Pre-exposure prophylaxis for HIV-1 prevention does not diminish the pregnancy prevention effectiveness of hormonal contraception

BACKGROUND

For women at risk of HIV-1, effective contraception and effective HIV-1 prevention are global priorities.

METHODOLOGY

In a clinical trial of pre-exposure prophylaxis (PrEP) for HIV-1 prevention in HIV-1-serodiscordant couples, we estimated the effectiveness of hormonal contraceptives (oral contraceptive pills, injectable depot medroxyprogesterone acetate, and hormonal implants) for pregnancy prevention relative to no contraception among 1785 HIV-1-uninfected women followed up to 36 months. We compared the effectiveness of each method among women assigned PrEP versus placebo. Contraception was not required for participation, but was offered on-site and was recorded monthly; incident pregnancy was determined by monthly urine testing.

RESULTS

For women using no contraception, overall pregnancy incidence was 15.4% per year. Women reporting oral contraceptive use had comparable pregnancy incidence to women using no contraception, and this lack of contraceptive effectiveness was similar for those assigned PrEP and placebo (17.7 and 10.0% incidence per year, respectively; P-value for difference in effect by PrEP use = 0.24). Women reporting injectable contraception had reduced pregnancy incidence compared to those reporting no contraception, which did not differ by arm (PrEP 5.1%, placebo 5.3% per year; P-value for difference = 0.47). Contraceptive effectiveness was highest among women using implants (pregnancy incidence <1% per year in both arms).

CONCLUSION

PrEP had no adverse impact on hormonal contraceptive effectiveness for pregnancy prevention. As seen previously in similar populations, women reporting contraceptive pill use had little protection from pregnancy, possibly due to poor adherence. Injectable or implantable hormonal contraception and PrEP provide effective prevention for pregnancy and HIV-1.

Pregnancy incidence and outcomes among women receiving preexposure prophylaxis for HIV prevention: a randomized clinical trial

IMPORTANCE

Antiretroviral preexposure prophylaxis (PrEP), using tenofovir disoproxil fumarate (TDF) and combination emtricitabine/tenofovir disoproxil fumarate (FTC+TDF), is efficacious for prevention of human immunodeficiency virus (HIV) acquisition. PrEP could reduce periconception HIV risk, but the effect on pregnancy outcomes is not well defined.

OBJECTIVE

To assess pregnancy incidence and outcomes among women using PrEP during the periconception period.

DESIGN, SETTING, AND PARTICIPANTS

Randomized trial among 1785 HIV-serodiscordant heterosexual couples (the Partners PrEP Study) in which the female partner was HIV uninfected that demonstrated that PrEP was efficacious for HIV prevention, conducted between July 2008 and June 2013 at 9 sites in Kenya and Uganda.

INTERVENTIONS

Daily oral TDF (n = 598), combination FTC+TDF (n = 566), or placebo (n = 621) through July 2011, when PrEP demonstrated efficacy for HIV prevention. Thereafter, participants continued receiving active PrEP without placebo. Pregnancy testing occurred monthly and study medication was discontinued when pregnancy was detected.

MAIN OUTCOMES AND MEASURES

Pregnancy incidence, birth outcomes (live births, pregnancy loss, preterm birth, congenital anomalies), and infant growth.

RESULTS

A total of 431 pregnancies occurred. Pregnancy incidence was 10.0 per 100 person-years among women assigned placebo, 11.9 among those assigned TDF (incidence difference, 1.9; 95% CI, -1.1 to 4.9 [P = .22 vs placebo]), and 8.8 among those assigned FTC+TDF (incidence difference, -1.3; 95% CI, -4.1 to 1.5 [P = .39 vs placebo]). Before discontinuation of the placebo treatment group in July 2011, the occurrence of pregnancy loss (96 of 288 pregnancies) was 42.5% for women receiving FTC+TDF compared with 32.3% for those receiving placebo (difference for FTC+TDF vs placebo, 10.2%; 95% CI, -5.3% to 25.7%; P = .16) and was 27.7% for those receiving TDF alone (difference vs placebo, -4.6%; 95% CI, -18.1% to 8.9%; P = .46). After July 2011, the frequency of pregnancy loss (52 of 143 pregnancies) was 37.5% for FTC+TDF and 36.7% for TDF alone (difference, 0.8%; 95% CI, -16.8% to 18.5%; P = .92). Occurrence of preterm birth, congenital anomalies, and growth throughout the first year of life did not differ significantly for infants born to women who received PrEP vs placebo.

CONCLUSIONS AND RELEVANCE

Among HIV-serodiscordant heterosexual African couples, differences in pregnancy incidence, birth outcomes, and infant growth were not statistically different for women receiving PrEP with TDF alone or combination FTC+TDF compared with placebo at conception. Given that PrEP was discontinued when pregnancy was detected and that CIs for the birth outcomes were wide, definitive statements about the safety of PrEP in the periconception period cannot be made. These results should be discussed with HIV-uninfected women receiving PrEP who are considering becoming pregnant.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00557245.

