Animal models for microbicide safety and efficacy testing

Expression, Activity, and Regulation of Phosphorylating Enzymes in Tissues and Cells Relevant to HIV-1 Sexual Transmission

Phosphorylating enzymes (PEs) are responsible for activating nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) such as tenofovir (TFV) and are critical for their conversion to obtain intracellular antiviral activity. However, there are limited data available regarding the expression of PEs and their activity in the female genital tract. This work compared the messenger RNA (mRNA) expression levels of PEs in human female genital tissue, immune cells, and animal models that are commonly used in human immunodeficiency virus (HIV) research. Furthermore, the effect of contraceptive hormones and proinflammatory cytokines on tenofovir diphosphate (TFV-DP) formation and efficacy in human vaginal, epithelial, and immune cells was also evaluated. We found that human vaginal and ectocervical tissues had similar mRNA expression for seven PEs tested. Polymerase chain reaction results revealed that creatine kinase brain (CKB), mitochondrial creatine kinase 1 (CKMT1), mitochondrial creatine kinase 2 (CKMT2), adenylate kinase AK3L1 (AK4), and nucleoside diphosphate kinase 1 (NME1) exhibited a 10- to 10,000-fold higher expression level in a vaginal epithelial cell line, VK2, compared with CD4⁺ T cells (p < .05). Medroxyprogesterone acetate (MPA)/progesterone (P4) and IL-1β/IL-8 treatment resulted in altered TFV-DP levels in VK2 and PM1 cells. MPA and P4 at concentrations above 0.1 μM, as well as IL-1β and IL-8 at concentrations above 10 ng/mL, significantly decreased HIV-1_BaL inhibition in PM1 cells when 1 μM TFV was added. However, this observed effect of hormones and cytokines was abrogated when TFV concentration was raised to 1 mM. These in vitro results elucidate the role of PEs in TFV metabolism and provide information regarding differences in PE tissue expression for animal models commonly used in HIV testing. This information can be applied to better understand and interpret data obtained using these models.

Characterization of the Ovine Vaginal Microbiome and Inflammation Patterns as an Improved Testing Model of Human Vaginal Irritation

The development of therapies targeted to improve the health of women has utilized direct vaginal delivery as a more effective and less toxic method of protection from HIV and other pathogens. Vaginal applicants and delivery devices that provide sustained effects have been met with increasing acceptability, but the efficacy and toxicity outcomes have not been successfully predicted by preclinical in vitro studies and animal modeling. We have explored the utilization of sheep as a model for testing the safety of vaginal applicants and devices based on spatial and structural similarities to the human vagina. As recently noted by the FDA, an additional safety measure is an impact on the vaginal microbiome (VMB) that is known to contribute to vaginal health and influence pathogen susceptibility and drug metabolism. To advance the utility of the sheep vaginal model, we completed a thorough molecular characterization of the ovine VMB utilizing both next-generation sequencing (NGS) and PCR methods. The process also created a custom PCR array to quantify ovine VMB community profiles in an affordable, higher throughput fashion. The results from vaginal swabs (&gt;475 samples) collected from non-pregnant crossbred Dorset and Merino ewes treated with selected vaginal applicants or collected as sham samples established 16 VMB community types (VMB CTs). To associate VMB CTs with eubiosis or dysbiosis, we also completed custom ELISAs for six cytokines identifying IL1B, IL8, TNFa, and CXCL10 as useful markers to support the characterization of ovine vaginal inflammation. The results indicated that Pasteurella, Actinobacillus, Pseudomonas, Bacteroides, Leptotrichia, and E. coli were common markers of eubiosis (low inflammatory marker expression), and that Haemophilus, Ureaplasma, and Corynebacterium were associated with dysbiosis (high cytokine levels). Utilizing the optimized workflow, we also confirmed the utility of three commonly used vaginal applicants for impact on the VMB and inflammatory state, producing a dataset that supports the recommendation for the use of sheep for testing of vaginal applicants and devices as part of preclinical pipelines.

A Review of Murine Cytomegalovirus as a Model for Human Cytomegalovirus Disease-Do Mice Lie?

