Deborah Donnell

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.).

Heterosexual HIV-1 transmission after initiation of antiretroviral therapy: a prospective cohort analysis

BACKGROUND High plasma HIV-1 RNA concentrations are associated with increased risk of HIV-1 transmission. Initiation of antiretroviral therapy (ART) reduces plasma HIV-1 concentrations. We aimed to assess the effect of ART use by patients infected with HIV-1 on risk of transmission to their uninfected partners. METHODS Participants in our prospective cohort analysis were from a randomised placebo-controlled trial that enrolled heterosexual African adults who were seropositive for both HIV-1 and herpes simplex virus type 2, and their HIV-1 seronegative partners. At enrolment, HIV-1 infected participants had CD4 counts of 250 cells per microL or greater and did not meet national guidelines for ART initiation; during 24 months of follow-up, CD4 counts were measured every 6 months and ART was initiated in accordance with national guidelines. Uninfected partners were tested for HIV-1 every 3 months. The primary outcome was genetically-linked HIV-1 transmission within the study partnership. We assessed rates of HIV-1 transmission by ART status of infected participants. FINDINGS 3381 couples were eligible for analysis. 349 (10%) participants with HIV-1 initiated ART during the study, at a median CD4 cell count of 198 (IQR 161-265) cells per microL. Only one of 103 genetically-linked HIV-1 transmissions was from an infected participant who had started ART, corresponding to transmission rates of 0.37 (95% CI 0.09-2.04) per 100 person-years in those who had initiated treatment and 2.24 (1.84-2.72) per 100 person-years in those who had not-a 92% reduction (adjusted incidence rate ratio 0.08, 95% CI 0.00-0.57, p=0.004). In participants not on ART, the highest HIV-1 transmission rate (8.79 per 100 person-years) was from those with CD4 cell counts lower than 200 cells per microL. In couples in whom the untreated HIV-1 infected partner had a CD4 cell count greater than 200 cells per microL, 66 (70%) of 94 transmissions occurred when plasma HIV-1 concentrations exceeded 50 000 copies per mL. INTERPRETATION Low CD4 cell counts and high plasma HIV-1 concentrations might guide use of ART to achieve an HIV-1 prevention benefit. Provision of ART to HIV-1 infected patients could be an effective strategy to achieve population-level reductions in HIV-1 transmission. FUNDING Bill & Melinda Gates Foundation; US National Institutes of Health.

Use of hormonal contraceptives and risk of HIV-1 transmission: a prospective cohort study.

BACKGROUND Hormonal contraceptives are used widely but their effects on HIV-1 risk are unclear. We aimed to assess the association between hormonal contraceptive use and risk of HIV-1 acquisition by women and HIV-1 transmission from HIV-1-infected women to their male partners. METHODS In this prospective study, we followed up 3790 heterosexual HIV-1-serodiscordant couples participating in two longitudinal studies of HIV-1 incidence in seven African countries. Among injectable and oral hormonal contraceptive users and non-users, we compared rates of HIV-1 acquisition by women and HIV-1 transmission from women to men. The primary outcome measure was HIV-1 seroconversion. We used Cox proportional hazards regression and marginal structural modelling to assess the effect of contraceptive use on HIV-1 risk. FINDINGS Among 1314 couples in which the HIV-1-seronegative partner was female (median follow-up 18·0 [IQR 12·6-24·2] months), rates of HIV-1 acquisition were 6·61 per 100 person-years in women who used hormonal contraception and 3·78 per 100 person-years in those who did not (adjusted hazard ratio 1·98, 95% CI 1·06-3·68, p=0·03). Among 2476 couples in which the HIV-1-seronegative partner was male (median follow-up 18·7 [IQR 12·8-24·2] months), rates of HIV-1 transmission from women to men were 2·61 per 100 person-years in couples in which women used hormonal contraception and 1·51 per 100 person-years in couples in which women did not use hormonal contraception (adjusted hazard ratio 1·97, 95% CI 1·12-3·45, p=0·02). Marginal structural model analyses generated much the same results to the Cox proportional hazards regression. INTERPRETATION Women should be counselled about potentially increased risk of HIV-1 acquisition and transmission with hormonal contraception, especially injectable methods, and about the importance of dual protection with condoms to decrease HIV-1 risk. Non-hormonal or low-dose hormonal contraceptive methods should be considered for women with or at-risk for HIV-1. FUNDING US National Institutes of Health and the Bill & Melinda Gates Foundation.