Daily oral tenofovir and emtricitabine-tenofovir preexposure prophylaxis reduces herpes simplex virus type 2 acquisition among heterosexual HIV-1-uninfected men and women: a subgroup analysis of a randomized trial

BACKGROUND

Daily oral preexposure prophylaxis (PrEP) using the antiretroviral tenofovir disoproxil fumarate (TDF) alone or in combination with emtricitabine (FTC-TDF) reduces the risk for HIV-1 acquisition. Tenofovir has in vitro activity against herpes simplex virus type 2 (HSV-2).

OBJECTIVE

To assess the efficacy of daily oral PrEP with tenofovir and FTC-TDF in the prevention of HSV-2 acquisition.

DESIGN

Subgroup analysis of data from a randomized, placebo-controlled trial with concealed allocation. (ClinicalTrials.gov: NCT00557245).

SETTING

Multiple sites in Kenya and Uganda.

PARTICIPANTS

Heterosexual men and women who were seronegative for HIV-1 and HSV-2 and at high risk for HIV-1 acquisition due to having an HIV-1-infected partner.

INTERVENTION

Once-daily oral tenofovir disoproxil fumarate (TDF), alone or combined with emtricitabine (FTC-TDF), compared with placebo.

MEASUREMENTS

HSV-2 seroconversion.

RESULTS

A total of 131 participants seroconverted to HSV-2 (79 of 1041 assigned to tenofovir or FTC-TDF PrEP [HSV-2 incidence, 5.6 per 100 person-years] and 52 of 481 assigned to placebo [HSV-2 incidence, 7.7 per 100 person-years]). The hazard ratio (HR) for HSV-2 acquisition with daily oral PrEP was 0.70 (95% CI, 0.49 to 0.99; P = 0.047) compared with placebo, and the absolute risk reduction was 2.1 per 100 person-years. Among the 1044 participants with HSV-2-infected partners, the HR for PrEP was 0.67 (CI, 0.46 to 0.98; P = 0.038) compared with placebo, and the absolute risk reduction was 3.1 per 100 person-years.

LIMITATION

Randomization was not stratified by HSV-2 status, and diagnostic tests to exclude participants with acute HSV-2 at baseline are not available.

CONCLUSION

Daily oral tenofovir-based PrEP significantly reduced the risk for HSV-2 acquisition among heterosexual men and women. Modest protection against HSV-2 is an added benefit of HIV-1 prevention with oral tenofovir-based PrEP.

PRIMARY FUNDING SOURCE

Bill & Melinda Gates Foundation.

Effect of community-based voluntary counselling and testing on HIV incidence and social and behavioural outcomes (NIMH Project Accept; HPTN 043): a cluster-randomised trial

BACKGROUND

Although several interventions have shown reduced HIV incidence in clinical trials, the community-level effect of effective interventions on the epidemic when scaled up is unknown. We investigated whether a multicomponent, multilevel social and behavioural prevention strategy could reduce HIV incidence, increase HIV testing, reduce HIV risk behaviour, and change social and behavioural norms.

METHODS

For this phase 3 cluster-randomised controlled trial, 34 communities in four sites in Africa and 14 communities in Thailand were randomly allocated in matched pairs to receive 36 months of community-based voluntary counselling and testing for HIV (intervention group) or standard counselling and testing alone (control group) between January, 2001, and December, 2011. The intervention was designed to make testing more accessible in communities, engage communities through outreach, and provide support services after testing. Randomisation was done by a computer-generated code and was not masked. Data were collected at baseline (n=14 567) and after intervention (n=56.683) by cross-sectional random surveys of community residents aged 18-32 years. The primary outcome was HIV incidence and was estimated with a cross-sectional multi-assay algorithm and antiretroviral drug screening assay. Thailand was excluded from incidence analyses because of low HIV prevalence. This trial is registered at ClinicalTrials.gov, number NCT00203749.

FINDINGS

The estimated incidence of HIV in the intervention group was 1.52% versus 1.81% in the control group with an estimated reduction in HIV incidence of 13.9% (relative risk [RR] 0.86, 95% CI 0.73-1.02; p=0.082). HIV incidence was significantly reduced in women older than 24 years (RR=0.70, 0.54-0.90; p=0.0085), but not in other age or sex subgroups. Community-based voluntary counselling and testing increased testing rates by 25% overall (12-39; p=0.0003), by 45% (25-69; p<0·0001) in men and 15% (3-28; p=0.013) in women. No overall effect on sexual risk behaviour was recorded. Social norms regarding HIV testing were improved by 6% (95% CI 3-9) in communities in the intervention group.

