The development of rectal microbicides for HIV prevention

A conjoint experiment of three placebo rectal products used with receptive anal sex: results from MTN-035

INTRODUCTION

End-user perspectives are vital to the design of new biomedical HIV prevention products. Conjoint analysis can support the integration of end-user perspectives by examining their preferences of potential pre-exposure prophylaxis (PrEP) products. The Microbicides Trial Network (MTN) 035 protocol examined three placebo rectal dosage forms (insert, enema and suppository) that could deliver PrEP prior to receptive anal sex (RAS).

METHODS

Between April 2019 and July 2020, we enrolled 217 HIV-negative, cisgender men who have sex with men (MSM; n = 172; 79.3%) and transgender people (n = 47; 20.7%) ages 18-35 into a randomized cross-over trial across Malawi, Peru, South Africa, Thailand and the United States. Participants used each product prior to RAS over 4-week periods. Participants completed a conjoint experiment where they selected between random profiles using seven features (dosage form, timing of use before sex, side effects, duration of protection, effectiveness, frequency of use and need for a prescription).

RESULTS

Effectiveness was the strongest determinant of choice (30.4%), followed by modality (18.0%), potential side effects (17.2%), frequency of use (10.8%), duration of protection (10.4%), timing of use before sex (7.4%) and need for a prescription (5.9%). Relative utility scores indicated that the most desirable combination of attributes was a product with 95% efficacy, used 30 minutes before sex, offering a 3- to 5-day protection window, used weekly, having no side effects, in the form of an enema and available over-the-counter.

CONCLUSIONS

Choice in next-generation PrEP products is highly desired by MSM and transgender people, as no one-size-fits-all approach satisfies all the preferences. MTN-035 participants weighed product features differently, recognizing the need for diverse, behaviourally congruent biomedical options that fit the needs of intended end-users.

A latent trajectory analysis of young sexual and gender minorities' adherence to three rectal microbicide placebo formulations (MTN-035; a randomized crossover trial)

BACKGROUND

Rectal microbicides (RM) are biomedical HIV prevention products that aim to prevent or reduce the transmission of HIV and other sexually transmitted infections (STIs). RM modalities may be beneficial for populations who have complex lifestyles, difficulties adhering to pre-exposure prophylaxis (PrEP) regimens, and/or have limited access to care. MTN-035 (DESIRE; Developing and Evaluating Short-Acting Innovations for Rectal Use), a randomized crossover trial, aimed to evaluate the safety and acceptability of, and adherence to, three placebo RM modalities (douche, insert, and suppository) prior to receptive anal intercourse.

METHODS

We conducted latent trajectory analysis to identify clusters of individuals who shared similar trajectories in acceptability and adherence for each product (douche, insert, and suppository) over time. We analyzed weekly short messaging service (SMS) use reports for each modality as reported by enrolled sexual and gender minority (SGM) participants.

RESULTS

Two trajectories for each product were identified: a "protocol compliant" trajectory (i.e., at least one product use occasion per week) and "high use" trajectory (i.e., more than three product use occasions per week). Participants with high use were more likely to lack access to PrEP and have higher intentions to utilize RM modalities compared to those who were protocol compliant.

CONCLUSIONS

This study highlighted high adherence to RM modalities among SGM. As research into viable HIV prevention modalities continues to evolve, tailored intervention strategies are needed to support the uptake of and adherence to alternative prevention modalities that are behaviorally congruent with targeted users.

TRIAL REGISTRATION

NCT03671239 (14/09/2018).

A randomized trial of safety, acceptability and adherence of three rectal microbicide placebo formulations among young sexual and gender minorities who engage in receptive anal intercourse (MTN-035)

Efforts to develop a range of HIV prevention products that can serve as behaviorally congruent viable alternatives to consistent condom use and oral pre-exposure prophylaxis (PrEP) remain crucial. MTN-035 was a randomized crossover trial seeking to evaluate the safety, acceptability, and adherence to three placebo modalities (insert, suppository, enema) prior to receptive anal intercourse (RAI). If participants had no RAI in a week, they were asked to use their assigned product without sex. We hypothesized that the modalities would be acceptable and safe for use prior to RAI, and that participants would report high adherence given their behavioral congruence with cleansing practices (e.g., douches and/or enemas) and their existing use to deliver medications (e.g., suppositories; fast-dissolving inserts) via the rectum. Participants (N = 217) were sexual and gender minorities enrolled in five different countries (Malawi, Peru, South Africa, Thailand, and the United States of America). Mean age was 24.9 years (range 18-35 years). 204 adverse events were reported by 98 participants (45.2%); 37 (18.1%) were deemed related to the study products. The proportion of participants reporting "high acceptability" was 72% (95%CI: 65% - 78%) for inserts, 66% (95%CI: 59% - 73%) for suppositories, and 73% (95%CI: 66% - 79%) for enemas. The proportion of participants reporting fully adherent per protocol (i.e., at least one use per week) was 75% (95%CI: 69% - 81%) for inserts, 74% (95%CI: 68% - 80%) for suppositories, and 83% (95%CI: 77% - 88%) for enemas. Participants fully adherent per RAI-act was similar among the three products: insert (n = 99; 58.9%), suppository (n = 101; 58.0%) and enema (n = 107; 58.8%). The efficacy and effectiveness of emerging HIV prevention drug depends on safe and acceptable delivery modalities that are easy to use consistently. Our findings demonstrate the safety and acceptability of, and adherence to, enemas, inserts, and suppositories as potential modalities through which to deliver a rectal microbicide.

Acceptability of PC-1005 Gel Administered Rectally to HIV-1 Seronegative Adults at Three Different Volume Levels (MTN-037)

Multipurpose prevention technologies (MPT) have been increasingly researched for their dual-purpose preventative properties against HIV and other STIs. The acceptability of PC-1005, a topical MPT candidate, was explored among men and women participating in the MTN-037 Phase I trial at two U.S. sites (Pittsburgh, PA, and Birmingham, AL). We triangulated quantitative and qualitative assessments of the acceptability of three volumes (4 mL, 16 mL, 32 mL) of PC-1005 administered rectally (N = 12; 6 males, 6 females). Participants rated overall gel acceptability on a scale of 1-10, with a median of 7.17 (SD = 2.04) and had positive feelings about all three dose volumes, citing them to be very comfortable or comfortable (dose 1 = 91.7%; dose 2 = 91.7%; dose 3 = 83.3%). High acceptability of and comfort with all three dose volumes shows promise for PC-1005 as an MPT to prevent HIV and STIs, warranting future clinical development.

