Prevention of vaginal simian immunodeficiency virus transmission in macaques by postexposure prophylaxis with zidovudine, lamivudine and indinavir

Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV - CDC Recommendations, United States, 2025

Nonoccupational postexposure prophylaxis (nPEP) for HIV is recommended when a nonoccupational (e.g., sexual, needle, or other) exposure to nonintact skin or mucous membranes that presents a substantial risk for HIV transmission has occurred, and the source has HIV without sustained viral suppression or their viral suppression information is not known. A rapid HIV test (also referred to as point-of-care) or laboratory-based antigen/antibody combination HIV test is recommended before nPEP initiation. Health care professionals should ensure the first dose of nPEP is provided as soon as possible, and ideally within 24 hours, but no later than 72 hours after exposure. The initial nPEP dose should not be delayed due to pending results of any laboratory-based testing, and the recommended length of nPEP course is 28 days. The recommendations in these guidelines update the 2016 nPEP guidelines (CDC. Updated guidelines for antiretroviral postexposure prophylaxis after sexual, injection drug use, or other nonoccupational exposure to HIV - United States, 2016. Atlanta, GA: US Department of Health and Human Services, CDC; 2017). These 2025 nPEP guidelines update recommendations and considerations for use of HIV nPEP in the United States to include newer antiretroviral (ARV) agents, updated nPEP indication considerations, and emerging nPEP implementation strategies. The guidelines also include considerations for testing and nPEP regimens for persons exposed who have received long-acting injectable ARVs in the past. Lastly, testing recommendations for persons who experienced sexual assault were updated to align with the most recent CDC sexually transmitted infection treatment guidelines. These guidelines are divided into two sections: Recommendations and CDC Guidance. The preferred regimens for most adults and adolescents are now bictegravir/emtricitabine/tenofovir alafenamide or dolutegravir plus (tenofovir alafenamide or tenofovir disoproxil fumarate) plus (emtricitabine or lamivudine). However, the regimen can be tailored to the clinical circumstances. Medical follow-up for persons prescribed nPEP also should be tailored to the clinical situation; recommended follow-up includes a visit at 24 hours (remote or in person) with a medical provider, and clinical follow-up 4-6 weeks and 12 weeks after exposure for laboratory testing. Persons initiating nPEP should be informed that pre-exposure prophylaxis for HIV (PrEP) can reduce their risk for acquiring HIV if they will have repeat or continuing exposure to HIV after the end of the nPEP course. Health care professionals should offer PrEP options to persons with ongoing indications for PrEP and create an nPEP-to-PrEP transition plan for persons who accept PrEP.

Evaluation of Pediatric HIV Postexposure Prophylaxis Guideline Following Child Sexual Assault in Western Australia

BACKGROUND

HIV postexposure prophylaxis (PEP) following child sexual assault (CSA) is recommended in select cases. High rates of poor adherence to PEP are reported. We evaluated adherence to the recommended management of children following CSA at the tertiary pediatric facility in Western Australia and compared our approach with international guidelines.

METHODS

Medical records were reviewed for all children <16 years old assessed at Perth Children's Hospital between October 1, 2016 and November 30, 2020 following alleged CSA. Data, including exposure type, PEP adherence and follow-up, were collected. A review of contemporary national and international PEP guidelines was undertaken in parallel.

RESULTS

There were 511 alleged CSA events over the study period; 62/511 (12%) were appropriately risk-assessed as requiring PEP by the treating clinician. PEP was not prescribed in 8/62 (13%) events, with a reason documented for 6/8 (75%). Overall, less than half of children who were eligible for PEP were adherent to the 28-day regimen (23/54, 43%). Gastrointestinal upset contributed to early cessation in 5/54 (9%). Final 3-month blood-borne virus serology results were available in less than one in 3 children. A review of international clinical practice revealed significant heterogeneity of criteria for the provision of PEP and a paucity of pediatric-specific data.

CONCLUSIONS

We identified several areas of our PEP management that required strengthening, with limited direction available in current international guidelines. We have adopted a broader use of fixed drug combinations and implemented a multifaceted follow-up program. It will be essential to review the impact of these changes.