Since murine cytomegalovirus (MCMV) was first described in 1954, it has been used to model human cytomegalovirus (HCMV) diseases. MCMV is a natural pathogen of mice that is present in wild mice populations and has been associated with diseases such as myocarditis. The species-specific nature of HCMV restricts most research to cell culture-based studies or to the investigation of non-invasive clinical samples, which may not be ideal for the study of disseminated disease. Initial MCMV research used a salivary gland-propagated virus administered via different routes of inoculation into a variety of mouse strains. This revealed that the genetic background of the laboratory mice affected the severity of disease and altered the extent of subsequent pathology. The advent of genetically modified mice and viruses has allowed new aspects of disease to be modeled and the opportunistic nature of HCMV infection to be confirmed. This review describes the different ways that MCMV has been used to model HCMV diseases and explores the continuing difficulty faced by researchers attempting to model HCMV congenital cytomegalovirus disease using the mouse model.

Emergence of Nanotechnology to Fight HIV Sexual Transmission: The Trip of G2-S16 Polyanionic Carbosilane Dendrimer to Possible Pre-Clinical Trials

Development of new, safe, and effective microbicides to prevent human immunodeficiency virus HIV sexual transmission is needed. Unfortunately, most microbicides proved ineffective to prevent the risk of HIV-infection in clinical trials. We are working with G2-S16 polyanionic carbosilane dendrimer (PCD) as a new possible vaginal topical microbicide, based on its short reaction times, wide availability, high reproducibility, and quantitative yields of reaction. G2-S16 PCD exerts anti-HIV activity at an early stage of viral replication, by blocking gp120/CD4/CCR5 interaction, and providing a barrier against infection for long periods of time. G2-S16 PCD was stable at different pH values, as well as in the presence of seminal fluids. It maintained the anti-HIV activity against R5/X4 HIV over time, did not generate any type of drug resistance, and retained the anti-HIV effect when exposed to semen-enhanced viral infection. Importantly, G2-S16 PCD did not modify vaginal microbiota neither in vitro or in vivo. Histopathological examination did not show vaginal irritation, inflammation, lesions, or damage in the vaginal mucosa, after administration of G2-S16 PCD at different concentrations and times in female mice and rabbit animal models. Based on these promising data, G2-S16 PCD could become a good, safe, and readily available candidate to use as a topical vaginal microbicide against HIV.

Major Scientific Hurdles in HIV Vaccine Development: Historical Perspective and Future Directions

Following the discovery of HIV as a causative agent of AIDS, the expectation was to rapidly develop a vaccine; but thirty years later, we still do not have a licensed vaccine. Progress has been hindered by the extensive genetic variability of HIV and our limited understanding of immune responses required to protect against HIV acquisition. Nonetheless, valuable knowledge accrued from numerous basic and translational science research studies and vaccine trials has provided insight into the structural biology of the virus, immunogen design and novel vaccine delivery systems that will likely constitute an effective vaccine. Furthermore, stakeholders now appreciate the daunting scientific challenges of developing an effective HIV vaccine, hence the increased advocacy for collaborative efforts among academic research scientists, governments, pharmaceutical industry, philanthropy, and regulatory entities. In this review, we highlight the history of HIV vaccine development efforts, highlighting major challenges and future directions.

T Cells in the Female Reproductive Tract Can Both Block and Facilitate HIV Transmission

Because HIV is sexually transmitted, there is considerable interest in defining the nature of anti-HIV immunity in the female reproductive tract (FRT) and in developing ways to elicit antiviral immunity in the FRT through vaccination. Although it is assumed that the mucosal immune system of the FRT is of central importance for protection against sexually transmitted diseases, including HIV, this arm of the immune system has only recently been studied. Here we provide a brief review of the role of T cells in the FRT in blocking and facilitating HIV transmission.

