Per-contact risk of human immunodeficiency virus transmission between male sexual partners

BRIEF - SYNOPSIS OF THE CURRENT EVIDENCE ON THE RISK OF HIV TRANSMISSION

BACKGROUND

Knowledge of the risk of HIV transmission has evolved over the past decade as evidence on the impact of biological and behavioural co-factors, such as viral load, has come to light. We undertook a comprehensive review of the evidence on the risk of HIV transmission.

METHODS

A search was conducted for literature published between January 2001 and May 2012. The search focused on systematic, meta-analytic, and narrative reviews. For topics where no reviews existed, primary research studies were included.

RESULTS

The risk estimates for the sexual transmission of HIV, per sex act, ranged from 0.5% to 3.38% (with mid-range estimates of 1.4% to 1.69%) for receptive anal intercourse; 0.06% to 0.16% for insertive anal intercourse; 0.08% to 0.19% for receptive vaginal intercourse; and approximately 0.05% to 0.1% for insertive vaginal intercourse. For people who inject drugs, the risk of transmission from a contaminated needle, per injection, was estimated to be between 0.7% and 0.8%. A number of factors impact the risk, including viral load, the presence of other sexually transmitted infections (STIs), and male circumcision.

CONCLUSIONS

Within each route of transmission, estimates of the risk of transmission varied widely, likely due to the role of behavioural and biological co-factors. Viral load appears to be an important predictor of transmission, regardless of the route of transmission. However, the evidence indicates that viral load is not the only determinant and that certain co-factors play a role in increasing (e.g., STIs) or decreasing (e.g., male circumcision) the risk of transmission.

Antiretroviral therapy for prevention of HIV transmission: implications for Europe

The aim of this review is to summarise the evidence on the population-level effect of antiretroviral therapy (ART) in preventing HIV infections, and to discuss potential implications in the European context of recommending starting ART when the CD4 count is above 350 cells/mm3. The ability of ART to reduce the risk of HIV transmission has been reported in observational studies and in a randomised controlled trial (HPTN 052), in which ART initiation reduced HIV transmission by 96% within serodiscordant couples. As yet, there is no direct evidence for such an effect among men having sex with men or people who inject drugs. HPTN 052 led international organisations to develop recommendations with a higher CD4 threshold for ART initiation. However, there remains a lack of strong evidence of clinical benefit for HIV-positive individuals starting ART with CD4 count above 350 cells/mm3. The main goal of ART provision should be to increase ART coverage for all those in need, based on the current guidelines, and the offer of ART to those who wish to reduce infectivity; increased HIV testing is therefore a key requirement. Other proven prevention means such as condom use and harm reduction for people who inject drugs remain critical.

Sex, HIV, and the Internet: Exploring Variations in the Online Profiles of MSM in the United States

With the increasing pervasiveness of social media, the Internet has become an important venue for dating and sex. Not only does the Internet introduce a unique array of opportunities and risks for men who have sex with men (MSM), it also presents a valuable means through which to study sexual behavior. In this study, data on what men report in their online profiles were collected from two dating/hookup websites to explore possible geographical differences in men's sexual preferences and expectations (N = 5,588). Across the 15 selected cities, significant differences emerged in reported HIV status and stated preference for safer sex (condom use). These patterns suggest important contextual and demographic variations and point to a need for targeted, population-specific interventions and further research to identify the underlying social and psychological constructs. With a better understanding of the local factors driving risky sexual behavior, health communication messages and tailored online interventions could be developed to address the needs and concerns of specific groups.

The increase in global HIV epidemics in MSM

Epidemics of HIV in MSM continue to expand in most low, middle, and upper income countries in 2013 and rates of new infection have been consistently high among young MSM. Current prevention and treatment strategies are insufficient for this next wave of HIV spread. We conducted a series of comprehensive reviews of HIV prevalence and incidence, risks for HIV, prevention and care, stigma and discrimination, and policy and advocacy options. The high per act transmission probability of receptive anal intercourse, sex role versatility among MSM, network level effects, and social and structural determinants play central roles in disproportionate disease burdens. HIV can be transmitted through large MSM networks at great speed. Molecular epidemiologic data show marked clustering of HIV in MSM networks, and high proportions of infections due to transmission from recent infections. Prevention strategies that lower biological risks, including those using antiretrovirals, offer promise for epidemic control, but are limited by structural factors including, discrimination, criminalization, and barriers to healthcare. Subepidemics, including among racial and ethnic minority MSM in the United States and UK, are particularly severe and will require culturally tailored efforts. For the promise of new and combined bio-behavioral interventions to be realized, clinically competent healthcare is necessary and community leadership, engagement, and empowerment are likely to be key. Addressing the expanding epidemics of HIV in MSM will require continued research, increased resources, political will, policy change, structural reform, community engagement, and strategic planning and programming, but it can and must be done.

Anal sex role segregation and versatility among men who have sex with men: EXPLORE Study

Anal sex role patterns and correlates during unprotected anal sex were examined longitudinally among HIV-negative men who have sex with men. Nearly 9.6% were exclusively receptive, 16.7% exclusively insertive, and 63.0% versatile. Versatility was more likely with primary and HIV-negative/unknown status partners and among younger men and substance users but less likely among Blacks and with higher number of partners. Exclusively receptive role was more likely with HIV-negative/unknown status partners and among younger men and substance users but less likely with higher number of partners. Examining anal sex role patterns helps understand the factors that drive the epidemic among men who have sex with men.

Sexual sensation seeking and Internet sex-seeking of Middle Eastern men who have sex with men

Despite recent evidence of stabilization in many developed nations, new human immunodeficiency virus (HIV) infections remain a public health concern globally. Efforts remain fragile in a number of world regions due to incomplete or inconsistent social policies concerning HIV, criminalization of same-sex encounters, social stigma, and religious doctrine. Middle Eastern men who have sex with men (MSM) remain one of the most hidden and stigmatized of all HIV risk groups. High-risk sexual bridging networks from these men to low prevalence populations (e.g., to spouse to offspring) are emerging HIV transmission pathways throughout the region. This cross-sectional, exploratory study investigated Sexual Sensation Seeking Scale (SSSS) scores to predict numbers of recent MSM sexual activities and to predict any recent unprotected receptive anal intercourse (URAI) activities in 86 Middle Eastern MSM who resided in the Middle East and who used the Internet to sex-seek. In a multivariate hierarchical regression, higher SSSS scores predicted higher numbers of recent MSM sexual activities (p = .028) and URAI (p = .022). In a logistic regression, higher SSSS scores increased the likelihood of engaging in URAI activities threefold (OR 3.0, 95 % CI 1.15-7.85, p = .025). Age and drug/alcohol use during sexual activities served as covariates in the regression models and were not significant in any analyses. Despite numerous hurdles, adopting Internet-based, non-restricted HIV education and prevention public health programs in the Middle East could instrumentally enhance efforts toward reducing the likelihood of new HIV transmissions in MSM and their sexual partners, ultimately contributing to an improved quality of life.

