Postcoital bioavailability and antiviral activity of 0.5% PRO 2000 gel: implications for future microbicide clinical trials

Women for science and science for women: Gaps, challenges and opportunities towards optimizing pre-exposure prophylaxis for HIV-1 prevention

Preventing new HIV infections remains a global challenge. Young women continue to bear a disproportionate burden of infection. Oral pre-exposure prophylaxis (PrEP), offers a novel women-initiated prevention technology and PrEP trials completed to date underscore the importance of their inclusion early in trials evaluating new HIV PrEP technologies. Data from completed topical and systemic PrEP trials highlight the role of gender specific physiological and social factors that impact PrEP uptake, adherence and efficacy. Here we review the past and current developments of HIV-1 prevention options for women with special focus on PrEP considering the diverse factors that can impact PrEP efficacy. Furthermore, we highlight the importance of inclusion of female scientists, clinicians, and community advocates in scientific efforts to further improve HIV prevention strategies.

Evaluating the impact of three progestin-based hormonal contraceptive methods on immunologic changes in the female genital tract and systemically (CHIME Study): a prospective cohort study protocol

BACKGROUND

Gonadal hormones can modify immune function, which may impact susceptibility to infectious diseases, including Human Immunodeficiency Virus (HIV). There is limited knowledge about how hormonal contraceptives (HC) influence the immune response during the course of use. The CHIME study aims to evaluate the effect of long-acting progestin-based hormonal contraceptives (depot medroxyprogesterone acetate, etonogestrel implant, and levonorgestrel intrauterine device) on immunologic changes in the female genital tract (FGT) and systemic compartment.

METHODS

CHIME is an observational cohort study where participants attend 2 visits prior to initiating the HC method of their choice, and then attend 6 visits over 12 months with biological sampling (vaginal swabs, cervicovaginal lavage, cytobrush and blood) for immunological, bacteriological, and virological analyses at each visit. Immune profiling will be evaluated by multi-color flow cytometry to determine how different T-cell subsets, in particular the CD4 T-cell subsets, change during the course of contraceptive use and whether they have different profiles in the FGT compared to the systemic compartment. The study aims are (1) to characterize the alterations in FGT and systemic immune profiles associated with three long-acting progestin-only HC and (2) to evaluate the vaginal microenvironment, determined by 16 s rRNA sequencing, as an individual-level risk factor and moderator of genital and systemic immune profile changes following exposure to three commonly used HC. Data collection started in March 2019 and is scheduled to be completed in October 2024.

DISCUSSION

The CHIME study aims to contribute to the body of research designed to evaluate the comparative impact of three long-acting progestin-only HC on innate and adaptive immune functions to understand how immunologic effects alter STI and HIV susceptibility.

Broad-Spectrum Antiviral Peptides and Polymers

As the human cost of the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still being witnessed worldwide, the development of broad-spectrum antiviral agents against emerging and re-emerging viruses is seen as a necessity to hamper the spread of infections. Various targets during the viral life-cycle can be considered to inhibit viral infection, from viral attachment to viral fusion or replication. Macromolecules represent a particularly attractive class of therapeutics due to their multivalency and versatility. Although several antiviral macromolecules hold great promise in clinical applications, the emergence of resistance after prolonged exposure urges the need for improved solutions. In the present article, the recent advancement in the discovery of antiviral peptides and polymers with diverse structural features and antiviral mechanisms is reviewed. Future perspectives, such as, the development of virucidal peptides/polymers and their coatings against SARS-CoV-2 infection, standardization of antiviral testing protocols, and use of artificial intelligence or machine learning as a tool to accelerate the discovery of antiviral macromolecules, are discussed.

Semen: A modulator of female genital tract inflammation and a vector for HIV-1 transmission

In order to establish productive infection in women, HIV must transverse the vaginal epithelium and gain access to local target cells. Genital inflammation contributes to the availability of HIV susceptible cells at the female genital mucosa and is associated with higher HIV transmission rates in women. Factors that contribute to genital inflammation may subsequently increase the risk of HIV infection in women. Semen is a highly immunomodulatory fluid containing several bioactive molecules with the potential to influence inflammation and immune activation at the female genital tract. In addition to its role as a vector for HIV transmission, semen induces profound mucosal changes to prime the female reproductive tract for conception. Still, most studies of mucosal immunity are conducted in the absence of semen or without considering its immune impact on the female genital tract. This review discusses the various mechanisms by which semen exposure may influence female genital inflammation and highlights the importance of routine screening for semen biomarkers in vaginal specimens to account for its impact on genital inflammation.

Evaluation of the novel vaginal contraceptive agent PPCM in preclinical studies using sperm hyaluronan binding and acrosome status assays

Background

Polyphenylene carboxymethylene (PPCM) sodium salt is a promising multipurpose technology for prevention of both sexually transmitted infections (STIs) and pregnancy. In preclinical studies, PPCM has demonstrated significant (1) antimicrobial activity against several important viral and bacterial pathogens and (2) contraceptive activity associated with premature acrosome loss.

Objective

To further evaluate a vaginal antimicrobial compound as a contraceptive agent in preclinical studies utilizing a repurposed hyaluronan binding assay (HBA).

Materials and methods

Semen samples containing either neat semen or washed spermatozoa were treated with increasing concentrations of PPCM or calcium ionophore A23187 (positive control). Sperm inactivation was measured by two methods: (1) double acrosome staining (AS), and (2) a hyaluronan binding assay (HBA^®). Percentage of inactivated sperm was compared between untreated control sperm and those treated with PPCM or A23187.

Results

PPCM had a significant (p < 0.05) and dose‐dependent effect on sperm inactivation in both assays, with HBA detecting a higher proportion of inactivated sperm than AS. PPCM did not affect sperm motility and exhibited equivalent responses in the neat and washed samples.

Discussion

Both HBA and AS confirmed that spermatozoa were rapidly inactivated at PPCM concentrations likely present in the vagina under actual use conditions and in a time‐frame comparable to in vivo migration of spermatozoa out of seminal plasma into cervical mucus.

Conclusion

PPCM vaginal gel may provide contraceptive protection as well as help with STI prevention. HBA may be a sensitive and much needed biomarker for sperm activity in future contraceptive development.

The use of PSA as a biomarker of recent semen exposure in female reproductive health studies

Semen contains potent soluble proteins, bacteria, viruses, activated immune cells as well as anti- and pro-inflammatory cytokines that may influence the inflammatory response and alter microbial composition of the female genital tract. The presence of semen in the female genital mucosa may be a significant confounder that most studies have failed to control for in their analysis. Prostate-specific antigen (PSA), a protein secreted by the prostate into the urethra during ejaculation, is a well-established biomarker of semen exposure. Several studies have demonstrated discordance between self-reports of sexual behavior and the presence of PSA. Recent semen exposure has been shown to promote pro-inflammatory responses, stimulate the recruitment of activated immune cells and decrease Lactobacilli abundance in the female genital mucosa. As a result, it is important to understand the concordance between self-reported consistent condom use and the presence of semen biomarkers. Furthermore, to ensure that the interpretation of data in clinical studies of the immunological and microbial environment in the female genital mucosa are accurate, it is essential to establish whether semen is present in the vaginal fluid. This review explores the impact of semen exposure on the mucosal microenvironment and assesses the use of the PSA as an objective biomarker of semen exposure to reduce reliance on self-reported sexual intercourse.

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.