Acceptability of a Dapivirine/Placebo Gel Administered Rectally to HIV-1 Seronegative Adults (MTN-026)

This study describes the acceptability of a rectal microbicide gel formulation using dapivirine (DPV) among men and women from two countries (United States and Thailand) participating in the Microbicide Trials Network-026 trial. We evaluated participants' acceptability of a rectal DPV/placebo gel as part of a Phase I trial (N = 26; 18 male, 8 female). Participants reported favorable acceptability of the study gel, with most participants reporting that they liked the gel the same (n = 14; 53.8%) or more (n = 11; 42.4%) than when they started the trial. Over half of participants noted that they would prefer the gel over condoms (n = 13; 50%) or that they liked condoms and the gel equally (n = 8; 30.8%). Side effects across products included leakage (n = 8; 30.8%), diarrhea (n = 4; 15.4%), or soiling (n = 1; 3.8%). The high acceptability of a rectal gel underscores its promise as a short-acting biomedical prevention, warranting future research for HIV prevention.Trial Registration: NCT03239483.

Acceptability of a Dapivirine Gel Administered Rectally to HIV-1 Seronegative Adults (MTN-033 Study)

We triangulated quantitative and qualitative assessments to evaluate participants' acceptability of 0.05% dapivirine rectal microbicide (RM) gel administered via two separate modalities (a rectal applicator and an artificial phallus for use as a coital simulation device) as part of a Phase I trial (N = 14) among men who have sex with men (MSM) randomized using a 1:1 ratio. Overall, participants reported favorable acceptability of the gel (n = 11; 78.6%), the same or more at the end of the study compared to when they started the study. Additionally, when discussing their preferred administration modality, they noted that both methods had positive qualities but also potential areas of improvement. Our findings underscore the need to create multiple delivery methods for a future microbicide gel (i.e., with and without the need for an applicator) and highlight the importance of offering MSM choices in how biomedical HIV prevention strategies are delivered.

Prevalence and correlates of anal intercourse among female sex workers in eSwatini

INTRODUCTION

As HIV is very effectively acquired during condomless receptive anal intercourse (AI) with serodiscordant and viremic partners, the practice could contribute to the high prevalence among female sex workers (FSW) in eSwatini (formerly known as Swaziland). We aim to estimate the proportion reporting AI (AI prevalence) among Swazi FSW and to identify the correlates of AI practice in order to better inform HIV prevention interventions among this population.

METHODS

Using respondent-driven sampling (RDS), 325 Swazi FSW were recruited in 2011. We estimated the prevalence of AI and AI with inconsistent condom use in the past month with any partner type, and inconsistent condom use during AI and vaginal intercourse (VI) by partner type. Univariate and multivariable logistic regression models were used to identify behavioural and structural correlates associated with AI and AI with inconsistent condom use.

RESULTS

RDS-adjusted prevalence of AI and AI with inconsistent condom use was high, at 44%[95% confidence interval (95%CI):35-53%]) and 34%[95%CI:26-42%], respectively and did not vary by partner type. HIV prevalence was high in this sample of FSW (70%), but knowledge that AI increases HIV acquisition risk low, with only 10% identifying AI as the riskiest sex act. Those who reported AI were more likely to be better educated (adjusted odds ratio(aOR) = 1.92[95%CI:1.03-3.57]), to have grown up in rural areas (aOR = 1.90[95%CI:1.09-3.32]), have fewer new clients in the past month (aOR = 0.33[95%CI:0.16-0.68]), and for last sex with clients to be condomless (aOR = 2.09[95%CI:1.07-4.08]). Although FSW reporting AI in past month were more likely to have been raped (aOR = 1.95[95%CI:1.05-3.65]) and harassed because of being a sex worker (aOR = 2.09[95%CI:1.16-3.74]), they were also less likely to have ever been blackmailed (aOR = 0.50[95%CI:0.25-0.98]) or been afraid to walk in public places (aOR = 0.46[95%CI:0.25-0.87]). Correlates of AI with inconsistent condom use were similar to those of AI.

CONCLUSIONS

AI is commonly practised and condom use is inconsistent among Swazi FSW. Sex act data are needed to determine how frequently AI is practiced. Interventions to address barriers to condom use are needed, as are biomedical interventions that reduce acquisition risk during AI.

HIV incidence among gay men and other men who have sex with men in 2020: where is the epidemic heading?

The goal to effectively prevent new HIV infections among gay, bisexual, and other men who have sex with men (MSM) is more challenging now than ever before. Despite declines in the late 1990s and early 2000s, HIV incidence among MSM is now increasing in many low- and high-income settings including the US, with young, adolescent, and racial/ethnic minority MSM being among those at highest risk. Potentiating HIV risks across all settings are individual-, network-, and structural-level factors such as stigma and lack of access to pre-exposure prophylaxis (PrEP) and antiretroviral treatment as prevention. To make a sustained impact on the epidemic, a concerted effort must integrate all evidence-based interventions that will most proximally decrease HIV acquisition and transmission risks, together with structural interventions that will support improved coverage and retention in care. Universal HIV treatment, increased access to HIV testing, and daily oral PrEP have emerged as integral to the prevention of HIV transmission, and such efforts should be immediately expanded for MSM and other populations disproportionately affected by HIV. Respect for human rights and efforts to combat stigma and improve access to prevention services are needed to change the trajectory of the HIV pandemic among MSM.

Pharmaceutical Vehicles for Vaginal and Rectal Administration of Anti-HIV Microbicide Nanosystems

Prevention strategies play a key role in the fight against HIV/AIDS. Vaginal and rectal microbicides hold great promise in tackling sexual transmission of HIV-1, but effective and safe products are yet to be approved and made available to those in need. While most efforts have been placed in finding and testing suitable active drug candidates to be used in microbicide development, the last decade also saw considerable advances in the design of adequate carrier systems and formulations that could lead to products presenting enhanced performance in protecting from infection. One strategy demonstrating great potential encompasses the use of nanosystems, either with intrinsic antiviral activity or acting as carriers for promising microbicide drug candidates. Polymeric nanoparticles, in particular, have been shown to be able to enhance mucosal distribution and retention of promising antiretroviral compounds. One important aspect in the development of nanotechnology-based microbicides relates to the design of pharmaceutical vehicles that allow not only convenient vaginal and/or rectal administration, but also preserve or even enhance the performance of nanosystems. In this manuscript, we revise relevant work concerning the selection of vaginal/rectal dosage forms and vehicle formulation development for the administration of microbicide nanosystems. We also pinpoint major gaps in the field and provide pertinent hints for future work.