Anal sex role, circumcision status, and HIV infection among men who have sex with men in Chongqing, China

Men who have sex with men (MSM) in China face a rapidly expanding HIV epidemic. Anal sex role plays a significant role in HIV infection. Research has already begun in China investigating the potential for circumcision-based interventions to slow the rise of HIV among Chinese MSM. Using peer referral recruitment, we sampled 491 men who reported anal sex role preference. We analyzed preferred anal sex role, enacted sex role during recent sexual behavior, and circumcision status and HIV infection among MSM in one Chinese city. Men reported on their anal sex role preference and reported on up to three male sexual partners. Men were asked to report on whether they were "top" or "bottom" with each of the partners. Those that preferred being bottom and versatile were significantly younger than those who preferred being top. Men who preferred bottoming and those that preferred the versatile role were significantly more likely to be HIV-infected than those who preferred to be tops. There was no significant association between circumcision and HIV infection among men who maintained their preferred top role. In terms of anal sex role behavior, prevalence was not statistically different across anal sex roles. Circumcision conferred no additional protection to men who preferred and who engaged the top role during anal sex. HIV interventions will need to address anal sex roles in more sophisticated ways than perhaps originally thought. Simplistic assumptions that anal sex role is a fixed behavior undermines interventions such as circumcision among MSM.

Charges for criminal exposure to HIV and aggravated prostitution filed in the Nashville, Tennessee Prosecutorial Region 2000-2010

This paper examines comprehensive data on arrests for HIV-specific crimes within a single jurisdiction, the Nashville Tennessee prosecutorial region, over 11 years. There were 25 arrests for HIV exposure and 27 for aggravated prostitution. Eleven of the arrests for HIV exposure involved nonsexual behaviors; none alleged transmission. Sixteen of the arrests for HIV exposure involved sexual behavior; three alleged transmission. Aggravated prostitution cases (i.e. prostitution while knowing one has HIV) often involved solicitation of oral sex; none alleged transmission. Maximum sentences for HIV-specific crimes ranged from 5 to 8 years. We conclude that enforcement of US HIV-specific laws is underestimated. Fifty-two arrests over 11 years were recorded in one jurisdiction. Over half of the arrests involved behaviors posing minimal or no HIV transmission risk. Despite concerns about malicious, intentional HIV transmission, no cases alleged malice or intention.

Condom distribution in jail to prevent HIV infection

To determine if a structural intervention of providing one condom a week to inmates in the Los Angeles County Men’s Central Jail MSM unit reduces HIV transmissions and net social cost, we estimated numbers of new HIV infections (1) when condoms are available; and (2) when they are not. Input data came from a 2007 survey of inmates, the literature and intervention program records. Base case estimates showed that condom distribution averted 1/4 of HIV transmissions. We predict .8 new infections monthly among 69 HIV-negative, sexually active inmates without condom distribution, but .6 new infections with condom availability. The discounted future medical costs averted due to fewer HIV transmissions exceed program costs, so condom distribution in jail reduces total costs. Cost savings were sensitive to the proportion of anal sex acts protected by condoms, thus allowing inmates more than one condom per week could potentially increase the program’s effectiveness.

The implications of respondent concurrency on sex partner risk in a national, web-based study of men who have sex with men in the United States

BACKGROUND

Men who have sex with men (MSM) represent the largest HIV risk group in the United States. Sexual concurrency catalyzes HIV transmission in populations by increasing the indirect exposure of one's sex partners to one another. Although individual-level (egocentric) designs have demonstrated a high prevalence of concurrency among MSM respondents, methods are lacking for understanding the exposure implications for partners (dyads) reported in such studies.

METHODS

A new technique for manipulating egocentrically collected partnership timing data to measure the degree to which respondents' patterns of concurrency and serial monogamy resulted in the indirect exposure of respondents' partners to other partners was developed. Two outcomes were constructed for each partner: any concurrent or serially monogamous exposure to another partner (any exposure) and any concurrent exposure to another partner, irrespective of serial monogamy (any concurrent exposure). Reports of unprotected anal intercourse (UAI) were incorporated to construct the outcomes of 'any UAI exposure' and 'any concurrent UAI exposure.' This method was applied to an online study of MSM aged ≥18 years, with comparisons made by partner's race-ethnicity, age, type, and meeting location.

RESULTS

Among 4060 repeat partners of 2449 MSM, 73% had any exposure in the previous 6 months; 58% had any concurrent exposure. Among UAI partners, 37% had concurrent UAI exposure. Black UAI partners were more likely than whites to have any concurrent UAI exposure [unadjusted odds ratio (95% confidence interval) = 1.34 (1.05 to 1.70)], as were casual UAI partners relative to main partners [unadjusted odds ratio (95% confidence interval) = 4.37 (3.58 to 5.35)]. In adjusted models, black UAI partners were significantly more likely to have any UAI exposure, but not concurrent UAI exposure. Casual UAI partners remained more exposed by both outcomes.

CONCLUSIONS

Sex partners of MSM, particularly casual and black non-Hispanic partners, face a high degree of exposure to other partners.

Sexually transmitted infections screening at HIV treatment centers for MSM can be cost-effective

OBJECTIVE

To estimate the cost-effectiveness of anorectal chlamydia screening among men who have sex with men (MSM) in care at HIV treatment centers.

DESIGN

Transmission model combined with economic analysis over a 20-year period.

SETTING AND PARTICIPANTS

MSM in care at HIV treatment centers.

INTERVENTION

Once-yearly or twice-yearly screening for anorectal chlamydia among MSM in care at HIV treatment centers.

MAIN OUTCOME MEASURES

Averted HIV and chlamydia infections; discounted quality-adjusted life-years and costs; incremental cost-effectiveness ratio (ICER).

RESULTS

Costs will be saved by routine chlamydia screening of MSM in care at HIV treatment centers if these patients seek little or no screening elsewhere. Nonroutine screening is considerably more expensive than routine screening offered within a scheduled visit. Adding once-yearly chlamydia screening for MSM in care at HIV treatment centers is cost saving when 30% or fewer of those men seek once-yearly screening elsewhere (1.5 to 8.1 million euro saved). Twice-yearly routine screening at HIV treatment centers is cost-effective only when routine screening takes place without additional nonroutine screening (1.9 million euro saved).

CONCLUSIONS

Adding annual chlamydia screening to the HIV consultation will be cost saving as long as only a limited proportion of men are nonroutinely screened. The ICER was most sensitive to the percentage of MSM that continue to be screened elsewhere.

The Gap Between Knowledge and Practice of Risky Sexual Behaviors for HIV Among University Students and Staff in Moshi Town in Tanzania

Knowledge on HIV spread is important in combating HIV/AIDS, however its impact can only be realized if put into practice. This study was carried out in a Higher Learning Institution in Moshi Township in Kilimanjaro Region to assess the level of awareness of university communities about HIV/AIDs and its link with practice of risky sexual behaviors (RSB). We have found an adequate level of knowledge on the spread, risk behaviors and methods for protection leading to attendance to voluntary testing and counseling by 61% of respondents. Conversely, we have observed great extent of practice of RSBs including early sexual debut (16.7 years), having multiple and extramarital partners, involvement in practices that lead to unprotected sexual intercourse. We report an obvious gap between knowledge and behavior. This study therefore recommends that serious operational interventions must be put in place targeting the most sexually active groups, the youth in preliminary schools to sensitize on RSBs and ways to avoid them before they are engaged in sexual activities.

A social ecology of rectal microbicide acceptability among young men who have sex with men and transgender women in Thailand

INTRODUCTION

With HIV-incidence among men who have sex with men (MSM) in Bangkok among the highest in the world, a topical rectal microbicide would be a tremendous asset to prevention. Nevertheless, ubiquitous gaps between clinical trial efficacy and real-world effectiveness of existing HIV preventive interventions highlight the need to address multi-level factors that may impact on rectal microbicide implementation. We explored the social ecology of rectal microbicide acceptability among MSM and transgender women in Chiang Mai and Pattaya, Thailand.

