Antibody Maturation in Women Who Acquire HIV Infection While Using Antiretroviral Preexposure Prophylaxis

Impact of pre-exposure prophylaxis uptake among gay, bisexual, and other men who have sex with men in urban centers in Brazil: a modeling study

BACKGROUND

Men who have sex with men (MSM) in Brazil remain disproportionately affected by HIV. We estimated the potential incidence reduction by five years with increased uptake of publicly-funded, daily, oral tenofovir/emtricitabine (TDF/FTC) for HIV pre-exposure prophylaxis (PrEP) among MSM using the Cost Effectiveness of Preventing AIDS Complications microsimulation model. We used national data, local studies, and literature to inform model parameters for three cities: Rio de Janeiro, Salvador, and Manaus.

RESULTS

In Rio de Janero, a PrEP intervention achieving 10% uptake within 60 months would decrease incidence by 2.3% whereas achieving 60% uptake within 24 months would decrease incidence by 29.7%; results were similar for Salvador and Manaus. In sensitivity analyses, decreasing mean age at PrEP initiation from 33 to 21 years increased incidence reduction by 34%; a discontinuation rate of 25% per year decreased it by 12%.

CONCLUSION

Targeting PrEP to young MSM and minimizing discontinuation could substantially increase PrEP's impact.

Facilitating Next-Generation Pre-Exposure Prophylaxis Clinical Trials Using HIV Recent Infection Assays: A Consensus Statement from the Forum HIV Prevention Trial Design Project

Standard-of-care HIV pre-exposure prophylaxis (PrEP) is highly efficacious, but uptake of and persistence on a daily oral pill is low in many settings. Evaluation of alternate PrEP products will require innovation to avoid the unpractically large sample sizes in noninferiority trials. We propose estimating HIV incidence in people not on PrEP as an external counterfactual to which on-PrEP incidence in trial subjects can be compared. HIV recent infection testing algorithms (RITAs), such as the limiting antigen avidity assay plus viral load used on specimens from untreated HIV positive people identified during screening, is one possible approach. Its feasibility is partly dependent on the sample size needed to ensure adequate power, which is impacted by RITA performance, the number of recent infections identified, the expected efficacy of the intervention, and other factors. Screening sample sizes to support detection of an 80% reduction in incidence for 3 key populations are more modest, and comparable to the number of participants in recent phase III PrEP trials. Sample sizes would be significantly larger in populations with lower incidence, where the false recency rate is higher or if PrEP efficacy is expected to be lower. Our proposed counterfactual approach appears to be feasible, offers high statistical power, and is nearly contemporaneous with the on-PrEP population. It will be important to monitor the performance of this approach during new product development for HIV prevention. If successful, it could be a model for preventive HIV vaccines and prevention of other infectious diseases.

Recent Advances in the Excipients Used in Modified Release Vaginal Formulations

The formulation of an ideal vaginal drug delivery system (DDS), with the requisite properties, with respect to safety, efficacy, patient compliance, aesthetics, harmonization with the regulatory requirements, and cost, requires a meticulous selection of the active ingredients and the excipients used. Novel excipients defined by diversity and multifunctionality are used in order to ameliorate drug delivery attributes. Synthetic and natural polymers are broadly used in pharmaceutical vaginal formulations (solid, semi-solid dosage forms, implantable devices, and nanomedicines) with a promising perspective in improving stability and compatibility issues when administered topically or systemically. Moreover, the use of biopolymers is aiming towards formulating novel bioactive, biocompatible, and biodegradable DDSs with a controllable drug release rate. Overviewing vaginal microenvironment, which is described by variable and perplexed features, a perceptive choice of excipients is essential. This review summarizes the recent advances on the excipients used in modified vaginal drug delivery formulations, in an attempt to aid the formulation scientist in selecting the optimal excipients for the preparation of vaginal products.

Altered Antibody Responses in Persons Infected with HIV-1 While Using Preexposure Prophylaxis

Preexposure prophylaxis (PrEP) is an effective HIV prevention tool, although effectiveness is dependent upon adherence. It is important to characterize the impact of PrEP on HIV antibody responses in people who experience breakthrough infections to understand the potential impact on timely diagnosis and treatment. Longitudinal HIV-1-specific antibody responses were evaluated in 42 people who inject drugs (PWID) from the Bangkok Tenofovir Study (BTS) (placebo = 28; PrEP = 14) who acquired HIV while receiving PrEP. HIV-1 antibody levels and avidity to three envelope proteins (gp41, gp160, and gp120) were measured in the plasma using a customized Bio-Plex (Bio-Rad Laboratories, Hercules, CA) assay. A time-to-event analysis was performed for each biomarker to compare the distribution of times at which study subjects exceeded the recent/long-term assay threshold, comparing PrEP and placebo treatment groups. We fit mixed-effects models to identify longitudinal differences in antibody levels and avidity between groups. Overall, longitudinal antibody levels and avidity were notably lower in the PrEP breakthrough group compared to the placebo group. Time-to-event analyses demonstrated a difference in time to antibody reactivity between treatment groups for all Bio-Plex biomarkers. Longitudinal gp120 antibody levels within the PrEP breakthrough group were decreased compared to the placebo group. When accounting for PrEP adherence, both gp120 and gp160 antibody levels were lower in the PrEP breakthrough group compared to the placebo group. We demonstrate hindered envelope antibody maturation in PWID who became infected while receiving PrEP in the BTS, which has significant implications for HIV diagnosis. Delayed maturation of the antibody response to HIV may increase the time to detection for antibody-based tests. Clinical Trial Registration Number, NCT00119106.

