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

Relation between HIV viral load and infectiousness: a model-based analysis

BACKGROUND

A consensus statement released on behalf of the Swiss Federal Commission for HIV/AIDS suggests that people receiving effective antiretroviral therapy-ie, those with undetectable plasma HIV RNA (<40 copies per mL)-are sexually non-infectious. We analysed the implications of this statement at a population level.

METHODS

We used a simple mathematical model to estimate the cumulative risk of HIV transmission from effectively treated HIV-infected patients (HIV RNA <10 copies per mL) over a prolonged period. We investigated the risk of unprotected sexual transmission per act and cumulatively over many exposures, within couples initially discordant for HIV status.

FINDINGS

Assuming that each couple had 100 sexual encounters per year, the cumulative probability of transmission to the serodiscordant partner each year is 0.0022 (uncertainty bounds 0.0008-0.0058) for female-to-male transmission, 0.0043 (0.0016-0.0115) for male-to-female transmission, and 0.043 (0.0159-0.1097) for male-to-male transmission. In a population of 10 000 serodiscordant partnerships, over 10 years the expected number of seroconversions would be 215 (80-564) for female-to-male transmission, 425 (159-1096) for male-to-female transmission, and 3524 (1477-6871) for male-to-male transmission, corresponding to an increase in incidence of four times compared with incidence under current rates of condom use.

INTERPRETATION

Our analyses suggest that the risk of HIV transmission in heterosexual partnerships in the presence of effective treatment is low but non-zero and that the transmission risk in male homosexual partnerships is high over repeated exposures. If the claim of non-infectiousness in effectively treated patients was widely accepted, and condom use subsequently declined, then there is the potential for substantial increases in HIV incidence.

FUNDING

Australian Research Council.

Behavioral interventions to reduce risk for sexual transmission of HIV among men who have sex with men

BACKGROUND

Men who have sex with men (MSM) remain at great risk for HIV infection. Program planners and policy makers need descriptions of interventions and quantitative estimates of intervention effects to make informed decisions concerning prevention funding and research. The number of intervention strategies for MSM that have been examined with strong research designs has increased substantially in the past few years.

OBJECTIVES

1. To locate and describe outcome studies evaluating the effects of behavioral HIV prevention interventions for MSM.2. To summarize the effectiveness of these interventions in reducing unprotected anal sex.3. To identify study characteristics associated with effectiveness.4. To identify gaps and indicate future research, policy, and practice needs.

SEARCH STRATEGY

We searched electronic databases, current journals, manuscripts submitted by researchers, bibliographies of relevant articles, conference proceedings, and other reviews for published and unpublished reports from 1988 through December 2007. We also asked researchers working in HIV prevention about new and ongoing studies.

SELECTION CRITERIA

Studies were considered in scope if they examined the effects of behavioral interventions aimed at reducing risk for HIV or STD transmission among MSM. We reviewed studies in scope for criteria of outcome relevance (measurement of at least one of a list of behavioral or biologic outcomes, e.g., unprotected sex or incidence of HIV infections) and methodologic rigor (randomized controlled trials or certain strong quasi-experimental designs with comparison groups).

DATA COLLECTION AND ANALYSIS

We used fixed and random effects models to summarize rate ratios (RR) comparing intervention and control groups with respect to count outcomes (number of occasions of or partners for unprotected anal sex), and corresponding prevalence ratios (PR) for dichotomous outcomes (any unprotected anal sex vs. none). We used published formulas to convert effect sizes and their variances for count and dichotomous outcomes where necessary. We accounted for intraclass correlation (ICC) in community-level studies and adjusted for baseline conditions in all studies. We present separate results by intervention format (small group, individual, or community-level) and by type of intervention delivered to the comparison group (minimal or no HIV prevention in the comparison condition versus standard or other HIV prevention in the comparison condition). We examine rate ratios stratified according to characteristics of participants, design, implementation, and intervention content. For small group and individual-level interventions we used a stepwise selection process to identify a multivariable model of predictors of reduction in occasions of or partners for unprotected anal sex. We used funnel plots to examine publication bias, and Q (a chi-squared statistic with degrees of freedom = number of interventions minus 1) to test for heterogeneity.

MAIN RESULTS

We found 44 studies evaluating 58 interventions with 18,585 participants. Formats included 26 small group interventions, 21 individual-level interventions, and 11 community-level interventions. Sixteen of the 58 interventions focused on HIV-positives. The 40 interventions that were measured against minimal to no HIV prevention intervention reduced occasions of or partners for unprotected anal sex by 27% (95% confidence interval [CI] = 15% to 37%). The other 18 interventions reduced unprotected anal sex by 17% beyond changes observed in standard or other interventions (CI = 5% to 27%). Intervention effects were statistically homogeneous, and no independent variable was statistically significantly associated with intervention effects at alpha=.05. However, a multivariable model selected by backward stepwise elimination identified four study characteristics associated with reduction in occasions of or partners for unprotected anal sex among small group and individual-level interventions at alpha=.10. The most favorable reductions in episodes of or partners for unprotected anal sex (33% to 35% decreases) were observed among studies with count outcomes, those with shorter intervention spans (<=1 month), those with better retention in the intervention condition than in the comparison condition, and those with minimal to no HIV prevention intervention delivered to the comparison condition. Because there were only 11 community-level studies we did not search for a multivariable model for community-level interventions. In stratified analyses including only one variable at a time, the greatest reductions (40% to 54% decreases) in number of episodes of or partners for unprotected anal sex among community-level interventions were observed among studies where groups were assigned randomly rather than by convenience, studies with shorter recall periods and longer follow-up, studies with more than 25% non-gay identifying MSM, studies in which at least 90% of participants were white, and studies in which the intervention addressed development of personal skills.