INTERPRETATION

These results are sufficiently robust, especially when taking into consideration the combined results of modest reductions in HIV incidence combined with increases in HIV testing and reductions in HIV risk behaviour, to recommend the Project Accept approach as an integral part of all interventions (including treatment as prevention) to reduce HIV transmission at the community level.

FUNDING

US National Institute of Mental Health, the Division of AIDS of the US National Institute of Allergy and Infectious Diseases, and the Office of AIDS Research of the US National Institutes of Health.

A prospective study of the effect of pregnancy on CD4 counts and plasma HIV-1 RNA concentrations of antiretroviral-naive HIV-1-infected women

BACKGROUND

In HIV-1-infected women, CD4 count declines occur during pregnancy, which has been attributed to hemodilution. However, for women who have not initiated antiretroviral therapy, it is unclear if CD4 declines are sustained beyond pregnancy and accompanied by increased viral levels, which could indicate an effect of pregnancy on accelerating HIV-1 disease progression.

METHODS

In a prospective study among 2269 HIV-1-infected antiretroviral therapy-naive women from 7 African countries, we examined the effect of pregnancy on HIV-1 disease progression. We used linear mixed models to compare CD4 counts and plasma HIV-1 RNA concentrations between pregnant, postpartum, and nonpregnant periods.

RESULTS

Women contributed 3270 person-years of follow-up, during which time 476 women became pregnant. In adjusted analysis, CD4 counts were an average of 56 (95% confidence interval: 39 to 73) cells/mm lower during pregnant compared with nonpregnant periods and 70 (95% confidence interval: 53 to 88) cells/mm lower during pregnant compared with postpartum periods; these results were consistent when restricted to the subgroup of women who became pregnant. Plasma HIV-1 RNA concentrations were not different between pregnant and nonpregnant periods (P = 0.9) or pregnant and postpartum periods (P = 0.3). Neither CD4 counts nor plasma HIV-1 RNA levels were significantly different in postpartum compared with nonpregnant periods.

CONCLUSIONS

CD4 count declines among HIV-1-infected women during pregnancy are temporary and not sustained in postpartum periods. Pregnancy does not have a short-term impact on plasma HIV-1 RNA concentrations.

HPTN 071 (PopART): a cluster-randomized trial of the population impact of an HIV combination prevention intervention including universal testing and treatment: mathematical model

Background

The HPTN 052 trial confirmed that antiretroviral therapy (ART) can nearly eliminate HIV transmission from successfully treated HIV-infected individuals within couples. Here, we present the mathematical modeling used to inform the design and monitoring of a new trial aiming to test whether widespread provision of ART is feasible and can substantially reduce population-level HIV incidence.

Methods and Findings

The HPTN 071 (PopART) trial is a three-arm cluster-randomized trial of 21 large population clusters in Zambia and South Africa, starting in 2013. A combination prevention package including home-based voluntary testing and counseling, and ART for HIV positive individuals, will be delivered in arms A and B, with ART offered universally in arm A and according to national guidelines in arm B. Arm C will be the control arm. The primary endpoint is the cumulative three-year HIV incidence.

We developed a mathematical model of heterosexual HIV transmission, informed by recent data on HIV-1 natural history. We focused on realistically modeling the intervention package. Parameters were calibrated to data previously collected in these communities and national surveillance data.

We predict that, if targets are reached, HIV incidence over three years will drop by >60% in arm A and >25% in arm B, relative to arm C. The considerable uncertainty in the predicted reduction in incidence justifies the need for a trial. The main drivers of this uncertainty are possible community-level behavioral changes associated with the intervention, uptake of testing and treatment, as well as ART retention and adherence.

Conclusions

The HPTN 071 (PopART) trial intervention could reduce HIV population-level incidence by >60% over three years. This intervention could serve as a paradigm for national or supra-national implementation. Our analysis highlights the role mathematical modeling can play in trial development and monitoring, and more widely in evaluating the impact of treatment as prevention.

Daily short message service surveys to measure sexual behavior and pre-exposure prophylaxis use among Kenyan men and women

Pre-exposure prophylaxis (PrEP) is a novel HIV prevention strategy which requires high adherence. We tested the use of daily short message service (i.e., SMS/text message) surveys to measure sexual behavior and PrEP adherence in Kenya. Ninety-six HIV-uninfected adult individuals, taking daily oral PrEP in a clinical trial, received daily SMS surveys for 60 days. Most participants (96.9 %) reported taking PrEP on ≥80 % days, but 69.8 % missed at least one dose. Unprotected sex was reported on 4.9 % of days; however, 47.9 % of participants reported unprotected sex at least once. Unprotected sex was not correlated with PrEP use (OR = 0.95). Participants reporting more sex were less likely to report PrEP non-adherence and those reporting no sex were most likely to report missing a PrEP dose (adjusted OR = 1.87). PrEP adherence was high, missed doses were correlated with sexual abstinence, and unprotected sex was not associated with decreased PrEP adherence.