A behavioral economics approach to enhancing HIV preexposure and postexposure prophylaxis implementation

PURPOSE OF REVIEW

The 'PrEP cliff' phenomenon poses a critical challenge in global HIV PrEP implementation, marked by significant dropouts across the entire PrEP care continuum. This article reviews new strategies to address 'PrEP cliff'.

RECENT FINDINGS

Canadian clinicians have developed a service delivery model that offers presumptive PEP to patients in need and transits eligible PEP users to PrEP. Early findings are promising. This service model not only establishes a safety net for those who were not protected by PrEP, but it also leverages the immediate salience and perceived benefits of PEP as a natural nudge towards PrEP use. Aligning with Behavioral Economics, specifically the Salience Theory, this strategy holds potential in tackling PrEP implementation challenges.

SUMMARY

A natural pathway between PEP and PrEP has been widely observed. The Canadian service model exemplifies an innovative strategy that leverages this organic pathway and enhances the utility of both PEP and PrEP services. We offer theoretical insights into the reasons behind these PEP-PrEP transitions and evolve the Canadian model into a cohesive framework for implementation.

Post-exposure prophylaxis to prevent HIV: new drugs, new approaches, and more questions

Post-exposure prophylaxis (PEP) to prevent HIV acquisition has been recommended for over three decades, but remains underutilised. Over the past decade, clinical trials have established the safety and tolerability of newer PEP regimens, particularly those containing integrase strand transfer inhibitors (INSTIs) combined with a tenofovir and lamivudine or emtricitabine backbone. Several of these regimens were better tolerated than historical controls. Studies in macaques found that shorter courses of PEP with INSTIs were effective, particularly if dosing occurred close to the time of retroviral exposure. Despite the increase in well tolerated options, PEP seems to be underused globally and links to other prevention services are suboptimal. Interventions to increase provider and community awareness of PEP are needed.

UK guideline for the use of HIV post-exposure prophylaxis 2021

We present the updated British Association for Sexual Health and HIV (BASHH) guidelines for post-exposure prophylaxis (PEP) to HIV following sexual exposures, occupational exposures and other nonoccupational exposures in the community. This serves as an update to the 2015 BASHH guideline on PEP following sexual exposures and the 2008 Expert Advisory Group on AIDS guidelines on HIV PEP. We aim to provide evidence-based guidance on best clinical practice in the provision, monitoring and support of PEP for the prevention of HIV acquisition following sexual, occupational and other nonoccupational exposures in the community. The guideline covers when to prescribe PEP, what antiretroviral agents to use and how to manage PEP. This includes (i) evidence of PEP efficacy; (ii) evidence relating to individual-level efficacy of antiretroviral therapy to prevent the sexual transmission of HIV; (iii) data on the detectable (transmissible) prevalence of HIV in specific populations; (iv) risk of HIV transmission following different types of sexual and occupational exposure; (v) baseline risk assessment; (vi) drug regimens and dosing schedules; (vii) monitoring PEP; (viii) baseline and follow-up blood-borne virus testing; (ix) the role of PEP within broader HIV prevention strategies, for example, HIV pre-exposure prophylaxis (PrEP). The guideline also covers special scenarios such as PEP in pregnancy, breastfeeding and chronic hepatitis B virus infection, and when PEP should be considered in people using HIV PrEP. The guidelines are aimed at clinical professionals directly involved in PEP provision and other stakeholders in the field. A proforma to assist PEP consultations is included. A public consultation process was undertaken prior to finalizing the recommendations.

The "Side Effects" of HIV PEP Use: Forced Reflections and Introspections on Sexual Decision-Making

Postexposure prophylaxis (PEP) for HIV prevention involves giving antiretroviral medications to HIV-negative people to prevent seroconversion after HIV exposure. Available literature suggests this intervention is >80% effective. Accordingly, we implemented a nurse-led PEP program in two sexually transmitted and HIV testing clinics. As part of evaluating this project, we undertook semistructured interviews with participants who accessed PEP to understand their experiences. Twelve men participated: all were HIV-negative males who sought PEP for condomless anal sex with men. Unique to this article is the presentation of the participants' descriptions of the "side effects" they experienced. Notably, the main side effect they described related to emotional distress. Simply put, having to take a medication for 28 days forced reflection and introspection on their sexual decision-making. We feel HIV prevention workers should consider this emotional reaction when designing interventions, and ensure they provide adequate preparation and support to patients.