Noncovalent PEG Coating of Nanoparticle Drug Carriers Improves the Local Pharmacokinetics of Rectal Anti-HIV Microbicides

Antiretroviral drug nanocarriers hold great promise for developing anti-human immunodeficiency virus (HIV) rectal microbicides. However, challenges remain, namely, concerning which properties are more suited for enhancing colorectal distribution and retention of microbicide compounds. In this work, we developed and assessed the in vitro and in vivo performance of poly(lactic- co-glycolic acid) (PLGA)-based nanoparticles (NPs) as carriers for the model drug efavirenz (EFV). We particularly focused on the effect of noncovalent poly(ethylene glycol) coating of PLGA NPs (PEG-PLGA NPs) conferring a mucus-diffusive behavior on the pharmacokinetics (PK) of EFV following rectal administration to mice. Drug-loaded PLGA NPs and PEG-PLGA NPs (200-225 nm) were obtained by nanoprecipitation. Both types of systems were able to retain native antiretroviral activity of EFV in vitro, while featuring lower cytotoxicity against different epithelial cell lines and HIV target cells. Also, PLGA NPs and PEG-PLGA NPs were readily taken up by colorectal cell lines and mildly reduced EFV permeation while increasing membrane retention in Caco-2 and Caco-2/HT29-MTX cell monolayer models. When administered intrarectally to CD-1 mice in phosphate-buffered saline (pH 7.4), EFV-loaded PEG-PLGA NPs consistently provided higher drug levels in colorectal tissues and lavages, as compared to free EFV or drug-loaded PLGA NPs. Mean values for the area-under-the-curve between 15 min and 12 h following administration were particularly higher for PEG-PLGA NPs in distal and middle colorectal tissues, with relative bioavailability values of 3.7 and 29, respectively, as compared to free EFV (2.2 and 6.0 over PLGA NPs, respectively). Systemic exposure to EFV was reduced for all treatments. NPs were further shown safe after once-daily administration for 14 days, as assessed by histological analysis of colorectal tissues and chemokine/cytokine assay of rectal lavages. Overall, PEG-PLGA NPs demonstrated to be safe carriers for rectal microbicide drug delivery and able to provide enhanced local PK that could be valuable in preventing rectal HIV transmission.

Are Anal Sex Roles Associated with Preferences for Pre-Exposure Prophylaxis Administration Modalities Among Men Who Have Sex with Men?

The current study sought to examine awareness of, willingness to use, and preferences for available and theoretical administration modalities for HIV pre-exposure prophylaxis (PrEP) and the association of anal sex roles with these concepts among a sample of men who have sex with men (MSM) in Paris, France. Broadcast advertisements were placed on a popular geosocial-networking smartphone application for MSM to direct users to complete a Web-based survey. MSM answered questions on their recent engagement in condomless anal intercourse and awareness of and willingness to use PrEP in the form of once daily and event-driven pill regimens, long-acting injections, and penile and rectal microbicides as well as sexual roles. Multinomial regression models were fit to assess the association between behaviorally classified anal sexual role and preferences for one of these biomedical prevention modalities. A total of 482 HIV-uninfected MSM completed the survey, 48.1% of whom engaged in some form of condomless anal intercourse in the preceding 3 months. Most respondents (85.3%) had heard of once daily PrEP, but fewer respondents had heard of other prevention strategies. Assuming equal effectiveness, long-acting injections were the most commonly preferred (21.8%). Behaviorally defined "bottom" and "versatile" MSM more frequently preferred long-acting injections (32.9% of "bottoms" and 25.3% of "versatiles"). The development of long-acting injections to deliver antiretroviral drugs and topical microbicides may offer more convenient and acceptable options for HIV prevention among MSM, as MSM in this sample were willing to use them and would prefer to use them over currently available pill regimens.

Current State of Microbicide Development

Efforts in developing an effective vaccine for human immunodeficiency virus (HIV) has been challenging as HIV strains are highly variable and exhibit extraordinary mutability. Despite condom usage and pre-exposure prophylaxis as excellent prevention strategies, lack of accessibility in some developing countries and low adherence due to sociocultural factors continue to act as barriers in reducing the HIV epidemic. Microbicides are topical therapies developed to prevent HIV and other sexually transmitted infections during intercourse. Microbicides applied vaginally or rectally are intended to prevent HIV infection at the site of transmission by either inhibiting its entry into immune cells or prevent viral replication. This review will summarize some of the current state-of-the-art microbicide formulations that are in preclinical and clinical stages of development and discuss some of the challenges associated with microbicide development.

3-Hydroxyphthalic Anhydride- Modified Rabbit Anti-PAP IgG as a Potential Bifunctional HIV-1 Entry Inhibitor

Several studies have reported that amyloid fibrils in human semen formed from a naturally occurring peptide fragment of prostatic acidic phosphatase (PAP248-286), known as semen-derived enhancer of viral infection (SEVI), could dramatically enhance human immunodeficiency virus type 1 (HIV-1) infection. Accordingly, SEVI might serve as a novel target for new antiviral drugs or microbicide candidates for the prevention of sexually transmitted HIV. Theoretically, a special anti-PAP or anti-SEVI antibody could reduce the enhancement of viral infection by blocking the binding of HIV and SEVI fibrils. Here, 3-hydroxyphthalic anhydride modified anti-PAP248-286 antibody, named HP-API, exhibited broad-spectrum and highly effective anti-HIV-1 activities on different subtypes and tropism. By using time-of-addition, cell–cell fusion and a single-cycle HIV-1 infection assays, we demonstrated that HP-API is an HIV-1 entry/fusion inhibitor. Mechanism studies suggest that HP-API inhibited HIV-1 entry/fusion by targeting both HIV-1 gp120 envelop and CD4 receptor on the host cell specifically. It is noteworthy that HP-API abrogated the formation of SEVI fibrils and partially interfered with SEVI-mediated enhancement of HIV-1 infection. Based on these findings, HP-API could be considered a bifunctional HIV-1 entry/fusion inhibitor with high potential.