Effect of HIV pre-exposure prophylaxis (PrEP) on detection of early infection and its impact on the appropriate post-PrEP deferral period

INTRODUCTION

HIV antivirals for pre-exposure prophylaxis (PrEP) are known to affect detection of early HIV infection through suppression of viral load and delayed seroconversion. To cover potential delay in HIV detection associated with PrEP use by blood donors in the context of international reductions in sexual activity-based deferral periods, we analysed the available data to determine the appropriate minimum post-PrEP deferral period for blood donation.

MATERIALS AND METHODS

Published cases of incident HIV infection when PrEP use was objectively demonstrable were identified, consisting principally of seroconverters from the Partners PrEP study (a clinical trial of PrEP efficacy). Data were reviewed to determine the impact of PrEP on the detection of HIV RNA, p24 Ag and seroconversion delay.

RESULTS

Nucleic acid testing (NAT) detected early HIV infection in the presence of PrEP prior to or in concordance with serological testing in approximately 90% of cases. Undetectable HIV RNA would rebound to detectable levels within two months of PrEP cessation. PrEP delayed p24 antigen detection and antibody seroconversion by about 7 days.

CONCLUSION

Even when daily PrEP is continued, it is likely that the majority of early HIV infections are detectable by individual donation (ID)-NAT, with p24 Ag or antibody seroconversion occurring conservatively within four weeks of exposure. HIV RNA levels also rebound rapidly in the absence of PrEP. In Australia, a three-month deferral period for blood donation after the last dose of PrEP provides an appropriate safety margin to mitigate the residual risk of transfusion-transmitted HIV.

Topical Tenofovir Pre-exposure Prophylaxis and Mucosal HIV-Specific Fc-Mediated Antibody Activities in Women

The RV144 HIV-vaccine trial highlighted the importance of envelope-specific non-neutralizing antibody (nNAb) Fc-mediated functions as immune correlates of reduced risk of infection. Since pre-exposure prophylaxis (PrEP) and HIV-vaccines are being used as a combination prevention strategy in at risk populations, the effects of PrEP on nNAb functions both mucosally and systemically remain undefined. Previous animal and human studies demonstrated reduced HIV-specific antibody binding avidity post-HIV seroconversion with PrEP, which in turn may affect antibody functionality. In seroconverters from the CAPRISA 004 tenofovir gel trial, we previously reported significantly higher detection and titres of HIV-specific binding antibodies in the plasma and genital tract (GT) that distinguished the tenofovir from the placebo arm. We hypothesized that higher HIV-specific antibody titres and detection reflected corresponding increased antibody-dependent neutrophil-mediated phagocytosis (ADNP) and NK-cell-activated antibody-dependent cellular cytotoxic (ADCC) activities. HIV-specific V1V2-gp70, gp120, gp41, p66, and p24 antibodies in GT and plasma samples of 48 seroconverters from the CAPRISA 004 tenofovir gel trial were tested for ADCP and ADCC at 3, 6- and 12-months post-HIV-infection. GT gp41- and p24-specific ADNP were significantly higher in the tenofovir than the placebo arm at 6 and 12 months respectively (p < 0.05). Plasma gp120-, gp41-, and p66-specific ADNP, and GT gp41-specific ADCC increased significantly over time (p < 0.05) in the tenofovir arm. In the tenofovir arm only, significant inverse correlations were observed between gp120-specific ADCC and gp120-antibody titres (r = −0.54; p = 0.009), and gp41-specific ADNP and gp41-specific antibody titres at 6 months post-infection (r = −0.50; p = 0.015). In addition, in the tenofovir arm, gp41-specific ADCC showed significant direct correlations between the compartments (r = 0.53; p = 0.045). Certain HIV-specific nNAb activities not only dominate specific immunological compartments but can also exhibit diverse functions within the same compartment. Our previous findings of increased HIV specific antibody detection and titres in women who used tenofovir gel, and the limited differences in nNAb activities between the arms, suggest that prior PrEP did not modulate these nNAb functions post-HIV seroconversion. Together these data provide insight into envelope-specific-nNAb Fc-mediated functions at the site of exposure which may inform on ensuing immunity during combination HIV prevention strategies including PrEP and HIV vaccines.