An Exploratory Study of a Nurse-Led HIV Postexposure Prophylaxis Program

The provision of HIV medications to HIV-negative persons after exposure to HIV is known as postexposure prophylaxis (PEP). Because this prevention strategy is primarily only available in emergency rooms, we piloted a nurse-led community-based PEP program in Ottawa from September 2013 through August 2015. As part of evaluating this program, we conducted qualitative interviews with persons who initiated PEP. Twelve men who had engaged in condomless anal sex with other males participated. Thematic analysis of the interview transcripts highlighted that PEP was considered unmentionable because the participants' saw it as proof of past behavior that was perceived negatively. Our results thus revealed that PEP was stigmatized, which made our participants reluctant to answer health care professionals' "questions" about why they needed PEP. To do so was to be exposed to stigma. The use of PEP for our participants was a balance between wanting to minimize the risks of HIV acquisition against the risks of disclosing the unmentionable. We take these findings to mean that clinicians and health service policy workers should move PEP into community clinics (decentralizing it from hospitals, and increase the involvement of nurses); aim to provide all required PEP services in community settings (consolidate PEP provision in these clinics); and ensure PEP services are streamlined to remove extraneous data collection (meaning history and exam tools should be standardized to minimize needless questions that may impede PEP access). Together, these recommendations may increase patients' access to PEP, and maximize its HIV prevention effects.

Results from the post-exposure prophylaxis pilot program (P-QUAD) demonstration project in Los Angeles County

Post-exposure prophylaxis (PEP) is a promising but under-utilized strategy for HIV prevention in high-risk populations. Between March 2010 and June 2011, two community-based clinics in Los Angeles County provided PEP in a pilot program to 267 unique individuals. Courses were primarily dispensed to men who have sex with men (84%) and consisted overwhelmingly of a three-drug antiretroviral therapy regimen containing two nucleoside reverse transcriptase inhibitors and either an integrase inhibitor (raltegravir) or a boosted protease inhibitor (lopinavir/ritonavir). Approximately 64% of all PEP courses were followed for at least 12 weeks, and seven individuals seroconverted. Of the seven seroconversions, six had subsequent re-exposure. The low rate of PEP failure calls for expanded funding for PEP in other jurisdictions.

Optimal HIV Postexposure Prophylaxis Regimen Completion With Single Tablet Daily Elvitegravir/Cobicistat/Tenofovir Disoproxil Fumarate/Emtricitabine Compared With More Frequent Dosing Regimens

STRUCTURE

The study evaluated elvitegravir/cobicistat/tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC) ("Quad pill") for postexposure prophylaxis (PEP).

BACKGROUND

HIV-exposed individuals may benefit from PEP, but completion rates have been suboptimal because of regimen complexity and side effects. Newer antiretroviral combinations coformulated as single daily pills may optimize PEP adherence.

SETTING

One hundred HIV-uninfected individuals who presented to a Boston community health center after an acute HIV sexual exposure were enrolled and initiated PEP with the daily, single-pill combination Quad pill for a 28-day course.

METHODS

Side effects and medication completion rates from study participants were compared with historical controls who had used PEP regimens consisting of TDF/FTC daily and raltegravir twice daily, or earlier regimens of twice daily zidovudine (AZT)/lamivudine (3TC) and a protease inhibitor, using χ tests for independence.

RESULTS

Of the 100 participants who initiated the Quad pill for PEP after a high-risk sexual exposure, 71% completed the 28-day Quad pill regimen, which was significantly greater than historical controls who used TDF/FTC and raltegravir (57%, P < 0.05) or AZT/3TC plus a protease inhibitor (39%, P < 0.001). The most common side effects reported by Quad pill users were as follows: abdominal discomfort or pain, gas or bloating (42%), diarrhea (38%), fatigue (28%), nausea or vomiting (28%), headache (14%), or dizziness or lightheadedness (6%). Most symptoms were mild, limited, and did not result in medication discontinuation. No participants became HIV infected.

CONCLUSIONS

Fixed-dose combination of elvitegravir/cobicistat/TDF/FTC was safe and well tolerated for PEP, with higher regimen completion rates than more frequently dosed PEP regimens.