AUTHORS' CONCLUSIONS

Behavioral interventions reduce self-reported unprotected anal sex among MSM. These results indicate that HIV prevention for this population can work and should be supported. Results of previous studies provide a benchmark for expectations in new studies. Meta-analysis can inform future design and implementation in terms of sample size, target populations, settings, goals for process measures, and intervention content. When effects differ by design variables, which are deliberately selected and planned, awareness of these characteristics may be beneficial to future designs. Researchers designing future small group and individual-level studies should keep in mind that to date, effects of the greatest magnitude have been observed in studies that used count outcomes and a shorter intervention span (up to 1 month). Among small group and individual-level studies, effects were also greatest when the comparison condition included minimal to no HIV prevention content. Nevertheless, statistically significant favorable effects were also seen when the comparison condition included standard or other HIV prevention content. Researchers choosing the latter option for new studies should plan for larger sample sizes based on the smaller expected net intervention effect noted above. When effects differ by implementation variables, which become evident as the study is conducted but are not usually selected or planned, caution may be advised so that future studies can reduce bias. Because intervention effects were somewhat stronger (though not statistically significantly so) in studies with a greater attrition in the comparison condition, differential retention may be a threat to validity. Extra effort should be given to retaining participants in comparison conditions. Among community-level interventions, intervention effects were strongest among studies with random assignment of groups or communities. Therefore the inclusion of studies where assignment of groups or communities was by convenience did not exaggerate the summary effect. The greater effectiveness of interventions including more than 25% non-gay identifying MSM suggests that when they can be reached, these men may be more responsive than gay-identified men to risk reduction efforts. Non-gay identified MSM may have had less exposure to previous prevention messages, so their initial exposure may have a greater impact. The greater effectiveness of interventions that include efforts to promote personal skills such as keeping condoms available and behavioral self-management indicates that such content merits strong consideration in development and delivery of new interventions for MSM. And the finding that interventions were most effective for majority white populations underscores the critical need for effective interventions for MSM of African and Latino descent. Further research measuring the incidence of HIV and other STDs is needed. Because most studies were conducted among mostly white men in the US and Europe, more evaluations of interventions are needed for African American and Hispanic MSM as well as MSM in the developing world. More research is also needed to further clarify which behavioral strategies (e.g., reducing unprotected anal sex, having oral sex instead of anal sex, reducing number of partners, avoiding serodiscordant partners, strategic positioning, or reducing anal sex even with condom use) are most effective in reducing transmission among MSM, the messages most effective in promoting these behaviors, and the methods and settings in which these messages can be most effectively delivered.

Persisting with prevention: the importance of adherence for HIV prevention

BACKGROUND

Only four out of 31 completed randomized controlled trials (RCTs) of HIV prevention strategies against sexual transmission have shown significant efficacy. Poor adherence may have contributed to the lack of effect in some of these trials. In this paper we explore the impact of various levels of adherence on measured efficacy within an RCT.

ANALYSIS

We used simple quantitative methods to illustrate the impact of various levels of adherence on measured efficacy by assuming a uniform population in terms of sexual behavior and the binomial model for the transmission probability per partnership.At 100% adherence the measured efficacy within an RCT is a reasonable approximation of the true biological efficacy. However, as adherence levels fall, the efficacy measured within a trial substantially under-estimates the true biological efficacy. For example, at 60% adherence, the measured efficacy can be less than half of the true biological efficacy.

CONCLUSION

Poor adherence during a trial can substantially reduce the power to detect an effect, and improved methods of achieving and maintaining high adherence within trials are needed. There are currently 12 ongoing HIV prevention trials, all but one of which require ongoing user-adherence. Attention must be given to methods of maximizing adherence when piloting and designing RCTs and HIV prevention programmes.

Sexual risk behaviour and knowledge of HIV status among community samples of gay men in the UK

OBJECTIVES

Undiagnosed infection presents a potential risk for the onward transmission of HIV and denies men early interventions for their health. Little is known about the differences between men who are, and are not, aware of their HIV status in the UK.

METHODS

Cross-sectional surveys of men in commercial gay venues in London, Brighton, Manchester, Glasgow, and Edinburgh (2003-2005). Anonymous, self-completion questionnaires, and oral fluid samples (tested for HIV antibodies) were obtained from 3672 men (61% response rate).

RESULTS

Of 3501 men with a confirmed positive or negative oral fluid result, 318 were HIV positive (9.1%). Of these, 131 (41.2%) were undiagnosed; 81.1% of men with undiagnosed HIV had previously tested (92.2% tested negative; the remainder did not know the result); 62.3% still thought that they were negative. Undiagnosed and diagnosed men reported greater sexual risk and sexually transmitted infections than HIV-negative men. Compared with HIV-negative men, the adjusted odds ratio of unprotected anal intercourse with two or more partners was higher among undiagnosed men (odds ratio 2.21, 95% confidence interval 1.17-4.20), but highest among diagnosed men (odds ratio 6.80, 95% confidence interval 4.39-10.52).

CONCLUSION

A high proportion of the HIV-positive men were undiagnosed and not receiving benefits of clinical care, but sexual risk and sexually transmitted infections were highest among men who were aware of their HIV-positive status. Clinics should proactively offer testing to reduce undiagnosed HIV, target repeat testing at high-risk men who have previously tested negative, and initiate evidence-based behavioural interventions to reduce sexual risk among men living with diagnosed HIV as well as those testing negative.

The economics of sexuality: the effect of HIV/AIDS on homosexual behavior in the United States

In this paper, I test a simple microeconomic theory of sexuality. I apply the theory to make predictions about the effect of AIDS on sexuality, since AIDS dramatically altered the cost of sexual activities. Using a nationally representative dataset on sexuality in the United States, I estimate the effect of AIDS on male and female homosexual behavior. To do so, I postulate that people who have a relative with AIDS, on average, have more knowledge, awareness, and fear of AIDS. Empirically, this variable is uncorrelated with a number of individual background characteristics. I present evidence that AIDS causes some men to shift from homosexual to heterosexual behavior, whereas AIDS causes some women to shift from heterosexual to homosexual behavior. Thus, sexual behavior may respond to incentives. I consider alternative hypotheses, including biological theories of sexual orientation and stigma-related survey bias, and argue that they are unlikely to explain the results.