Surface modification with polyethylene glycol enhances colorectal distribution and retention of nanoparticles

Dense surface modification with short chain polyethylene glycol (PEG) has been previously demonstrated as favoring the transport of nanoparticles (NPs) across mucus. However, the ability of such approach to influence the distribution and retention of NPs along the length of the colorectum after rectal delivery has not been previously established. Herein, the distribution and retention of poly(lactic-co-glycolic acid) NPs modified with PEG in a non-covalent fashion are reckoned in a mouse model. Despite overall rapid depletion, both PEG-modified and non-modified NPs are able to reach the middle segment of the colon. PEG-modified NPs are able to enhance retention up to at least two hours post-administration, contrasting with nearly residual levels observed for non-modified NPs after 15 min. The ability of PEG-modified NPs to putatively cross mucus also appears to promote association with tissues. Overall, the work provides significant insights as to the behavior of NPs in the colorectum, which could be valuable for the development of rectal nanomedicines. It further reinforces the potential usefulness of PEG-modified NPs as mucus-penetrating carriers for mucosal drug delivery.

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

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

Patterns of a Rectal Microbicide Placebo Gel Use in a Preparatory Stage for a Phase I Trial Among Young Men Who Have Sex with Men

We examined young gay, bisexual, and other men who have sex with men's (YGBMSM) usage patterns of a pre-coital, applicator-administered rectal placebo gel. An ethnically diverse sample of 94 YGBMSM (aged 18-30 years) were asked to insert hydroxyethylcellulose placebo gel rectally before receptive anal intercourse (RAI) and report their gel use through an interactive voice response system (IVRS) across 12 weeks. We used trajectory analyses to characterize participants' use of the rectal gel over the 12 weeks, and examine whether these trajectories varied based on participants' sociodemographic characteristics, sexual behaviors, application and insertion behaviors, and experiences using the placebo gel. A cubic model was the best fit for these longitudinal data, with two distinct trajectories of gel use observed. The first trajectory ('High with Varying Gel Use per Week') represented YGBMSM (N = 38; 40.3%) who reported using the rectal gel on several occasions per week. The second trajectory ('Low and Consistent Gel Use per Week') represented participants (N = 56; 59.7%) who reported a consistent average use of one gel per week. Participants in the High with Varying Gel Use Trajectory reported trying out a greater number of positions when inserting the gel across the 12-weeks than peers in the Low and Consistent Gel Use Trajectory. YGBMSM reporting more RAI occasions during the trial were more likely be present in the High with Varying Gel Use Trajectory than peers in the Low and Consistent Gel Use Trajectory. Future research examining how to facilitate gel application and adherence among YGBMSM is merited.

Impact of antiretroviral drugs on the microbiome: unknown answers to important questions

PURPOSE OF REVIEW

Little is known on how different antiretroviral (ARV) drugs affect the gut microbiome in HIV infection; and conflicting data exists on the effect of ARV drugs on residual inflammation/immune activation and microbial translocation.

RECENT FINDINGS

Gut microbiome involvement in the transmission and pathogenesis of HIV infection is increasingly being recognized. Various studies have shown that antiretroviral therapy (ART) is unable to restore gut health despite effective suppression of plasma HIV viremia. Indeed, the resolution of residual inflammation and gut microbial translocation is partial under ART. Very recent studies have provided new evidence that ARV combinations can differentially affect the gut microbiome, immune activation and microbial translocation. Furthermore, a recent article uncovered a link between drug metabolism and specific microbial species indicating that microbes can directly metabolically degrade ARV drugs when administered topically.

SUMMARY

There are still many unanswered questions regarding ARVs and the gut microbiome. It is, therefore, critical for researchers to address the effect of distinct ARV drugs on the microbiome and vice versa: the effects of the microbiome on ARV drug metabolism, and speculate about possible therapeutic avenues.

Nanotechnologies for early diagnosis, in situ disease monitoring, and prevention

Nanotechnology is an enabling technology with great potential for applications in stem cell research and regenerative medicine. Fluorescent nanodiamond (FND), an inherently biocompatible and nontoxic nanoparticle, is well suited for such applications. We had developed a prospective isolation method using CD157, CD45, and CD54 to obtain lung stem cells. Labeling of CD45⁻CD54⁺CD157⁺ cells with FNDs did not eliminate their abilities for self-renewal and differentiation. The FND labeling in combination with cell sorting, fluorescence lifetime imaging microscopy, and immunostaining identified transplanted stem cells allowed tracking of their engraftment and regenerative capabilities with single-cell resolution. Time-gated fluorescence (TGF) imaging in mouse tissue sections indicated that they reside preferentially at the bronchoalveolar junctions of lungs, especially in naphthalene-injured mice. Our results presented in Subchapter 1.1 demonstrate not only the remarkable homing capacity and regenerative potential of the isolated stem cells, but also the ability of finding rare lung stem cells in vivo using FNDs.

The topical use of antiretroviral-based microbicides, namely of a dapivirine ring, has been recently shown to partially prevent transmission of HIV through the vaginal route. Among different formulation approaches, nanotechnology tools and principles have been used for the development of tentative vaginal and rectal microbicide products. Subchapter 1.2 provides an overview of antiretroviral drug nanocarriers as novel microbicide candidates and discusses recent and relevant research on the topic. Furthermore, advances in developing vaginal delivery platforms for the administration of promising antiretroviral drug nanocarriers are reviewed. Although mostly dedicated to the discussion of nanosystems for vaginal use, the development of rectal nanomicrobicides is also addressed.

Infectious diseases are currently responsible for over 8 million deaths per year. Efficient treatments require accurate recognition of pathogens at low concentrations, which in the case of blood infection (septicemia) can go as low as 1 mL^–1. Detecting and quantifying bacteria at such low concentrations is challenging and typically demands cultures of large samples of blood (∼1 mL) extending over 24–72 h. This delay seriously compromises the health of patients and is largely responsible for the death toll of bacterial infections. Recent advances in nanoscience, spectroscopy, plasmonics, and microfluidics allow for the development of optical devices capable of monitoring minute amounts of analytes in liquid samples. In Subchapter 1.3 we critically discuss these recent developments that will, in the future, enable the multiplex identification and quantification of microorganisms directly on their biological matrix with unprecedented speed, low cost, and sensitivity.