METHODS

We used a qualitative approach guided by a social ecological model. Five focus groups were conducted in Thai using a semi-structured interview guide. All interviews were digitally recorded, transcribed verbatim in Thai and translated into English. We conducted thematic analysis using line-by-line and axial coding and a constant comparative method. Transcripts and codes were uploaded into a customized database programmed in Microsoft Access. We then used content analysis to calculate theme frequencies by group, and Chi-square tests and Fisher's exact test to compare themes by sexual orientation/gender expression and age.

RESULTS

Participant's (n=37) mean age was 24.8 years (SD=4.2). The majority (70.3%) self-identified as gay, 24.3% transgender women. Product-level themes (side effects, formulation, efficacy, scent, etc.) accounted for 42%, individual (increased sexual risk, packaging/portability, timing/duration of protection) 29%, interpersonal (trust/communication, power/negotiation, stealth) 8% and social-structural (cost, access, community influence, stigma) 21% of total codes, with significant differences by sexual orientation/gender identity. The intersections of multi-level influences included product formulation and timing of use preferences contingent on interpersonal communication and partner type, in the context of constraints posed by stigma, venues for access and cost.

DISCUSSION

The intersecting influence of multi-level factors on rectal microbicide acceptability suggests that social-structural interventions to ensure widespread access, low cost and to mitigate stigma and discrimination against gay and other MSM and transgender women in the Thai health care system and broader society will support the effectiveness of rectal microbicides, in combination with other prevention technologies, in reducing HIV transmission. Education, outreach and small-group interventions that acknowledge differences between MSM and transgender women may support rectal microbicide implementation among most-at-risk populations in Thailand.

Quantitative and qualitative differences in the T cell response to HIV in uninfected Ugandans exposed or unexposed to HIV-infected partners

HIV-exposed and yet persistently uninfected individuals have been an intriguing, repeated observation in multiple studies, but uncertainty persists on the significance and implications of this in devising protective strategies against HIV. We carried out a cross-sectional analysis of exposed uninfected partners in a Ugandan cohort of heterosexual serodiscordant couples (37.5% antiretroviral therapy naive) comparing their T cell responses to HIV peptides with those of unexposed uninfected individuals. We used an objective definition of exposure and inclusion criteria, blinded ex vivo and cultured gamma interferon (IFN-γ) enzyme-linked immunospot assays, and multiparameter flow cytometry and intracellular cytokine staining to investigate the features of the HIV-specific response in exposed versus unexposed uninfected individuals. A response rate to HIV was detectable in unexposed uninfected (5.7%, 95% confidence interval [CI] = 3.3 to 8.1%) and, at a significantly higher level (12.5%, 95% CI = 9.7 to 15.4%, P = 0.0004), in exposed uninfected individuals. The response rate to Gag was significantly higher in exposed uninfected (10/50 [20.%]) compared to unexposed uninfected (1/35 [2.9%]) individuals (P = 0.0004). The magnitude of responses was also greater in exposed uninfected individuals but not statistically significant. The average number of peptide pools recognized was significantly higher in exposed uninfected subjects than in unexposed uninfected subjects (1.21 versus 0.47; P = 0.0106). The proportion of multifunctional responses was different in the two groups, with a higher proportion of single cytokine responses, mostly IFN-γ, in unexposed uninfected individuals compared to exposed uninfected individuals. Our findings demonstrate both quantitative and qualitative differences in T cell reactivity to HIV between HESN (HIV exposed seronegative) and HUSN (HIV unexposed seronegative) subject groups but do not discriminate as to whether they represent markers of exposure or of protection against HIV infection.

Seroadaptation in a sample of very poor Los Angeles area men who have sex with men

Data from 635 very poor men who have sex with men (MSM) were used to identify seroadaptation with 1,102 male partners reported between 2005 and 2007 in Los Angeles as part of the Sexual Acquisition and Transmission of HIV Cooperative Agreement Program. The mean age of the sample was 41.7 years; 53 % had experienced homelessness in the past year. Condoms were reported in 51 % of sexual events involving anal intercourse. HIV seroconcordance was reported in 41 % of sexual partnerships among HIV-positive participants. HIV-positive men were more likely to have oral-only or unprotected receptive anal intercourse and less likely to have unprotected insertive anal intercourse with HIV-negative or unknown partners compared to HIV-positive partners. Even in the face of poverty, HIV-positive MSM report mitigating risks of HIV-transmission though seroadaptation in the context of modest rates of condom use.

What is the potential impact of adult circumcision on the HIV epidemic among men who have sex with men in San Francisco?

With the help of a community-based survey, we assess the potential effect of circumcision on the HIV epidemic among men who have sex with men (MSM) in San Francisco. Only a small minority of MSM would both derive benefit from circumcision (i.e., were uncircumcised, HIV-negative, predominantly insertive, and reported unprotected insertive anal sex) and be willing to participate in circumcision trials (0.7%) or be circumcised if proven effective as a prevention strategy (0.9%). Circumcision would have limited public health significance for MSM in San Francisco.

HIV-negative gay men's perceived HIV risk hierarchy: imaginary or real?

HIV-related risk perceptions and risk practices among gay men have changed over time. We revisited perceived HIV risk and engagement in anal intercourse with casual partners among HIV-negative gay men who participated in one of the Sydney Gay Community Periodic Surveys (GCPS). Perceived HIV risk was assessed by a range of anal intercourse practices combined with pre-specified casual partners' HIV status and viral load levels. Perceived HIV risk forms a potential hierarchy, broadly reflecting differences in the probability of HIV transmission through various anal intercourse practices. To a lesser extent, it also varies by casual partners' HIV status and viral load. Men who had unprotected anal intercourse with casual partners (UAIC) perceived lower HIV risk than those who used condoms consistently in the 6 months prior to survey. Recognising the complex associations between risk perceptions and risk practices helps to better address challenges arising from the 'Treatment as Prevention' (TasP).

Further research needed to support a policy of antiretroviral therapy as an HIV prevention initiative

The results from the HPTN 052 trial have increased the focus on use of antiretroviral therapy (ART) for prevention of HIV transmission; however, condom use also effectively prevents HIV transmission. Studies in heterosexual serodiscordant couples with viral suppression have so far only reported follow-up data for 330 couple-years when condoms were not being used. Data are even more limited for anal sex in men who have sex with men. Additional data on the effectiveness of ART as prevention when practicing condom-less sex is urgently needed.

Evidence of an explosive epidemic of HIV infection in a cohort of men who have sex with men in Thailand

OBJECTIVE

To assess HIV-prevalence, incidence and risk factors in a cohort of men who have sex with men (MSM) in Bangkok.

DESIGN

: Cohort study with 4-monthly follow-up visits conducted between April 2006 and July 2012 at a dedicated study clinic in a central Bangkok hospital. Participants were 1744 homosexually active Thai men, at least 18 years old and residents of Bangkok.

METHODS

Men were tested for HIV-infection at every study visit and for sexually transmitted infections at baseline. Demographic and behavioural data were collected by audio-computer-assisted self-interview. Logistic regression analysis was used to evaluate risk factors for HIV-prevalence and Cox proportional hazard analysis to evaluate risk factors for HIV-incidence.