Heterogeneity of HIV-1 Replication in Ectocervical and Vaginal Tissue Ex Vivo

In clinical trials evaluating HIV-1 prevention products, ex vivo exposure of mucosal tissue to HIV-1 is performed to inform drug levels needed to suppress viral infection. Understanding assay and participant variables that influence HIV-1 replication will help with assay implementation. Demographic and behavioral data were obtained from 61 healthy women aged 21-45. Paired cervical tissue (CT) and vaginal tissue (VT) biopsies were collected and treated with HIV-1_BaL or HIV-1_JR-CSF, washed, and cultured. On days 3, 7, and/or 11, culture supernatant was collected, and viral replication was monitored by p24 ELISA. Tissue was extracted at study end, and HIV-1 relative RNA copies were determined by polymerase chain reaction. Cumulative p24 and RNA were log-transformed and analyzed using a linear mixed model, t-test, and an intraclass correlation coefficient (ICC). HIV replication was similar between CT and VT for each virus, but HIV-1_BaL had 1.5 log₁₀ and 0.9 log₁₀ higher levels of p24 than HIV-1_JR-CSF in CT and VT, respectively (p < .001), which correlated with HIV-1 relative RNA copies. Cumulative p24 and RNA copies in both tissues demonstrated low intraperson correlation for both viruses (ICC ≤0.513 HIV-1_BaL; ICC ≤0.419 HIV-1_JR-CSF). Enrollment into previous clinical studies in which genital biopsies were collected modestly decreased the HIV-1_BaL cumulative p24 for CT, but not for VT. To improve the ex vivo challenge assay, viruses should be evaluated for replication in mucosal tissue before study implementation, baseline mucosal tissue is not needed if a placebo/no treatment group is included within the clinical trial, and previous biopsy sites should be avoided.

First-in-Human Trial of MIV-150 and Zinc Acetate Coformulated in a Carrageenan Gel: Safety, Pharmacokinetics, Acceptability, Adherence, and Pharmacodynamics

OBJECTIVE

To evaluate the safety and pharmacokinetics of MIV-150 and zinc acetate in a carrageenan gel (PC-1005). Acceptability, adherence, and pharmacodynamics were also explored.

DESIGN

A 3-day open-label safety run-in (n = 5) preceded a placebo-controlled, double-blind trial in healthy, HIV-negative, abstinent women randomized (4:1) to vaginally apply 4 mL of PC-1005 or placebo once daily for 14 days.

METHODS

Assessments included physical examinations, safety labs, colposcopy, biopsies, cervicovaginal lavages (CVLs), and behavioral questionnaires. MIV-150 (plasma, CVL, tissue), zinc (plasma, CVL), and carrageenan (CVL) concentrations were determined with LC-MS/MS, ICP-MS, and ELISA, respectively. CVL antiviral activity was measured using cell-based assays. Safety, acceptability, and adherence were analyzed descriptively. Pharmacokinetic parameters were calculated using noncompartmental techniques and actual sampling times. CVL antiviral EC50 values were calculated using a dose-response inhibition analysis.

RESULTS

Participants (n = 20) ranged from 19-44 years old; 52% were black or African American. Among those completing the trial (13/17, PC-1005; 3/3, placebo), 11/17 reported liking the gel overall; 7 recommended reducing the volume. Adverse events, which were primarily mild and/or unrelated, were comparable between groups. Low systemic MIV-150 levels were observed, without accumulation. Plasma zinc levels were unchanged from baseline. Seven of seven CVLs collected 4-hour postdose demonstrated antiviral (HIV, human papillomavirus) activity. High baseline CVL anti-herpes-simplex virus type-2 (HSV-2) activity precluded assessment of postdose activity.

CONCLUSIONS

PC-1005 used vaginally for 14 days was well tolerated. Low systemic levels of MIV-150 were observed. Plasma zinc levels were unchanged. Postdose CVLs had anti-HIV and anti-human papillomavirus activity. These data warrant further development of PC-1005 for HIV and sexually transmitted infection prevention.

Efficacy of carbosilane dendrimers with an antiretroviral combination against HIV-1 in the presence of semen-derived enhancer of viral infection

Amyloid fibrils, which are present in semen, were considered to be a cause of topical vaginal gel ineffectiveness in vivo after microbicides failed as HIV-1 prophylaxis. Therefore, it was necessary to determine whether a dendrimer was suitable for further evaluation in an in vitro model of semen-enhanced viral infection (SEVI). We demonstrated that SEVI in TZM.bl cell cultures increased the infectivity of R5-HIV-1_NL(AD8), pTHRO.c and pCH058.c isolates, causing higher IC₅₀ values for two polyanionic carbosilane dendrimers, G2-STE16 and G3-S16. However, both dendrimers maintained protection rates of 90% at non-toxic concentrations. When dendrimers were combined with Tenofovir/Maraviroc (TDF/MVC), the anti-HIV-1 effect remained at a minimum IC₅₀ increase between 1- and 7-fold in the presence of amyloid fibrils. In peripheral blood mononuclear cells (PBMC), IC₅₀ values were slightly influenced by the presence of semen. In brief, dendrimers combined with antiretrovirals showed a synergistic effect. This result plays a crucial role in new microbicide formulations, as it overcomes the negative effects of amyloid fibrils.

Nanoparticles-in-film for the combined vaginal delivery of anti-HIV microbicide drugs

Combining two or more antiretroviral drugs in one medical product is an interesting but challenging strategy for developing topical anti-HIV microbicides. We developed a new vaginal delivery system comprising the incorporation of nanoparticles (NPs) into a polymeric film base - NPs-in-film - and tested its ability to deliver tenofovir (TFV) and efavirenz (EFV). EFV-loaded poly(lactic-co-glycolic acid) NPs were incorporated alongside free TFV into fast dissolving films during film manufacturing. The delivery system was characterized for physicochemical properties, as well as genital distribution, local and systemic 24h pharmacokinetics (PK), and safety upon intravaginal administration to mice. NPs-in-film presented suitable technological, mechanical and cytotoxicity features for vaginal use. Retention of NPs in vivo was enhanced both in vaginal lavages and tissue when associated to film. PK data evidenced that vaginal drug levels rapidly decreased after administration but NPs-in-film were still able to enhance drug concentrations of EFV. Obtained values for area-under-the-curve for EFV were around one log10 higher than those for the free drugs in aqueous vehicle (phosphate buffered saline). Film alone also contributed to higher and more prolonged local drug levels as compared to the administration of TFV and EFV in aqueous vehicle. Systemic exposure to both drugs was low. NPs-in-film was found to be safe upon once daily vaginal administration to mice, with no significant genital histological changes or major alterations in cytokine/chemokine profiles being observed. Overall, the proposed NPs-in-film system seems to be an interesting delivery platform for developing combination vaginal anti-HIV microbicides.

Efficacy of HIV antiviral polyanionic carbosilane dendrimer G2-S16 in the presence of semen

The development of a safe and effective microbicide to prevent the sexual transmission of human immunodeficiency virus (HIV)-1 is urgently needed. Unfortunately, the majority of microbicides, such as poly(L-lysine)-dendrimers, anionic polymers, or antiretrovirals, have proved inactive or even increased the risk of HIV infection in clinical trials, most probably due to the fact that these compounds failed to prevent semen-exposed HIV infection. We showed that G2-S16 dendrimer exerts anti-HIV-1 activity at an early stage of viral replication, blocking the gp120/CD4/CCR5 interaction and providing a barrier to infection for long periods, confirming its multifactorial and nonspecific ability. Previously, we demonstrated that topical administration of G2-S16 prevents HIV transmission in humanized BLT mice without irritation or vaginal lesions. Here, we demonstrated that G2-S16 is active against mock- and semen-exposed HIV-1 and could be a promising microbicide against HIV infection.