Radiolabeled nanoparticles (NPs) are finding an increasing interest in a broad range of biomedical applications. They may be used to detect and characterize diseases, to deliver relevant therapeutics, and to study the pharmacokinetic/pharmacodynamic parameters of nanomaterials. The use of radiotracer techniques in the research of novel NPs offers many advantages, but there are still some limitations. The binding of radionuclides to NPs has to be irreversible to prevent their escape to other tissues or organs. Due to the short half-lives of radionuclides, the manufacturing process is time limited and difficult, and there is also a risk of contamination. Subchapter 1.4 presents the main selection criteria for radionuclides and applicable radiolabeling procedures used for the radiolabeling of various NPs. Also, an overview of different types of NPs that have so far been labeled with radionuclides is presented.

"Fusion and binding inhibition" key target for HIV-1 treatment and pre-exposure prophylaxis: targets, drug delivery and nanotechnology approaches

More than 35 million people are living with HIV worldwide with approximately 2.3 million new infections per year. Cascade of events (cell entry, virus replication, assembly and release of newly formed virions) is involved in the HIV-1 transmission process. Every single step offers a potential therapeutic strategy to halt this progression and HIV fusion into the human host cell is one such stage. Controlling the initial event of HIV-1 transmission is the best way to control its dissemination especially when prophylaxis is concerned. Action is required either on the HIV’s or host’s cell surface which is logically more rational when compared with other intracellular acting moieties. Aim of this manuscript is to detail the significance and current strategies to halt this initial step, thus blocking the entry of HIV-1 for further infection. Both HIV-1 and the possible host cell’s receptors/co-receptors are under focus while specifying the targets available for inhibiting this fusion. Current and under investigation moieties are categorized based on their versatile mechanisms. Advanced drug delivery and nanotechnology approaches present a key tool to exploit the therapeutic potential in a boosted way. Current drug delivery and the impact of nanotechnology in potentiating this strategy are detailed.

Acceptability and Preferences for Hypothetical Rectal Microbicides among a Community Sample of Young Men Who Have Sex with Men and Transgender Women in Thailand: A Discrete Choice Experiment

Rectal microbicides (RMs) may offer substantial benefits in expanding HIV prevention options for key populations. From April to August 2013, we conducted Tablet-Assisted Survey Interviewing, including a discrete choice experiment, with participants recruited from gay entertainment venues and community-based organizations in Chiang Mai and Pattaya, Thailand. Among 408 participants, 74.5 % were young men who have sex with men, 25.5 % transgender women, with mean age = 24.3 years. One-third (35.5 %) had ≤9th grade education; 63.4 % engaged in sex work. Overall, 83.4 % reported they would definitely use a RM, with more than 2-fold higher odds of choice of a RM with 99 versus 50 % efficacy, and significantly higher odds of choosing gel versus suppository, intermittent versus daily dosing, and prescription versus over-the-counter. Sex workers were significantly more likely to use a RM immediately upon availability, with greater tolerance for moderate efficacy and daily dosing. Engaging key populations in assessing RM preferences may support biomedical research and evidence-informed interventions to optimize the effectiveness of RMs in HIV prevention.

Human Immunodeficiency Virus Immune Cell Receptors, Coreceptors, and Cofactors: Implications for Prevention and Treatment

In the last three decades, extensive research on human immunodeficiency virus (HIV) has highlighted its capability to exploit a variety of strategies to enter and infect immune cells. Although CD4(+) T cells are well known as the major HIV target, with infection occurring through the canonical combination of the cluster of differentiation 4 (CD4) receptor and either the C-C chemokine receptor type 5 (CCR5) or C-X-C chemokine receptor type 4 (CXCR4) coreceptors, HIV has also been found to enter other important immune cell types such as macrophages, dendritic cells, Langerhans cells, B cells, and granulocytes. Interestingly, the expression of distinct cellular cofactors partially regulates the rate in which HIV infects each distinct cell type. Furthermore, HIV can benefit from the acquisition of new proteins incorporated into its envelope during budding events. While several publications have investigated details of how HIV manipulates particular cell types or subtypes, an up-to-date comprehensive review on HIV tropism for different immune cells is lacking. Therefore, this review is meant to focus on the different receptors, coreceptors, and cofactors that HIV exploits to enter particular immune cells. Additionally, prophylactic approaches that have targeted particular molecules associated with HIV entry and infection of different immune cells will be discussed. Unveiling the underlying cellular receptors and cofactors that lead to HIV preference for specific immune cell populations is crucial in identifying novel preventative/therapeutic targets for comprehensive strategies to eliminate viral infection.

Project Gel a Randomized Rectal Microbicide Safety and Acceptability Study in Young Men and Transgender Women

OBJECTIVES

The purpose of Project Gel was to determine the safety and acceptability of rectal microbicides in young men who have sex with men (MSM) and transgender women (TGW) at risk of HIV infection.

METHODS

MSM and TGW aged 18-30 years were enrolled at three sites; Pittsburgh, PA; Boston, MA; and San Juan, PR. Stage 1A was a cross-sectional assessment of sexual health and behavior in MSM and TGW. A subset of participants from Stage 1A were then enrolled in Stage 1B, a 12-week evaluation of the safety and acceptability of a placebo rectal gel. This was followed by the final phase of the study (Stage 2) in which a subset of participants from Stage 1B were enrolled into a Phase 1 rectal safety and acceptability evaluation of tenofovir (TFV) 1% gel.

RESULTS

248 participants were enrolled into Stage 1A. Participants' average age was 23.3 years. The most common sexually transmitted infection (STIs) at baseline were Herpes simplex (HSV)-2 (16.1% by serology) and rectal Chlamydia trachomatis (CT) (10.1% by NAAT). 134 participants were enrolled into Stage 1B. During the 12 week period of follow-up 2 HIV, 5 rectal CT, and 5 rectal Neisseria gonorrhea infections were detected. The majority of adverse events (AEs) were infections (N = 56) or gastrointestinal (N = 46) and were mild (69.6%) or moderate (28.0%). Of the participants who completed Stage 1B, 24 were enrolled into Stage 2 and randomized (1:1) to receive TFV or placebo gel. All participants completed Stage 2. The majority of AEs were gastrointestinal (N = 10) and of mild (87.2%) or moderate (10.3%) severity.