Tackling HIV and AIDS: contributions by non-human primate models

During the past three decades, non-human primate (NHP) models have gained an increasing importance in HIV basic and translational research. In contrast to natural host models, infection of macaques with virulent simian or simian-human immunodeficiency viruses (SIV, SHIV) results in a disease that closely resembles HIV infection and AIDS. Although there is no perfect animal model, and each of the available models has its benefits and limitations, carefully designed NHP studies with selection of experimental variables have unraveled important questions of basic pathogenesis and have provided the tools to explore and screen intervention strategies. For example, NHP studies have advanced our understanding of the crucial events during early infection, and have provided proof-of-concept of antiretroviral drug treatment and prevention strategies such as pre-exposure prophylaxis (PrEP) regimes that are increasingly used worldwide, and upon overcoming further barriers of implementation, have the potential to make the next generation AIDS-free. Remaining goals include the pursuit of an effective HIV vaccine, and HIV cure strategies that would allow HIV-infected people to ultimately stop taking antiretroviral drugs. Through a reiterative process with feed-back from results of human studies, NHP models can be further validated and strengthened to advance our scientific knowledge and guide clinical trials.

The Effect of Commonly Used Excipients on the Epithelial Integrity of Human Cervicovaginal Tissue

Pharmaceutical excipients are widely used in vaginal drug products. The epithelial integrity of the cervicovaginal tissue is important for HIV-1 prevention. However, the effects of excipients on cervicovaginal epithelium remain unknown. This study aims at assessing the effects of vaginal product excipients on the integrity of human cervicovaginal epithelium and on a lead HIV prevention antiretroviral drug, tenofovir (TFV). In the current study, nine excipients commonly used in vaginal formulations were incubated for 6 h with excised human ectocervical tissue. The effects of the excipients were examined by measuring the transepithelial electrical resistance (TEER), epithelial morphology, paracellular/transcellular permeability, and cell viability. The efficacy of TFV for preventing HIV-1 infection in the ex vivo cultured ectocervix was also tested. We found that disodium ethyl-enediaminetetraacetate (EDTA), sorbic acid, and benzoic acid had no effect on the tissue TEER. Butylated hydroxyanisole, glycerin, propylene glycol, methylparaben, and propylparaben slightly to moderately decreased tissue TEER, whereas citric acid significantly decreased the TEER in a time-dependent manner. Tissue morphology observed post-exposure strongly correlated with TEER data; however, a less strong correlation was observed between paracellular permeability and TEER data after exposure to different excipients. In addition, treatment with EDTA, methylparaben, and propylene glycol at tested levels had no effect on the efficacy of TFV in preventing tissue HIV-1 infection. In conclusion, the combined measurements of TEER, morphology, permeability, and viability using human cervicovaginal tissue represent a clinically relevant platform for safety evaluation of excipients and formulated products for HIV-1 prevention.

Combining biomedical preventions for HIV: Vaccines with pre-exposure prophylaxis, microbicides or other HIV preventions

Biomedical preventions for HIV, such as vaccines, microbicides or pre-exposure prophylaxis (PrEP) with antiretroviral drugs, can each only partially prevent HIV-1 infection in most human trials. Oral PrEP is now FDA approved for HIV-prevention in high risk groups, but partial adherence reduces efficacy. If combined as biomedical preventions (CBP) an HIV vaccine could provide protection when PrEP adherence is low and PrEP could prevent vaccine breakthroughs. Other types of PrEP or microbicides may also be partially protective. When licensed, first generation HIV vaccines are likely to be partially effective. Individuals at risk for HIV may receive an HIV vaccine combined with other biomedical preventions, in series or in parallel, in clinical trials or as part of standard of care, with the goal of maximally increasing HIV prevention. In human studies, it is challenging to determine which preventions are best combined, how they interact and how effective they are.

Animal models can determine CBP efficacy, whether additive or synergistic, the efficacy of different products and combinations, dose, timing and mechanisms. CBP studies in macaques have shown that partially or minimally effective candidate HIV vaccines combined with partially effective oral PrEP, vaginal PrEP or microbicide generally provided greater protection than either prevention alone against SIV or SHIV challenges. Since human CBP trials will be complex, animal models can guide their design, sample size, endpoints, correlates and surrogates of protection. This review focuses on animal studies and human models of CBP and discusses implications for HIV prevention.