Impact of Sex on the Pharmacokinetics and Pharmacodynamics of 1% Tenofovir Gel

BACKGROUND

Tenofovir (TFV) gel partially protected against human immunodeficiency virus (HIV) in one but not subsequent trials. The disappointing results were attributed largely to poor adherence. However, timing of gel application relative to sex may impact pharmacokinetics and contribute to outcomes. Thus, we conducted a single-dose pharmacokinetic study of TFV gel applied 1 or 24 hours before or 1 hour before and 1 hour after (BAT) sex and compared results with dosing without sex.

METHODS

Twenty-four couples were enrolled; cervicovaginal lavage (CVL) and tissue were collected 2 hours after sex with matching timed collections at no sex visits and assayed for drug concentrations and CVL anti-HIV activity.

RESULTS

Compared with dosing without sex, median TFV concentrations after sex decreased 72% and 78% (P < .001) in CVL, 75% and 71% (P < .001) in vaginal tissue, and 75% (P = .06) and 55% (P < .001) in cervical tissue with -1 hour and -24 hour dosing, respectively. Median concentration of TFV-diphosphate also decreased significantly in cervical tissue with -1 hour, dosing. BAT dosing resulted in drug levels at least as great as those in the absence of sex. Percent inhibition of HIV infection by post-coital CVL increased significantly from median (interquartile range) of 55% (54%) in the absence of gel to 99% (7%), 77% (57%), and 100% (0.4%) with -1 hour, -24 hour, or BAT dosing, respectively, and correlated significantly with drug concentration.

CONCLUSIONS

Timing of TFV gel application relative to sex significantly impacts drug levels. BAT dosing or sustained delivery may be optimal for preexposure prophylaxis.

Loss of Innate Host Defense Following Unprotected Vaginal Sex

BACKGROUND

Multiple host defense mechanisms protect the female genital tract from pathogens, but the impact of sexual intercourse on defense is unknown.

METHODS

As part of a hypothesis-generating study, 17 women provided cervicovaginal lavage (CVL) specimens at baseline (all had abstained from sexual intercourse, masturbation, and vaginal product use for 72 hours prior to screening), 2-6 hours and 10-14 hours after vaginal intercourse with a male condom, and 2-6 hours and 10-14 hours after vaginal intercourse without a male condom (5 visits total, including the baseline visit). Vaginal pH, concentrations of immune molecules, and antimicrobial activity at postcoital visits were compared to baseline values.

RESULTS

Vaginal pH and the transforming growth factor β1 level increased, but human beta-defensin 2 (HBD-2), HBD-3, and interleukin 8 levels decreased after unprotected sex. Median Escherichia coli inhibitory activity in CVL specimens decreased significantly from baseline at the visit 2-6 hours after unprotected sex (63% [range, -34% to 99%] vs 5% [range, -51% to 100%]; P = .02) and remained low at the visit 10-14 hours after unprotected sex (6% [range, -19% to 92%]; P = .02). Pooled human seminal plasma enhanced E. coli growth in vitro in a dose-dependent manner and, when added to CVL samples with high anti-E. coli activity, reversed the inhibition.

CONCLUSIONS

Unprotected vaginal sex results in a reduction in endogenous anti-E. coli activity, which may reflect, in part, enhancement of bacterial growth by seminal plasma. This finding may contribute to the risk of E. coli vaginal colonization following sexual intercourse.

'HIV has a woman's face': vaginal microbicides and a case of ambiguous failure

The case is a primary unit of knowledge production in the field of HIV research, yet the work that is done to construct cases often goes unremarked. In this paper, the case takes centre stage in an analysis of a set of apparent failures in HIV prevention research, namely a series of clinical trials to test vaginal microbicides. Returning to the genesis of the microbicide concept in the early 1990s, I examine how the discourse of women's empowerment was linked to HIV prevention in a way that mobilized a particular vision of the case, which was both politically and scientifically expedient. Drawing on an in-depth empirical study of one particular trial, I show the success of the case in mobilizing funds and interest in the research, as well its success in accounting for the failure of the pharmaceutical technology. Drawing in alternative scientific accounts of the failure of microbicides, however, a different version of events is indicated, in which what can ultimately be said to have failed is not the technology itself, but the act of casing upon which its testing was founded.

Use of partial least squares path modelling to assess the willingness of Chinese female sex workers to participate in a microbicide trial

OBJECTIVES

To investigate the willingness of Chinese female sex workers (FSWs) to participate (WTP) in a clinical trial of microbicides; to explore the potential hindrances and facilitating factors; and to provide support for future microbicide clinical trials by tailoring their design to better meet the specific needs of FSWs.

STUDY DESIGN

Cross-sectional study.

METHODS

In total, 404 FSWs were investigated using structured questionnaires. Exploratory factor analysis and partial least squares path modelling were used to explore the correlations between several influencing factors and WTP.

RESULTS

The WTP of FSWs enrolled in this study was high (53.47%, 216/404). Possible benefits from enrolment in the trial were positively associated with WTP, while concern about a hypothetical microbicide, potential physical harm, economic loss from participation, and fear of family or social isolation were negatively associated with WTP.

CONCLUSION

FSWs are appropriate participants in microbicide clinical trials, and are likely to benefit from effective microbicides. In a microbicide clinical trial, it is imperative to ensure protection of the rights, dignity, safety, confidentiality and welfare of FSW participants.

Semen enhances HIV infectivity and impairs the antiviral efficacy of microbicides

Topically applied microbicides potently inhibit HIV in vitro but have largely failed to exert protective effects in clinical trials. One possible reason for this discrepancy is that the preclinical testing of microbicides does not faithfully reflect the conditions of HIV sexual transmission. We report that candidate microbicides that target HIV components show greatly reduced antiviral efficacy in the presence of semen, the main vector for HIV transmission. This diminished antiviral activity was dependent on the ability of amyloid fibrils in semen to enhance the infectivity of HIV. Thus, the anti-HIV efficacy of microbicides determined in the absence of semen greatly underestimated the drug concentrations needed to block semen-exposed virus. One notable exception was maraviroc. This HIV entry inhibitor targets the host cell CCR5 co-receptor and was highly active against both untreated and semen-exposed HIV. These data help to explain why microbicides have failed to protect against HIV in clinical trials and suggest that antiviral compounds targeting host factors hold promise for further development. These findings also suggest that the in vitro efficacy of candidate microbicides should be determined in the presence of semen to identify the best candidates for the prevention of HIV sexual transmission.

Nanotech-derived topical microbicides for HIV prevention: the road to clinical development

More than three decades since its discovery, HIV infection remains one of the most aggressive epidemics worldwide, with more than 35 million people infected. In sub-Saharan Africa, heterosexual transmissions represent nearly 80% of new infections, with 50% of these occurring in women. In an effort to stop the dramatic spread of the HIV epidemic, new preventive treatments, such as microbicides, have been developed. Nanotechnology has revolutionized this field by designing and engineering novel highly effective nano-sized materials as microbicide candidates. This review illustrates the most recent advances in nanotech-derived HIV prevention strategies, as well as the main steps required to translate promising in vitro results into clinical trials.