CD4-mimetic sulfopeptide conjugates display sub-nanomolar anti-HIV-1 activity and protect macaques against a SHIV162P3 vaginal challenge

The CD4 and the cryptic coreceptor binding sites of the HIV-1 envelope glycoprotein are key to viral attachment and entry. We developed new molecules comprising a CD4 mimetic peptide linked to anionic compounds (mCD4.1-HS₁₂ and mCD4.1-PS1), that block the CD4-gp120 interaction and simultaneously induce the exposure of the cryptic coreceptor binding site, rendering it accessible to HS₁₂- or PS1- mediated inhibition. Using a cynomolgus macaque model of vaginal challenge with SHIV162P3, we report that mCD4.1-PS1, formulated into a hydroxyethyl-cellulose gel provides 83% protection (5/6 animals). We next engineered the mCD4 moiety of the compound, giving rise to mCD4.2 and mCD4.3 that, when conjugated to PS1, inhibited cell-free and cell-associated HIV-1 with particularly low IC₅₀, in the nM to pM range, including some viral strains that were resistant to the parent molecule mCD4.1. These chemically defined molecules, which target major sites of vulnerability of gp120, are stable for at least 48 hours in conditions replicating the vaginal milieu (37 °C, pH 4.5). They efficiently mimic several large gp120 ligands, including CD4, coreceptor or neutralizing antibodies, to which their efficacy compares very favorably, despite a molecular mass reduced to 5500 Da. Together, these results support the development of such molecules as potential microbicides.

Community-based, nurse-led post-exposure prophylaxis: results and implications

HIV medications can be used as post-exposure prophylaxis to efficaciously prevent an HIV-negative person who has come into contact with HIV from becoming HIV-positive. Traditionally, these medications have been available in emergency departments, which have constituted a barrier for the members of many minority groups who are greatly affected by HIV transmission (i.e. gay, bisexual and other men who have sex with men, and persons who use injection drugs). From 5 September 2013 through 4 September 2015, we sought to increase the use of HIV post-exposure prophylaxis by having registered nurses provide these medications, when indicated, in community clinics in Ottawa, Canada. We undertook a chart review of patients who accessed services for HIV post-exposure prophylaxis in this period. Over the two years of data collection, 112 persons requested HIV post-exposure prophylaxis and 64% (n = 72) initiated these medications. Most (93%, or n = 67, of the 72 initiations) were among men, with 88% (n = 59) of these men reporting same sex sexual partners. Among these 58 men, 31% (n = 18) had sexual contact with other men known to be HIV-positive. Among women (n = 8), five initiated post-exposure prophylaxis: three after needle-sharing contact or sexual contact with a male partner who reportedly shared needles, and two after unprotected vaginal sex with a male partner known to be HIV-positive. Overall, no one was diagnosed with HIV at the four-month HIV testing follow-up, although six persons were diagnosed with HIV from the baseline HIV testing, and an additional four were diagnosed with HIV during routine HIV testing one year after completing post-exposure prophylaxis. In total, nine persons in our sample were thus diagnosed with HIV during the study period, which accounted for 9.4% (n = 10 of 106) of all reported HIV diagnoses in Ottawa during this time. We conclude that nurse-initiated HIV post-exposure prophylaxis can be an effective way to provide HIV prevention services to persons who are at high-risk for HIV.

Mucosal Topical Microbicide Candidates Exert Influence on the Subsequent SIV Infection and Survival by Regulating SIV-Specific T-Cell Immune Responses

OBJECTIVE

To determine whether mucosal topical microbicides have any influence on disease progression during subsequent simian immunodeficiency virus (SIV) infection.

DESIGN

A 2-phase study was performed in primate monkeys. The first phase mimicked microbicide efficacy studies; the second phase served to determine the disease progression in a productive infection model.

METHODS

During the first phase, monkeys were intrarectally pretreated with tenofovir, sifuvirtide (SFT), or maraviroc-formulated microbicides and then challenged with low-dose SHIV-1157ipd3N4. Second, all monkeys were rechallenged with a single high dose of SIVmac239 to generate productive infections. The survival rate, viral loads, CD4(+) T-cell counts, and SIV-specific T-cell responses were determined during the 104-week following up.