Genital HIV-1 RNA Predicts Risk of Heterosexual HIV-1 Transmission

Genital HIV-1 RNA quantity predicts risk of heterosexual HIV-1 transmission independently of plasma HIV-1 concentration. Elucidating the Insidious Transmission of a Deadly Pathogen The deadly HIV-1 retrovirus that causes AIDS has been a scourge of humanity for nearly 30 years. Although combination therapy with antiretroviral drugs has proved successful, the complex drug regimen and great cost have prevented their widespread use in the developing world where they are most needed. The goal of developing a vaccine that would protect individuals from becoming infected with HIV-1 has remained elusive. Given that 90% of all HIV infections worldwide are due to sexual transmission, there has been much interest in developing new strategies that could block HIV infection through the genital mucosa. However, the mechanisms underlying mucosal transmission of HIV are still poorly understood. Higher amounts of HIV-1 in genital secretions are thought to reflect a greater chance of sexual transmission, but testing this correlation is a difficult undertaking. Baeten and colleagues have taken on this challenge with their prospective study in Africa of 2521 heterosexual serodiscordant couples (one partner is HIV-infected and the other partner is not). These investigators evaluated the relationship between the quantity of HIV-1 RNA in the genital secretions of the infected partner and the risk of HIV-1 transmission to the uninfected partner in each couple. They tested the amount of HIV-1 RNA in endocervical swabs from 1805 HIV-1–infected women including 46 women known to have transmitted the virus to their male partners. They also tested the amount of HIV-1 RNA in semen from 716 men, including 32 who had transmitted HIV-1 to their female partners. The authors demonstrate that higher concentrations of HIV-1 RNA in genital secretions are associated with a greater risk of heterosexual transmission of HIV-1, and that these concentrations provide a new biomarker for predicting the infectiousness of HIV-1–infected individuals. The authors propose that HIV-1 RNA concentrations in genital secretions could also be used as a biomarker to monitor the efficacy of new microbicides and other interventions designed to block mucosal transmission of the virus. High plasma HIV-1 RNA concentrations are associated with an increased risk of HIV-1 transmission. Although plasma and genital HIV-1 RNA concentrations are correlated, no study has evaluated the relationship between genital HIV-1 RNA and the risk of heterosexual HIV-1 transmission. In a prospective study of 2521 African HIV-1 serodiscordant couples, we assessed genital HIV-1 RNA quantity and HIV-1 transmission risk. HIV-1 transmission linkage was established within the partnership by viral sequence analysis. We tested endocervical samples from 1805 women, including 46 who transmitted HIV-1 to their partner, and semen samples from 716 men, including 32 who transmitted HIV-1 to their partner. There was a correlation between genital and plasma HIV-1 RNA concentrations: For endocervical swabs, Spearman’s rank correlation coefficient ρ was 0.56, and for semen, ρ was 0.55. Each 1.0 log10 increase in genital HIV-1 RNA was associated with a 2.20-fold (for endocervical swabs: 95% confidence interval, 1.60 to 3.04) and a 1.79-fold (for semen: 95% confidence interval, 1.30 to 2.47) increased risk of HIV-1 transmission. Genital HIV-1 RNA independently predicted HIV-1 transmission risk after adjusting for plasma HIV-1 quantity (hazard ratio, 1.67 for endocervical swabs and 1.68 for semen). Seven female-to-male and four male-to-female HIV-1 transmissions (incidence <1% per year) occurred from persons with undetectable genital HIV-1 RNA, but in all 11 cases, plasma HIV-1 RNA was detected. Thus, higher genital HIV-1 RNA concentrations are associated with greater risk of heterosexual HIV-1 transmission, and this effect was independent of plasma HIV-1 concentrations. These data suggest that HIV-1 RNA in genital secretions could be used as a marker of HIV-1 sexual transmission risk.

Bacterial vaginosis associated with increased risk of female-to-male HIV-1 transmission: a prospective cohort analysis among African couples

In a prospective study, Craig Cohen and colleagues investigate the association between bacterial vaginosis and the risk of female-to-male HIV-1 transmission.

Increased risk of HIV-1 transmission in pregnancy: a prospective study among African HIV-1-serodiscordant couples.