Decreased Seroreactivity in Individuals Initiating Antiretroviral Therapy during Acute HIV Infection

Antiretroviral therapy (ART) during acute HIV infection (AHI) interrupts viral dynamics and may delay the emergence of serological markers targeted by current HIV screening and confirmatory assays, thus creating challenges for correctly classifying HIV infection status. The performance of three HIV antigen/antibody combination (HIV Ag/Ab Combo) assays (the Bio-Rad GS, Abbott Architect, and Bio-Rad BioPlex 2200 assays) was evaluated with samples collected from RV254/South East Asia Research Collaboration in HIV 010 (RV254/SEARCH010) study (Bangkok, Thailand) participants at weeks 12 and 24 following the initiation of ART at Fiebig stage I (FI) (n = 23), FII (n = 39), or FIII/IV (n = 22). Supplemental, confirmatory testing was performed by the Geenius HIV 1/2 and HIV-1 Western blot assays (Bio-Rad). Samples from 30 untreated, HIV-1-infected individuals demonstrated robust HIV Ag/Ab Combo assay reactivity with well-developed HIV-1 Western blotting profiles by 24 weeks after infection. In contrast, 52.2% of samples from individuals initiating ART at FI, 7.7% of samples from individuals initiating ART at FII, and 4.5% of samples from individuals initiating ART at FIII/IV were nonreactive by the HIV Ag/Ab Combo assays, with 36.4 to 39.1% of samples having low signal-to-cutoff (S/CO) results by the Architect and BioPlex assays (S/CO < 10). Seroreversion from a reactive to a nonreactive status was observed in 10 individuals initiating ART at FII and 3 individuals initiating ART at FIII/IV. The Geenius and HIV-1 Western blot assay results were negative or indeterminate for 73.9% and 69.6% of individuals, respectively, treated at FI; 50.0% and 26.3% of individuals, respectively, treated at FII; and 54.5% and 40.9% of individuals, respectively, treated at FIII/IV. Virologic suppression of HIV-1 by ART during AHI impedes seroconversion to biomarkers of infection, limiting the utility of HIV Ag/Ab Combo and supplemental, confirmatory assays for infection status determination.

The cost-effectiveness of HIV pre-exposure prophylaxis in men who have sex with men and transgender women at high risk of HIV infection in Brazil

Introduction

Men who have sex with men (MSM) and transgender women (TGW) in Brazil experience high rates of HIV infection. We examined the clinical and economic outcomes of implementing a pre‐exposure prophylaxis (PrEP) programme in these populations.

Methods

We used the Cost‐Effectiveness of Preventing AIDS Complications (CEPAC)‐International model of HIV prevention and treatment to evaluate two strategies: the current standard of care (SOC) in Brazil, including universal ART access (No PrEP strategy); and the current SOC plus daily tenofovir/emtracitabine PrEP (PrEP strategy) until age 50. Mean age (31 years, SD 8.4 years), age‐stratified annual HIV incidence (age ≤ 40 years: 4.3/100 PY; age > 40 years: 1.0/100 PY), PrEP effectiveness (43% HIV incidence reduction) and PrEP drug costs ($23/month) were from Brazil‐based sources. The analysis focused on direct medical costs of HIV care. We measured the comparative value of PrEP in 2015 United States dollars (USD) per year of life saved (YLS). Willingness‐to‐pay threshold was based on Brazil's annual per capita gross domestic product (GDP; 2015: $8540 USD).

Results

Lifetime HIV infection risk among high‐risk MSM and TGW was 50.5% with No PrEP and decreased to 40.1% with PrEP. PrEP increased per‐person undiscounted (discounted) life expectancy from 36.8 (20.7) years to 41.0 (22.4) years and lifetime discounted HIV‐related medical costs from $4100 to $8420, which led to an incremental cost‐effectiveness ratio (ICER) of $2530/YLS. PrEP remained cost‐effective (<1x GDP) under plausible variation in key parameters, including PrEP effectiveness and cost, initial cohort age and HIV testing frequency on/off PrEP.

Conclusion

Daily tenofovir/emtracitabine PrEP among MSM and TGW at high risk of HIV infection in Brazil would increase life expectancy and be highly cost‐effective.