RESULTS

Repeated rectal challenges did not result in productive infection in all groups, evidenced by undetectable viral loads with occasional viral blips during the first phase of this study. All monkeys were productively infected after the high-dose rechallenge with SIVmac239. Two groups, including maraviroc-treated and tenofovir-treated groups, experienced 100% mortality during the 104-week following up. In contrast, the SFT-treated group showed significantly higher survival, and only 25% died at week 95. Interestingly, SIV-specific T-cell responses were also significantly higher in the SFT group. Transcriptomic analyses evidenced immune imprint in immune system among different microbicide-treated groups.

CONCLUSIONS

This study provides preliminary but important evidence for the influence of prophylactically applied microbicides on disease progression of subsequent SIV infection and suggests that the long-term immune safety concern for microbicides should be also considered in the effort to develop effective microbicides.

UK guideline for the use of HIV Post-Exposure Prophylaxis Following Sexual Exposure, 2015

We present the updated British Association for Sexual Health and HIV guidelines for HIV post-exposure prophylaxis following sexual exposure (PEPSE). This document includes a review of the current data to support the use of PEPSE, considers how to calculate the risks of infection after a potential exposure, and provides recommendations on when PEPSE should and should not be considered. We also review which medications to use for PEPSE, provide a checklist for initial assessment, and make recommendations for monitoring individuals receiving PEPSE. Special scenarios, cost-effectiveness of PEPSE, and issues relating to service provision are also discussed. Throughout the document, the place of PEPSE within the broader context of other HIV prevention strategies is considered.

Efficacy of HIV Postexposure Prophylaxis: Systematic Review and Meta-analysis of Nonhuman Primate Studies

BACKGROUND

The efficacy of antiretrovirals as postexposure prophylaxis (PEP) to prevent viral acquisition was demonstrated in nonhuman primate models of human immunodeficiency virus (HIV) in the early 1990s. To complement the evidence base for efficacy of HIV PEP in humans, we systematically reviewed the published data on PEP efficacy across animal studies.

METHODS

PubMed, Web of Science, and Embase were searched from inception to 31 May 2014 for randomized and nonrandomized studies reporting seroconversions among uninfected animals exposed to HIV or simian immunodeficiency virus, irrespective of route of exposure. Seroconversion risk data were pooled using random-effects models, and associations explored through meta-regression.

RESULTS

Twenty-five studies (408 primates) were included for review. The risk of serconversion was 89% lower among animals exposed to PEP compared with those that did not receive PEP (odds ratio, 0.11 [95% confidence interval, .05-.23]). Heterogeneity was low (I(2) = 0.0%). In meta-regression, a significant association was found between timing of PEP and seroconversion and the use of tenofovir compared with other drugs.

CONCLUSIONS

This review provides further evidence of the protective benefit of PEP in preventing HIV acquisition, and the importance of initiating PEP as early as possible following virus exposure.

Antiretrovirals for primary HIV prevention: the current status of pre- and post-exposure prophylaxis

In light of the 2 million HIV infections that occur globally each year, there is a need to optimize strategies that integrate biomedical and behavioral approaches to HIV prevention. Post-exposure prophylaxis (PEP) immediately after acute high-risk exposures and pre-exposure prophylaxis (PrEP) for those who engage in recurrent high-risk behaviors are promising bio-behavioral approaches to decreasing HIV transmission. Guidelines have recommended PEP for occupational and non-occupational exposures for over 15 years, but uptake of PEP has been limited, partly as a result of insufficient awareness of this intervention among persons at highest risk for acquiring HIV. However, since the publication of large randomized clinical trials demonstrating the efficacy of PrEP, and the dissemination of guidelines endorsing its use, there is a renewed focus on bio-behavioral prevention. Numerous studies have recently assessed the acceptability of bio-behavioral prevention programs among diverse populations or described experiences implementing these programs in "real-world" settings. As research and clinical data informing optimal utilization of PEP and PrEP are rapidly accumulating, this review provides a timely summary of recent progress in bio-behavioral prevention. By contextualizing the most noteworthy recent findings regarding PEP and PrEP, this review seeks to inform the successful implementation of these promising prevention approaches.