RESULTS

Baseline HIV-prevalence was 21.3% (n = 372) and 60 months cumulative HIV-incidence was 23.9% (n = 222). Overall HIV-incidence density was 5.9 per 100 person-years. Multivariate risk factors for HIV-prevalence were older age, secondary/vocational education (vs. university or higher), employed or unemployed (vs. studying), nitrate inhalation, drug use for sexual pleasure, receptive anal intercourse, history of sexual coercion, no prior HIV-testing, and anti-HSV-1 and 2 and Treponema pallidum positivity at baseline. Multivariate risk factors for HIV-incidence were younger age, living alone or with roommate (vs. with a partner or family), drug use for sexual pleasure, inconsistent condom use, receptive anal intercourse, group sex, and anti-HSV-1 and 2 and T. pallidum positivity at baseline. Having no anal intercourse partners was inversely associated with HIV-incidence.

CONCLUSION

The high HIV prevalence and incidence in this cohort of Bangkok MSM documents an explosive epidemic. Additional preventive interventions for MSM are urgently needed.

Sociodemographic characteristics explain differences in unprotected sexual behavior among young HIV-negative gay, bisexual, and other YMSM in New York City

Young gay, bisexual, and other men who have sex with men (YMSM) under age 30 in New York City are at high risk for acquiring HIV. Using the theoretical framing of fundamental causes, this analysis examined the extent to which sociodemographic factors (race/ethnicity, perceived familial socioeconomic status [SES], U.S.-born status, and sexual orientation) explain the likelihood that HIV-negative YMSM ages 18 and 19 engage in unprotected sexual behavior, which may place them at risk for serconversion. Data were drawn from the baseline (Wave 1) assessment of a cohort study (N=592) collected between July 2009 and May 2011. The sample consisted predominantly of racial/ethnic minority YMSM (70.8%). A high level of association was demonstrated for each of the demographic factors with unprotected sexual behaviors. Multinomial logistic regression analyses were undertaken to examine associations between demographic covariates with the likelihood of engaging in unprotected sexual behaviors with male partners (any unprotected anal intercourse, as well as unprotected receptive anal, insertive anal, and receptive oral intercourse) irrespective of partner serostatus, in the month prior to assessment. U.S-born status and perceived socioeconomic status consistently were significant in differentiating risk behaviors. Being born outside the U.S. and perceiving a lower SES was associated with greater levels of risk. These findings suggest that efforts to address the disproportionate burden of HIV disease among YMSM in the United States must not focus solely on issues of race/ethnicity, but must be tailored and targeted to low SES and foreign-born young gay and bisexual men. It is posited that these demographic factors may lead to disproportionate levels of psychosocial burdens, which engender risk.

Depression, substance use and HIV risk in a probability sample of men who have sex with men

The persistent HIV epidemic among men who have sex with men (MSM) suggests that continued research on factors associated with risky sexual behavior is necessary. Drawing on prior literature, the role of depression and substance use in HIV risk is also inconclusive. Generalizability of past findings may also be limited to the extent that research has not employed probability samples. Here we report on one of the few probability samples of MSM to examine the role of depressive symptoms and substance use on risky sexual behavior (RSB). Multinomial logistic regression analysis suggested that depression and substance use are independently linked to our risk measure, such that those reporting high levels of depressive symptoms or substance use were more likely to report both unprotected receptive anal intercourse and unprotected insertive anal intercourse, and sex with a risky partner. Implications for prevention and treatment are discussed.

Acceptability of potential rectal microbicide delivery systems for HIV prevention: a randomized crossover trial

We assessed the acceptability of three of over-the-counter products representative of potential rectal microbicide (RM) delivery systems. From 2009 to 2010, 117 HIV-uninfected males (79 %) and females (21 %) who engage in receptive anal intercourse participated in a 6-week randomized crossover acceptability trial. Participants received each of three products (enema, lubricant-filled applicator, suppository) every 2 weeks in a randomized sequence. CASI and T-ACASI scales assessed product acceptability via Likert responses. Factor analysis was used to identify underlying factors measured by each scale. Random effects models were fit to examine age and gender effects on product acceptability. Three underlying factors were identified: Satisfaction with Product Use, Sexual Pleasure, and Ease of Product Use. For acceptability, the applicator ranked highest; however, differences between product acceptability scores were greatest among females and younger participants. These findings indicate that RM delivery systems impact their acceptability and should be considered early in RM development to enhance potential use.

Acceptability of oral versus rectal HIV preexposure prophylaxis among men who have sex with men and transgender women in Peru

OBJECTIVE

Oral preexposure prophylaxis (PrEP) with antiretrovirals (ARVs) is at the forefront of biomedical HIV prevention research, and ARVs are also being tested for rectal administration to target people practicing unprotected receptive anal intercourse (URAI) and at risk of HIV infection. This study assessed the acceptability of daily oral PrEP and rectal PrEP during URAI among men who have sex with men (MSM) and transgender women (TGW) in Peru.

METHODS

During the 2008 HIV sentinel surveillance survey conducted in 3 Peruvian cities (Lima, Iquitos, and Pucallpa), MSM and TGW reported being "versatile," "most of the time receptive," and "exclusively receptive" during anal sex behavior where surveyed on their acceptability of oral and rectal PrEP.

RESULTS

Among 532 individuals, high acceptance of either oral (96.2%) or rectal (91.7%) PrEP products was reported. If both products were efficacious/available, 28.6% would prefer a pill, 57.3% a rectal lubricant, and 14.1% either. A trend toward higher acceptance was observed as receptive anal sex behavior exclusivity rose (P = .013). Being receptive most of the time (adjusted odds ratio [aOR]: 9.1, P = .01) and exclusively receptive (aOR: 7.5, P = .01), compared to being versatile, were independently associated with oral PrEP acceptability. A similar association was found with the acceptability of rectal formulations (aOR: 2.3, P = .07; and aOR: 2.5, P = .02; respectively).

CONCLUSIONS

Oral and rectal PrEP were highly acceptable among Peruvian MSM and TGW, particularly among those at the highest HIV infection risk. These data can guide the implementation of PrEP programs in Peru and similar settings and populations.

Changes in seroadaptive practices from before to after diagnosis of recent HIV infection among men who have sex with men

OBJECTIVE

We assessed changes in sexual behavior among men who have sex with men (MSM), before and for several years after HIV diagnosis, accounting for adoption of a variety of seroadaptive practices.

METHODS

We collected self-reported sexual behavior data every 3 months from HIV-positive MSM at various stages of HIV infection. To establish population level trends in sexual behavior, we used negative binomial regression to model the relationship between time since diagnosis and several sexual behavior variables: numbers of (a) total partners, (b) potentially discordant partners (PDP; i.e., HIV-negative or unknown-status partners), (c) PDPs with whom unprotected anal intercourse (UAI) occurred, and (d) PDPs with whom unprotected insertive anal intercourse (uIAI) occurred.

RESULTS

A total of 237 HIV-positive MSM contributed 502 interviews. UAI with PDPs occurred with a mean of 4.2 partners in the 3 months before diagnosis. This declined to 0.9 partners/3 months at 12 months after diagnosis, and subsequently rose to 1.7 partners/3 months at 48 months, before falling again to 1.0 partners/3 months at 60 months. The number of PDPs with whom uIAI occurred dropped from 2.4 in the pre-diagnosis period to 0.3 partners/3 months (an 87.5% reduction) by 12 months after enrollment, and continued to decline over time.