Cross-sectional HIV incidence estimation in an evolving epidemic

The cross-sectional approach to HIV incidence estimation overcomes some of the challenges with longitudinal cohort studies and has been successfully applied in many settings around the world. However, the cross-sectional approach does rely on an initial training data set to develop and calibrate the statistical methods to be used in cross-sectional surveys. The problem addressed in this paper is that the initial training data set may, over time, not reflect the current target population of interest because of evolution of the epidemic. For example, the mismatch between the target population and the initial data set could occur because of increasing use of anti-retroviral therapy among HIV-infected persons throughout the world. We developed methods to adjust the initial training data set with the goal that the adjusted data sets better reflect the target population. These adjustment procedures could help avoid the time and expense of collecting a completely new training data set from the current target population. We report the results of a simulation study to evaluate the procedures. We applied the methods to a dataset of HIV subtype B infection. The adjustment procedures could be applicable in situations other than cross-sectional incidence estimation where complex statistical analyses are to be conducted using an initial data set but those results may not be directly transportable to a new target population of interest. The approach we have proposed could offer a practical and cost-effective way to apply cross-sectional incidence methods to new target populations as the epidemic evolves.

Semen IgM, IgG1, and IgG3 Differentially Associate With Pro-Inflammatory Cytokines in HIV-Infected Men

Genital inflammation significantly increases the risk for HIV infection. The seminal environment is enriched in pro-inflammatory cytokines and chemokines. Here, we investigated the interplay between semen cytokines and humoral immunity to understand whether the characteristics of semen antibodies are associated with genital inflammation. In 36 HIV-infected and 40 HIV-uninfected mens' semen, HIV-specific antibodies (gp120, gp41, p66, and p24), immunoglobulin (Ig) subclasses, isotypes and cytokines, using multiplex assays, were measured. Semen IgG1, IgG3, and IgM were significantly higher in HIV-infected compared to HIV-uninfected men (p < 0.05). In HIV-uninfected men, pro-inflammatory cytokines IL-6, IL-8, and MCP-1 significantly correlated with IgG1 and total IgG (IgG1+IgG2+IgG3+IgG4) (both r≥0.55; p≤0.001). Total IgG in HIV-infected men correlated to HIV-specific antibodies in the semen irrespective of antiretroviral (ARV) use. In HIV-infected, ARV-treated men, p66 and gp41-specific antibodies were inversely correlated with IL-6 and MIP-1α (both r≥−0.65, p≤0.03). In HIV-infected, ARV-naïve men, p24 and gp120-specific antibodies correlated significantly with pro-inflammatory TNF-α (r≥0.44, p≤0.03), while p24 antibodies correlated significantly with chemokine MIP-1β (r = 0.45; p = 0.02). Local cytokines/chemokines were associated with the mucosal-specific Ig subclasses which likely effect specific antibody functions. Together, these data inform on mucosal-specific immunity that may be elicited in the male genital tract (MGT) in future vaccines and/or combination HIV prevention strategies.

Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines. Update April 2018

Daily use of coformulated tenofovir and emtricitabine for HIV pre-exposure prophylaxis (PrEP) by populations at high risk of HIV infection is now recommended in guidelines from the United States, Europe and Australia and globally through the 2015 WHO guidelines. These 2017 Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine's (ASHM) PrEP Guidelines are an updated adaptation of the 2014 US Centers for Disease Control's PrEP guidelines and are designed to: •Support the prescription of PrEP using forms of coformulated tenofovir and emtricitabine that have been registered in Australia by the Therapeutic Goods Administration and other bioequivalent generic drugs that are available in Australia through self-importation, private prescription or Australian PrEP clinical trials•Assist clinicians in the evaluation of patients who are seeking PrEP•Assist clinicians in commencing and monitoring patients on PrEP including PrEP dosing schedules, management of side-effects and toxicity, use of PrEP in pregnancy and in chronic hepatitis B infection and how to cease PrEP Daily PrEP with co-formulated tenofovir and emtricitabine, used continuously or for shorter periods of time, is recommended in these guidelines as a key HIV-prevention option for men who have sex with men (MSM), transgender men and women, heterosexual men and women, and people who inject drugs (PWID) at substantial risk of HIV acquisition. These guidelines were updated in April 2018 and include changes to the recommendations regarding the choice of daily or on-demand PrEP.

Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines. Update April 2018

Daily use of coformulated tenofovir and emtricitabine for HIV pre-exposure prophylaxis (PrEP) by populations at high risk of HIV infection is now recommended in guidelines from the United States, Europe and Australia and globally through the 2015 WHO guidelines. These 2017 Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine's (ASHM) PrEP Guidelines are an updated adaptation of the 2014 US Centers for Disease Control's PrEP guidelines and are designed to: •Support the prescription of PrEP using forms of coformulated tenofovir and emtricitabine that have been registered in Australia by the Therapeutic Goods Administration and other bioequivalent generic drugs that are available in Australia through self-importation, private prescription or Australian PrEP clinical trials•Assist clinicians in the evaluation of patients who are seeking PrEP•Assist clinicians in commencing and monitoring patients on PrEP including PrEP dosing schedules, management of side-effects and toxicity, use of PrEP in pregnancy and in chronic hepatitis B infection and how to cease PrEP Daily PrEP with co-formulated tenofovir and emtricitabine, used continuously or for shorter periods of time, is recommended in these guidelines as a key HIV-prevention option for men who have sex with men (MSM), transgender men and women, heterosexual men and women, and people who inject drugs (PWID) at substantial risk of HIV acquisition. These guidelines were updated in April 2018 and include changes to the recommendations regarding the choice of daily or on-demand PrEP.