Practical guidance for nonoccupational postexposure prophylaxis to prevent HIV infection: an editorial review

Postexposure prophylaxis (PEP) with antiretroviral medication has been used as an HIV-prevention strategy for nearly 20 years. The fact that approximately 50 000 new HIV infections occur in the United States each year reflects marked underutilization of nonoccupational PEP (NPEP). There have been several advances in NPEP in the past 10 years. Clinical trials from different countries have demonstrated better tolerability, completion rates, and fewer drug-drug interactions with newer antiretroviral agents. Notably, there has been a shift from zidovudine-based to tenofovir-based regimens. Three-drug therapy is now favored for all potential HIV exposures. More recently, the US Public Health Service and the New York State Department of Health recommended tenofovir/emtricitabine and raltegravir as the first-line regimen universally for PEP. Advances in HIV testing technology may also allow shorter duration of follow-up HIV testing after a high-risk exposure. This review will discuss challenges with previously recommended regimens, newer potential candidate agents and the rationale for using them, intervals for laboratory monitoring, and cost considerations for NPEP. NPEP can be viewed as an educable moment and a potential bridge to preexposure prophylaxis, as part of a combination prevention package, for those who are likely to have recurrent higher-risk exposures. Thus, risk-reduction counseling should be an integral aspect of NPEP.

Non-human primate models of hormonal contraception and HIV

PROBLEM

Recent concerns that hormonal contraception (HC) may increase risk of HIV acquisition has led to keen interest in using non-human primates (NHP) to understand the underlying mechanism and the magnitude of the risk. This is, in part, because some experiments which would be difficult or logistically impossible in women are more easily conducted in NHP.

METHOD OF STUDY

NHP models of HIV can inform HIV acquisition and pathogenesis research and identify and evaluate biomedical preventions and treatments for HIV/AIDS. Widely used species include rhesus, pigtail, and cynomolgous macaques.

RESULTS

This paper reviews past, current and proposed NHP research around the intersection of HIV and HC.

CONCLUSION

NHP research may lead to the identification of hormonally regulated biomarkers that correlate with HIV-acquisition risk, to a ranking of existing or next-generation HC along an HIV-acquisition risk profile, and inform research around new biomedical preventions for HIV.

Overviewing a Nurse-Led, Community-Based HIV PEP Program: Applying the Extant Literature in Frontline Practice

This clinical concept paper overviews a program to facilitate access to postexposure prophylaxis (PEP) for gay, bisexual, and other men who have sex with men. The project, which was a collaborative initiative involving the local School of Nursing, public health unit, AIDS service organization, hospital-based HIV clinic, and an outpatient pharmacy, was implemented to circumvent common barriers to care identified in the literature. In this project, persons who present to one of the two participating clinics after having come, or likely having come, into contact with HIV within the previous 72 hr, are offered rapid HIV testing, also known as point-of-care (POC) testing, to rule out existing HIV infection, and provided with a follow-up appointment booked at the HIV clinic. Clients are also offered comprehensive STI testing, and HIV prevention counseling. The implementation of this collaborative community-based access-to-PEP project demonstrates the application of research to a real-world health care setting, and it is hoped that others will adapt this model to their local setting, enabling ease of access to PEP for members of groups that are disproportionately affected by HIV.

Protective effect of vaginal application of neutralizing and nonneutralizing inhibitory antibodies against vaginal SHIV challenge in macaques

Definition of antibody (Ab) functions capable of preventing mucosal HIV transmission may be critical to both effective vaccine development and the prophylactic use of monoclonal Abs. Although direct antibody-mediated neutralization is highly effective against cell-free virus, increasing evidence suggests an important role for immunoglobulin G (IgG) Fcγ receptor (FcγR)-mediated inhibition of HIV replication. Thus, a panel of well-known neutralizing (NAbs) and nonneutralizing Abs (NoNAbs) were screened for their ability to block HIV acquisition and replication in vitro in either an independent or FcγR-dependent manner. Abs displaying the highest Fc-mediated inhibitory activity in various in vitro assays were selected, formulated for topical vaginal application in a microbicide gel, and tested for their antiviral activity against SHIVSF162P3 vaginal challenge in non-human primates (NHPs). A combination of three NAbs, 2G12, 2F5, and 4E10, fully prevented simian/human immunodeficiency virus (SHIV) vaginal transmission in 10 out of 15 treated NHPs, whereas a combination of two NoNAbs, 246-D and 4B3, although having no impact on SHIV acquisition, reduced plasma viral load. These results indicate that anti-HIV Abs with distinct neutralization and inhibitory functions differentially affect in vivo HIV acquisition and replication, by interfering with early viral replication and dissemination. Therefore, combining diverse Ab properties may potentiate the protective effects of anti-HIV-Ab-based strategies.