CONCLUSION

Within months after being diagnosed with HIV, MSM adopted seroadaptive practices, especially seropositioning, where the HIV-positive partner was not in the insertive position during UAI, resulting in a sustained decline in the sexual activity associated with the highest risk of HIV transmission.

Innate immune recognition of HIV-1

In contrast to the extraordinary body of knowledge gained over the past three decades on the virology, pathogenesis, and immunology of HIV-1 infection, innate sensors that detect HIV-1 had remained elusive until recently. By virtue of integration, retroviridae makes up a substantial portion of our genome. Thus, immune strategies that deal with endogenous retroviruses are, by necessity, those of self-preservation and not of virus elimination. Some of the principles of such strategies may also apply for defense against exogenous retroviruses including HIV-1. Here, I highlight several sensors that have recently been revealed to be capable of recognizing distinct features of HIV-1 infection, while taking into account the host-retrovirus relationship that converges on avoiding pathogenic inflammatory consequences.

What drives the US and Peruvian HIV epidemics in men who have sex with men (MSM)?

In this work, we estimate the proportions of transmissions occurring in main vs. casual partnerships, and by the sexual role, infection stage, and testing and treatment history of the infected partner, for men who have sex with men (MSM) in the US and Peru. We use dynamic, stochastic models based in exponential random graph models (ERGMs), obtaining inputs from multiple large-scale MSM surveys. Parallel main partnership and casual sexual networks are simulated. Each man is characterized by age, race, circumcision status, sexual role behavior, and propensity for unprotected anal intercourse (UAI); his history is modeled from entry into the adult population, with potential transitions including HIV infection, detection, treatment, AIDS diagnosis, and death. We implemented two model variants differing in assumptions about acute infectiousness, and assessed sensitivity to other key inputs. Our two models suggested that only 4–5% (Model 1) or 22–29% (Model 2) of HIV transmission results from contacts with acute-stage partners; the plurality (80–81% and 49%, respectively) stem from chronic-stage partners and the remainder (14–16% and 27–35%, respectively) from AIDS-stage partners. Similar proportions of infections stem from partners whose infection is undiagnosed (24–31%), diagnosed but untreated (36–46%), and currently being treated (30–36%). Roughly one-third of infections (32–39%) occur within main partnerships. Results by country were qualitatively similar, despite key behavioral differences; one exception was that transmission from the receptive to insertive partner appears more important in Peru (34%) than the US (21%). The broad balance in transmission contexts suggests that education about risk, careful assessment, pre-exposure prophylaxis, more frequent testing, earlier treatment, and risk-reduction, disclosure, and adherence counseling may all contribute substantially to reducing the HIV incidence among MSM in the US and Peru.

Detectable signals of episodic risk effects on acute HIV transmission: strategies for analyzing transmission systems using genetic data

Episodic high-risk sexual behavior is common and can have a profound effect on HIV transmission. In a model of HIV transmission among men who have sex with men (MSM), changing the frequency, duration and contact rates of high-risk episodes can take endemic prevalence from zero to 50% and more than double transmissions during acute HIV infection (AHI). Undirected test and treat could be inefficient in the presence of strong episodic risk effects. Partner services approaches that use a variety of control options will be likely to have better effects under these conditions, but the question remains: What data will reveal if a population is experiencing episodic risk effects? HIV sequence data from Montreal reveals genetic clusters whose size distribution stabilizes over time and reflects the size distribution of acute infection outbreaks (AIOs). Surveillance provides complementary behavioral data. In order to use both types of data efficiently, it is essential to examine aspects of models that affect both the episodic risk effects and the shape of transmission trees. As a demonstration, we use a deterministic compartmental model of episodic risk to explore the determinants of the fraction of transmissions during acute HIV infection (AHI) at the endemic equilibrium. We use a corresponding individual-based model to observe AIO size distributions and patterns of transmission within AIO. Episodic risk parameters determining whether AHI transmission trees had longer chains, more clustered transmissions from single individuals, or different mixes of these were explored. Encouragingly for parameter estimation, AIO size distributions reflected the frequency of transmissions from acute infection across divergent parameter sets. Our results show that episodic risk dynamics influence both the size and duration of acute infection outbreaks, thus providing a possible link between genetic cluster size distributions and episodic risk dynamics.

Can HIV-1 incidence be estimated from plasma viral load and sexual behaviour?

To estimate the impact of sexual practices and HIV-1 viral load status on HIV-1 incidence, we surveyed 38 men who have sex with men (MSM) on their sexual practices in the past three months. HIV-1 RNA load was measured in semen and blood contemporaneously. A Bernoulli model was developed incorporating seminal plasma viral load (SPVL), number and serostatus of partners, and number of protected and unprotected episodes of anal intercourse. Probability of transmission according to SPVL was determined by sensitivity analysis based on the correlation between blood plasma viral load (BPVL) and SPVL. There was a BPVL threshold below which SPVL was low or undetectable and above which SPVL increased geometrically. Seven subjects infected 0.93 HIV-1-negative partners and 13 subjects infected 4.28 unknown serostatus partners. Probability estimates were heavily skewed by a small number of subjects with high rates of unprotected sex and multiple sexual partners. We conclude that more HIV-1 infections may occur from increased episodes of unprotected sex with multiple partners of unknown HIV-1 serostatus. The model can be used to counsel individuals or predict epidemics, and to assess behaviour change or the impact of public health interventions.

Condom Use, Disclosure, and Risk for Unprotected Sex in HIV-Negative Midlife and Older Men Who Have Sex With Men

Sexual risk behaviors account for most HIV infections in men who have sex with men (MSM), and the risk of exposure from each sexual encounter increases with age. The focus of this study was to investigate which behaviors in midlife and older MSM influence their sexual risk/protection. Cross-sectional data were collected from a community-based sample of 802 MSM aged 40 years and older from community venues (e.g., bars) who completed an anonymous questionnaire. Data from a subset of 420 MSM who were HIV-negative (aged 40-81 years) were used to investigate which behaviors were associated with greater risk for unprotected anal sex. Regression analyses indicated that erection difficulties (odds ratio [OR] = 4.7; 95% confidence interval [CI] = 1.8-12.2), practicing safe sex with outside partners but not with one’s primary partner (OR = 0.54; 95% CI = 0.3-0.94), and recreational drug use (OR = 2.6; 95% CI = 1.3-5.1) were associated with higher risk for unprotected receptive anal intercourse. Younger age (OR = 0.96; 95% CI = 0.9- 0.9), not telling partners about HIV status (OR = 3.2; 95% CI = 1.5-6.5), finding partners in backrooms/sex clubs (OR = 2.8; 95% CI = 1.1- 6.8), and erection difficulties (OR = 10.3; 95% CI = 2.8-37.8) were associated with higher risk for unprotected insertive anal intercourse. These data indicate there may be certain factors specific to older MSM that influence their sexual risk taking behaviors. Programs may be more effective if they are tailored for older cohorts of MSM and address interpersonal communication, erection problems, and substance use to reduce health risks and promote healthier lifestyles.