The cost-effectiveness of counseling strategies to improve adherence to highly active antiretroviral therapy among men who have sex with men

OBJECTIVE

Inadequate adherence to highly active antiretroviral therapy (HAART) may lead to poor health outcomes and the development of HIV strains that are resistant to HAART. The authors developed a model to evaluate the cost-effectiveness of counseling interventions to improve adherence to HAART among men who have sex with men (MSM).

METHODS

The authors developed a dynamic compartmental model that incorporates HIV treatment, adherence to treatment, and infection transmission and progression. All data estimates were obtained from secondary sources. The authors evaluated a counseling intervention given prior to initiation of HAART and before all changes in drug regimens, combined with phone-in support while on HAART. They considered a moderate-prevalence and a high-prevalence population of MSM.

RESULTS

If the impact of HIV transmission is ignored, the counseling intervention has a cost-effectiveness ratio of $25,500 per quality-adjusted life year (QALY) gained. When HIV transmission is included, the cost-effectiveness ratio is much lower: $7400 and $8700 per QALY gained in the moderate- and high-prevalence populations, respectively. When the intervention is twice as costly per counseling session and half as effective as estimated in the base case (in terms of the number of individuals who become highly adherent, and who remain highly adherent), then the intervention costs $17,100 and $19,600 per QALY gained in the 2 populations, respectively.

CONCLUSIONS

Counseling to improve adherence to HAART increased length of life, modestly reduced HIV transmission, and cost substantially less than $50,000 per QALY gained over a wide range of assumptions but did not reduce the proportion of drug-resistant strains. Such counseling provides only modest benefit as a tool for HIV prevention but can provide significant benefit for individual patients at an affordable cost.

Determinants of HIV seroconversion among men who have sex with men living in a low HIV incidence population in the era of highly active antiretroviral therapies

OBJECTIVE

To estimate human immunodeficiency virus (HIV) incidence and associated risk factors among men who have sex with men (MSM) participating in the Omega Cohort Study in Montreal, 1996-2003.

METHODS

Longitudinal study of 1587 MSM seronegative at baseline with > or =1 six-month follow-up visit. Multivariate Cox regression with time-dependent variables was used for data analysis.

RESULTS

HIV incidence was 0.62 per 100 person-years (95% confidence interval: 0.41-0.84). In multivariate analyses compared with subjects not reporting any anal sex with serodiscordant or casual partners, those reporting anal sex with such partners (all P values <0.05), whether consistently protected [hazard ratio (HR) = 3.4], or unprotected exclusively receptive (HR = 12.0), exclusively insertive (HR = 4.7), or both receptive and insertive (HR = 8.3), were at increased risk of seroconversion. Sexual behaviors with seroconcordant regular partners were not associated with seroconversion.

CONCLUSION

These results observed in a cohort of MSM with low HIV incidence provide new insights regarding the debate about harm-reduction strategies to prevent sexual HIV transmission.

Correlates of Substance Use in Relation to Sexual Behavior in Black Gay and Bisexual Men: Implications for HIV Prevention

Since the onset of the AIDS epidemic, Black gay and bisexual men have been at a substantial risk for acquiring HIV. Substance use has been identified as a significant risk factor for engaging in HIV sexual risk behavior. The purpose of this formative research investigation was to examine substance use in relation to sexual behavior through differentiating users versus nonusers of alcohol and recreational drugs before or during sex in a community-based sample of 481 Black gay and bisexual men in the New York metropolitan area. Binary logistic regression results demonstrated that alcohol use before or during sex was predictive of having a primary sex partner, casual sex partner, higher income, previous sexually transmitted infection testing, and a higher number of male sex partners. Recreational drug use before or during sex was predictive of having an HIV positive status, casual sex partner, unprotected anal intercourse with a male sex partner, and being younger. These findings present significant formative implications for the influence of substance use in relation to HIV sexual risk behavior in Black gay and bisexual men.

The public health impact of widespread availability of nonoccupational postexposure prophylaxis against HIV

OBJECTIVE

The aim of the study was to describe the use of nonoccupational postexposure prophylaxis (NPEP) in Australia, and to estimate the number of HIV infections that its use prevented.

METHODS

We conducted a population-based observational cohort study of people who presented to antiretroviral prescribers in Eastern Australia, and reported a high-risk nonoccupational exposure to HIV, in 1998-2004. Prescribers collected data at baseline, 4 weeks and 6 months. Data collected included details of HIV exposure, drug regimens and HIV serostatus.

RESULTS

The great majority of the 1601 participants were male (95%) and presented after male homosexual exposure (87%). Only 32% of exposures were to HIV-positive sources. Two antiretroviral drugs were prescribed after 48% of events, and three or more drugs after 52% of events. The median time to receipt of NPEP was 23 h. Side effects were reported by 66% of participants. No case of NPEP failure in an adherent individual was identified. It was estimated that 0.9-9.2 HIV infections had been prevented. This compared with a total of 1138 newly acquired HIV infections notified in the geographical area covered by the study.

CONCLUSIONS

In Australia, NPEP has been widely prescribed and is mainly targeted at high-risk exposures. Although there were no identified failures of NPEP, it is likely that only a small proportion of new HIV infections in the study area were prevented. NPEP may be a valuable preventive intervention for an individual, but it can only play a minor role in HIV prevention at the population level unless targeting can be further improved.

How homosexual men believe they became infected with HIV: the role of risk-reduction behaviors

OBJECTIVES

A range of HIV risk reduction strategies has been described in homosexual men who practice unprotected anal intercourse (UAI), including serosorting, strategic positioning, and negotiating around an HIV-positive partner's viral load. It is uncertain how commonly these behaviors might result in HIV infection. We describe sexual behaviors and associated risk reduction strategies reported by homosexual men in their accounts of their recent seroconversion.

