions between HIV-1-infected cells or cell-free HIV-1 and the reproductive epithelium, the transmission of HIV-1 by infected cells or cell-free virus across human cervical epithelial cells was examined using a Transwell culture system. Cell-associated HIV-1 was transmitted more efficiently than cell-free virus, and monocyte-associated virus was transmitted most efficiently. Abs to ICAM-1 added to the apical side of the epithelium blocked cell-mediated transepithelial HIV-1 transmission in vitro. When used in a previously described model of vaginal HIV-1 transmission in human PBL-SCID mice, anti-murine ICAM-1 Abs (0.4 microg/10 microl) also blocked vaginal transmission of cell-associated HIV-1 in vivo. To evaluate a candidate delivery system for the use of this Ab as an anti-HIV-1 microbicide, anti-ICAM single-chain variable fragment Abs secreted by transformed lactobacilli were evaluated for their protective efficacy in the Transwell model. Like the intact Ab and Fab derived from it, the single-chain variable fragment at a concentration of 6.7 microg/100 microl was able to reduce HIV-1 transmission by 70 +/- 5%. These data support the potential efficacy of an anti-ICAM Ab delivered by lactobacilli for use as an anti-HIV-1 microbicide.

Prioritizing prevention of HIV and sexually transmitted infections: first-generation vaginal microbicides

PURPOSE OF REVIEW

As the HIV/AIDS pandemic continues unabated, novel control measures for the spread of HIV and other sexually transmitted infections are urgently needed. Topical microbicides are designed to prevent transmission of sexually transmitted infections when applied vaginally. The microbicides discussed in this review may provide a new opportunity for decreasing the spread of HIV and other sexually transmitted infections.

RECENT FINDINGS

Epidemiological studies suggest a synergistic relationship between HIV and sexually transmitted infections, particularly between HIV and genital herpes infection. Compounds have been developed to block transmission of HIV-1 and herpes simplex virus, as well as Neisseria gonorrhoea and Chlamydia trachomatis. Several of these compounds have advanced to clinical trials as candidate microbicides. Candidate compounds fall into the following categories: detergents or surfactants that inactivate viral particles, anionic polymers that block attachment of virus to target cells, vaginal acid-buffering agents that maintain a protective vaginal pH, and antiretroviral drugs specific for HIV. Evaluation of the safety of topical microbicides remains problematic. Clinical experiences indicate that current models to assess safety in vitro and in vivo may be insufficient to assess the safety of vaginal microbicides. A critical direction of future studies is to identify which assay(s) provide surrogate laboratory markers of safety that correlate with clinical outcomes.

SUMMARY

The spread of HIV, and its increasing burden of disease in women, necessitates the development of novel prophylactic strategies. Topical microbicides offer women an empowering preventative option but require vigorous testing for safety and effectiveness.

Erosion of microbicide formulation coating layers: Effects of contact and shearing with vaginal fluid or semen

An effective vaginal microbicide formulation must distribute and maintain an epithelial coating layer. The post-application durability of this coating is significantly affected by the vaginal environment. A new in vitro assay quantified coating layer erosion after contact and shear with simulated vaginal fluid or semen. Coating layer persistence and viscosity of both fluid and gel layers were assessed versus time. Five vaginal formulations were studied. In all gels, there was an overall trend of rapid ( approximately 30 min) and significant viscosity loss. Although there were differences across gels and between simulants, greater erosion occurred after contact with the low-pH vaginal fluid simulant (>50% viscosity decrease), as compared to an alkaline semen simulant. These in vitro results suggest significant differences in vivo of vaginal coating retention by the test gels. This new assay can be diversified to create a spectrum of biologically relevant conditions which collectively simulate the natural history of vaginal formulation residence.

Evaluating the potential impact of vaginal microbicides to reduce the risk of acquiring HIV in female sex workers

OBJECTIVES

The following questions were addressed: would the introduction of vaginal microbicides substantially reduce the risk of female sex workers (FSWs) acquiring HIV? Which factor would it be most important to maximize, microbicide efficacy or microbicide use? What level of microbicide efficacy and use would be necessary to counterbalance a possible reduction in condom use?

DESIGN

Mathematical modeling, with parameter estimations from available literature.

METHODS

Risk equations were developed and Monte Carlo simulations were performed to model a FSW's daily risk of HIV acquisition currently, and after, microbicide introduction. Uncertainty and sensitivity analyses were used as well as tornado plots for two ranges of microbicide efficacy (30-50%) and (50-80%). Risk was estimated for FSWs whose clients sometimes (10-50%) use condoms, and those whose clients never use condoms. An analytical threshold for which reducing condom use increases risk was estimated.

RESULTS

For both groups of FSWs, daily risk would decrease by approximately 17% or approximately 28% using 30-50% or 50-80% effective microbicides, respectively. Increasing microbicide use would have greater impact on reducing risk than increasing microbicide efficacy. The microbicide efficacy and usage required to ensure that 'condom replacement' does not increase a FSW's risk of acquiring HIV was calculated.

CONCLUSIONS

Microbicides could substantially reduce FSWs' risk of acquiring HIV; absolute decrease in risk would be greatest in high-prevalence regions. The public health impact of microbicides will depend upon usage and efficacy. Even if the microbicides that become available are only low-to-moderately effective, the probability that risk in FSWs will increase (due to replacing condoms with microbicides) is low.