Frequency, patterns, and preferences of lubricant use during anal intercourse within male sexual partnerships in Lima, Peru: implications for a rectal microbicide HIV prevention intervention

Understanding current practices of lubricant use during anal intercourse can help to assess the contexts for the introduction of topical rectal microbicides as an HIV prevention tool for men who have sex with men (MSM). We used quantitative and qualitative methods to assess: current patterns of lubricant use; preferred characteristics of commercial lubricant formulations; and social and behavioral contexts of lubricant use within male sexual partnerships in Lima, Peru. Between 2007 and 2008, we conducted a quantitative behavioral survey with 547 MSM followed by qualitative individual and group interviews with 36 MSM from Lima, Peru. Approximately half of all participants in the quantitative survey (50.3%) reported using commercial lubricant during intercourse occasionally or consistently during the preceding two months, with lack of availability at the time of intercourse the most commonly reported reason for non-use. No clear preferences regarding the color, smell, taste, or viscosity of commercial lubricants were identified, and all participants who reported using a commercial lubricant used the same product ("Love-Lub"). In the qualitative analysis, participants characterized lubricant use as a sexual practice consistently controlled by the receptive partner, who typically obtained and applied lubricant independently, with or without the consent of the insertive partner. Quantitative findings supported this differential pattern of lubricant use, with men who reported sexual identities or roles consistent with receptive anal intercourse, including unprotected receptive intercourse, more likely to report lubricant use than MSM who claimed an exclusively insertive sexual role. Given the social, behavioral, and biological factors contributing to increased vulnerability for HIV and STI acquisition by the receptive partner in anal intercourse, delivery of a topical rectal microbicide as a lubricant formulation could provide an important HIV prevention resource for at-risk MSM in Lima, Peru.

An economic case for providing free access to antiretroviral therapy for HIV-positive people in South Australia

BACKGROUND

As financial constraints can be a barrier to accessing HIV antiretroviral therapy (ART), we argue for the removal of copayment requirements from HIV medications in South Australia.

METHODS

Using a simple mathematical model informed by available behavioural and biological data and reflecting the HIV epidemiology in South Australia, we calculated the expected number of new HIV transmissions caused by persons who are not currently on ART compared with transmissions for people on ART. The extra financial investment required to cover the copayments to prevent an HIV infection was compared with the treatment costs saved due to averting HIV infections.

RESULTS

It was estimated that one HIV infection is prevented per year for every 31.4 persons (median, 24.0-42.7 interquartile range (IQR)) who receive treatment. By considering the incremental change in costs and outcomes of a change in program from the current status quo, it would cost the health sector $17860 per infection averted (median, $13651-24287 IQR) if ART is provided as a three-dose, three-drug combination without requirements for user-pay copayments.

CONCLUSIONS

The costs of removing copayment fees for ART are less than the costs of treating extra HIV infections that would result under current conditions. Removing the copayment requirement for HIV medication would be cost-effective from a governmental perspective.

Prevalence of human immunodeficiency virus infection among transgender men in Rawalpindi (Pakistan)

BACKGROUND

Transgender males are at high risk for sexually transmitted diseases including AIDS caused by the notorious Human Immunodeficiency Virus (HIV), yet little consideration is given by the policy makers, researchers and non-governmental organizations (NGOs) towards this sensitive issue in Pakistan.

METHODS

In this study, we have investigated the prevalence of HIV infection among 306 transgender males with a median age of 29 years (range 15-64 years) residing in Rawalpindi, Pakistan. Rapid HIV antibody-screening methods including the strip test and Enzyme Linked Immuno-absorbent tests were employed to detect HIV antibodies among the subjects. For further confirmation, Polymerase Chain Reaction (PCR) was carried out. Statistical analytical techniques utilized included logistic regression and chi-square.

RESULTS

HIV-1 was found to be the predominant viral subtype. PCR confirmed 21.6% (Confidence Interval 0.17-0.26) of the respondents were reported being HIV positive. 15.7% of the transgender men who shave at home and 13.7% of the transgender men who were educated below 5th grade were found to have HIV.

CONCLUSION

This study shows a very high prevalence of HIV among transgender males. Unawareness among these individuals about the ramifications of this infection owes largely to lack of education. The spread rate is alarming and HIV epidemic is imminent if awareness is not widespread.

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.

The Promise of Antiretrovirals for HIV Prevention

With an estimated 2.6 million new HIV infections diagnosed annually, the world needs new prevention strategies to partner with condom use, harm reduction approaches for injection drug users, and male circumcision. Antiretrovirals can reduce the risk of mother-to-child HIV transmission and limit HIV acquisition after occupational exposure. Macaque models and clinical trials demonstrate efficacy of oral or topical antiretrovirals used prior to HIV exposure to prevent HIV transmission, ie pre-exposure prophylaxis (PrEP). Early initiation of effective HIV treatment in serodiscordant couples results in a 96% decrease in HIV transmission. HIV testing to determine serostatus and identify undiagnosed persons is foundational to these approaches. The relative efficacy of different approaches, adherence, cost and long-term safety will affect uptake and impact of these strategies. Ongoing research will help characterize the role for oral and topical formulations and help quantify potential benefits in sub-populations at risk for HIV acquisition.

Risk reduction practices in men who have sex with men in Switzerland: serosorting, strategic positioning, and withdrawal before ejaculation

The aim of this study was to identify predictors of intentional use of the HIV risk reduction practices of serosorting, strategic positioning, and withdrawal before ejaculation during unprotected anal intercourse (UAI) with casual partners. A cross-sectional survey pertaining to the Swiss HIV behavioral surveillance system, using an anonymous self-administered questionnaire, was conducted in 2007 in a self-selected sample of men having sex with other men (MSM). Analysis was restricted to participants with UAI with casual partner(s) (N = 410). Logistic regression was used to estimate factors associated with intentional use of serosorting, strategic positioning, and withdrawal before ejaculation. In the previous 12 months, 71% of participants reported having UAI with a casual partner of different or unknown HIV-status. Of these, 47% reported practicing withdrawal, 38% serosorting, and 25% strategic positioning. In the 319 participants with known HIV-status, serosorting was associated with frequent Internet use to find partners (OR = 2.32), STI (OR = 2.07), and HIV testing in the past 12 months (OR = 1.81). Strategic positioning was associated with HIV-status (OR = 0.13) and having UAI with a partner of different or unknown HIV-status (OR = 3.57). Withdrawal was more frequently practiced by HIV-negative participants or participants reporting high numbers of sexual partners (OR = 2.48) and having UAI with a partner of unknown or different serostatus (OR = 2.08). Risk reduction practices are widely used by MSM, each practice having its own specificities. Further research is needed to determine the contextual factors surrounding harm reduction practices, particularly the strategic or opportunistic nature of their use.

A complex systems approach to evaluate HIV prevention in metropolitan areas: preliminary implications for combination intervention strategies

BACKGROUND

HIV transmission among injecting and non-injecting drug users (IDU, NIDU) is a significant public health problem. Continuing propagation in endemic settings and emerging regional outbreaks have indicated the need for comprehensive and coordinated HIV prevention. We describe the development of a conceptual framework and calibration of an agent-based model (ABM) to examine how combinations of interventions may reduce and potentially eliminate HIV transmission among drug-using populations.