Retinal Structure and Gene Therapy Outcome in Retinoschisin-Deficient Mice Assessed by Spectral-Domain Optical Coherence Tomography

Purpose

Spectral-domain optical coherence tomography (SD-OCT) was used to characterize the retinal phenotype, natural history, and treatment responses in a mouse model of X-linked retinoschisis (Rs1-KO) and to identify new structural markers of AAV8-mediated gene therapy outcome.

Methods

Optical coherence tomography scans were performed on wild-type and Rs1-KO mouse retinas between 1 and 12 months of age and on Rs1-KO mice after intravitreal injection of AAV8-scRS/IRBPhRS (AAV8-RS1). Cavities and photoreceptor outer nuclear layer (ONL) thickness were measured, and outer retina reflective band (ORRB) morphology was examined with age and after AAV8-RS1 treatment. Outer retina reflective band morphology was compared to immunohistochemical staining of the outer limiting membrane (OLM) and photoreceptor inner segment (IS) mitochondria and to electron microscopy (EM) images of IS.

Results

Retinal cavity size in Rs1-KO mice increased between 1 and 4 months and decreased thereafter, while ONL thickness declined steadily, comparable to previous histologic studies. Wild-type retina had four ORRBs. In Rs1-KO, ORRB1was fragmented from 1 month, but was normal after 8 months; ORRB2 and ORRB3 were merged at all ages. Outer retina reflective band morphology returned to normal after AAV-RS1 therapy, paralleling the recovery of the OLM and IS mitochondria as indicated by anti–β-catenin and anti-COX4 labeling, respectively, and EM.

Conclusions

Spectral-domain OCT is a sensitive, noninvasive tool to monitor subtle changes in retinal morphology, disease progression, and effects of therapies in mouse models. The ORRBs may be useful to assess the outcome of gene therapy in the treatment of X-linked retinoschisis patients.

Expression, regulation, and function of drug transporters in cervicovaginal tissues of a mouse model used for microbicide testing

P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance protein 4 (MRP4) are three efflux transporters that play key roles in the pharmacokinetics of antiretroviral drugs used in the pre-exposure prophylaxis of HIV sexual transmission. In this study, we investigated the expression, regulation, and function of these transporters in cervicovaginal tissues of a mouse model. Expression and regulation were examined using real-time RT-PCR and immunohistochemical staining, in the mouse tissues harvested at estrus and diestrus stages under natural cycling or after hormone synchronization. The three transporters were expressed at moderate to high levels compared to the liver. Transporter proteins were localized in various cell types in different tissue segments. Estrous cycle and exogenous hormone treatment affected transporter mRNA and protein expression, in a tissue- and transporter-dependent manner. Depo-Provera-synchronized mice were dosed vaginally or intraperitoneally with (3)H-TFV, with or without MK571 co-administration, to delineate the function of cervicovaginal Mrp4. Co-administration of MK571 significantly increased the concentration of vaginally-administered TFV in endocervix and vagina. MK571 increased the concentration of intraperitoneally-administered TFV in the cervicovaginal lavage and vagina by several fold. Overall, P-gp, Bcrp, and Mrp4 were positively expressed in mouse cervicovaginal tissues, and their expression can be regulated by the estrous cycle or by exogenous hormones. In this model, the Mrp4 transporter impacted TFV distribution in cervicovaginal tissues.

Topical Delivery of Tenofovir Disoproxil Fumarate and Emtricitabine from Pod-Intravaginal Rings Protects Macaques from Multiple SHIV Exposures