METHODS

Homosexual men recently diagnosed with primary HIV infection between 2003 and 2006 were invited to participate in a nurse-administered survey.

RESULTS

Among 158 men enrolled, 143 (91%) were able to identify the high-risk event that they believed led to their HIV seroconversion, and this involved UAI in 102 (71%). Among these 102 men, 21 (21%) reported they were certain that the source partner was HIV-negative. Ten men (10%) reported insertive UAI as the highest risk behavior. Of the 21 men who reported knowing the HIV-positive partner's viral load, 9 reported that the man had an undetectable viral load (43%).

CONCLUSION

In 38% of the high-risk events involving UAI, infection occurred when the reported risk event involved serosorting, strategic positioning, or intercourse with a man whose viral load was believed to be undetectable.

Human seminal plasma abrogates the capture and transmission of human immunodeficiency virus type 1 to CD4+ T cells mediated by DC-SIGN

Dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) is expressed by dendritic cells (DCs) at mucosal surfaces and appears to play an important role in the dissemination of human immunodeficiency virus type 1 (HIV-1) infection. DC-SIGN binds HIV-1 gp120 and efficiently transmits the virus to T CD4(+) cells, which become the center of viral replication. Semen represents the main vector for HIV-1 dissemination worldwide. In the present study we show that human seminal plasma (SP), even when used at very high dilutions (1:10(4) to 1:10(5)), markedly inhibits the capture and transmission of HIV-1 to T CD4(+) cells mediated by both DCs and B-THP-1-DC-SIGN cells. In contrast, SP does not inhibit the capture of HIV-1 by DC-SIGN-negative target cells, such as the T-cell line SupT-1, monocytes, and activated peripheral blood mononuclear cells. The SP inhibitor has a high molecular mass (>100 kDa) and directly interacts with DC-SIGN-positive target cells but not with HIV-1. Moreover, the inhibitor binds to concanavalin A, suggesting that it contains high-mannose N-linked carbohydrates. Of note, using biotin-labeled SP we found that the binding of SP components to DCs was abrogated by mannan, while their interaction with B-THP-1 cells was almost completely dependent on the expression of DC-SIGN. Since epithelium integrity is often compromised after vaginal or anal intercourse, as well as in the presence of ulcerative-sexually transmitted diseases, our results support the notion that components of the SP might be able to access to the subepithelium, inhibiting the recognition of HIV-1 gp120 by DC-SIGN-positive DCs.

Explaining disparities in HIV infection among black and white men who have sex with men: a meta-analysis of HIV risk behaviors

OBJECTIVE

To identify factors that contribute to the racial disparity in HIV prevalence between black and white men who have sex with men (MSM) in the United States.

METHODS

A comprehensive literature search of electronic databases, online bibliographies, and publication reference lists yielded 53 quantitative studies of MSM published between 1980 and 2006 that stratified HIV risk behaviors by race. Meta-analyses were performed to compare HIV risks between black and white MSM across studies.

RESULTS

Compared with white MSM, black MSM reported less overall substance use [odds ratio (OR), 0.71; 95% confidence interval (CI), 0.53-0.97], fewer sex partners (OR, 0.64; 95% CI, 0.45-0.92), less gay identity (OR, 0.29; 95% CI, 0.17-0.48), and less disclosure of same sex behavior (OR, 0.42; 95% CI, 0.30-0.60). HIV-positive black MSM were less likely than HIV-positive white MSM to report taking antiretroviral medications (OR, 0.43; 95% CI, 0.30-0.61). Sexually transmitted diseases were significantly greater among black MSM than white MSM (OR, 1.64; 95% CI, 1.07-2.53). There were no statistically significant differences by race in reported unprotected anal intercourse, commercial sex work, sex with a known HIV-positive partner, or HIV testing history.

CONCLUSIONS

Behavioral risk factors for HIV infection do not explain elevated HIV rates among black MSM. Continued emphasis on risk behaviors will have only limited impact on the disproportionate rates of HIV infection among black MSM. Future research should focus on the contribution of other factors, such as social networks, to explain racial disparities in HIV infection rates.

Declining rates in male circumcision amidst increasing evidence of its public health benefit

Background

Recent experimental evidence has demonstrated the benefits of male circumcision for the prevention of human immunodeficiency virus (HIV) infection. Studies have also shown that male circumcision is cost-effective and reduces the risk for certain ulcerative sexually transmitted diseases (STDs). The epidemiology of male circumcision in the United States is poorly studied and most prior reports were limited by self-reported measures. The study objective was to describe male circumcision trends among men attending the San Francisco municipal STD clinic, and to correlate the findings with HIV, syphilis and sexual orientation.

Methods and Findings

A cross sectional study was performed by reviewing all electronic records of males attending the San Francisco municipal STD clinic between 1996 and 2005. The prevalence of circumcision over time and by subpopulation such as race/ethnicity and sexual orientation were measured. The findings were further correlated with the presence of syphilis and HIV infection. Circumcision status was determined by physical examination and disease status by clinical evaluation with laboratory confirmation. Among 58,598 male patients, 32,613 (55.7%, 95% Confidence Interval (CI) 55.2–56.1) were circumcised. Male circumcision varied significantly by decade of birth (increasing between 1920 and 1950 and declining overall since the 1960's), race/ethnicity (Black: 62.2%, 95% CI 61.2–63.2, White: 60.0%, 95% CI 59.46–60.5, Asian Pacific Islander: 48.2%, 46.9–49.5 95% CI, and Hispanic: 42.2%, 95% CI 41.3–43.1), and sexual orientation (gay/bisexual: 73.0%, 95% CI 72.6–73.4; heterosexual: 66.0%, 65.5–66.5). Male circumcision may have been modestly protective against syphilis in HIV-uninfected heterosexual men (PR 0.92, 95% C.I. 0.83–1.02, P = 0.06).

Conclusions

Male circumcision was common among men seeking STD services in San Francisco but has declined substantially in recent decades. Male circumcision rates differed by race/ethnicity and sexual orientation. Given recent studies suggesting the public health benefits of male circumcision, a reconsideration of national male circumcision policy is needed to respond to current trends.