CONCLUSIONS

In this study we were able to enroll a sexually active population of young MSM and TGW who were willing to use rectal microbicides. TFV gel was safe and acceptable and should be further developed as an alternative HIV prevention intervention for this population.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01283360.

Perceptions among Dutch men who have sex with men and their willingness to use rectal microbicides and oral pre-exposure prophylaxis to reduce HIV risk--a preliminary study

Oral pre-exposure prophylaxis (PrEP) with antiretroviral (ARV) tablets and topical PrEP or microbicides containing ARV drugs could help to reduce HIV incidence. These methods hold promise for men who have sex with men (MSM) who are at higher risk of acquiring HIV. This mixed-methods study in the Netherlands explored perceptions of MSM and their willingness to use oral PrEP and rectal microbicides (RM) if made available. Recruited through social media (Facebook and Twitter), 108 MSM completed online questionnaires. Seven of them consented to discuss the survey results in semi-structured interviews. Survey participants preferred a RM that could be applied before and after anal intercourse (60.8%) to daily oral PrEP (20.3%). This preference was based on anticipated user friendliness, hypothetically fewer expected adverse events, and perceptions that RM would be less likely to be confused with ARVs for treatment. Those who preferred oral PrEP had stronger beliefs in the effectiveness of pills, perceived its use as easy, and viewed not requiring sexual partner awareness as advantages. No predictive factors were found for the choice of one prevention method over the other. Although Dutch MSM perceive both oral and topical PrEP positively, many barriers exist to the introduction of these products in the Netherlands. These include lack of regulatory approval of oral PrEP, no proven efficacy as yet for RM, and strong HIV stigma within the MSM population. In-depth qualitative research is needed to further explore the perceptions of MSM to inform implementation of programmes should these HIV prevention methods become available.

Maraviroc and reverse transcriptase inhibitors combinations as potential preexposure prophylaxis candidates

OBJECTIVE

Receptive anal intercourse in both men and women is associated with the highest probability for sexual acquisition of HIV infection. As part of a program to develop an effective prevention strategy, we performed an ex-vivo preclinical evaluation to determine the efficacy of multiple double combinations of maraviroc (MVC) and reverse transcriptase inhibitors (RTIs).

DESIGN

The entry inhibitor, MVC, a nucleotide RTI, tenofovir and two non-nucleoside RTIs, UC781 and TMC120 (dapivirine, DPV), were used in double, combinations against a panel of CCR5-using clade B and clade C HIV-1 isolates and against MVC-escape variants. A gel-formulated version of MVC-DPV combination was also tested.

METHODS

Indicator cells, cocultures of immature dendritic cells with CD4T cells, and colorectal tissue explants were used to assess antiviral activity of drug combinations.

RESULTS

All dual MVC-RTI combinations tested inhibited MVC-sensitive and resistant isolates in cellular and colorectal explants models. All the combinations were positive with no reduction in the activity of MVC. In tissue explants, the combinations against all viral isolates tested produced an increase in the activity of MVC. An initial gel-formulation of MVC-DPV combination showed greater and prolonged antiviral activity of MVC in mucosal tissue explants.

CONCLUSION

This study demonstrates that combinations based on antiretroviral drugs inhibiting HIV transmission at viral entry and reverse transcription have potential as prevention strategies against colorectal transmission of HIV-1 including MVC-resistant isolates. Preclinical evaluation with colorectal tissue explants indicates that a gel-formulation of MVC-DPV is an effective candidate colorectal microbicide.

HIV-Related Stigma and HIV Prevention Uptake Among Young Men Who Have Sex with Men and Transgender Women in Thailand

HIV-related stigma is a pervasive structural driver of HIV. With an HIV epidemic among young men who have sex with men (MSM) and transgender women (TG) in Thailand characterized as explosive, we conducted a cross-sectional survey among MSM and TG aged 18-30 years. From April-August 2013, participants recruited using venue-based sampling from gay entertainment sites and community-based organizations completed a tablet-assisted survey interview in Thai language. We conducted multiple logistic regression to assess correlations between HIV-related stigma (felt-normative, vicarious domains) and socio-demographic variables, HIV vulnerabilities (gay entertainment employment, sex work, forced sex history), and HIV prevention uptake (condom use, HIV testing, rectal microbicide acceptability). Among participants (n = 408), 54% identified as gay, 25% transgender, and 21% heterosexual. Two-thirds (65.7%) were employed at gay entertainment venues, 67.0% had more than three male partners (past month), 55.6% had been paid for sex, and 4.5% were HIV-positive. One-fifth (21.3%) reported forced sex. Most participants reported experiencing felt-normative and vicarious HIV-related stigma. Adjusting for socio-demographics, participants with higher total HIV-related stigma scores had significantly lower odds of HIV testing and rectal microbicide acceptability, and higher odds of having experienced forced sex. Both vicarious and felt-normative dimensions of HIV-related stigma were inversely associated with HIV testing and rectal microbicide acceptability. Our findings suggest that HIV-related stigma harms the health of HIV-negative MSM and TG at high risk for HIV infection. HIV-related interventions and research among young MSM and TG in Thailand should address multiple dimensions of HIV-related stigma as a correlate of risk and a barrier to accessing prevention.

To Use a Rectal Microbicide, First Insert the Applicator: Gel and Applicator Satisfaction Among Young Men Who Have Sex With Men

We examined how experiences with a rectal placebo gel and applicator used with receptive anal intercourse (RAI) related to young men who have sex with men's (YMSM) likelihood of using a rectal microbicide gel and applicator in the future. An ethnically diverse sample of 95 YMSM (aged 18 to 30 years) were asked to insert hydroxyethylcellulose (HEC) placebo gel rectally before RAI during 12 weeks and report the product's acceptability (i.e., satisfaction with applicator and gel, respectively; perceived gel side effects; and sexual satisfaction when gel was used) and likelihood of future microbicide use. Main and interaction effects predicting future use intentions were tested using linear regression. We found a positive association between future use intentions and applicator satisfaction (b = .33, p < .001). In a subsequent interaction effects model, we found that greater gel satisfaction was associated with increased future use intentions; however, the strength of this relationship was magnified when YMSM reported greatest satisfaction with the rectal applicator. Applicator satisfaction may be a salient factor in YMSM's decision-making to use a rectal microbicide in the future. Although the importance of developing a satisfactory rectal microbicide gel for YMSM is undeniable for its future use, our results also emphasize the importance of developing strategies that increase YMSM's comfort and skill when using a rectal applicator. Future research examining how to optimize the design, properties, and characteristics of a rectal applicator as a strategy to promote greater satisfaction and use among YMSM is merited.