Topical preexposure prophylaxis (PrEP) against HIV has been marginally successful in recent clinical trials with low adherence rates being a primary factor for failure. Controlled, sustained release of antiretroviral (ARV) drugs may help overcome these low adherence rates if the product is protective for extended periods of time. The oral combination of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) is currently the only FDA-approved ARV drug for HIV PrEP. A novel pod-intravaginal ring (IVR) delivering TDF and FTC at independently controlled rates was evaluated for efficacy at preventing SHIV162p3 infection in a rigorous, repeat low-dose vaginal exposure model using normally cycling female pigtailed macaques. Six macaques received pod-IVRs containing TDF (65 mg) and FTC (68 mg) every two weeks, and weekly vaginal exposures to 50 TCID₅₀ of SHIV162p3 began one week after the first pod-IVR insertion. All pod-IVR-treated macaques were fully protected throughout the study (P = 0.0002, Log-rank test), whereas all control animals became infected with a median of 4 exposures to infection. The topical, sustained release of TDF and FTC from the pod-IVR maintained protective drug levels in macaques over four months of virus exposures. This novel and versatile delivery system has the capacity to deliver and maintain protective levels of multiple drugs and the protection observed here warrants clinical evaluation of this pod-IVR design.

Longitudinal analysis reveals characteristically high proportions of bacterial vaginosis-associated bacteria and temporal variability of vaginal microbiota in northern pig-tailed macaques (Macaca leonina)

The complex and dynamic vaginal microbial ecosystem is critical to both health and disease of the host. Studies focusing on how vaginal microbiota influences HIV-1 infection may face limitations in selecting proper animal models. Given that northern pig-tailed macaques (Macaca leonina) are susceptible to HIV-1 infection, they may be an optimal animal model for elucidating the mechanisms by which vaginal microbiota contributes to resistance and susceptibility to HIV-1 infection. However, little is known about the composition and temporal variability of vaginal microbiota of the northern pig-tailed macaque. Here, we present a comprehensive catalog of the composition and temporal dynamics of vaginal microbiota of two healthy northern pig-tailed macaques over 19 weeks using 454-pyrosequencing of 16S rRNA genes. We found remarkably high proportions of a diverse array of anaerobic bacteria associated with bacterial vaginosis. Atopobium and Sneathia were dominant genera, and interestingly, we demonstrated the presence of Lactobacillus-dominated vaginal microbiota. Moreover, longitudinal analysis demonstrated that the temporal dynamics of the vaginal microbiota were considerably individualized. Finally, network analysis revealed that vaginal pH may influence the temporal dynamics of the vaginal microbiota, suggesting that inter-subject variability of vaginal bacterial communities could be mirrored in inter-subject variation in correlation profiles of species with each other and with vaginal pH over time. Our results suggest that the northern pig-tailed macaque could be an ideal animal model for prospective investigation of the mechanisms by which vaginal microbiota influence susceptibility and resistance to HIV-1 infection in the context of highly polymicrobial and Lactobacillus-dominated states.

Animal and human mucosal tissue models to study HIV biomedical interventions: can we predict success?

Introduction

Preclinical testing plays an integral role in the development of HIV prevention modalities. Several models are used including humanized mice, non-human primates and human mucosal tissue cultures.

Discussion

Pharmaceutical development traditionally uses preclinical models to evaluate product safety. The HIV prevention field has extended this paradigm to include models of efficacy, encompassing humanized mice, non-human primates (typically Asian macaques) and human mucosal tissue (such as cervical and colorectal). As our understanding of the biology of HIV transmission improves and includes the influence of human behaviour/biology and co-pathogens, these models have evolved as well to address more complex questions. These three models have demonstrated the effectiveness of systemic (oral) and topical use of antiretroviral drugs. Importantly, pharmacokinetic/pharmacodynamic relationships are being developed and linked to information gathered from human clinical trials. The models are incorporating co-pathogens (bacterial and viral) and the effects of coitus (mucosal fluids) on drug distribution and efficacy. Humanized mice are being tailored in their immune reconstitution to better represent humans. Importantly, human mucosal tissue cultures are now being used in early clinical trials to provide information on product efficacy to more accurately characterize efficacious products to advance to larger clinical trials. While all of these models have made advancements in product development, each has limitations and the data need to be interpreted by keeping these limitations in mind.