Brief Report: Selection of HIV-1 Variants With Higher Transmission Potential by 1% Tenofovir Gel Microbicide

Supplemental Digital Content is Available in the Text.

Background:

Women in the CAPRISA 004 trial assigned to use 1% tenofovir (TFV) microbicide gel, who became HIV-1 infected, had higher viral load set-point and slower antibody avidity maturation compared with placebo participants. We investigated whether TFV gel was selected for viruses with altered genetic characteristics.

Setting:

The participants of the CAPRISA 004 trial (n = 28 TFV and 43 placebo) were from KwaZulu-Natal Province, South Africa and were infected with HIV-1 subtype C. After HIV-1 diagnosis, they were recruited into the CAPRISA 002 cohort.

Methods:

We analyzed gag sequences from the earliest time point post infection (within 3 months of estimated time of infection). Transmission index was measured using a model which predicts the likelihood of an amino acid to be transmitted. Phylogenetic distance from a regional consensus sequence was calculated from a maximum likelihood phylogenetic tree.

Results:

Transmission index and distance from the most common (consensus) sequence have been shown to be markers of transmission fitness. We found that viruses infecting TFV gel recipients were closer to the consensus sequence of regional strains (P = 0.003) and had higher transmission index (P = 0.01). The transmission index was weakly correlated with concomitant viral load (Spearman r = 0.22, P = 0.06).

Conclusion:

Decreased acquisition risk may have increased the barrier to infection therefore selecting for fitter, more consensus-like viruses. Such virus fitness effects will need to be considered for future pre-exposure prophylaxis and vaccine trials.

Characterization of HIV Seroconverters in a TDF/FTC PrEP Study: HPTN 067/ADAPT

BACKGROUND

HIV Prevention Trials Network (HPTN) 067/ADAPT evaluated tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) pre-exposure prophylaxis (PrEP) in women (South Africa) and men who have sex with men (Thailand, US). Participants received once-weekly directly observed therapy (DOT) of TDF/FTC, and were then randomized to daily, time-driven, or event-driven PrEP. This report describes characterization of 12 HIV seroconversion events in this trial.

METHODS

HIV rapid testing was performed at study sites. Retrospective testing included fourth generation assays, HIV RNA testing, Western blot, an HIV-1/2 discriminatory assay, resistance testing, and antiretroviral drug testing.

RESULTS

Six of the 12 seroconverters received TDF/FTC in the DOT phase, but were not randomized (3 were acutely infected at enrollment; 2 were infected during the DOT phase; 1 was not randomized because of pregnancy). One of the 6 randomized participants had acute infection at randomization but was not diagnosed for 3-4 months because HIV rapid tests were nonreactive; continued daily PrEP use was associated with false-negative antibody tests and low HIV RNA levels. The 5 participants infected after randomization included 4 with low adherence to the PrEP regimen, and one who reported a 7-day period without dosing before infection. Three participants had TDF/FTC resistance (M184I, K65R), including 2 who received only 4 once-weekly TDF/FTC doses; most TDF/FTC mutations were detected by next generation sequencing only.

CONCLUSIONS

In HPTN 067/ADAPT, participants who acquired HIV infection had infrequent PrEP dosing or low/suboptimal adherence. Sensitive assays improved detection of HIV infection and drug resistance. Drug resistance was observed with limited PrEP exposure.

The effect of oral preexposure prophylaxis on the progression of HIV-1 seroconversion

OBJECTIVE

To investigate whether oral preexposure prophylaxis (PrEP) alters timing and patterns of seroconversion when PrEP use continues after HIV-1 infection.

DESIGN

Retrospective testing of the timing of Fiebig stage HIV-1 seroconversion in the Partners PrEP Study, a randomized placebo-controlled clinical trial of PrEP conducted in Kenya and Uganda.

METHODS

Specimens from 138 seroconverters were collected every 3 months and when HIV-1 infection was suspected based on monthly rapid HIV-1 tests. Progression of seroconversion was compared between randomized groups (PrEP versus placebo) and per-protocol groups (placebo versus PrEP participants with detectable tenofovir during the seroconversion period) using laboratory assessment of Fiebig stage. Delay in site-detection of seroconversion and association with PrEP drug-regimen resistant virus were assessed using logistic regression. Analysis of time to each Fiebig stage used maximum likelihood estimation with a parametric model to accommodate the varying lengths of HIV-infection intervals.