Pre-exposure prophylaxis to prevent HIV infection: current status, future opportunities and challenges

As the global incidence of HIV exceeds 2 million new infections annually, effective interventions to decrease HIV transmission are needed. Randomized, placebo-controlled studies have demonstrated that daily oral antiretroviral pre-exposure prophylaxis (PrEP) with a fixed-dose combination tablet containing tenofovir disoproxil fumarate and emtricitabine can significantly reduce HIV incidence among diverse at-risk populations. In these studies, the efficacy of PrEP was correlated with levels of adherence. Official guidelines recommend provision of PrEP to people at greatest risk of HIV acquisition, and demonstration projects suggest that high levels of uptake and adherence are possible outside of controlled studies. However, several potential barriers to implementing PrEP remain. These challenges include low awareness and utilization of PrEP by at-risk individuals, uncertainty about adherence in 'real-world' settings, the majority of healthcare providers being untrained in PrEP provision, limited data about potential adverse effects from long-term use of tenofovir-emtricitabine, high costs of PrEP medications, and stigma associated with PrEP use and the behaviors that would warrant PrEP. Innovative pharmacologic chemoprophylactic approaches could provide solutions to some of these challenges. Less-than-daily oral dosing regimens and long-acting injectable medications could reduce pill burdens and facilitate adherence, and local delivery of PrEP medications to genital compartments via gels, rings and films may limit systemic drug exposure and potential toxicities. As the portfolio of chemoprophylactic agents and delivery systems expands to meet the diverse sexual health needs and product preferences of individuals who may benefit from PrEP, it is hoped that antiretroviral chemoprophylaxis could become an acceptable, feasible, and highly effective addition to existing HIV prevention strategies.

Simultaneous Evaluation of Safety, Acceptability, Pericoital Kinetics, and Ex Vivo Pharmacodynamics Comparing Four Rectal Microbicide Vehicle Candidates

Preexposure prophylaxis (PrEP) of HIV infection with tenofovir-containing regimens is effective, but plagued by poor adherence in some studies. Options for safe, effective, and acceptable PrEP products, especially for men and women at risk of HIV via receptive anal intercourse (RAI), are needed. We performed a randomized, partially blinded, first-in-human evaluation of four candidate rectal microbicide vehicles-aqueous gel, aqueous fluid, lipid gel, and lipid fluid-to select a prototype for further clinical development. Eight seronegative participants received three doses of each product with each dose separated by at least 2 weeks: one dose was given alone without simulated RAI in clinic, another dose was followed by simulated RAI in clinic, and another dose was self-administered at home in the context of RAI with a partner. Assessments included safety, acceptability, colon histology, ex vivo HIV infectivity of colon tissue explants, and colonic luminal distribution of vehicle and HIV surrogates. Adverse events were all mild and mainly sigmoidoscopy associated. There were minor differences in colon distribution of products and little effect of RAI. Vehicle distribution covered 95% (±7% standard deviation) of the distribution of an HIV surrogate in the colonic lumen. The lipid fluid vehicle increased HIV colon tissue infectability 5-fold [log10 p24 0.68 (95% confidence interval 0.08, 1.28)] and aqueous gel provided 6-fold protection [log10 p24 0.80 (95% confidence interval 0.20, 1.41)] compared to no product baseline. Colon permeability of lipid vehicles was more than 10-fold greater than aqueous vehicles. All products received similar acceptability ratings, though trends favored the gel products. Intensive simultaneous assessment of safety and toxicity, luminal and tissue distribution, ex vivo HIV infectivity, and product acceptability in relevant sexual contexts provided clear differentiation among candidate gels very early in product development. We selected the aqueous gel for further development as a rectal microbicide vehicle.

Development of water-soluble polyanionic carbosilane dendrimers as novel and highly potent topical anti-HIV-2 microbicides

The development of topical microbicide formulations for vaginal delivery to prevent HIV-2 sexual transmission is urgently needed. Second- and third-generation polyanionic carbosilane dendrimers with a silicon atom core and 16 sulfonate (G2-S16), napthylsulfonate (G2-NS16) and sulphate (G3-Sh16) end-groups have shown potent and broad-spectrum anti-HIV-1 activity. However, their antiviral activity against HIV-2 and mode of action have not been probed. Cytotoxicity, anti-HIV-2, anti-sperm and antimicrobial activities of dendrimers were determined. Analysis of combined effects of triple combinations with tenofovir and raltegravir was performed by using CalcuSyn software. We also assessed the mode of antiviral action on the inhibition of HIV-2 infection through a panel of different in vitro antiviral assays: attachment, internalization in PBMCs, inactivation and cell-based fusion. Vaginal irritation and histological analysis in female BALB/c mice were evaluated. Our results suggest that G2-S16, G2-NS16 and G3-Sh16 exert anti-HIV-2 activity at an early stage of viral replication inactivating the virus, inhibiting cell-to-cell HIV-2 transmission, and blocking the binding of gp120 to CD4, and the HIV-2 entry. Triple combinations with tenofovir and raltegravir increased the anti-HIV-2 activity, consistent with synergistic interactions (CIwt: 0.33-0.66). No vaginal irritation was detected in BALB/c mice after two consecutive applications for 2 days with 3% G2-S16. Our results have clearly shown that G2-S16, G2-NS16 and G3-Sh16 have high potency against HIV-2 infection. The modes of action confirm their multifactorial and non-specific ability, suggesting that these dendrimers deserve further studies as potential candidate microbicides to prevent vaginal/rectal HIV-1/HIV-2 transmission in humans.