Sexual behaviour of heterosexual men and women receiving antiretroviral pre-exposure prophylaxis for HIV prevention: a longitudinal analysis

BACKGROUND

Scarce data are available to assess sexual behaviour of individuals using antiretroviral pre-exposure prophylaxis for HIV prevention. Increased sexual risk taking by individuals using effective HIV prevention strategies, like pre-exposure prophylaxis, could offset the benefits of HIV prevention. We studied whether the use of pre-exposure prophylaxis in HIV-uninfected men and women in HIV-serodiscordant couples was associated with increased sexual risk behaviour.

METHODS

We undertook a longitudinal analysis of data from the Partners PrEP Study, a double-blind, randomised, placebo-controlled trial of daily oral pre-exposure prophylaxis among HIV-uninfected partners of heterosexual HIV-serodiscordant couples (n=3163, ≥18 years of age). Efficacy for HIV prevention was publicly reported in July 2011, and participants continued monthly follow-up thereafter. We used regression analyses to compare the frequency of sex-unprotected by a condom-during the 12 months after compared with the 12 months before July 2011, to assess whether knowledge of pre-exposure prophylaxis efficacy for HIV prevention caused increased sexual risk behaviour.

RESULTS

We analysed 56 132 person-months from 3024 HIV-uninfected individuals (64% male). The average frequency of unprotected sex with the HIV-infected study partner was 59 per 100 person-months before unmasking versus 53 after unmasking; we recorded no immediate change (p=0·66) or change over time (p=0·25) after July, 2011. We identified a significant increase in unprotected sex with outside partners after July, 2011, but the effect was small (average of 6·8 unprotected sex acts per year vs 6·2 acts in a predicted counterfactual scenario had patients remained masked, p=0·04). Compared with before July, 2011, we noted no significant increase in incident sexually transmitted infections or pregnancy after July, 2011.

INTERPRETATION

Pre-exposure prophylaxis, provided as part of a comprehensive prevention package, might not result in substantial changes in risk-taking sexual behaviour by heterosexual couples.

FUNDING

The Bill & Melinda Gates Foundation and the US National Institute of Mental Health.

Recent patterns in population-based HIV prevalence in Swaziland

Background

The 2011 Swaziland HIV Incidence Measurement Survey (SHIMS) was conducted as part of a national study to evaluate the scale up of key HIV prevention programs.

Methods

From a randomly selected sample of all Swazi households, all women and men aged 18-49 were considered eligible, and all consenting adults were enrolled and received HIV testing and counseling. In this analysis, population-based measures of HIV prevalence were produced and compared against similarly measured HIV prevalence estimates from the 2006-7 Swaziland Demographic and Health. Also, measures of HIV service utilization in both HIV infected and uninfected populations were documented and discussed.

Results

HIV prevalence among adults aged 18-49 has remained unchanged between 2006-2011 at 31-32%, with substantial differences in current prevalence between women (39%) and men (24%). In both men and women, between since 2006-7 and 2011, prevalence has fallen in the young age groups and risen in the older age groups. Over a third (38%) of the HIV-infected population was unaware of their infection status, and this differed markedly between men (50%) and women (31%). Of those aware of their HIV-positive status, a higher percentage of men (63%) than women (49%) reported ART use.

Conclusions

While overall HIV prevalence remains roughly constant, age-specific changes strongly suggest both improved survival of the HIV-infected and a reduction in new HIV infections. Awareness of HIV status and entry into ART services has improved in recent years but remains too low. This study identifies opportunities to improve both HIV preventive and care services in Swaziland.

Differential regulatory T cell activity in HIV type 1-exposed seronegative individuals

The potential role of conventional and regulatory T cells (Tregs) in protection from HIV-1 infection remains unclear. To address this question, we analyzed samples from 129 HIV-1-exposed seronegative individuals (HESN) from an HIV-1-serodiscordant couples cohort. To assess the presence of HIV-specific T cell responses and Treg function, we measured the proliferation of T cells in response to HIV-1 peptide pools in peripheral blood mononuclear cells (PBMCs) and PBMCs depleted of Tregs. We identified HIV-specific CD4(+) and CD8(+) T cell responses and, surprisingly, the overall CD4(+) and CD8(+) T cell response rate was not increased when Tregs were removed from cell preparations. Of the 20 individuals that had HIV-1-specific CD4(+) T cell responses, only eight had Tregs that could suppress this proliferation. When compared with individuals whose Tregs could suppress HIV-1-specific CD4(+) T cell proliferation, individuals with Tregs unable to suppress showed a trend toward increased T cell activation and Treg frequency and a significant increase in HIV-1-specific production of microphage inflammatory protein-1β (MIP-1β) by CD4(+) T cells, autocrine production of which has been shown to be protective in terms of HIV-1 infection of CD4(+) T cells.