RESULTS

There was a significant increase in delayed site detection of infection associated with PrEP (odds ratio = 3.49, P = 0.044). Delay in detection was not associated with increased risk of resistance in the PrEP arm (odds ratio = 0.93, P = 0.95). Estimated time to each Fiebig stage was elongated in seroconverters with evidence of ongoing PrEP use, significantly for only Stage 5 (28 versus 17 days, P = 0.05). Adjusted for Fiebig stage, viral RNA was ∼2/3 log lower in those assigned to PrEP compared with placebo; no differences were found in Architect signal to cut-off at any stage.

CONCLUSION

Ongoing PrEP use in seroconverters may delay detection of infection and elongate seroconversion, although the delay does not increase risk of resistance.

Modeling HIV vaccine trials of the future

PURPOSE OF REVIEW

Models of implementation of known-effective interventions for HIV prevention indicate that an efficacious vaccine to prevent HIV infection would be critical for controlling the HIV pandemic. Key issues in the design of future HIV vaccine trials are: first, how to develop reliable immunological correlates of vaccine efficacy, second, how to down-select candidate vaccine regimens into efficacy trials, and third, how to learn about vaccine efficacy in the context of the evolving HIV prevention landscape.

RECENT FINDINGS

Whereas in the past phase-I/-II HIV vaccine trials have addressed the first and second points using a small set of immunological assays and readouts, recently they have used a battery of assays with highly multivariate readouts. In addition, systems vaccinology studies of other pathogens measuring PBMC transcriptomics and other immunological features pre- and postfirst vaccination are demonstrating value, for example, providing discoveries that preimmunization and early postimmunization cell population markers can predict the influenza-specific antibody titer that is a correlate of vaccine protection. The HIV prevention landscape continues to evolve, and the design and analysis of vaccine trials is evolving alongside, to accommodate increasingly dynamic and regional standards of HIV prevention.

SUMMARY

Development of interpretable and robust functional assays, in addition to the associated bioinformatics and statistical analytic tools, is needed to improve the assessment of correlates of protection in efficacy trials and the down-selection of candidate vaccine regimens into efficacy trials. Moreover, high-priority trials should integrate systems vaccinology, including the analysis of prevaccination and early postvaccination markers.

A multiplex assay for detection of SHIV plasma and mucosal IgG and IgA

Evaluating antibody maturation provides valuable data to characterize immune responses to HIV infection and can provide insight into biomedical intervention efficacy. It is important to develop assays that evaluate antibody maturation in both plasma and mucosal compartments. The nonhuman primate model provides a controlled system to collect temporal data that are integral to assessing intervention strategies. We report the development of a novel multiplex assay, based on the Bio-Plex platform, to evaluate plasma and mucosal IgG and IgA avidity and maturation against simian/human immunodeficiency virus (SHIV) in this controlled system. Vaginal mucosa and plasma samples were collected from a prior study evaluating the efficacy of a tenofovir disoproxil fumarate (TDF) intravaginal ring (IVR) against SHIVSF162P3 challenge in female pigtailed macaques. For validation of the multiplex assay, specimens from six SHIV-infected placebo animals and one TDF breakthrough animal were evaluated. For SHIV and HIV envelope analytes, antibody levels and avidity in both compartments continued to mature post-infection. Maturation of IgG and IgA levels was similar in each compartment, however, mucosal antibody levels tended to be more variable. This SHIV assay elucidates IgG/IgA antibody kinetics in the plasma and vaginal mucosa and will be a valuable tool in vaccine and other biomedical intervention studies in the nonhuman primate model.

Antiviral Functions of Human Immunodeficiency Virus Type 1 (HIV-1)-Specific IgG Antibodies: Effects of Antiretroviral Therapy and Implications for Therapeutic HIV-1 Vaccine Design