[Microbicides for preventing sexually transmitted infections: Current status and strategies for preclinical evaluation of new candidates]

Microbicides are a new tool, still under investigation, which could help prevent infection by the human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs). Increasing evidence shows that the complexity of sexual transmission of viral pathogens requires the identification of compounds able to block the early events during the cycle of viral infection. In this manuscript we provide a comprehensive review of the different microbicide strategies that have been studied or are currently being considered for STI prevention, particularly emphasizing those having the potential to block HIV infection. The manuscript also reviews the complex process that is required to conduct future clinical studies in humans and concludes with a brief discussion of the strategies that could be part of the immediate future in microbicide research.

Herpes simplex virus 2 infection: molecular association with HIV and novel microbicides to prevent disease

Infection with herpes simplex viruses is one of the most ancient diseases described to affect humans. Infection with these viruses produces vexing effects to the host, which frequently recur. Infection with herpes simplex viruses is lifelong, and currently there is no vaccine or drug to prevent or cure infection. Prevalence of herpes simplex virus 2 (HSV-2) infection varies significantly depending on the geographical region and nears 20 % worldwide. Importantly, HSV-2 is the first cause of genital ulcers in the planet. HSV-2 affects approximately 500 million people around the globe and significantly increases the likelihood of acquiring the human immunodeficiency virus (HIV), as well as its shedding. Thus, controlling HSV-2 infection and spread is of public health concern. Here, we review the diseases produced by herpes simplex viruses, the factors that modulate HSV-2 infection, the relationship between HSV-2 and HIV and novel therapeutic and prophylactic microbicides/antivirals under development to prevent infection and pathological outcomes produced by this virus. We also review mutations associated with HSV-2 resistance to common antivirals.

Surfactant protein D inhibits HIV-1 infection of target cells via interference with gp120-CD4 interaction and modulates pro-inflammatory cytokine production

Surfactant Protein SP-D, a member of the collectin family, is a pattern recognition protein, secreted by mucosal epithelial cells and has an important role in innate immunity against various pathogens. In this study, we confirm that native human SP-D and a recombinant fragment of human SP-D (rhSP-D) bind to gp120 of HIV-1 and significantly inhibit viral replication in vitro in a calcium and dose-dependent manner. We show, for the first time, that SP-D and rhSP-D act as potent inhibitors of HIV-1 entry in to target cells and block the interaction between CD4 and gp120 in a dose-dependent manner. The rhSP-D-mediated inhibition of viral replication was examined using three clinical isolates of HIV-1 and three target cells: Jurkat T cells, U937 monocytic cells and PBMCs. HIV-1 induced cytokine storm in the three target cells was significantly suppressed by rhSP-D. Phosphorylation of key kinases p38, Erk1/2 and AKT, which contribute to HIV-1 induced immune activation, was significantly reduced in vitro in the presence of rhSP-D. Notably, anti-HIV-1 activity of rhSP-D was retained in the presence of biological fluids such as cervico-vaginal lavage and seminal plasma. Our study illustrates the multi-faceted role of human SP-D against HIV-1 and potential of rhSP-D for immunotherapy to inhibit viral entry and immune activation in acute HIV infection.

In vitro and in vivo evaluation of two carrageenan-based formulations to prevent HPV acquisition

Commercial vaccines against human papillomavirus (HPV) have low uptake due to parental autonomy, dosing regimen, cost, and cold chain storage requirements. Carrageenan (CG)-based formulations prevent HPV infection in vitro and in vivo but data are needed on the durability of anti-HPV activity and the effect of seminal plasma (SP). The Population Council's PC-515 gel and the lubricant Divine 9 were tested for their physicochemical properties and anti-HPV activity against HPV16, 18, and 45 pseudoviruses (PsVs). Anti-PsV activity was estimated using the luciferase assay in HeLa cells and the HPV PsV luciferase mouse model. Formulations were applied intravaginally either 2h pre/2h post (-2h/+2h) or 24h pre (-24h) relative to challenge with HPV16 or 45 PsV in PBS or SP/PBS. Both formulations showed broad-spectrum anti-HPV activity in vitro (IC50: 1-20ng/ml), significantly decreasing HPV PsV infection in the mouse model (-2h/+2h, p<0.0001). PC-515 protected better than Divine 9 in the -24h dosing regimen (p<0.0001) and comparable to Divine 9 in the -2h/+2h regimen (p=0.9841). PC-515 retained full activity in the murine model when PsV solutions contained human SP. The durable, potential broad-spectrum anti-HPV activity of CG formulations in the presence of SP supports their further development to prevent HPV acquisition.

Evaluation of PD 404,182 as an anti-HIV and anti-herpes simplex virus microbicide

PD 404,182 (PD) is a synthetic compound that was found to compromise HIV integrity via interaction with a nonenvelope protein viral structural component (A. M. Chamoun et al., Antimicrob. Agents Chemother. 56:672-681, 2012). The present study evaluates the potential of PD as an anti-HIV microbicide and establishes PD's virucidal activity toward another pathogen, herpes simplex virus (HSV). We show that the anti-HIV-1 50% inhibitory concentration (IC50) of PD, when diluted in seminal plasma, is ∼1 μM, similar to the IC50 determined in cell culture growth medium, and that PD retains full anti-HIV-1 activity after incubation in cervical fluid at 37°C for at least 24 h. In addition, PD is nontoxic toward vaginal commensal Lactobacillus species (50% cytotoxic concentration [CC50], >300 μM), freshly activated human peripheral blood mononuclear cells (CC50, ∼200 μM), and primary CD4(+) T cells, macrophages, and dendritic cells (CC50, >300 μM). PD also exhibited high stability in pH-adjusted Dulbecco's phosphate-buffered saline with little to no activity loss after 8 weeks at pH 4 and 42°C, indicating suitability for formulation for transportation and storage in developing countries. Finally, for the first time, we show that PD inactivates herpes simplex virus 1 (HSV-1) and HSV-2 at submicromolar concentrations. Due to the prevalence of HSV infection, the ability of PD to inactivate HSV may provide an additional incentive for use as a microbicide. The ability of PD to inactivate both HIV-1 and HSV, combined with its low toxicity and high stability, warrants additional studies for the evaluation of PD's microbicidal candidacy in animals and humans.

Novel preclinical models of topical PrEP pharmacodynamics provide rationale for combination of drugs with complementary properties

Background

The limited success of recent HIV topical pre-exposure prophylaxis clinical trials highlights the need for more predictive models of drug efficacy that better simulate what may happen during sexual exposure. To address this gap, we developed complementary in vitro models to evaluate the ability of drugs to retain anti-HIV activity if cells were washed with seminal plasma (simulating what may happen following exposure to ejaculate), and to protect drug-naive T cells (representing newly recruited immune cells) co-cultured with explants that had been pretreated with drug. We focused on tenofovir disoproxil fumarate (TDF), the non-nucleoside reverse transcriptase inhibitors dapivirine (DPV) and IQP-0528, and the entry inhibitors maraviroc (MVC) and the D-peptide chol-PIE-12 trimer (PIE12). Studies were extended to macaques and the ability of cervical biopsies obtained from animals treated with an intravaginal ring formulation of IQP-0528 to protect ex vivo co-cultured T cells was determined. The antiviral activity of cervicovaginal lavage samples against a primary Clade C isolate was also measured and correlated with drug levels.