Cross-sectional HIV incidence estimation in HIV prevention research

Accurate methods for estimating HIV incidence from cross-sectional samples would have great utility in prevention research. This report describes recent improvements in cross-sectional methods that significantly improve their accuracy. These improvements are based on the use of multiple biomarkers to identify recent HIV infections. These multiassay algorithms (MAAs) use assays in a hierarchical approach for testing that minimizes the effort and cost of incidence estimation. These MAAs do not require mathematical adjustments for accurate estimation of the incidence rates in study populations in the year before sample collection. MAAs provide a practical, accurate, and cost-effective approach for cross-sectional HIV incidence estimation that can be used for HIV prevention research and global epidemic monitoring.

Study design considerations for evaluating efficacy of systemic preexposure prophylaxis interventions

BACKGROUND

The development of interventions for systemic pre-exposure prophylaxis (PrEP) faces several significant challenges following the US Food and Drug Administration's approval of emtricitabine/tenofovir (FTC/TDF) for HIV prevention. This development is particularly complex because of inconsistency of efficacy results of FTC/TDF PrEP trials for HIV prevention.

METHODS

Possible designs for a PrEP phase 3 efficacy trial are obtained by considering scenarios for potential experimental PrEP and control regimens, including consideration of placebo and active controls, longer acting PrEP and alternate dosing schedules.

RESULTS

Noninferiority (NI) trials with hazard ratio NI margins ranging from 1.10 to 1.25 can be justified in the contexts of the 3 PrEP trials demonstrating efficacy of FTC/TDF. However, these HIV endpoint trials may require extremely large number of participants, particularly in settings where FTC/TDF has been shown to reduce the risk of HIV acquisition. NI trials also are often difficult to interpret because they depend on previous placebo-controlled efficacy results. Superiority trials for PrEP are plausible in settings where FTC/TDF efficacy is not yet established, possibly due to low adherence (ie, women at risk as in FemPrEP and VOICE): a new product with potential for higher adherence and potency would be a promising candidate in this setting.

CONCLUSIONS

Following Food and Drug Administration's approval of FTC/TDF for PrEP, trials to establish efficacy of new PrEP regimens require stringent design standards, together with rigorous debate about adherence within study populations and many important ethical issues.

Estimation of HIV incidence in a large, community-based, randomized clinical trial: NIMH project accept (HIV Prevention Trials Network 043)

BACKGROUND

National Institute of Mental Health Project Accept (HIV Prevention Trials Network [HPTN] 043) is a large, Phase III, community-randomized, HIV prevention trial conducted in 48 matched communities in Africa and Thailand. The study intervention included enhanced community-based voluntary counseling and testing. The primary endpoint was HIV incidence, assessed in a single, cross-sectional, post-intervention survey of >50,000 participants.

METHODS

HIV rapid tests were performed in-country. HIV status was confirmed at a central laboratory in the United States. HIV incidence was estimated using a multi-assay algorithm (MAA) that included the BED capture immunoassay, an avidity assay, CD4 cell count, and HIV viral load.

RESULTS

Data from Thailand was not used in the endpoint analysis because HIV prevalence was low. Overall, 7,361 HIV infections were identified (4 acute, 3 early, and 7,354 established infections). Samples from established infections were analyzed using the MAA; 467 MAA positive samples were identified; 29 of those samples were excluded because they contained antiretroviral drugs. HIV prevalence was 16.5% (range at study sites: 5.93% to 30.8%). HIV incidence was 1.60% (range at study sites: 0.78% to 3.90%).

CONCLUSIONS

In this community-randomized trial, a MAA was used to estimate HIV incidence in a single, cross-sectional post-intervention survey. Results from this analysis were subsequently used to compare HIV incidence in the control and intervention communities.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00203749.

The dynamic relationship between social norms and behaviors: the results of an HIV prevention network intervention for injection drug users

AIMS

Social norms are a key source of influence on health behaviors. This study examined changes in social norms and relationships between HIV injection risk behaviors and social norms among injection drug users (IDUs) involved in an experimental intervention.

DESIGN

Randomized clinical trial.

SETTING

An HIV Prevention Trials Network study, Philadelphia, USA.

PARTICIPANTS

IDUs, called indexes, and their social network members, who were drug or sex partners, were recruited for an HIV prevention intervention and followed for up to 30 months (n = 652). Indexes were randomized into a peer education intervention or control condition.

MEASUREMENTS

Outcomes of injection-related HIV risk behaviors (sharing needles, sharing cookers, sharing cotton, front-/back-loading) were measured every 6 months and the social norms of these four risk behaviors were assessed every 12 months.