Primary care issues for HIV-infected patients

HIV primary care is determined by the intersection of the unique aspects of the infection and its treatment, the unique aspects of the populations affected by HIV, and the challenges of disease prevention and health maintenance in the general population. Any primary care provider may be called on to care for a patient living with HIV, and it is incumbent on all medical providers to become proficient in the management of this complex infection. This proficiency includes an awareness of local resources for referral, including medical and surgical specialists, mental health providers, and social service organizations. Given the complexity of HIV care in the twenty-first century and the potential for involvement of multiple consultants, the role of primary care provider is perhaps more critical for the HIV-infected patient than for the average patient.

Role versatility among men who have sex with men in urban Peru

Role versatility refers to the practice in which individual men who have sex with men (MSM) play both insertive and receptive sexual roles over time. Versatility has been thought to be relatively uncommon among Latin American MSM but possibly rising. Versatility has also been shown to be a potentially large population-level risk factor for HIV infection. In this study we examine the correlates of versatile behavior and identity among 2,655 MSM in six Peruvian cities. Versatile behavior with recent male partners was found in 9% of men and versatile ("moderno") identity was reported by 16%. Significant predictors included high education, white-collar occupation, sex work, and residence in Lima. Age was not significant in any analysis. Since sex work is negatively correlated with other predictors, versatile men appear to comprise two distinct sub-populations. Insertive-only men appear to play a strong role in bridging the HIV epidemic between MSM and women.

Differences between HIV-positive gay men who 'frequently', 'sometimes' or 'never' engage in unprotected anal intercourse with serononconcordant casual partners: positive Health cohort, Australia

By measuring the actual number of risk acts engaged in by HIV-positive men participating in the Positive Health (PH) cohort study, this paper sets out to document the distribution of risk acts, to report on the proportion of acts of unprotected anal intercourse with casual (UAIC) partners that occurred between HIV-positive men (i.e. seroconcordant positive) and to examine the factors that differentiated men who 'frequently' compared with 'sometimes' or 'never' engaged in unsafe UAIC (i.e. UAIC with serononconcordant partners: partners who have not tested positive for HIV). The findings show that 42.6% of all UAIC acts occurred between seroconcordant HIV-positive partners, posing no risk of HIV infection to an HIV-negative person. A minority of participants (10%) accounted for the majority (70.7%) of the unsafe acts of UAIC. The HIV-positive men who 'sometimes' engaged in unsafe UAIC had higher treatment optimism scores and were more likely to use Viagra in comparison with those who did not engage in such risk. Those who reported 'frequent' engagement in unsafe UAIC were more likely to engage in a range of esoteric sexual practices, be slightly less well educated and be taking antiretroviral therapy compared with HIV-positive men who 'sometimes' engaged in unsafe UAIC. As such, taking ART but not viral load, predicted frequent unsafe UAIC. When considered alongside earlier studies, these results suggest that HIV-negative men who engage in esoteric sexual practices may be at increased risk of HIV transmission, not necessarily because they engage in esoteric sex practices but because of the sub-cultural milieu in which esoteric sex is occurring. The findings from this study also endorse the measurement of UAIC acts as a useful gauge of risk.

The role of bathhouses and sex clubs in HIV transmission: findings from a mathematic model

Bathhouses and sex clubs were identified as primary venues for HIV transmission during the original HIV epidemic. Because HIV incidence is increasing in some high-risk groups, their potential role in HIV transmission is being examined again. We present an extension of the Bernoulli process model of HIV transmission to incorporate subpopulations with different behaviors in sex acts, condom use, and choice of partners in a single period of time. With this model, we study the role that bathhouses and sex clubs play in HIV transmission using data from the 1997 Urban Men's Health Study. If sexual activity remains the same, we find that bathhouse closures would likely lead to a small increase in HIV transmission in the period examined by this study, although this impact is less than that which would be achieved through a 1% change in current condom use rates. If, conversely, bathhouse closure leads to a reduction of the sexual activity that was in the bathhouse by at least 2%, HIV transmission would be lowered.

Tonsil epithelial factors may influence oropharyngeal human immunodeficiency virus transmission

Tonsil epithelium has been implicated in human immunodeficiency virus (HIV) pathogenesis, but its role in oral transmission remains controversial. To study characteristics of this tissue, which may influence susceptibility or resistance to HIV, we performed microarray analysis of the tonsil epithelium. Our data revealed that genes related to immune functions such as antibody production and antigen processing were increasingly expressed in tonsil compared with the epithelium of another oropharyngeal site, the gingival epithelium. Importantly, tonsil epithelium highly expressed genes associated with HIV entrapment and/or transmission, including the HIV co-receptor CXCR4 and the potential HIV-binding molecules FcRgammaIII, complement receptor 2, and various complement components. Immunohistochemical staining confirmed the increased presence of CXCR4 in the tonsil epithelium compared with multiple oral epithelial sites, particularly in basal and parabasal layers. This increased expression of molecules involved in viral recognition, binding, and entry may favor virus-epithelium interactions in an environment with reduced innate antiviral mechanisms. Specifically, secretory leukocyte protease inhibitor, an innate molecule with anti-HIV activity, was minimal in the tonsil epithelium, in contrast to oral mucosa. Collectively, our data suggest that increased expression of molecules associated with HIV binding and entry coupled with decreased innate antiviral factors may render the tonsil a potential site for oral transmission.