Results

Cells exposed to TDF were equally protected from HIV whether or not the drug-treated cells were washed with medium or seminal plasma prior to challenge. In contrast, several-fold higher concentrations of NNRTIs and entry inhibitors were needed to attain similar levels of HIV inhibition following a wash with seminal plasma. Conversely, the NNRTIs and PIE12, but not TDF or MVC, were effectively transferred from ex vivo treated explants and protected co-cultured T cells. Biopsies obtained from IQP-0528 ring-treated macaques also protected co-cultured T cells with viral inhibition ranging from 42-72%. Antiviral activity correlated with the concentration of drug recovered. Combinations of TDF with IQP-0528 protected in both in vitro models.

Conclusions

Together, these models suggest that intracellularly retained drugs such as TDF may protect resident immune cells following coitus but sustained delivery may be required to protect immune cells subsequently recruited into the genital tract. Sustained delivery may also be critical for NNRTIs, which are rapidly transported out of cells and could be lost following sexual intercourse. An ideal approach may be a combination of drugs with complementary bioavailability profiles formulated for sustained delivery.

Intravaginal ring eluting tenofovir disoproxil fumarate completely protects macaques from multiple vaginal simian-HIV challenges

Topical preexposure prophylaxis interrupts HIV transmission at the site of mucosal exposure. Intermittently dosed vaginal gels containing the HIV-1 reverse transcriptase inhibitor tenofovir protected pigtailed macaques depending on the timing of viral challenge relative to gel application. However, modest or no protection was observed in clinical trials. Intravaginal rings (IVRs) may improve efficacy by providing long-term sustained drug delivery leading to constant mucosal antiretroviral concentrations and enhancing adherence. Although a few IVRs have entered the clinical pipeline, 100% efficacy in a repeated macaque vaginal challenge model has not been achieved. Here we describe a reservoir IVR technology that delivers the tenofovir prodrug tenofovir disoproxil fumarate (TDF) continuously over 28 d. With four monthly ring changes in this repeated challenge model, TDF IVRs generated reproducible and protective drug levels. All TDF IVR-treated macaques (n = 6) remained seronegative and simian-HIV RNA negative after 16 weekly vaginal exposures to 50 tissue culture infectious dose SHIV162p3. In contrast, 11/12 control macaques became infected, with a median of four exposures assuming an eclipse of 7 d from infection to virus RNA detection. Protection was associated with tenofovir levels in vaginal fluid [mean 1.8 × 10(5) ng/mL (range 1.1 × 10(4) to 6.6 × 10(5) ng/mL)] and ex vivo antiviral activity of cervicovaginal lavage samples. These observations support further advancement of TDF IVRs as well as the concept that extended duration drug delivery devices delivering topical antiretrovirals could be effective tools in preventing the sexual transmission of HIV in humans.

Microbicides: topical prevention against HIV

Microbicides represent a potential intervention strategy for preventing HIV transmission. Vaginal microbicides would meet the need for a discreet method that women could use to protect themselves against HIV. Although early-generation microbicides failed to demonstrate efficacy, newer candidates are based on more potent antiretroviral (ARV) products. Positive data from the CAPRISA 004 trial of tenofovir gel support use in women and represent a turning point for the field. This article reviews current progress in development of ARV-based microbicides. We discuss the consensus on selection criteria, the potential for drug resistance, rationale for drug combinations, and the use of pharmacokinetic (PK)/pharmacodynamic (PD) assessment in product development. The urgent need for continued progress in development of formulations for sustained delivery is emphasized. Finally, as the boundaries between different prevention technologies become increasingly blurred, consideration is given to the potential synergy of diverse approaches across the prevention landscape.

Development of sulphated and naphthylsulphonated carbosilane dendrimers as topical microbicides to prevent HIV-1 sexual transmission

OBJECTIVES

For the last 20 years, the idea of alternative prevention strategies based on the use of topical vaginally products to inhibit HIV-1 infection in women has been established. The concept of a 'microbicide' product has been born out of the unavailability of a vaccine against HIV-1 and the problems of women in negotiating the use of preventive prophylaxis by their partners, especially in developing countries.

DESIGN

We have developed and evaluated polyanionic carbosilane dendrimers G3-S16 and G2-NF16 with sulphated and naphthylsulphonated end groups as nonspecific microbicides.

METHODS

Cellular in-vitro or in-vivo models were used to evaluate the safety, biocompatibility and anti-HIV ability of two polyanionic carbosilane dendrimers.

RESULTS

Both dendrimers showed high biosafety in human epithelial cell lines derived from uterus and vagina and in primary blood human cells (PBMC). These dendrimers not only have a partial capacity to block the entry of different X4 and R5 HIV-1 isolates inside epithelial cells but protect the epithelial monolayer from cell disruption and also reduce HIV-1 infection of activated PBMC. Additionally, treatment of epithelial cells with G3-S16 or G2-NF16 dendrimers did not produce changes in proinflammatory cytokines profile, in proliferation of PBMC, on microbiota or sperm survival. Finally, no irritation or vaginal lesions were detected in female CD1(ICR) mice after dendrimers vaginal administration.

CONCLUSION

These interesting results suggest that G3-S16 or G2-NF16 could be effective to inhibit HIV infection and transmission within genital mucosa as well as the spread of HIV transmission to human PBMC.

Griffithsin protects mice from genital herpes by preventing cell-to-cell spread

Griffithsin, which binds N-linked glycans on gp120 to prevent HIV entry, has the most potent HIV-1 inhibitory activity described for any antiviral lectin and is being developed for topical preexposure prophylaxis. The current studies were designed to further assess its potential by exploring its activity against herpes simplex virus 2 (HSV-2), a cofactor for HIV acquisition, in vitro and in a murine model. Safety was evaluated by examining its impact on epithelial barrier integrity in polarized cultures and testing whether repeated intravaginal dosing potentiates the susceptibility of mice to genital herpes. Griffithsin displayed modest inhibitory activity against HSV-2 if present during viral entry but completely blocked plaque formation if present postentry, reduced plaque size, and prevented cell-to-cell spread. These in vitro findings translated to significant protection against genital herpes in mice treated with 0.1% griffithsin gel. Griffithsin, but not placebo gel, prevented viral spread (visualized with a luciferase-expressing virus), significantly reduced disease scores, and resulted in greater survival (P < 0.05, log rank test). Protection persisted when HSV-2 was introduced in seminal plasma. Although griffithsin triggered a small decline in transepithelial electrical resistance in polarized cultures, this did not translate to any significant increase in the ability of HIV to migrate from the apical to the basolateral chamber nor to an increase in susceptibility to HSV-2 in mice treated with griffithsin gel for 7 days. These findings demonstrate that griffithsin inhibits HSV-2 by a unique mechanism of blocking cell-to-cell spread and support its further development for HIV and HSV-2 prevention.

From the laboratory to clinical trials and back again: lessons learned from HIV prevention trials

PROBLEM

Inadequate, irrelevant, or inappropriate timing of biological specimen collection during clinical trials is a cause for delay in understanding and explaining correlates of protection and/or effectiveness, particularly at the portal of entry in the context of sexual HIV transmission and its prevention.

METHODS

We present examples of HIV prevention trials to illustrate the impact of preplanned versus unplanned laboratory science program on the interpretation of trial results and advancement of the field.

RESULTS

Of the five completed pre-exposure prophylaxis trials, only two announced main outcome results simultaneously with data on correlates of drug-related effectiveness. In four of the vaccine trials completed, the only one that showed a protective effect presented data on protection correlates significantly later.