FINDINGS

There was a statistically significant intervention effect on all four social norms of injection behaviors, with participants in the intervention reporting less risky social norms compared with controls (changes in mean score: needles, -0.24, P = 0.007; cookers, -0.33, P = .004; cottons, -0.28, P = .0165; front-/back-loading, -0.23, P = .002). There was also a statistically significant bidirectional association with social norms predicting injection risk behaviors at the next assessment and risk behaviors predicting social norms at the subsequent visit.

CONCLUSIONS

Through social network interventions it is feasible to change both injection risk behaviors and associated social norms. However, it is critical that social network interventions focus on publically highlighting behavior changes, as changing social norms without awareness of behaviors change may lead to relapse of risk behaviors.

Adherence to antiretroviral prophylaxis for HIV prevention: a substudy cohort within a clinical trial of serodiscordant couples in East Africa

BACKGROUND

Randomized clinical trials of oral antiretroviral pre-exposure prophylaxis (PrEP) for HIV prevention have widely divergent efficacy estimates, ranging from 0% to 75%. These discrepancies are likely due to differences in adherence. To our knowledge, no studies to date have examined the impact of improving adherence through monitoring and/or intervention, which may increase PrEP efficacy, or reported on objective behavioral measures of adherence, which can inform PrEP effectiveness and implementation.

METHODS AND FINDINGS

Within the Partners PrEP Study (a randomized placebo-controlled trial of oral tenofovir and emtricitabine/tenofovir among HIV-uninfected members of serodiscordant couples in Kenya and Uganda), we collected objective measures of PrEP adherence using unannounced home-based pill counts and electronic pill bottle monitoring. Participants received individual and couples-based adherence counseling at PrEP initiation and throughout the study; counseling was intensified if unannounced pill count adherence fell to <80%. Participants were followed monthly to provide study medication, adherence counseling, and HIV testing. A total of 1,147 HIV-uninfected participants were enrolled: 53% were male, median age was 34 years, and median partnership duration was 8.5 years. Fourteen HIV infections occurred among adherence study participants--all of whom were assigned to placebo (PrEP efficacy = 100%, 95% confidence interval 83.7%-100%, p<0.001). Median adherence was 99.1% (interquartile range [IQR] 96.9%-100%) by unannounced pill counts and 97.2% (90.6%-100%) by electronic monitoring over 807 person-years. Report of no sex or sex with another person besides the study partner, younger age, and heavy alcohol use were associated with <80% adherence; the first 6 months of PrEP use and polygamous marriage were associated with >80% adherence. Study limitations include potential shortcomings of the adherence measures and use of a convenience sample within the substudy cohort.

CONCLUSIONS

The high PrEP adherence achieved in the setting of active adherence monitoring and counseling support was associated with a high degree of protection from HIV acquisition by the HIV-uninfected partner in heterosexual serodiscordant couples. Low PrEP adherence was associated with sexual behavior, alcohol use, younger age, and length of PrEP use. Please see later in the article for the Editors' Summary.

Impact of mutation type and amplicon characteristics on genetic diversity measures generated using a high-resolution melting diversity assay

We adapted high-resolution melting (HRM) technology to measure genetic diversity without sequencing. Diversity is measured as a single numeric HRM score. Herein, we determined the impact of mutation types and amplicon characteristics on HRM diversity scores. Plasmids were generated with single-base changes, insertions, and deletions. Different primer sets were used to vary the position of mutations within amplicons. Plasmids and plasmid mixtures were analyzed to determine the impact of mutation type, position, and concentration on HRM scores. The impact of amplicon length and G/C content on HRM scores was also evaluated. Different mutation types affected HRM scores to varying degrees (1-bp deletion < 1-bp change < 3-bp insertion < 9-bp insertion). The impact of mutations on HRM scores was influenced by amplicon length and the position of the mutation within the amplicon. Mutations were detected at concentrations of 5% to 95%, with the greatest impact at 50%. The G/C content altered melting temperature values of amplicons but had no impact on HRM scores. These data are relevant to the design of assays that measure genetic diversity using HRM technology.

HIV incidence determination in the United States: a multiassay approach

BACKGROUND

Accurate testing algorithms are needed for estimating human immunodeficiency virus (HIV) incidence from cross-sectional surveys.

METHODS

We developed a multiassay algorithm (MAA) for HIV incidence that includes the BED capture enzyme immunoassay (BED-CEIA), an antibody avidity assay, HIV load, and CD4(+) T-cell count. We analyzed 1782 samples from 709 individuals in the United States who had a known duration of HIV infection (range, 0 to >8 years). Logistic regression with cubic splines was used to compare the performance of the MAA to the BED-CEIA and to determine the window period of the MAA. We compared the annual incidence estimated with the MAA to the annual incidence based on HIV seroconversion in a longitudinal cohort.