METHODOLOGY/PRINCIPAL FINDINGS

A multidisciplinary team of researchers from epidemiology, sociology, geography, and mathematics developed a conceptual framework based on prior ethnographic and epidemiologic research. An ABM was constructed and calibrated through an iterative design and verification process. In the model, "agents" represent IDU, NIDU, and non-drug users who interact with each other and within risk networks, engaging in sexual and, for IDUs, injection-related risk behavior over time. Agents also interact with simulated HIV prevention interventions (e.g., syringe exchange programs, substance abuse treatment, HIV testing) and initiate antiretroviral treatment (ART) in a stochastic manner. The model was constructed to represent the New York metropolitan statistical area (MSA) population, and calibrated by comparing output trajectories for various outcomes (e.g., IDU/NIDU prevalence, HIV prevalence and incidence) against previously validated MSA-level data. The model closely approximated HIV trajectories in IDU and NIDU observed in New York City between 1992 and 2002, including a linear decrease in HIV prevalence among IDUs. Exploratory results are consistent with empirical studies demonstrating that the effectiveness of a combination of interventions, including syringe exchange expansion and ART provision, dramatically reduced HIV prevalence among IDUs during this time period.

CONCLUSIONS/SIGNIFICANCE

Complex systems models of adaptive HIV transmission dynamics can be used to identify potential collective benefits of hypothetical combination prevention interventions. Future work will seek to inform novel strategies that may lead to more effective and equitable HIV prevention strategies for drug-using populations.

Perceptions of HIV transmission risk in commercial and public sex venues

BACKGROUND: Sexual behaviors of men who have sex with men (MSM) that occur in sexually charged venues (e.g., bathhouse, sex club, public park) are a target for research and intervention due to concerns about the role these venues may have in the transmission of HIV and other sexually transmitted infections (STIs). However, these efforts often exclude how individuals perceive HIV risk in terms of sex venue use. This paper analyzes how venue-specific perceptions of HIV transmission risk differ across venues and by onsite sexual behavior. METHOD: Cross-sectional data collected using an Internet survey completed by 139 MSM who attended at least one sex venue (e.g., bathhouse, sex club, gym/health club, public park) in the past month. RESULTS: Risk perceptions were highest for bathhouses and sex clubs, though no significant differences were detected between any of the venues. With few exceptions, men who reported not engaging in sex or low-risk behaviors (i.e., masturbation or mutual masturbation) during venue attendance perceived higher risks than those who engaged in high-risk behaviors (i.e., anal sex). Interestingly, risk perceptions of public bathrooms, parks, and video/buddy booths were lower for attendees who reported unprotected oral sex with ejaculation than men who reported safer or riskier behaviors. CONCLUSION: These findings provide important insights into how MSM perceive HIV risk in sex venues and highlight a need for expanded outreach and education in locations where sexual risk taking may be underestimated.

Using conjoint analysis to measure the acceptability of rectal microbicides among men who have sex with men in four South American cities

Conjoint Analysis (CJA), a statistical market-based technique that assesses the value consumers place on product characteristics, may be used to predict acceptability of hypothetical products. Rectal Microbicides (RM)-substances that would prevent HIV infection during receptive anal intercourse-will require acceptability data from potential users in multiple settings to inform the development process by providing valuable information on desirable product characteristics and issues surrounding potential barriers to product use. This study applied CJA to explore the acceptability of eight different hypothetical RM among 128 MSM in Lima and Iquitos, Peru; Guayaquil, Ecuador; and Rio de Janeiro, Brazil. Overall RM acceptability was highest in Guayaquil and lowest in Rio. Product effectiveness had the greatest impact on acceptability in all four cities, but the impact of other product characteristics varied by city. This study demonstrates that MSM from the same region but from different cities place different values on RM characteristics that could impact uptake of an actual RM. Understanding specific consumer preferences is crucial during RM product development, clinical trials and eventual product dissemination.

Successes and challenges of HIV prevention in men who have sex with men

Men who have sex with men (MSM) have been substantially affected by HIV epidemics worldwide. Epidemics in MSM are re-emerging in many high-income countries and gaining greater recognition in many low-income and middle-income countries. Better HIV prevention strategies are urgently needed. Our review of HIV prevention strategies for MSM identified several important themes. At the beginning of the epidemic, stand-alone behavioural interventions mostly aimed to reduce unprotected anal intercourse, which, although somewhat efficacious, did not reduce HIV transmission. Biomedical prevention strategies reduce the incidence of HIV infection. Delivery of barrier and biomedical interventions with coordinated behavioural and structural strategies could optimise the effectiveness of prevention. Modelling suggests that, with sufficient coverage, available interventions are sufficient to avert at least a quarter of new HIV infections in MSM in diverse countries. Scale-up of HIV prevention programmes for MSM is difficult because of homophobia and bias, suboptimum access to HIV testing and care, and financial constraints.

Weighting for sex acts to understand the spread of STI on networks

Human sexual networks exhibit a heterogeneous structure where few individuals have many partners and many individuals have few partners. Network theory predicts that the spread of sexually transmitted infections (STI) on such networks should exhibit striking properties (e.g. rapid spread). However, these properties cannot be found in epidemiological data. Current network models typically assume a constant STI transmission risk per partnership, which is unrealistic because it implies that sexual activity is proportional to the number of partners and that individuals have the same activity with each partner. We develop a framework that allows us to weight any sexual network based on biological assumptions. Our results indicate that STI spreading on the resulting weighted networks do not have heterogeneous-related properties, which is consistent with data and earlier studies.

Intervention outcomes among HIV-affected families over 18 months

We evaluate the efficacy of a family-based intervention over time among HIV-affected families. Mothers living with HIV (MLH; n = 339) in Los Angeles and their school-aged children were randomized to either an intervention or control condition and followed for 18 months. MLH and their children in the intervention received 16 cognitive-behavioral, small-group sessions designed to help them maintain physical and mental health, parent while ill, address HIV-related stressors, and reduce HIV-transmission behaviors. At recruitment, MLH reported few problem behaviors related to physical health, mental health, or sexual or drug transmission acts. Compared to MLH in the control condition, intervention MLH were significantly more likely to monitor their own CD4 cell counts and their children were more likely to decrease alcohol and drug use. Most MLH and their children had relatively healthy family relationships. Family-based HIV interventions should be limited to MLH who are experiencing substantial problems.

Comparison of sexual behavior and HIV risk between two HIV-1 serodiscordant couple cohorts: the CHAVI 002 study

BACKGROUND

The CHAVI002 study was designed to characterize immune responses, particularly HIV-specific T-cell responses, amongst 2 cohorts of HIV-exposed seronegative (HESN) individuals. The absence of a clear definition of HESNs has impaired comparison of research within and between such cohorts. This report describes two distinct HESN cohorts and attempts to quantify HIV exposure using a 'HIV risk index' (RI) model.

METHODS

HIV serodiscordant couples (UK; 24, Uganda; 72) and HIV unexposed seronegative (HUSN) controls (UK; 14, Uganda; 26 couples, 3 individuals) completed sexual behavior questionnaires every 3 months over a 9 month period. The two cohorts were heterogeneous, with most HESNs in the UK men who have sex with men (MSM), while all HESNs in Uganda were in heterosexual relationships. Concordance of responses between partners was determined. Each participant's sexual behavior score (SBS) was estimated based on the number and type of unprotected sex acts carried out in defined time periods. Independent HIV acquisition risk factors (partner plasma viral load, STIs, male circumcision, pregnancy) were integrated with the SBS, generating a RI for each HESN.

RESULTS

96 HIV serodiscordant couples completed 929 SBQs. SBSs remained relatively stable amongst the UK cohort, whilst decreasing from Visit 1 to 2 in the Ugandan cohort. Compared to the Ugandan cohort, SBSs and RIs in the UK cohort were lower at visit 1, and generally higher at later visits. Differences between the cohorts, with lower rates of ART use in Uganda and higher risk per-act sex in the UK, had major impacts on the SBSs and RIs of each cohort. There was one HIV transmission event in the UK cohort.