CONCLUSION

Clinical trials must preplan collaborative immunophysiological research and prioritize biological specimen collection and storage for enhancement of research on correlates of protection. Similarly appropriate specimens should be prioritized for pathogenesis research.

A perspective on progress and gaps in HIV prevention science

In the past few years, the transdisciplinary field of HIV prevention has reached several milestones. Topically applied tenofovir gel provided significant protection from sexual transmission of HIV in a large-scale clinical trial and oral Truvada (emtricitabine/tenofovir disoproxil fumarate) was recently approved for preexposure prophylaxis (PrEP) following two successful clinical trials in men and women. These achievements are tempered by the disappointing results of other clinical trials, which highlight the complexities of prevention research. In this perspective, we discuss scientific and developmental gaps for topical chemoprophylaxis of the sexual transmission of HIV, which depends on the complex interactions between the pharmacokinetics and pharmacodynamics of drugs, formulation and delivery systems, anatomic site of transmission, and host mucosal immune defenses. Despite the considerable time and resources devoted to unraveling the initial steps in sexual transmission of HIV, current knowledge is based on animal models and human explanted tissue, which may not fully recapitulate what happens clinically. Understanding these events, including the role that sex hormones, semen, and mucosal secretions play in transmission, and the interplay between innate immunity, the mucosal environment, and drug efficacy is paramount. This drives some of the most pressing questions in the field.

The safety, persistence, and acceptability of an antiretroviral microbicide candidate UC781

OBJECTIVE

: To evaluate the persistence and acceptability of a minimally absorbed vaginal gel antiretroviral designed to block the acquisition of HIV.

METHODS

: Sixty healthy women aged 18-45 participated in a phase-1 randomized placebo-controlled trial of a vaginal gel containing the nonnucleoside reverse transcriptase inhibitor UC781. Women underwent a single timed exposure ranging from 0 to 8 hours and were followed for 35 days. Safety was assessed by symptoms, physical exam, laboratory evaluation, and colposcopy. Persistence was assessed by drug levels in cervicovaginal lavage (CVL) and vaginal swab specimens.

RESULTS

: The participants' mean age was 26 years; 77% were white. The most frequently reported adverse events were genitourinary; however, the placebo and UC781 arms had a similar distribution of mild and moderate genitourinary events. All colposcopic findings were superficial. Measuring systemic UC781 levels in the plasma revealed that 2 (5%) women in the UC781 gel group had detectable UC781; however, the amount was below the limits of quantification (2.5 ng/mL) in both participants. UC781 was detected in 37 of 40 CVL samples obtained 1-2 days after drug exposure and initial CVL; the median level of UC781 was 4965 pmol/mL, significantly higher than the known IC50 of 10 pmol/mL. Eighty percent of participants reported that they would use the product if it were found to be protective against HIV.

CONCLUSION

: In this population of HIV-uninfected women, the gel was well tolerated and acceptable. Active levels of drug were detected in CVL and vaginal swab specimens at 1-2 days at concentrations supporting the role for daily dosing.

Controlled-release vaginal ring drug-delivery systems: a key strategy for the development of effective HIV microbicides

BACKGROUND

Over half of all HIV-infected adults are women and heterosexual intercourse is a significant mode of viral transmission. This review examines the potential for using polymeric vaginal ring systems to provide controlled delivery of HIV microbicides in order to prevent heterosexual transmission of the virus.

DISCUSSION

Continuous delivery of microbicides has the potential to be more effective than one-off dosing. Thus, controlled-release vaginal delivery devices are now a key area of HIV prevention research. Initial clinical trials on vaginal rings loaded with dapivirine (a candidate microbicide) have indicated that these products are safe and well tolerated by women. These devices are female-initiated, robust and capable of long-term delivery of the active agent.

CONCLUSIONS

Vaginal rings may offer an effective system for the controlled delivery of microbicides to prevent heterosexual transmission of HIV. Candidate vaginal ring microbicide products are now in clinical trials.

Factors Important to the Prioritization and Development of Successful Topical Microbicides for HIV-1

Significant advancements in topical microbicide development have occurred since the prevention strategy was first described as a means to inhibit the sexual transmission of HIV-1. The lack of clinical efficacy of the first generation microbicide products has focused development attention on specific antiretroviral agents, and these agents have proven partially successful in human clinical trials. With greater understanding of vaginal and rectal virus infection, replication, and dissemination, better microbicide products and delivery strategies should result in products with enhanced potency. However, a variety of development gaps exist which relate to product dosing, formulation and delivery, and pharmacokinetics and pharmacodynamics which must be better understood in order to prioritize microbicide products for clinical development. In vitro, ex vivo, and in vivo models must be optimized with regard to these development gaps in order to put the right product at the right place, at the right time, and at the right concentration for effective inhibition of virus transmission. As the microbicide field continues to evolve, we must harness the knowledge gained from unsuccessful and successful clinical trials and development programs to continuously enhance our preclinical development algorithms.

In vitro anti-HIV-1 activity in cervicovaginal secretions from pregnant and nonpregnant women

OBJECTIVE

To evaluate whether cervicovaginal secretions inhibit HIV-1 infectivity in an in vitro model, and estimate concentration of immune mediators.

STUDY DESIGN

We enrolled midtrimester pregnant and regularly menstruating (nonpregnant) women. Cervicovaginal lavage was collected at 2 visits and incubated with HIV-1 and TZM-bl cells. Infectivity was compared with positive controls. Concentrations of immune mediators were compared between groups.

RESULTS

At enrollment, cervicovaginal lavage inhibited IIIB virus 88.2% and 82.4%, and BaL virus 72.8% and 77.9%, among pregnant (n = 13) and nonpregnant women (n = 9), respectively. At second visit, cervicovaginal lavage inhibited IIIB 89.7% and 82.5%, and BaL 77.4% and 69.9% among pregnant (n = 15) and nonpregnant women (n = 8), respectively (all P ≤ .04). Adjusting for body mass index, race, and protein content of cervicovaginal lavage, antimicrobials were suppressed but cytokines and chemokines were not markedly different in pregnancy.

CONCLUSION

Cervicovaginal secretions significantly suppress HIV-1 infectivity in this model. Concentrations of certain immune mediators are altered in pregnancy.

UC781 microbicide gel retains anti-HIV activity in cervicovaginal lavage fluids collected following twice-daily vaginal application

The potent nonnucleoside reverse transcriptase inhibitor UC781 has been safety tested as a vaginal microbicide gel formulation for prevention of HIV-1 sexual transmission. To investigate whether UC781 retained anti-infective activity following exposure to the female genital tract, we conducted an ex vivo analysis of the UC781 levels and antiviral activity in cervicovaginal lavage (CVL) fluids from 25 Thai women enrolled in a 14-day safety trial of twice-daily vaginal application of two concentrations of the UC781 microbicide gel. CVL samples were collected from women in the 0.1% (n = 5), 0.25% (n = 15), and placebo (n = 5) gel arms following the first application of gel (T(15 min)) and 8 to 24 h after the final application (T(8-24 h)) and separated into cell-free (CVL-s) and pelletable (CVL-p) fractions. As UC781 is highly hydrophobic, there were significantly higher levels of UC781 in the CVL-p samples than in the CVL-s samples for the UC781 gel arms. In T(8-24 h) CVL-p samples, 2/5 and 13/15 samples collected from the 0.1% and 0.25% UC781 gel arms, respectively, efficiently blocked infection with ≥ 4 log(10) 50% tissue culture infective dose (TCID(50)) of a CCR5-tropic CRF01_AE HIV-1 virus stock. Independent of the arm, the 11 CVL-p samples with UC781 levels of ≥ 5 μg/CVL sample reduced infectious HIV by ≥ 4 log(10) TCID(50). Our results suggest that the levels and anti-infective activities of UC781 gel formulations are likely to be associated with a cellular or pelletable component in CVL samples. Therefore, cellular and pelletable fractions should be assayed for drug levels and anti-infective activity in preclinical studies of candidate microbicides.