RESULTS

The MAA had a window period of 141 days (95% confidence interval [CI], 94-150) and a very low false-recent misclassification rate (only 0.4% of 1474 samples from subjects infected for >1 year were misclassified as indicative of recent infection). In a cohort study, annual incidence based on HIV seroconversion was 1.04% (95% CI, .70%-1.55%). The incidence estimate obtained using the MAA was essentially identical: 0.97% (95% CI, .51%-1.71%).

CONCLUSIONS

The MAA is as sensitive for detecting recent HIV infection as the BED-CEIA and has a very low rate of false-recent misclassification. It provides a powerful tool for cross-sectional HIV incidence determination.

Seroadaptive practices: association with HIV acquisition among HIV-negative men who have sex with men

BACKGROUND

Although efficacy is unknown, many men who have sex with men (MSM) attempt to reduce HIV risk by adapting condom use, partner selection, or sexual position to the partner's HIV serostatus. We assessed the association of seroadaptive practices with HIV acquisition.

METHODOLOGY/PRINCIPAL FINDINGS

We pooled data on North American MSM from four longitudinal HIV-prevention studies. Sexual behaviors reported during each six-month interval were assigned sequentially to one of six mutually exclusive risk categories: (1) no unprotected anal intercourse (UAI), (2) having a single negative partner, (3) being an exclusive top (only insertive anal sex), (4) serosorting (multiple partners, all HIV negative), (5) seropositioning (only insertive anal sex with potentially discordant partners), and (6) UAI with no seroadaptive practices. HIV antibody testing was conducted at the end of each interval. We used Cox models to evaluate the independent association of each category with HIV acquisition, controlling for number of partners, age, race, drug use, and intervention assignment. 12,277 participants contributed to 60,162 six-month intervals with 663 HIV seroconversions. No UAI was reported in 47.4% of intervals, UAI with some seroadaptive practices in 31.8%, and UAI with no seroadaptive practices in 20.4%. All seroadaptive practices were associated with a lower risk, compared to UAI with no seroadaptive practices. However, compared to no UAI, serosorting carried twice the risk (HR = 2.03, 95%CI:1.51-2.73), whereas seropositioning was similar in risk (HR = 0.85, 95%CI:0.50-1.44), and UAI with a single negative partner and as an exclusive top were both associated with a lower risk (HR = 0.56, 95%CI:0.32-0.96 and HR = 0.55, 95%CI:0.36-0.84, respectively).

CONCLUSIONS/SIGNIFICANCE

Seroadaptive practices appear protective when compared with UAI with no seroadaptive practices, but serosorting appears to be twice as risky as no UAI. Condom use and limiting number of partners should be advocated as first-line prevention strategies, but seroadaptive practices may be considered harm-reduction for men at greatest risk.

Specificity of four laboratory approaches for cross-sectional HIV incidence determination: analysis of samples from adults with known nonrecent HIV infection from five African countries

Assays to determine cross-sectional HIV incidence misclassify some individuals with nonrecent HIV infection as recently infected, overestimating HIV incidence. We analyzed factors associated with false-recent misclassification in five African countries. Samples from 2197 adults from Botswana, Kenya, South Africa, Tanzania, and Uganda who were HIV infected > 12 months were tested using the (1) BED capture enzyme immunoassay (BED), (2) avidity assay, (3) BED and avidity assays with higher assay cutoffs (BED+ avidity screen), and (4) multiassay algorithm (MAA) that includes the BED+ avidity screen, CD4 cell count, and HIV viral load. Logistic regression identified factors associated with misclassification. False-recent misclassification rates and 95% confidence intervals were BED alone: 7.6% (6.6, 8.8); avidity assay alone: 3.5% (2.7, 4.3); BED+ avidity screen: 2.2% (1.7, 2.9); and MAA: 1.2% (0.8, 1.8). The misclassification rate for the MAA was significantly lower than the rates for the other three methods (each p < 0.05). Misclassification rates were lower when the analysis was limited to subtype C-endemic countries, with the lowest rate obtained for the MAA [0.8% (0.2, 1.9)]. Factors associated with misclassification were for BED alone: country of origin, antiretroviral treatment (ART), viral load, and CD4 cell count; for avidity assay alone: country of origin; for BED+ avidity screen: country of origin and ART. No factors were associated with misclassification using the MAA. In a multivariate model, these associations remained significant with one exception: the association of ART with misclassification was completely attenuated. A MAA that included CD4 cell count and viral load had lower false-recent misclassification than the BED or avidity assays (alone or in combination). Studies are underway to compare the sensitivity of these methods for detection of recent HIV infection.

Quantifying ongoing HIV-1 exposure in HIV-1-serodiscordant couples to identify individuals with potential host resistance to HIV-1

BACKGROUND

Immunogenetic correlates of resistance to HIV-1 in HIV-1-exposed seronegative (HESN) individuals with consistently high exposure may inform HIV-1 prevention strategies. We developed a novel approach for quantifying HIV-1 exposure to identify individuals remaining HIV-1 uninfected despite persistent high exposure.