Barebacking, the Internet, and harm reduction: an intercept survey with gay and bisexual men in Los Angeles and New York City

Researchers have suggested that intentional unprotected anal intercourse (UAI) among gay and bisexual men (colloquially called barebacking), is on the rise. Further, they have linked this increase in barebacking to the growth of the Internet as a medium for men to meet sex partners. Data were used from large-scale gay, lesbian, and bisexual (GLB) community events in New York and Los Angeles collected between 2003 and 2004. In total 1178 men who have sex with men (MSM) responded to questions about the use of the Internet, willingness to have unplanned UAI, intentions toward planned UAI, and "barebacker identity." Compared to nonbarebackers, barebackers spent significantly more time on the Internet looking for sex and looking for dates. Further, HIV-positive barebackers specifically spent the most time online looking for dates. Further analyses of willingness and intentions to have UAI, and the specific sexual behaviors of self-identified barebackers, found evidence of strategic positioning and serosorting, both harm reduction strategies. These data suggest both HIV-positive and HIV-negative barebackers may be engaged in efforts to reduce the risk of HIV transmission when engaged in unprotected sex.

The adult film industry: time to regulate?

The industry is putting the health of its employees, adult film perfomers, at risk by insisting that they work without condoms.

Probability Sample Estimates of Bathhouse Sexual Risk Behavior

OBJECTIVE

Previous research links high rates of unprotected anal intercourse (UAI) with men who go to bathhouses; however, the literature provides no prevalence estimates. An exit survey of a probability sample was conducted to describe the prevalence of risk activity at the bathhouse.

METHODS

Data are from a 2-stage probability sample of men exiting a gay bathhouse (n = 400).

RESULTS

During their visit, 91.5% of men had oral sex and 44.2% had anal sex (11.1% reported UAI and 5.5% reported unprotected receptive anal intercourse). In the prior 3 months, 85% reported having anal sex, which was more likely to be unprotected when it occurred in a private home or hotel as opposed to a public setting (P < 0.001). Moreover, having UAI at home was a significant correlate of risk during the bathhouse visit (P < 0.001).

CONCLUSIONS

Most men at the bathhouse engaged in oral sex rather than anal sex, and most anal sex included use of condoms. Furthermore, men were more likely to have UAI in a private home than in any public setting. The bathhouse seems to have facilitated condom use when anal sex occurred on-site.

Risk factors for incident HIV infection in men having sex with men: a case-control study

BACKGROUND

HIV notifications affecting men having sex with men (MSM) in Victoria, Australia have been increasing. This study aimed to determine current risk factors for HIV infection in this population.

METHODS

Case-control study. Cases were MSM infected within the previous year (incident cases) as indicated by a previous negative test or seroconversion illness. Controls were MSM with a negative HIV test at the same clinic. From May 2001 to May 2003, cases and controls were interviewed about sexual behaviour, drug and alcohol use and mental health and sexually transmissible infections (STI) in the year before their HIV diagnosis.

RESULTS

Twenty-six cases and 52 controls were recruited. Risk factors in the year before diagnosis of incident HIV infection included: receptive unprotected anal intercourse (UAI) with ejaculation with casual partners (odds ratio [OR] and 95% confidence interval 57.2 [6.7, 489.4]); insertive UAI with ejaculation with >1 casual partners (OR 19.2 [2.2, 168.9]); having >14 casual partners at sex venues (OR 3.2 [1.1, 9.1]); and consuming >60 g alcohol at one sitting at least weekly (OR 3.6 [1.1, 11.4]). Cases were also more likely to have anal sex with >100 partners in their life and cases had more casual partners than controls in the year before the test. Cases were more likely to have consumed alcohol or amphetamines during a high-risk sexual episode in the year before the test.

CONCLUSIONS

UAI remains the most important behavioural risk for HIV in Australian MSM. Risk is increased by larger numbers of partners, partners met at sex venues and sex under the influence of alcohol.

Postexposure prophylaxis after sexual exposure to HIV

Increasing numbers of international, national and state/provincial health organizations in the developed and developing world recommend postexposure prophylaxis (PEP) following potential sexual exposure to HIV. The evidence for these policies is extrapolated from occupational healthcare worker, perinatal prophylaxis and animal studies. There is no direct evidence of PEP efficacy after sexual exposures. Studies addressing potential increases in risk behavior, toxicities and cost–effectiveness are encouraging. Considerations for offering PEP include the timing and characteristics of the exposure and the HIV status of the source and exposed individuals. PEP includes 28 days of a combination antiretroviral drug regimen containing two or more drugs and associated laboratory testing, counseling and referrals. PEP service delivery challenges include ensuring adequate access to services, optimizing PEP adherence and facilitating follow-up HIV testing and counseling. Men who have sex with men, sexual assault survivors, children and adolescents, and individuals in resource-limited settings present unique needs and challenges.

The effect of antiretroviral therapy on secondary transmission of HIV among men who have sex with men

BACKGROUND

Antiretroviral therapy (ART) reduces human immunodeficiency virus (HIV) RNA load and the probability of transmitting HIV to an HIV-uninfected partner. However, the potential reduction in secondary transmission associated with ART may be offset by the longer duration of infectiousness.

METHODS

To estimate the effects of ART on the secondary transmission of HIV among men who have sex with men, we used a previously published state-transition model of HIV disease to simulate the clinical and virologic course of HIV infection among 2 cohorts of men who have sex with men: (1) a cohort of individuals who were not receiving ART and (2) a cohort of individuals treated with US guideline-concordant ART. The model tracked the number of acts of unprotected insertive anal intercourse, transmission risk per act as determined by HIV RNA level, and the number of secondary cases generated in each cohort.

RESULTS

The estimated mean number of secondary transmissions from an HIV-infected individual after 10, 20, and 30 years of infection were 1.9, 2.5, and 2.5, respectively, in the untreated cohort, compared with 1.4, 1.8, and 2.3, respectively, in the treated cohort. The total number of transmissions for the treated cohort began to exceed the total number of transmissions for the untreated cohort 33 years after infection; over the entire course of infection, treatment with ART led to a 23% increase in secondary infections. All estimates of the impact of ART on secondary transmission were sensitive to changes in risk behaviors.

CONCLUSIONS

These results suggest that ART must be accompanied by effective HIV-related risk reduction interventions. Programs that target prevention to decrease further HIV transmission are crucial to epidemic control.