Background:Physiologic and behavioral changes during pregnancy may alter HIV-1 susceptibility and infectiousness. Prospective studies exploring pregnancy and HIV-1 acquisition risk in women have found inconsistent results. No study has explored the effect of pregnancy on HIV-1 transmission risk from HIV-1-infected women to male partners. Methods:In a prospective study of African HIV-1-serodiscordant couples, we evaluated the relationship between pregnancy and the risk of HIV-1 acquisition among women and HIV-1 transmission from women to men. Results:Three thousand three hundred and twenty-one HIV-1-serodiscordant couples were enrolled, 1085 (32.7%) with HIV-1 susceptible female partners and 2236 (67.3%) with susceptible male partners. HIV-1 incidence in women was 7.35 versus 3.01 per 100 person-years during pregnant and nonpregnant periods [hazard ratio 2.34, 95% confidence interval (CI) 1.33–4.09]. This effect was attenuated and not statistically significant after adjusting for sexual behavior and other confounding factors (adjusted hazard ratio 1.71, 95% CI 0.93–3.12). HIV-1 incidence in male partners of infected women was 3.46 versus 1.58 per 100 person-years when their partners were pregnant versus not pregnant (hazard ratio 2.31, 95% CI 1.22–4.39). This effect was not attenuated in adjusted analysis (adjusted hazard ratio 2.47, 95% CI 1.26–4.85). Conclusion:HIV-1 risk increased two-fold during pregnancy. Elevated risk of HIV-1 acquisition in pregnant women appeared in part to be explained by behavioral and other factors. This is the first study to show that pregnancy increased the risk of female-to-male HIV-1 transmission, which may reflect biological changes of pregnancy that could increase HIV-1 infectiousness.

Childhood Sexual Abuse Is Highly Associated With HIV Risk-Taking Behavior and Infection Among MSM in the EXPLORE Study

Background:Previous studies have found high rates of childhood sexual abuse (CSA) among US men who have sex with men (MSM). CSA history has been associated with a variety of negative effects later in life including behaviors that place MSM at greater risk for HIV acquisition and transmission. The present analysis is the first to examine the longitudinal association between CSA and HIV infection, unprotected anal sex, and serodiscordant unprotected anal sex, as well as mediators of these relationships among a large sample of HIV-uninfected MSM. Methods:The EXPLORE Study was a behavioral intervention trial conducted in 6 US cities over 48 months with HIV infection as the primary efficacy outcome. Behavioral assessments were done every 6 months via confidential computerized assessments. Longitudinal regression models were constructed, adjusting for randomization arm, geographical location of study site, age at enrollment, education, and race/ethnicity. Results:Of the 4295 participants enrolled, 39.7% had a history of CSA. Participants with a history of CSA [adjusted hazards ratio = 1.30, 95% confidence interval (CI): 1.02 to 1.69] were at increased risk for HIV infection over study follow-up. A significant association was seen between history of CSA and unprotected anal sex (adjusted odds ratio = 1.24, 95% CI: 1.12 to 1.36) and serodiscordant unprotected anal sex (adjusted odds ratio = 1.30, 95% CI: 1.18 to 1.43). Among participants reporting CSA, the EXPLORE intervention had no effect in reducing HIV infection rates. Participants reporting CSA were significantly more likely to have symptoms of depression and use nonprescription drugs. Conclusions:A predictive relationship between a history of CSA and subsequent HIV infection was observed among this large sample of HIV-uninfected MSM. Findings indicate that HIV-uninfected MSM with CSA histories are at greater risk for HIV infection, report higher rates of HIV sexual risk behavior, and may derive less benefit from prevention programs. Future HIV prevention interventions should address the specific mental health concerns of MSM with a history of CSA.

Coreceptor Tropism in Human Immunodeficiency Virus Type 1 Subtype D: High Prevalence of CXCR4 Tropism and Heterogeneous Composition of Viral Populations

ABSTRACT In human immunodeficiency virus type 1 (HIV-1) subtype B, CXCR4 coreceptor use ranges from ∼20% in early infection to ∼50% in advanced disease. Coreceptor use by non-subtype B HIV is less well characterized. We studied coreceptor tropism of subtype A and D HIV-1 collected from 68 pregnant, antiretroviral drug-naive Ugandan women (HIVNET 012 trial). None of 33 subtype A or 10 A/D-recombinant viruses used the CXCR4 coreceptor. In contrast, nine (36%) of 25 subtype D viruses used both CXCR4 and CCR5 coreceptors. Clonal analyses of the nine subtype D samples with dual or mixed tropism revealed heterogeneous viral populations comprised of X4-, R5-, and dual-tropic HIV-1 variants. In five of the six samples with dual-tropic strains, V3 loop sequences of dual-tropic clones were identical to those of cocirculating R5-tropic clones, indicating the presence of CXCR4 tropism determinants outside of the V3 loop. These dual-tropic variants with R5-tropic-like V3 loops, which we designated “dual-R,” use CCR5 much more efficiently than CXCR4, in contrast to dual-tropic clones with X4-tropic-like V3 loops (“dual-X”). These observations have implications for pathogenesis and treatment of subtype D-infected individuals, for the association between V3 sequence and coreceptor tropism phenotype, and for understanding potential mechanisms of evolution from exclusive CCR5 use to efficient CXCR4 use by subtype D HIV-1.