METHODS

We used longitudinal predictors of HIV-1 transmission in HIV-1 serodiscordant couples to score HIV-1 exposure and define HESN clusters with persistently high, low, and decreasing risk trajectories. The model was validated in an independent cohort of serodiscordant couples. We describe a statistical tool that can be applied to other HESN cohorts to identify individuals with high exposure to HIV-1.

RESULTS

HIV-1 exposure was best quantified by frequency of unprotected sex with, plasma HIV-1 RNA levels among, and presence of genital ulcer disease among HIV-1-infected partners and by age, pregnancy status, herpes simplex virus 2 serostatus, and male circumcision status among HESN participants. Overall, 14% of HESN individuals persistently had high HIV-1 exposure and exhibited a declining incidence of HIV-1 infection over time.

CONCLUSIONS

A minority of HESN individuals from HIV-1-discordant couples had persistent high HIV-1 exposure over time. Decreasing incidence of infection in this group suggests these individuals were selected for resistance to HIV-1 and may be most appropriate for identifying biological correlates of natural host resistance to HIV-1 infection.

Antiretroviral prophylaxis for HIV prevention in heterosexual men and women

BACKGROUND

Antiretroviral preexposure prophylaxis is a promising approach for preventing human immunodeficiency virus type 1 (HIV-1) infection in heterosexual populations.

METHODS

We conducted a randomized trial of oral antiretroviral therapy for use as preexposure prophylaxis among HIV-1-serodiscordant heterosexual couples from Kenya and Uganda. The HIV-1-seronegative partner in each couple was randomly assigned to one of three study regimens--once-daily tenofovir (TDF), combination tenofovir-emtricitabine (TDF-FTC), or matching placebo--and followed monthly for up to 36 months. At enrollment, the HIV-1-seropositive partners were not eligible for antiretroviral therapy, according to national guidelines. All couples received standard HIV-1 treatment and prevention services.

RESULTS

We enrolled 4758 couples, of whom 4747 were followed: 1584 randomly assigned to TDF, 1579 to TDF-FTC, and 1584 to placebo. For 62% of the couples followed, the HIV-1-seronegative partner was male. Among HIV-1-seropositive participants, the median CD4 count was 495 cells per cubic millimeter (interquartile range, 375 to 662). A total of 82 HIV-1 infections occurred in seronegative participants during the study, 17 in the TDF group (incidence, 0.65 per 100 person-years), 13 in the TDF-FTC group (incidence, 0.50 per 100 person-years), and 52 in the placebo group (incidence, 1.99 per 100 person-years), indicating a relative reduction of 67% in the incidence of HIV-1 with TDF (95% confidence interval [CI], 44 to 81; P<0.001) and of 75% with TDF-FTC (95% CI, 55 to 87; P<0.001). Protective effects of TDF-FTC and TDF alone against HIV-1 were not significantly different (P=0.23), and both study medications significantly reduced the HIV-1 incidence among both men and women. The rate of serious adverse events was similar across the study groups. Eight participants receiving active treatment were found to have been infected with HIV-1 at baseline, and among these eight, antiretroviral resistance developed in two during the study.

CONCLUSIONS

Oral TDF and TDF-FTC both protect against HIV-1 infection in heterosexual men and women. (Funded by the Bill and Melinda Gates Foundation; Partners PrEP ClinicalTrials.gov number, NCT00557245.).

Statistical considerations for the HPTN 052 Study to evaluate the effectiveness of early versus delayed antiretroviral strategies to prevent the sexual transmission of HIV-1 in serodiscordant couples

The HIV Prevention Trial Network (HPTN) 052 Study is a Phase III, two-arm, controlled, open-labeled, randomized clinical trial designed to determine whether early antiretroviral therapy (ART) can prevent the sexual transmission of human immunodeficiency virus type 1 (HIV-1). A total of 1763 couples in which one partner was HIV-1-positive and the other was HIV-1-negative were enrolled in four continents, nine countries and thirteen study sites. The HIV-1-positive partner was randomly assigned to either of the two arms: "immediate" (early) therapy with ART initiated upon enrollment plus HIV primary care, or "delayed" therapy with HIV primary care but ART initiated when the index case would have two consecutive measurements of a CD4+ cell count within or below the range of 200-250 cells/mm(3), or develop an AIDS-defining illness. In this paper, we describe several key statistical considerations for the design of this landmark study. Despite that the observed event rates were lower than expected, which might have compromised the study power, an early release of the trial results in May 2011 showed an overwhelming 96% risk reduction for the immediate therapy in the prevention of genetically linked HIV-1 incident transmissions. Nevertheless, the durability of its long-term effectiveness is yet to be assessed. The HPTN 052 Study is still ongoing and will not complete till 2015.