Mucosal innate immune response associated with a timely humoral immune response and slower disease progression after oral transmission of simian immunodeficiency virus to rhesus macaques

Mucosal transmission is the predominant mode of human immunodeficiency virus (HIV) infection worldwide, and the mucosal innate interferon response represents an important component of the earliest host response to the infection. Our goal here was to assess the changes in mRNA expression of innate mucosal genes after oral simian immunodeficiency virus (SIV) inoculation of rhesus macaques (Macaca mulatta) that were followed throughout their course of disease progression. The SIV plasma viral load was highest in the macaque that progressed rapidly to simian AIDS (99 days) and lowest in the macaque that progressed more slowly (>700 days). The mRNA levels of six innate/effector genes in the oral mucosa indicated that slower disease progression was associated with increased expression of these genes. This distinction was most evident when comparing the slowest-progressing macaque to the intermediate and rapid progressors. Expression levels of alpha and gamma interferons, the antiviral interferon-stimulated gene product 2'-5' oligoadenylate synthetase (OAS), and the chemokines CXCL9 and CXCL10 in the slow progressor were elevated at each of the three oral mucosal biopsy time points examined (day 2 to 4, 14 to 21, and day 70 postinfection). In contrast, the more rapidly progressing macaques demonstrated elevated levels of these cytokine/chemokine mRNA at lymph nodes, coincident with decreased levels at the mucosal sites, and a decreased ability to elicit an effective anti-SIV antibody response. These data provide evidence that a robust mucosal innate/effector immune response is beneficial following lentiviral exposure; however, it is likely that the anatomical location and timing of the response need to be coordinated to permit an effective immune response able to delay progression to simian AIDS.

Prevenção de infecção pelo HIV por intermédio da utilização do grupo operativo entre homens que fazem sexo com homens, São Paulo, Brasil

Este estudo focaliza o grupo operativo como intervenção preventiva de HIV para HSH (homens que fazem sexo com homens), usuários de serviços de saúde pública de São Paulo, Brasil. Foram distribuídos, por sorteio aleatório, 100 voluntários em dois grupos (intervenção e controle - 50 cada um). Todos eles responderam a questionários em duas fases distintas: antes da intervenção e seis meses depois de serem submetidos a ela. A avaliação do efeito da intervenção foi obtida pela variação do número médio de relações sexuais anais sem preservativo e análise de respostas sobre infecção pelo HIV. Terminaram o estudo 69 participantes (34 - grupo de intervenção; 35 - grupo de controle). No grupo de intervenção, observou-se, pelos dados obtidos, uma diminuição da prática de sexo anal desprotegida (p = 0,029) e aumento do número médio de respostas favoráveis à prevenção. Esses índices indicam ser a população estudada sensível à mudança em favor da adoção da prática de sexo mais seguro mediante participação no grupo operativo. Novos estudos são necessários para avaliar a possibilidade de utilização dessa abordagem nos serviços públicos de saúde e para outras populações.

[Prevention strategies to control the HIV epidemic. Successes, problems, and perspectives]

After the recognition of AIDS as a new disease entity and isolation of HIV as the causative agent in the early 1980s, a controversial debate about adequate measures to reduce the spread of HIV developed. In all developed countries a strategy based on education about modes of HIV transmission, condom promotion and harm reduction approaches to intravenous drug use finally succeeded and became instrumental for the relative containment of HIV within most at risk populations. However, in most developing countries as well as in the countries of Eastern Europe, the success of HIV pre vention remained limited for various reasons. In addition, for several years now, in the western developed countries sexual risk behaviour, newly diagnosed HIV infections, and the incidence of various other sexually transmitted infections seem to re-increase, especially among men who have sex with men (MSM). These increases coincide with a dramatic improvement of therapeutic options for the treatment of HIV infection. The relationship between improvement of therapy and changes in sexual risk behaviour has to be further defined. It is hypothesized that HIV serosorting as a predominant risk management strategy among MSM results in an accumulation of health risks in the HIV-positive MSM population. In addition to and beyond established condom promotion, additional biomedical approaches to reduce transmissibility and susceptibility for HIV will be necessary to regain control of the spread of HIV in highly sexually active populations.

Increases in sexually transmitted infections and sexual risk behaviour without a concurrent increase in HIV incidence among men who have sex with men in San Francisco: a suggestion of HIV serosorting?

BACKGROUND

Sexually transmitted infections (STI) and unprotected anal intercourse (UAI) have been increasing among men who have sex with men (MSM) in San Francisco. However, HIV incidence has stabilised.

OBJECTIVES

To describe recent trends in sexual risk behaviour, STI, and HIV incidence among MSM in San Francisco and to assess whether increases in HIV serosorting (that is, selective unprotected sex with partners of the same HIV status) may contribute to preventing further expansion of the epidemic.

METHODS

The study applies an ecological approach and follows the principles of second generation HIV surveillance. Temporal trends in biological and behavioural measures among MSM were assessed using multiple pre-existing

DATA SOURCES

STI case reporting, prevention outreach programmatic data, and voluntary HIV counselling and testing data.

RESULTS

Reported STI cases among MSM rose from 1998 through 2004, although the rate of increase slowed between 2002 and 2004. Rectal gonorrhoea cases increased from 157 to 389 while early syphilis increased from nine to 492. UAI increased overall from 1998 to 2004 (p<0.001) in community based surveys; however, UAI with partners of unknown HIV serostatus decreased overall (p<0.001) among HIV negative MSM, and among HIV positive MSM it declined from 30.7% in 2001 to a low of 21.0% in 2004 (p<0.001). Any UAI, receptive UAI, and insertive UAI with a known HIV positive partner decreased overall from 1998 to 2004 (p<0.001) among MSM seeking anonymous HIV testing and at the STI clinic testing programme. HIV incidence using the serological testing algorithm for recent HIV seroconversion (STARHS) peaked in 1999 at 4.1% at the anonymous testing sites and 4.8% at the STI clinic voluntary testing programme, with rates levelling off through 2004.