CONCLUSIONS

Employment of a risk quantification model facilitated quantification and comparison of HIV acquisition risk across two disparate HIV serodiscordant couple cohorts.

Reformulated tenofovir gel for use as a dual compartment microbicide

OBJECTIVES

Coital use of 1% tenofovir gel was shown to be modestly effective at preventing HIV transmission when applied vaginally in the CAPRISA 004 trial. Because the gel is hyperosmolar, which would reduce the integrity of the epithelium and induce fluid movement into the lumen, rectal use may not be acceptable. This study evaluated the pre-clinical safety and efficacy of a reformulated (reduced osmolality) tenofovir gel product.

METHODS

Reduced glycerine (RG)-tenofovir gel was compared with the original tenofovir gel for physiochemical characteristics, product safety and anti-HIV-1 activity.

RESULTS

The formulations were similar in all characteristics except for osmolality and spreadability/firmness. The RG-tenofovir gel had a 73% lower osmolality, a 29.6% increase in spreadability and a 27% decrease in firmness as compared with the original tenofovir gel. When applied to epithelial cell monolayers, tenofovir gel showed a transient reduction in the transepithelial resistance while the RG-tenofovir gel did not. Both gels retained ectocervical and colorectal explant viability. However, tenofovir gel treatment resulted in epithelial stripping that was absent after RG-tenofovir gel treatment of the polarized explants. Anti-HIV-1 activity was confirmed by lack of HIV-1 infection in polarized explants treated with either gel as compared with the control explants.

CONCLUSIONS

Reducing the osmolality of the tenofovir gel resulted in improved epithelial integrity, which suggests better safety upon rectal use. The improved gel safety did not compromise drug release or anti-HIV-1 activity. These data support the use of this gel as a dual compartment microbicide.

The association of intimate partner violence, recreational drug use with HIV seroprevalence among MSM

Intimate partner violence (IPV) has been significantly associated with HIV among heterosexual individuals. Yet a similar relationship has not been so clearly described among men who have sex with men (MSM). The aim of this study was to investigate the association of IPV with HIV seroprevalence among MSM. Participants consisted of 7,844 MSM clients who visited the Whitman Walker Clinic in Washington DC from 2000 through 2007, the majority of whom were Caucasian with a median age of 30. The univariate analysis showed that self-reported IPV was significantly associated with HIV (OR: 1.67, CI: 1.14-2.45) among the sampled MSM clients. However, when adjusting for sexually transmitted infection (STI) status and self-reported risk behaviors including recreational drug use, condom use, number of male sex partners, and having sex with a positive HIV partner, the association of IPV with HIV was not statistically significant. Results indicated that the strong independent association of recreational drug use with HIV seroprevalence decreased the association of IPV with HIV significantly (with recreational drug use, OR: 1.36, CI: 0.93-2.00 vs. without recreational drug use, OR: 1.51, CI: 1.03-2.22).

Will changes in gay men's sexual behavior reduce syphilis rates?

BACKGROUND

Reducing rates of partner change and increasing condom usage among gay men are obvious targets for potentially reducing syphilis transmission among gay men.

METHODS

We developed an agent-based stochastic model to examine syphilis transmission among a population of gay men, representative of gay men in Australia. This model was used to explore the potential impact of changes in sexual behavior over 1 month, 3 month, and indefinite time frames on syphilis epidemics.

RESULTS

Simulations of interventions showed that short-term reductions in rates of partner change and increased condom use would have negligible impact on the long-term trends of syphilis epidemics. If no interventions are introduced, then the model forecasts that the syphilis prevalence in the population could continue to rise, with an increase of 80% in the number of men infected with syphilis during the next decade. However, if changes in sexual behavior are maintained in the long-term, then syphilis epidemics can be mitigated. If condom use is sustained at 80% in partnerships that are HIV discordant or of unknown status, then the prevalence of syphilis is estimated to decrease by 9% over 10 years. Similarly, if partner acquisition rates decrease by 25%, then there will be a 22% reduction in syphilis prevalence.

CONCLUSIONS

Interventions promoting partner reduction or increased condom use would be ineffective in the short-term, and would have limited prospects for success in the long-term unless very large changes in behavior are sustained. Complementary social research indicates that such long-term changes in behavior are unlikely to be adopted, and therefore other intervention strategies need to be developed to reduce syphilis among gay men.

Differential innate immune responses to low or high dose oral SIV challenge in Rhesus macaques

Mucosal transmission of HIV predominately occurs during sexual intercourse or breast-feeding and generally results in a successful infection from just one or few founder virions. Here we assessed the impact of viral inoculum size on both viral and immune events within two groups of Rhesus macaques that were non-traumatically, orally inoculated with either multiple low (1000 to 4000 TCID(50)) or high (100,000 TCID(50)) doses of SIV. In agreement with previous studies, more diverse SIV variants were observed in macaques following infection with high dose oral SIV compared to a low dose challenge. In peripheral blood cells, the immune gene transcript levels of CXCL9, IFNγ, TNFα and IL10 remained similar to uninfected macaques. In contrast, OAS and CXCL10 were upregulated following SIV infection in both the high and low dosed macaques, with a more rapid kinetics (detectable by 7 days) following the high SIV dose challenge. In peripheral lymph nodes, an increase in CXCL10 was observed irrespective of viral dose while CXCL9 and OAS were differentially regulated in the two SIV dosed groups. Magnetic bead sorting of CD3+, CD14+ and CD3- /CD14- cells from peripheral blood identified the increase in OAS expression primarily within CD14+ monocytes, whereas the CXCL10 expression was primarily in CD3+ T cells. These findings provide insights into the impact of SIV challenge dose on viral and innate immune factors, which has the potential to inform future SIV/HIV vaccine efficacy trials in which vaccinated hosts have the potential to be infected with a range of viral challenge doses.

Adherence and Risk Behaviour in Patients with HIV Infection Receiving Antiretroviral Therapy in Bangkok

It could be postulated that due to lifestyle factors, patients with poor antiretroviral therapy (ART) adherence may also have risky sexual behaviour potentially leading to HIV transmission. There are limited data regarding unprotected sex risk and ART adherence in resource limited settings and our study set out to investigate these in an HIV clinic in Bangkok. Patients completed an anonymous questionnaire regarding their relationship details, ART adherence, sexual behaviour, alcohol and drug use and HIV transmission beliefs. Laboratory findings and medical history were also collected. Unprotected sex risk (USR) was defined as inconsistent condom use with a partner of negative or unknown HIV status. Five hundred and twelve patients completed the questionnaire. Fifty seven per cent of patients reported having taken ARV >95% of the time in the last month and 58% had been sexually active in the previous 30 days. Only 27 patients (5%) were classified as having USR in our cohort. Multivariate analysis showed USR was associated with female gender (OR 2.9, 95% CI 1.2-7.0, p0.02) but not with adherence, age, type or number of partners, recreational drug or alcohol use nor beliefs about HIV transmission whilst taking ART. Levels of USR in this resource limited setting were reassuringly low and not associated with poor ART adherence; as all USR patients had undetectable viral loads onward HIV transmission risk is likely to be low but not negligible. Nonetheless condom negotiation techniques, particularly in women, may be useful in this group.