Estimating the Impact of Plasma HIV-1 RNA Reductions on Heterosexual HIV-1 Transmission Risk

Background The risk of sexual transmission of HIV-1 is strongly associated with the level of HIV-1 RNA in plasma making reduction in HIV-1 plasma levels an important target for HIV-1 prevention interventions. A quantitative understanding of the relationship of plasma HIV-1 RNA and HIV-1 transmission risk could help predict the impact of candidate HIV-1 prevention interventions that operate by reducing plasma HIV-1 levels, such as antiretroviral therapy (ART), therapeutic vaccines, and other non-ART interventions. Methodology/Principal Findings We use prospective data collected from 2004 to 2008 in East and Southern African HIV-1 serodiscordant couples to model the relationship of plasma HIV-1 RNA levels and heterosexual transmission risk with confirmation of HIV-1 transmission events by HIV-1 sequencing. The model is based on follow-up of 3381 HIV-1 serodiscordant couples over 5017 person-years encompassing 108 genetically-linked HIV-1 transmission events. HIV-1 transmission risk was 2.27 per 100 person-years with a log-linear relationship to log10 plasma HIV-1 RNA. The model predicts that a decrease in average plasma HIV-1 RNA of 0.74 log10 copies/mL (95% CI 0.60 to 0.97) reduces heterosexual transmission risk by 50%, regardless of the average starting plasma HIV-1 level in the population and independent of other HIV-1-related population characteristics. In a simulated population with a similar plasma HIV-1 RNA distribution the model estimates that 90% of overall HIV-1 infections averted by a 0.74 copies/mL reduction in plasma HIV-1 RNA could be achieved by targeting this reduction to the 58% of the cohort with plasma HIV-1 levels ≥4 log10 copies/mL. Conclusions/Significance This log-linear model of plasma HIV-1 levels and risk of sexual HIV-1 transmission may help estimate the impact on HIV-1 transmission and infections averted from candidate interventions that reduce plasma HIV-1 RNA levels.

HIV protective efficacy and correlates of tenofovir blood concentrations in a clinical trial of prep for HIV prevention

Background:Antiretroviral pre-exposure prophylaxis (PrEP) is a novel HIV prevention strategy for which adherence is a known determinant of efficacy. Blood concentrations of PrEP medications are one objective marker of adherence. Methods:In a placebo-controlled PrEP efficacy trial of tenofovir disoproxil fumarate (TDF) and TDF with emtricitabine (FTC/TDF) among 4747 African women and men with an HIV-infected partner, we measured plasma tenofovir concentrations from participants in the active PrEP arms: 29 HIV seroconverters (cases) and 196 randomly selected controls who remained uninfected. Results:Among controls, 71% of visits had tenofovir concentrations >40 ng/mL, consistent with steady-state daily dosing, compared with 21% of cases at the visit HIV was first detected. Pill count data indicated that 96% of controls and 66% of cases had >80% adherence for these same visits. The estimated protective effect of PrEP against HIV, based on concentrations >40 ng/mL, was 88% (95% confidence interval: 60 to 96, P < 0.001) for individuals receiving TDF and 91% (95% confidence interval: 47 to 98, P = 0.008) for individuals receiving FTC/TDF. Controls had consistent patterns of PrEP concentrations during follow-up; among the 81% with concentrations >40 ng/mL at month 1, 75% maintained this concentration at month 12. Only 5 of 29 seroconverters seemed to be consistently adherent to PrEP. Tenofovir concentrations >40 ng/mL were associated with older age and shorter time on study; concentrations ⩽40 ng/mL occurred more commonly when participants reported no sex with their HIV-infected partner. Conclusions:Plasma concentrations of tenofovir consistent with daily dosing were highly predictive of protection from HIV acquisition. Most of those who took PrEP seemed to have high and consistent adherence.