Contemporary antiretroviral therapy (ART) is effective and tolerable for long periods of time but cannot eradicate human immunodeficiency virus type 1 (HIV-1) infection by either elimination of viral reservoirs or enhancement of HIV-1-specific immune responses. Boosting "protective" HIV-1-specific immune responses by active or passive immunization will therefore be necessary to control or eradicate HIV-1 infection and is currently the topic of intense investigation. Recently reported studies conducted in HIV patients and non-human primate (NHP) models of HIV-1 infection suggest that HIV-1-specific IgG antibody responses may contribute to the control of HIV-1 infection. However, production of IgG antibodies with virus neutralizing activity by vaccination remains problematic and while vaccine-induced natural killer cell-activating IgG antibodies have been shown to prevent the acquisition of HIV-1 infection, they may not be sufficient to control or eradicate established HIV-1 infection. It is, therefore, important to consider other functional characteristics of IgG antibody responses. IgG antibodies to viruses also mediate opsonophagocytic antibody responses against virions and capsids that enhance the function of phagocytic cells playing critical roles in antiviral immune responses, particularly conventional dendritic cells and plasmacytoid dendritic cells. Emerging evidence suggests that these antibody functions might contribute to the control of HIV-1 infection. In addition, IgG antibodies contribute to the intracellular degradation of viruses via binding to the cytosolic fragment crystallizable (Fc) receptor tripartite motif containing-21 (TRIM21). The functional activity of an IgG antibody response is influenced by the IgG subclass content, which affects binding to antigens and to Fcγ receptors on phagocytic cells and to TRIM21. The IgG subclass content and avidity of IgG antibodies is determined by germinal center (GC) reactions in follicles of lymphoid tissue. As HIV-1 infects cells in GCs and induces GC dysfunction, which may persist during ART, strategies for boosting HIV-1-specific IgG antibody responses should include early commencement of ART and possibly the use of particular antiretroviral drugs to optimize drug levels in lymphoid follicles. Finally, enhancing particular functions of HIV-1-specific IgG antibody responses by using adjuvants or cytokines to modulate the IgG subclass content of the antibody response might be investigated in NHP models of HIV-1 infection and during trials of therapeutic vaccines in HIV patients.

Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines

Daily use of coformulated tenofovir and emtricitabine for HIV pre-exposure prophylaxis (PrEP) by populations at high risk of HIV infection is now recommended in guidelines from the United States, Europe and Australia and globally through the 2015 WHO guidelines. These 2017 Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine's (ASHM) PrEP Guidelines are an updated adaptation of the 2014 US Centers for Disease Control's PrEP guidelines and are designed to: •Support the prescription of PrEP using forms of coformulated tenofovir and emtricitabine that have been registered in Australia by the Therapeutic Goods Administration and other bioequivalent generic drugs that are available in Australia through self-importation, private prescription or Australian PrEP clinical trials•Assist clinicians in the evaluation of patients who are seeking PrEP•Assist clinicians in commencing and monitoring patients on PrEP including PrEP dosing schedules, management of side-effects and toxicity, use of PrEP in pregnancy and in chronic hepatitis B infection and how to cease PrEP Daily PrEP with co-formulated tenofovir and emtricitabine, used continuously or for shorter periods of time, is recommended in these guidelines as a key HIV-prevention option for men who have sex with men (MSM), transgender men and women, heterosexual men and women, and people who inject drugs (PWID) at substantial risk of HIV acquisition.

Historical development of vaginal microbicides to prevent sexual transmission of HIV in women: from past failures to future hopes

Infection with human immunodeficiency virus (HIV) remains a global public health concern and is particularly serious in low- and middle-income countries. Widespread sexual violence and poverty, among other factors, increase the risk of infection in women, while currently available prevention methods are outside the control of most. This has driven the study of vaginal microbicides to prevent sexual transmission of HIV from men to women in recent decades. The first microbicides evaluated were formulated as gels for daily use and contained different substances such as surfactants, acidifiers and monoclonal antibodies, which failed to demonstrate efficacy in clinical trials. A gel containing the reverse transcriptase inhibitor tenofovir showed protective efficacy in women. However, the lack of adherence by patients led to the search for dosage forms capable of releasing the active principle for longer periods, and hence to the emergence of the vaginal ring loaded with dapivirine, which requires a monthly application and is able to reduce the sexual transmission of HIV. The future of vaginal microbicides will feature the use of alternative dosage forms, nanosystems for drug release and probiotics, which have emerged as potential microbicides but are still in the early stages of development. Protecting women with vaginal microbicide formulations would, therefore, be a valuable tool for avoiding sexual transmission of HIV.

Factors Associated With the Control of Viral Replication and Virologic Breakthrough in a Recently Infected HIV-1 Controller

HIV-1 controllers are patients who control HIV-1 viral replication without antiretroviral therapy. Control is achieved very early in the course of infection, but the mechanisms through which viral replication is restricted are not fully understood. We describe a patient who presented with acute HIV-1 infection and was found to have an HIV-1 RNA level of < 100 copies/mL. She did not have any known protective HLA alleles, but significant immune activation of CD8 + T cells and natural killer (NK) cells was present, and both cell types inhibited viral replication. Virus cultured from this patient replicated as well in vitro as virus isolated from her partner, a patient with AIDS who was the source of transmission. Virologic breakthrough occurred 9 months after her initial presentation and was associated with an increase in CD4 + T cell activation levels and a significant decrease in NK cell inhibitory capacity. Remarkably, CD8 + T cell inhibitory capacity was preserved and there were no new escape mutations in targeted Gag epitopes. These findings suggest that fully replication-competent virus can be controlled in acute HIV-1 infection in some patients without protective HLA alleles and that NK cell responses may contribute to this early control of viral replication.

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We show that an HIV-1 controller was infected with pathogenic virus yet maintained low viral loads during primary infection.