MiniCD4 microbicide prevents HIV infection of human mucosal explants and vaginal transmission of SHIV(162P3) in cynomolgus macaques

In complement to an effective vaccine, development of potent anti-HIV microbicides remains an important priority. We have previously shown that the miniCD4 M48U1, a functional mimetic of sCD4 presented on a 27 amino-acid stable scaffold, inhibits a broad range of HIV-1 isolates at sub-nanomolar concentrations in cellular models. Here, we report that M48U1 inhibits efficiently HIV-1(Ba-L) in human mucosal explants of cervical and colorectal tissues. In vivo efficacy of M48U1 was evaluated in nonhuman primate (NHP) model of mucosal challenge with SHIV(162P3) after assessing pharmacokinetics and pharmacodynamics of a miniCD4 gel formulation in sexually matured female cynomolgus macaques. Among 12 females, half were treated with hydroxyethylcellulose-based gel (control), the other half received the same gel containing 3 mg/g of M48U1, one hour before vaginal route challenge with 10 AID(50) of SHIV(162P3). All control animals were infected with a peak plasma viral load of 10(5)-10(6) viral RNA (vRNA) copies per mL. In animals treated with miniCD4, 5 out of 6 were fully protected from acquisition of infection, as assessed by qRT-PCR for vRNA detection in plasma, qPCR for viral DNA detection in PBMC and lymph node cells. The only infected animal in this group had a delayed peak of viremia of one week. These results demonstrate that M48U1 miniCD4 acts in vivo as a potent entry inhibitor, which may be considered in microbicide developments.

Impact of short-term HAART initiated during the chronic stage or shortly post-exposure on SIV infection of male genital organs

Background

The male genital tract is suspected to constitute a viral sanctuary as persistent HIV shedding is found in the semen of a subset of HIV-infected men receiving effective antiretroviral therapy (HAART). The origin of this persistent shedding is currently unknown. Phylogenetic studies indicated that HIV in semen from untreated men arises from local sources and/or passive diffusion from the blood. We previously demonstrated in human and macaque low levels and localized infection of several semen-producing organs by HIV/SIV. Using a macaque model, this study investigates the impact of short term HAART (2–4 weeks) initiated either during the asymptomatic chronic stage or 4 h post-intravenous inoculation of SIVmac251 on the infection of male genital organs.

Methodology/Principal Findings

Short term HAART during the chronic stage decreased blood viral load. No major impact of HAART was observed on SIV DNA levels in male genital organs using a sensitive nested PCR assay. Using in situ hybridization, SIV RNA+ cells were detected in all male genital tract organs from untreated and treated animals with undetectable blood viral load following HAART. Infected CD68+ myeloid cells and CD3+ T lymphocytes were detected pre- and post-HAART. In contrast, short term HAART initiated 4 h post-SIV exposure led to a drastic decrease of the male genital tissues infection, although it failed to prevent systemic infection. In both cases, HAART tended to decrease the number of CD3+ T cells in the male organs.

Conclusions

Our results indicate that the established infection of male genital organs is not greatly impacted by short term HAART, whereas the same treatment during pre-acute phase of the infection efficiently impairs viral dissemination to the male genital tract. Further investigations are now needed to determine whether infection of male genital organs is responsible for long term persistent HIV shedding in semen despite HAART.

Effect of a short-term HAART on SIV load in macaque tissues is dependent on time of initiation and antiviral diffusion

BACKGROUND

HIV reservoirs are rapidly established after infection, and the effect of HAART initiated very early during acute infection on HIV reservoirs remains poorly documented, particularly in tissue known to actively replicate the virus. In this context, we used the model of experimental infection of macaques with pathogenic SIV to assess in different tissues: (i) the effect of a short term HAART initiated at different stages during acute infection on viral dissemination and replication, and (ii) the local concentration of antiviral drugs.