Advances in HIV prevention for serodiscordant couples

Serodiscordant couples play an important role in maintaining the global HIV epidemic. This review summarizes biobehavioral and biomedical HIV prevention options for serodiscordant couples focusing on advances in 2013 and 2014, including World Health Organization guidelines and best evidence for couples counseling, couple-based interventions, and the use of antiviral agents for prevention. In the past few years, marked advances have been made in HIV prevention for serodiscordant couples and numerous ongoing studies are continuously expanding HIV prevention tools, especially in the area of pre-exposure prophylaxis. Uptake and adherence to antiviral therapy remains a key challenge. Additional research is needed to develop evidence-based interventions for couples, and especially for male-male couples. Randomized trials have demonstrated the prevention benefits of antiretroviral-based approaches among serodiscordant couples; however, residual transmission observed in recognized serodiscordant couples represents an important and resolvable challenge in HIV prevention.

Order of orifices: sequence of condom use and ejaculation by orifice during anal intercourse among women: implications for HIV transmission

BACKGROUND

For women, the order of penile insertion, condom use, and ejaculation by orifice during sexual events affects the probability of HIV transmission and design of HIV prevention methods.

METHODS

From October 2006 to June 2009, 431 women in Los Angeles and Baltimore in a rectal health study reported the sequence of penile insertion, condom use, and ejaculation by orifice location by computer-assisted self-interview. Multinomial logistic regression identified predictors of condom use by orifice among women who reported vaginal intercourse (VI) during their last anal intercourse (AI) event.

RESULTS

Of the 192 reporting on a last AI event, 96.3% (180/187) reported VI. Of these, 83.1% had VI before AI. Including the 36% who ejaculated in both the rectum and vagina, 66% report any ejaculation in the vagina and 45% in the rectum. One-third used a condom for both VI and AI, <10% for VI only or AI only, and half used no condoms. After adjusting for race, partner type, and substance use, compared with women who used condoms for both VI and AI at last AI, being older (units = 5 years) [adjusted odds ratio (AOR) = 0.76; 95% confidence interval (CI): 0.60 to 0.96], with serodiscordant partners (AOR = 0.22; 95% CI: 0.08 to 0.61), and HIV-positive with seroconcordant partners (AOR = 0.15; 95% CI: 0.04 to 0.54) were associated with not using condoms.

CONCLUSIONS

For most of the women in our study VI accompanied AI, with AI usually occurring after VI. This evidence for use of multiple orifices during the same sexual encounter and low use of condoms across orifices supports the need for a multicompartment HIV prevention strategy.

[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.

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

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

Commercial lubricant use among HIV-negative men who have sex with men in Los Angeles: implications for the development of rectal microbicides for HIV prevention

To inform the development and assess potential use of rectal microbicide gels for HIV prevention among men who have sex with men (MSM), we examined the dynamics and contexts of commercial lubricant use during receptive anal intercourse (RAI) within this population. From 2007 to 2010, 168 HIV-negative MSM living in Los Angeles who practice RAI completed computer-assisted self-interviews, which collected information on their last sexual event with ≤3 recent partners, at baseline, three months, and one-year study visits. Logistic generalized linear mixed models were used to identify individual- and sexual event-level characteristics associated with commercial lubricant use during RAI at the last sexual event within 421 partnerships reported by participants over the course of follow-up. During RAI at their last sexual event, 57% of partnerships used a condom and 69% used commercial lubricant. Among partnerships that used commercial lubricant, 56% reported lubricant application by both members of the partnership, 66% first applied lubricant during sex, but before penetration, and 98% applied lubricant at multiple locations. The relationship between substance use and commercial lubricant use varied by condom use (interaction p-value = 0.01). Substance use was positively associated with commercial lubricant use within partnerships that did not use condoms during RAI at their last sexual event (AOR = 4.47, 95% [corrected] [CI]: 1.63-12.28), but no association was observed within partnerships that did use condoms (AOR = 0.66, 95% CI: 0.23-1.85). Commercial lubricant use during RAI was also positively associated with reporting more sexual partners (AOR = 1.18, 95% CI: 1.05-1.31), while older age (units = 5 years; AOR = 0.75, 95% CI: 0.61-0.94), homelessness (past year; AOR = 0.32, 95% CI: 0.13-0.76), and having sex with an older (>10 years) partner (AOR = 0.37, 95% CI: 0.14-0.95) were negatively associated with commercial lubricant use. These factors should be considered in the development of rectal microbicide gels to enhance their acceptability and use among MSM.

Topical microbicides and HIV prevention in the female genital tract

Worldwide, HIV disproportionately affects women who are often unable to negotiate traditional HIV preventive strategies such as condoms. In the absence of an effective vaccine or cure, chemoprophylaxis may be a valuable self-initiated alternative. Topical microbicides have been investigated as one such option. The first generation topical microbicides were non-specific, broad-spectrum antimicrobial agents, including surfactants, polyanions, and acid buffering gels, that generally exhibited contraceptive properties. After extensive clinical study, none prevented HIV infection, and their development was abandoned. Second generation topical microbicides include agents with selective mechanisms of antiviral activity. Most are currently being used for, or have previously been explored as, drugs for treatment of HIV. The most advanced of these is tenofovir 1% gel: the first topical agent shown to significantly reduce HIV infection by 39% compared to placebo. This review summarizes the evolution of topical microbicides for HIV chemoprophylaxis, highlights important concepts learned, and offers current and future considerations for this area of research.

An overview of antiretroviral pre-exposure prophylaxis of HIV infection

Despite improvements in access to antiretroviral therapy and the use of simplified dosing regimens, HIV infection is still an important global public health problem. As a consequence, significant research efforts have been focused on the development of strategies to prevent the acquisition of HIV infection. These efforts have begun to produce results. The HPTN-052 study demonstrated the effectiveness of treating infected individuals as a means to prevent onward transmission of HIV infection. In addition, Phase 2B/3 studies have shown that the use of oral and topical antiretroviral pre-exposure prophylaxis (PrEP) can significantly reduce the acquisition of HIV infection in serodiscordant couples, young women in sub-Saharan Africa, men who have sex with men, and intravenous drug users. Despite these successes, challenges remain. Adherence to daily PrEP is variable, and some large studies have failed to demonstrate the effectiveness of PrEP in reducing HIV acquisition. Novel PrEP technologies, including sustained delivery intravaginal rings and long-acting injectable products, are being developed to try and circumvent adherence problems associated with daily PrEP regimens. The purpose of this article is to briefly summarize recent progress in the development of antiretroviral PrEP.