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She had activated NK cells and CD8+ T cells and both cell types suppressed HIV-1 replication shortly after infection.

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She eventually lost control of viral replication, and this was associated with a reduction in NK cell suppressive activity.

HIV-1 controllers are patients who control the virus without HIV-1 medications. These patients may teach us how to design a vaccine against HIV-1. Little is known about how the virus is controlled in the early phase of infection in these patients. Here we show that a recently infected HIV-1 controller had a strong natural killer cell response to the virus. Interestingly, she lost control of the virus 9 months later and her natural killer cell response to the virus was diminished. Our work suggests that natural killer cells may have contributed to viral control in the early phase of infection.

Pre-exposure prophylaxis: a useful tool to prevent human immunodeficiency virus infection?

The aim of preventive measures against human immunodeficiency virus (HIV) is to reduce the incidence of HIV infection in the general population and in high-risk groups, such as men having sex with men (MSM), and to reduce the risk that a given individual will contract or spread the virus. Male and female condoms, post-exposure prophylaxis and circumcision are preventive methods currently recognized or promoted worldwide. Although modest success has been reported in a phase-III vaccine trial, other methods are being evaluated, such as vaginal and rectal microbicides, and pre-exposure prophylaxis (PrEP). Herein, we discuss results from prevention trials, especially those focusing on PrEP and particularly on recent results from 'on-demand' PrEP regimens. The efficacy of PrEP (rates of 0%-86%) is strongly correlated with adherence and plasma concentrations of antiretrovirals. Adverse events are rare. Selection of emtricitabine-resistant strains is mainly reported in individuals with an undiagnosed HIV infection using PrEP. PrEP is now strongly recommended in WHO prevention programmes for individuals at substantial risk for HIV with a view to controlling this epidemic by 2030.

Potential Clinical and Economic Value of Long-Acting Preexposure Prophylaxis for South African Women at High-Risk for HIV Infection

BACKGROUND

For young South African women at risk for human immunodeficiency virus (HIV) infection, preexposure prophylaxis (PrEP) is one of the few effective prevention options available. Long-acting injectable PrEP, which is in development, may be associated with greater adherence, compared with that for existing standard oral PrEP formulations, but its likely clinical benefits and additional costs are unknown.

METHODS

Using a computer simulation, we compared the following 3 PrEP strategies: no PrEP, standard PrEP (effectiveness, 62%; cost per patient, $150/year), and long-acting PrEP (effectiveness, 75%; cost per patient, $220/year) in South African women at high risk for HIV infection (incidence of HIV infection, 5%/year). We examined the sensitivity of the strategies to changes in key input parameters among several outcome measures, including deaths averted and program cost over a 5-year period; lifetime HIV infection risk, survival rate, and program cost and cost-effectiveness; and budget impact.

RESULTS

Compared with no PrEP, standard PrEP and long-acting PrEP cost $580 and $870 more per woman, respectively, and averted 15 and 16 deaths per 1000 women at high risk for infection, respectively, over 5 years. Measured on a lifetime basis, both standard PrEP and long-acting PrEP were cost saving, compared with no PrEP. Compared with standard PrEP, long-acting PrEP was very cost-effective ($150/life-year saved) except under the most pessimistic assumptions. Over 5 years, long-acting PrEP cost $1.6 billion when provided to 50% of eligible women.

CONCLUSIONS

Currently available standard PrEP is a cost-saving intervention whose delivery should be expanded and optimized. Long-acting PrEP will likely be a very cost-effective improvement over standard PrEP but may require novel financing mechanisms that bring short-term fiscal planning efforts into closer alignment with longer-term societal objectives.

Distinct genital tract HIV-specific antibody profiles associated with tenofovir gel

The impact of topical antiretrovirals for pre-exposure prophylaxis on humoral responses following HIV infection is unknown. Using a binding antibody multiplex assay, we investigated HIV-specific IgG and IgA responses to envelope glycoproteins, p24 Gag and p66, in the genital tract (GT) and plasma following HIV acquisition in women assigned to tenofovir gel (n=24) and placebo gel (n=24) in the CAPRISA 004 microbicide trial to assess if this topical antiretroviral had an impact on mucosal and systemic antibody responses. Linear mixed effect modeling and partial least squares discriminant analysis was used to identify multivariate antibody signatures associated with tenofovir use. There were significantly higher response rates to gp120 Env (P=0.03), p24 (P=0.002), and p66 (P=0.009) in plasma and GT in women assigned to tenofovir than placebo gel at multiple time points post infection. Notably, p66 IgA titers in the GT and plasma were significantly higher in the tenofovir compared with the placebo arm (P<0.05). Plasma titers for 9 of the 10 HIV-IgG specificities predicted GT levels. Taken together, these data suggest that humoral immune responses are increased in blood and GT of individuals who acquire HIV infection in the presence of tenofovir gel.