Advances in HIV microbicide development

There is an urgent need control the spread of the global HIV pandemic. A microbicide, or topical drug applied to the mucosal environment to block transmission, is a promising HIV prevention strategy. The development of a safe and efficacious microbicide requires a thorough understanding of the mucosal environment and its role in HIV transmission. Knowledge of the key events in viral infection identifies points at which the virus might be most effectively targeted by a microbicide. The cervicovaginal and rectal mucosa play an important role in the innate defense against HIV, and microbicides must not interfere with these functions. In this review, we discuss the current research on HIV microbicide development.

Bridging the gap between preclinical and clinical microbicide trials: blind evaluation of candidate gels in murine models of efficacy and safety

Background

Despite significant protection in preclinical studies, cellulose sulfate (CS) failed to protect women against HIV-1/2 and was associated with a trend toward increased HIV-1 acquisition in one of the clinical trials. These results highlight the need for preclinical tests more predictive of clinical outcomes. The objective of this study was to test coded vaginal gels, including CS, in murine models of safety and efficacy to determine the models' utility for evaluating future products.

Methods

Four coded formulations, including 6% CS, 2% PRO 2000 and two placebo gels, were administered intravaginally to medroxyprogesterone-treated mice and their ability to prevent genital herpes (efficacy) or to alter the susceptibility to low dose HSV challenge (safety) was determined. Nonoyxnol-9 served as a positive toxicity control.

Results

CS and PRO 2000 significantly protected mice from genital herpes following infection with a laboratory or clinical isolate of HSV-2 introduced in buffer (p<0.001). However, protection was reduced when virus was introduced in seminal plasma. Moreover, mice were significantly more susceptible to infection with low doses of HSV-2 when challenged 12 h after the 7th daily dose of CS or nonoxynol-9 (p<0.05). The increased susceptibility was associated with alterations in epithelial architecture.

Conclusions

CS prevented genital herpes when present at the time of viral challenge, but increased the rate of infection when gel was applied daily for 7 days with a vaginal wash prior to viral inoculation. The findings presumably reflect altered epithelial architecture, which may have contributed to the trend towards increased HIV observed clinically.

SPL7013 Gel (VivaGel®) retains potent HIV-1 and HSV-2 inhibitory activity following vaginal administration in humans

SPL7013 Gel (VivaGel^®) is a microbicide in development for prevention of HIV and HSV. This clinical study assessed retention and duration of antiviral activity following vaginal administration of 3% SPL7013 Gel in healthy women. Participants received 5 single doses of product with ≥5 days between doses. A cervicovaginal fluid (CVF) sample was collected using a SoftCup™ pre-dose, and immediately, or 1, 3, 12 or 24 h post-dose. HIV-1 and HSV-2 antiviral activities of CVF samples were determined in cell culture assays. Antiviral activity in the presence of seminal plasma was also tested. Mass and concentration of SPL7013 in CVF samples was determined. Safety was assessed by reporting of adverse events. Statistical analysis was performed using the Wilcoxon signed-rank test with Bonferroni adjustment; p≤0.003 was significant. Eleven participants completed the study. Inhibition of HIV-1 and HSV-2 by pre-dose CVF samples was negligible. CVF samples obtained immediately after dosing almost completely inhibited (median, interquartile range) HIV-1 [96% (95,97)] and HSV-2 [86% (85,94)], and activity was maintained in all women at 3 h (HIV-1 [96% (95,98), p = 0.9]; HSV-2 [94% (91,97), p = 0.005]). At 24 h, >90% of initial HIV-1 and HSV-2 inhibition was maintained in 6/11 women. SPL7013 was recovered in CVF samples obtained at baseline (46% of 105 mg dose). At 3 and 24 h, 22 mg and 4 mg SPL7013, respectively, were recovered. More than 70% inhibition of HIV-1 and HSV-2 was observed if there was >0.5 mg SPL7013 in CVF samples. High levels of antiviral activity were retained in the presence of seminal plasma. VivaGel was well tolerated with no signs or symptoms of vaginal, vulvar or cervical irritation reported. Potent antiviral activity was observed against HIV-1 and HSV-2 immediately following vaginal administration of VivaGel, with activity maintained for at least 3 h post-dose. The data provide evidence of antiviral activity in a clinical setting, and suggest VivaGel could be administered up to 3 h before coitus.

Topical prophylaxis for HIV prevention in women: becoming a reality

Strategies to protect against sexual transmission of HIV include the development of products formulated for topical application, which limit the toxicities associated with systemic oral pre-exposure prophylaxis. Following several clinical trial failures, attention is now focused on antiretroviral (ARV) agents. Highly potent ARV topical formulations provide a female-controlled, targeted, and feasible option for HIV prevention. A recently completed tenofovir gel trial was the first to demonstrate significant protection against HIV acquisition. Topical ARVs have the advantage of delivering high concentration of drug at the site of transmission of HIV, with low systemic absorption. Sustained-release formulations, such as intravaginal rings, will likely improve adherence and can be designed to provide controlled and continuous delivery of ARV combinations. Further studies to test alternative dosing strategies and pharmacokinetic/pharmacodynamic relationships in the genital tract will provide valuable information as the field strives to improve upon the promising tenofovir gel trial results.

Performance of swabs, lavage, and diluents to quantify biomarkers of female genital tract soluble mucosal mediators

Background

Measurement of immune mediators and antimicrobial activity in female genital tract secretions may provide biomarkers predictive of risk for HIV-1 acquisition and surrogate markers of microbicide safety. However, optimal methods for sample collection do not exist. This study compared collection methods.

Methods

Secretions were collected from 48 women (24 with bacterial vaginosis [BV]) using vaginal and endocervical Dacron and flocked swabs. Cervicovaginal lavage (CVL) was collected with 10 mL of Normosol-R (n = 20), saline (n = 14), or water (n = 14). The concentration of gluconate in Normosol-R CVL was determined to estimate the dilution factor. Cytokine and antimicrobial mediators were measured by Luminex or ELISA and corrected for protein content. Endogenous anti-HIV-1 and anti-E. coli activity were measured by TZM-bl assay or E. coli growth.

Results

Higher concentrations of protein were recovered by CVL, despite a 10-fold dilution of secretions, as compared to swab eluents. After protein correction, endocervical swabs recovered the highest mediator levels regardless of BV status. Endocervical and vaginal flocked swabs recovered significantly higher levels of anti-HIV-1 and anti-E. coli activity than Dacron swabs (P<0.001). BV had a significant effect on CVL mediator recovery. Normosol-R tended to recover higher levels of most mediators among women with BV, whereas saline or water tended to recover higher levels among women without BV. Saline recovered the highest levels of anti-HIV-1 activity regardless of BV status.

Conclusions

Endocervical swabs and CVL collected with saline provide the best recovery of most mediators and would be the optimal sampling method(s) for clinical trials.