Conclusions

Development and refinement of each of these models has been an iterative process and linkages to data generated among each of them and from human clinical trials are needed to determine their reliability. Preclinical testing has evolved from simply identifying products that demonstrate efficacy prior to clinical trials to defining essential pharmacokinetic/pharmacodynamic relationships under a variety of conditions and has the potential to improve product selection prior to the initiation of large-scale human clinical trials. The goal is to provide researchers with ample information to make conversant decisions that guide optimized and efficient product development.

Macaque models of enhanced susceptibility to HIV

There are few nonhuman primate models of enhanced HIV susceptibility. Such models can improve comprehension of HIV acquisition risk factors and provide rigorous testing platforms for preclinical prevention strategies. This paper reviews past, current, and proposed research on macaque HIV acquisition risk models and identifies areas where modeling is significantly lacking. We compare different experimental approaches and provide practical considerations for designing macaque susceptibility studies. Modifiable (mucosal and systemic coinfections, hormonal contraception, and rectal lubricants) and non-modifiable (hormonal fluctuations) risk factors are highlighted. Risk acquisition models via vaginal, rectal, and penile challenge routes are discussed. There is no consensus on the best statistical model for evaluating increased susceptibility, and additional research is required. The use of enhanced susceptibility macaque models would benefit multiple facets of the HIV research field, including basic acquisition and pathogenesis studies as well as the vaccine and other biomedical preventions pipeline.

Tenofovir disoproxil fumarate intravaginal ring protects high-dose depot medroxyprogesterone acetate-treated macaques from multiple SHIV exposures

Preclinical HIV prevention models use either a single high-dose viral challenge in depot medroxyprogesterone acetate-treated macaques or repeated viral challenges in cycling macaques. We tested the efficacy of an intravaginal tenofovir disoproxil fumarate (TDF) ring in a model combining repeated 30-mg injections of depot medroxyprogesterone acetate every 6 weeks with vaginal viral challenges weekly for 12 weeks. Twelve macaques were randomized to TDF or placebo rings. All placebo macaques became infected after a median of 2 exposures, whereas only 1 TDF macaque became infected at the eighth exposure (P = 0.0012). The TDF ring provides durable protection in a stringent challenge model.

Development and optimization of a non-enzymatic method of leukocyte isolation from macaque tissues

BACKGROUND AND METHODS

Cell isolation from macaque tissues involves laborious enzymatic digestion. The Medimachine provides a simpler, quicker non-enzymatic method, yielding 1.5–5 million cells/g of vaginal or rectal tissue from pigtailed macaques.

RESULTS AND CONCLUSIONS

Flow cytometry analysis of the two methods revealed similar levels of cell viability and most major cell lineage and activation markers.

A polyvalent Clade B virus-like particle HIV vaccine combined with partially protective oral preexposure prophylaxis prevents simian-human immunodeficiency virus Infection in macaques and primes for virus-amplified immunity

Vaccination and preexposure prophylaxis (PrEP) with antiretrovirals have shown only partial protection from HIV-1 infection in human trials. Oral Truvada (emtricitabine/tenofovir disoproxil fumarate) is FDA approved as PrEP but partial adherence reduces efficacy. If combined as biomedical preventions (CBP), an HIV vaccine could protect when PrEP adherence is low and PrEP could prevent vaccine breakthroughs. The efficacy of combining oral PrEP with an HIV vaccine has not been evaluated in humans. We determined the efficacy of combining a DNA/virus-like particle (VLP) vaccine with partially effective intermittent PrEP in Indian rhesus macaques (RM). Eight RM received intramuscular inoculations of five DNA plasmids encoding four HIV-1 Clade B primary isolate Envs and SIVmac239 Gag (at weeks 0 and 4), followed by intramuscular and intranasal inoculations of homologous Gag VLPs and four Env VLPs (at weeks 12, 16, and 53). At week 61, we initiated weekly rectal exposures with heterologous SHIV162p3 (10 TCID50) along with oral Truvada (TDF, 22 mg/kg; FTC 20 mg/kg) dosing 2 h before and 22 h after each exposure. This PrEP regimen previously demonstrated 50% efficacy. Five controls (no vaccine, no PrEP) received weekly SHIV162p3. All controls were infected after a median of four exposures; the mean peak plasma viral load (VL) was 3.9×10(7) vRNA copies/ml. CBP protected seven of eight (87.5%) RM. The one infected CBP RM had a reduced peak VL of 8.8×10(5) copies/ml. SHIV exposures during PrEP amplified Gag and Env antibody titers in protected RM. These results suggest that combining oral PrEP with HIV vaccines could enhance protection against HIV-1 infection.