RESULTS

Here, we show that early treatment with AZT/3TC/IDV initiated either within 4 hours after intravenous infection of macaques with SIVmac251 (as a post exposure prophylaxis) or before viremia peak (7 days post-infection [pi]), had a strong impact on SIV production and dissemination in all tissues but did not prevent infection. When treatment was initiated after the viremia peak (14 days pi) or during early chronic infection (150 days pi), significant viral replication persists in the peripheral lymph nodes and the spleen of treated macaques despite a strong effect of treatment on viremia and gut associated lymphoid tissues. In these animals, the level of virus persistence in tissues was inversely correlated with local concentrations of 3TC: high concentrations of 3TC were measured in the gut whereas low concentrations were observed in the secondary lymphoid tissues. IDV, like 3TC, showed much higher concentration in the colon than in the spleen. AZT concentration was below the quantification threshold in all tissues studied.

CONCLUSIONS

Our results suggest that limited antiviral drug diffusion in secondary lymphoid tissues may allow persistent viral replication in these tissues and could represent an obstacle to HIV prevention and eradication.

Antiretroviral treatment start-time during primary SIV(mac) infection in macaques exerts a different impact on early viral replication and dissemination

Background

The time of infection is rarely known in human cases; thus, the effects of delaying the initiation of antiretroviral therapy (ART) on the peripheral viral load and the establishment of viral reservoirs are poorly understood.

Methodology/Principal Findings

Six groups of macaques, infected intravenously with SIV_mac251, were given placebo or antiretroviral therapy to explore reservoir establishment; macaques were treated for 2 weeks, with treatment starting 4 hours, 7 or 14 days after infection. Viral replication and dissemination were measured in the gut (rectum), in the lung and in blood and lymphoid tissues (peripheral lymph nodes), by quantifying viral RNA, DNA and 2LTR circles. We used immunohistochemistry (CD4 and CD68) to assess the impact of these treatments on the relative amount of virus target cells in tissue. Treatment that was started 4 hours post-infection (pi) decreased viral replication and dissemination in blood and tissue samples, which were assessed on day 14 (RNA/DNA/2LTR circles). The virus remained detectable and lymphoid tissues were activated in LN and the gut in both placebo- and ART-treated animals. Viral RNA in plasma continued to be lower in macaques treated seven days after infection; however, this was not the case for viral DNA in peripheral blood mononuclear cells. There was a small but significant difference in RNA and DNA levels in tissues between placebo- and ART-treated animals on day 21. When started 14 days after infection, treatment resulted in a limited decrease in the plasma viral load.

Conclusions

Treatment that was started 4 hours after infection significantly reduced viral replication and dissemination. When started 7 days after infection, it was of slight virological benefit in peripheral blood and in tissues, and treatment was even less effective if started 14 days pi. These data favor starting ART no longer than one week after intravenous SIV_mac251 exposure.

Dynamics of viral replication in blood and lymphoid tissues during SIVmac251 infection of macaques

Background

Extensive studies of primary infection are crucial to our understanding of the course of HIV disease. In SIV-infected macaques, a model closely mimicking HIV pathogenesis, we used a combination of three markers -- viral RNA, 2LTR circles and viral DNA -- to evaluate viral replication and dissemination simultaneously in blood, secondary lymphoid tissues, and the gut during primary and chronic infections. Subsequent viral compartmentalization in the main target cells of the virus in peripheral blood during the chronic phase of infection was evaluated by cell sorting and viral quantification with the three markers studied.

Results

The evolutions of viral RNA, 2LTR circles and DNA levels were correlated in a given tissue during primary and early chronic infection. The decrease in plasma viral load principally reflects a large decrease in viral replication in gut-associated lymphoid tissue (GALT), with viral RNA and DNA levels remaining stable in the spleen and peripheral lymph nodes. Later, during chronic infection, a progressive depletion of central memory CD4+ T cells from the peripheral blood was observed, accompanied by high levels of viral replication in the cells of this subtype. The virus was also found to replicate at this point in the infection in naive CD4+ T cells. Viral RNA was frequently detected in monocytes, but no SIV replication appeared to occur in these cells, as no viral DNA or 2LTR circles were detected.

Conclusion

We demonstrated the persistence of viral replication and dissemination, mostly in secondary lymphoid tissues, during primary and early chronic infection. During chronic infection, the central memory CD4+ T cells were the major site of viral replication in peripheral blood, but viral replication also occurred in naive CD4+ T cells. The role of monocytes seemed to be limited to carrying the virus as a cargo because there was an observed lack of replication in these cells. These data may have important implications for the targeting of HIV treatment to these diverse compartments.