HIV transmission: time for translational studies to bridge the gap

More than 7000 new HIV infections are documented each day worldwide. In this Perspective, we dissect new results from a large clinical trial showing that genital and plasma HIV-1 RNA loads predict the risk of heterosexual transmission and that genital tract viral RNA load does so independently of plasma viral load. Furthermore, beyond its defined study end points, this well-conducted trial identified new research directions that should be pursued in smaller intensive basic and translational studies.

Enhancement of HIV-1 infectivity by simple, self-assembling modular peptides

Semen-derived enhancer of viral infection (SEVI), an amyloid fibril formed from a cationic peptide fragment of prostatic acidic phosphatase (PAP), dramatically enhances the infectivity of human immunodeficiency virus type 1 (HIV-1). Insoluble, sedimentable fibrils contribute to SEVI-mediated enhancement of virus infection. However, the SEVI-forming PAP(248-286) peptide is able to produce infection-enhancing structures much more quickly than it forms amyloid fibrils. This suggests that soluble supramolecular assemblies may enhance HIV-1 infection. To address this question, non-SEVI amyloid-like fibrils were derived from general amphipathic peptides of sequence Ac-K(n)(XKXE)(2)-NH(2). These cationic peptides efficiently self-assembled to form soluble, fibril-like structures that were, in some cases, able to enhance HIV-1 infection even more efficiently than SEVI. Experiments were also performed to determine whether agents that efficiently shield the charged surface of SEVI fibrils block SEVI-mediated infection-enhancement. To do this, we generated self-assembling anionic peptides of sequence Ac-E(n)(XKXE)(2)-NH(2). One of these peptides completely abrogated SEVI-mediated enhancement of HIV-1 infection, without altering HIV-1 infectivity in the absence of SEVI. Collectively, these data suggest that soluble SEVI assemblies may mediate infection-enhancement, and that anionic peptide supramolecular assemblies have the potential to act as anti-SEVI microbicides.

Topical microbicides to prevent the transmission of HIV: formulation gaps and challenges

The efforts of the topical microbicide field to identify a safe and effective topical microbicide were realized in July of 2010 with the reporting of the results of the Centre for the AIDS Programme of Research in South Africa 004 trial. In this trial, a 1% tenofovir gel was found to reduce women's risk for HIV acquisition by 39% compared to placebo. To understand the impact of this trial on future microbicide development, we must view it from the historical perspective of previous phases 2 and 3 clinical trials with detergents and sulfated polyanions. This knowledge and emerging information must then be parlayed into the next steps needed to create a safe, effective, and acceptable topical microbicide. This review will look at the lessons learned from preclinical and clinical development of topical microbicides, focusing on two significant future challenges: (1) topical microbicide formulation safety and (2) the critical role that adherence to product use has in determining safety and efficacy in clinical trials and ultimately commercial viability of the licensed product. In addition to framing these issues within our current understanding of formulation and prevention of HIV acquisition, recent advances in our understanding of the mechanism of HIV transmission and how it informs on future formulation strategies will be briefly discussed.

The rise and fall of polyanionic inhibitors of the human immunodeficiency virus type 1

Infection by the human immunodeficiency virus type 1 (HIV-1) is an ordered, multistep process involving binding and entry, reverse transcription, integration, viral gene transcription, translation, processing, and finally assembly. Numerous therapeutic and preventive compounds, which are currently available for clinical use or are under preclinical and clinical development, act on at least one of these steps. Polyanionic HIV-1 inhibitors comprise a family of compounds that are generally considered entry inhibitors. The main mechanism of anti-HIV-1 activity associated with these compounds involves electrostatic interactions with HIV-1 glycoprotein 120 that ultimately prevent binding of the virus to target cells. A number of these compounds have been considered for systemic use and for use as microbicides, which are products designed to prevent sexual HIV-1 transmission. These compounds have been studied extensively using in vitro assays of activity, cytotoxicity, and mechanism of action, ex vivo models of HIV-1 transmission, and animal models of in vivo efficacy and toxicity. Three of these polyanionic compounds - cellulose sulfate, carrageenan, and PRO 2000 - were advanced into clinical trials of microbicide safety and efficacy. Although phase I and phase II clinical trials showed these compounds to be safe and well tolerated, none of the phase III trials provided any evidence that these compounds were effective against heterosexual HIV-1 transmission. Furthermore, clinical and in vitro results suggest enhancement of HIV-1 infection in the presence of polyanionic compounds. We discuss the preclinical development of polyanionic HIV-1 inhibitors, the clinical trials of polyanionic compounds used systemically and as topical vaginal microbicides, and the prospects for the future development of these compounds as inhibitors of HIV-1 infection.

A randomized trial to assess anti-HIV activity in female genital tract secretions and soluble mucosal immunity following application of 1% tenofovir gel

Background

Preclinical and early phase clinical microbicide studies have not consistently predicted the outcome of efficacy trials. To address this gap, candidate biomarkers of microbicide pharmacodynamics and safety were evaluated in a double-blind, placebo-controlled trial of tenofovir gel, the first microbicide to demonstrate significant protection against HIV acquisition.

Methods

30 women were randomized to apply a single daily dose of tenofovir or placebo gel for 14 consecutive days. Anti-HIV activity was measured in cervicovaginal lavage (CVL) on Days 0, 3, 7, 14 and 21 by luciferase assay as a surrogate marker of pharmacodynamics. Endogenous activity against E. coli and HSV-2 and concentrations of immune mediators were quantified in CVL as candidate biomarkers of safety. Tenofovir levels were measured in CVL and blood.

Results

A significant increase in anti-HIV activity was detected in CVL from women who applied tenofovir gel compared to their endogenous anti-HIV activity in genital tract secretions on Day 0 and compared to activity in CVL from women in the placebo group. The activity correlated significantly with CVL concentration of tenofovir (r = 0.6, p<0.001) and fit a sigmoid E_max pharmacodynamic model. Anti-HIV activity in CVL from women who applied tenofovir persisted when virus was introduced in semen, whereas endogenous anti-HIV activity decreased. Tenofovir did not trigger an inflammatory response or induce sustained loss in endogenous antimicrobial activity or immune mediators.

Conclusions

Tenofovir gel had no deleterious impact on soluble mucosal immunity. The increased anti-HIV activity in CVL, which persisted in the presence of semen and correlated with tenofovir concentration, is consistent with the efficacy observed in a recent clinical trial. These results promote quantified CVL anti-HIV activity as a surrogate of tissue pharmacodynamics and as a potential biomarker of adherence to product. This simple, feasible and inexpensive bioassay may promote the development of models more predictive of microbicide efficacy.

Trial Registration

ClinicalTrials.gov NCT00594373

Clinical parameters essential to methodology and interpretation of mucosal responses

Research aimed at putting an end to the HIV pandemic is dynamic given the marked advances in understanding of pathogenesis since its origin. Attention has shifted from systemic management of disease to a focus on the most common site of acquisition, the female genital tract. Research on the female genital tract of humans requires consideration of a number of specific clinical parameters. If such parameters are not considered when enrolling subjects into studies, it could lead to faulty data ascertainment. This article reviews important clinical characteristics to consider when conducting studies of the human female genital tract in regard to mucosal immunity and HIV disease. Important topics to consider include the method and source of sample collection, the individual patient characteristics, and in the case of recruitment of HIV-infected women, HIV disease characteristics.