Why primate models matter

Research involving nonhuman primates (NHPs) has played a vital role in many of the medical and scientific advances of the past century. NHPs are used because of their similarity to humans in physiology, neuroanatomy, reproduction, development, cognition, and social complexity-yet it is these very similarities that make the use of NHPs in biomedical research a considered decision. As primate researchers, we feel an obligation and responsibility to present the facts concerning why primates are used in various areas of biomedical research. Recent decisions in the United States, including the phasing out of chimpanzees in research by the National Institutes of Health and the pending closure of the New England Primate Research Center, illustrate to us the critical importance of conveying why continued research with primates is needed. Here, we review key areas in biomedicine where primate models have been, and continue to be, essential for advancing fundamental knowledge in biomedical and biological research.

HIV pre-exposure prophylaxis: mucosal tissue drug distribution of RT inhibitor Tenofovir and entry inhibitor Maraviroc in a humanized mouse model

Pre-exposure prophylaxis (PrEP) strategies utilizing anti-retroviral drugs show considerable promise for HIV prevention. However there is insufficient pharmacokinetic (PK) data on drug concentrations required for protection at the relevant mucosal tissues where the infection is initiated. Here we evaluated the utility of a humanized mouse model to derive PK data on two leading drugs, the RT inhibitor Tenofovir (TFV) and CCR5 inhibitor Maraviroc (MVC). Following oral dosing, both the drugs and the intracellular active TFV-diphosphate could be detected in vaginal, rectal and intestinal tissues. The drug exposures (AUC₂₄ h) were found to be higher in vaginal tissue compared to plasma with even higher levels detected in rectal and intestinal tissues. The overall trends of drug concentrations seen in humanized mice reflect those seen in the human thus establishing the utility of this model complementing the present non-human primate (NHP) models for future pre-clinical evaluations of promising HIV PrEP drug candidates.

A potent combination microbicide that targets SHIV-RT, HSV-2 and HPV

Prevalent infection with human herpes simplex 2 (HSV-2) or human papillomavirus (HPV) is associated with increased human immunodeficiency virus (HIV) acquisition. Microbicides that target HIV as well as these sexually transmitted infections (STIs) may more effectively limit HIV incidence. Previously, we showed that a microbicide gel (MZC) containing MIV-150, zinc acetate (ZA) and carrageenan (CG) protected macaques against simian-human immunodeficiency virus (SHIV-RT) infection and that a ZC gel protected mice against HSV-2 infection. Here we evaluated a modified MZC gel (containing different buffers, co-solvents, and preservatives suitable for clinical testing) against both vaginal and rectal challenge of animals with SHIV-RT, HSV-2 or HPV. MZC was stable and safe in vitro (cell viability and monolayer integrity) and in vivo (histology). MZC protected macaques against vaginal (p<0.0001) SHIV-RT infection when applied up to 8 hours (h) prior to challenge. When used close to the time of challenge, MZC prevented rectal SHIV-RT infection of macaques similar to the CG control. MZC significantly reduced vaginal (p<0.0001) and anorectal (p = 0.0187) infection of mice when 10(6) pfu HSV-2 were applied immediately after vaginal challenge and also when 5×10(3) pfu were applied between 8 h before and 4 h after vaginal challenge (p<0.0248). Protection of mice against 8×10(6) HPV16 pseudovirus particles (HPV16 PsV) was significant for MZC applied up to 24 h before and 2 h after vaginal challenge (p<0.0001) and also if applied 2 h before or after anorectal challenge (p<0.0006). MZC provides a durable window of protection against vaginal infection with these three viruses and, against HSV-2 and HPV making it an excellent candidate microbicide for clinical use.