CONCLUSIONS

HIV incidence among MSM appears to have stabilised at a plateau following several years of resurgence. Increases in the selection of sexual partners of concordant HIV serostatus may be contributing to the stabilisation of the epidemic. However, current incidence rates of STI and HIV remain high. Moreover, a strategy of risk reduction by HIV serosorting can be severely limited by imperfect knowledge of one's own and one's partners' serostatus.

Amphetamine use and sexual risk among men who have sex with men: results from the National HIV Behavioral Surveillance study--New York City

A 2004-2005 survey among 503 men who have sex with men who attend public venues in New York City was used to examine the relationship of amphetamine use with sexual risk behaviors. Among the men recruited, 51.1% were under 30 years of age, 27.4% were Latino, and 23.3% were African American. Most identified as either gay (78.9%) or bisexual (18.1%). A standardized questionnaire collected data on demographics, sexual risk behaviors, drug and alcohol use, history of HIV testing, and occurrences of sexually transmitted infections. Amphetamine use in the past year was reported by 13.8%. Of those, 71.0% used amphetamines with sex. Amphetamine use was associated with unprotected receptive anal intercourse with non-main partners. In event-specific analysis, amphetamine use was higher with unprotected encounters compared with protected encounters. This study confirms the association between amphetamine use and sexual risk furthers our understanding of risky circumstances and lays the groundwork for the design of interventions.

Microbicides: a new frontier in HIV prevention

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections (STIs) including HIV-1. Despite more than two decades of HIV-1 vaccine research, there is still no efficacious HIV-1 vaccine, and the scientific community appears skeptical about the short or long-term feasibility of developing a vaccine that has the ability to induce sterilizing immunity against HIV-1. In this setting, microbicide research has gathered momentum. Currently, 16 candidate microbicides are in clinical development and five products are being evaluated in large-scale Phase 2B/3 effectiveness studies. Initial data from these trials will be available within the next 2-3 years, and it is feasible that there could be one or more licensed microbicides by the end of the decade. The first generation of surfactant microbicides had a non-specific mechanism of action. However, subsequent candidate microbicides have been developed to target specific steps in the process of viral transmission. The purpose of this article is to provide an overview of microbicide development and an update on the candidate pipeline.

The intent and practice of condom use among HIV-positive men who have sex with men in Japan

To evaluate the intent and practice of condom use among Japanese HIV-positive men who have sex with men (MSM), a survey using anonymous questionnaires was carried out and 117 respondents were investigated. For anal sex and oral sex, respectively, 58.1% and 15.2% intended to use condoms and 47.2% and 12.4% used condoms all of the time. The intent of condom use decisively affected the practice of condom use and was closely related to the perceived risk level of HIV/sexually transmitted (STI) transmission. In anal sex, willingness to protect sexual partners from HIV infection was strongly related not only to the intent but also to the practice. Enhancement of willingness to protect oneself from STI was suggested to enhance willingness to protect his/her sexual partners from HIV infection with secondary enhancement of the intent or the practice of condom use. Specific support of MSM with HIV for improving the intent and practice of condom use is urgently needed.

Knowledge of sexual partner's HIV serostatus and serosorting practices in a California population-based sample of men who have sex with men

OBJECTIVES

To describe knowledge of primary and secondary sexual partner's HIV serostatus and sexual practices, including serosorting, among men who have sex with men (MSM) living in California.

METHODS

Men who self-identified as gay/bisexual in the 2001 California Health Interview Survey, a statewide biennial random-digit-dial survey interviewing more than 50,000 adults on a variety of health topics, were recontacted in 2002 and interviewed by telephone about injection drug use, their own and partner's HIV serostatus, and sexual risk behaviors.

RESULTS

Among 220 men who reported a primary partner, 86% [95% confidence interval (CI): 77-92] knew their primary partner's serostatus; 62% (95% CI, 52-70) of the 250 men who reported a secondary partner knew their most recent secondary partner's HIV serostatus. Knowledge of one's most recent secondary partner's HIV serostatus was inversely related to history of injecting recreational drugs (odds ratio, 0.22; P < 0.01), and reporting a primary partner in the past year (odds ratio, 0.37; P < 0.05). Two-fifths (41%) of HIV-positive men and three-fifths (62%) of HIV-negative men engaged in serosorting (serocordant unprotected anal intercourse) with their primary partners, whereas 33% HIV-positive men and 20% HIV-negative men did so with their most recent secondary partners.

CONCLUSIONS

This population-based survey documented the extent to which MSM know their partners' serostatus and practice serosorting behaviors. The findings emphasize the need for studies to report serocordant and serodiscordant unprotected anal intercourse separately, as the former presents significant lower risk of HIV transmission.

Partner-Specific Sexual Behavioral Differences Between Phase 3 HIV Vaccine Efficacy Trial Participants and Controls

OBJECTIVE

To assess and compare sexual behaviors using partner-specific data between HIV-negative men who have sex with men (MSM) recruited for an HIV vaccine efficacy trial and a control group.

METHODS

HIV-negative MSM from an HIV vaccine trial (n = 525) and controls (n = 732) were recruited by similar strategies and interviewed about behaviors with the 3 most recent partners in the past 6 months, obtained by audio computer-assisted self-interview (A-CASI).

RESULTS

Vaccine trial participants were more likely than controls to report an HIV-positive partner (24.7% and 14.1%, respectively) or an HIV-positive primary partner (16.1% and 6.8%, respectively) and were less likely to report occasional or single-time partners of unknown HIV status (51.6% and 63.2%, respectively; P < 0.05 for each comparison). Vaccine trial participants more often reported receptive unprotected anal intercourse (UAI) during their last sexual encounter with an HIV-positive partner (adjusted odds ratio [OR] = 2.7, 95% confidence interval [CI]: 1.0 to 7.9). Most believed their HIV-positive partners were receiving antiretroviral treatment (ART), however, and after adjustment for perceived ART use, the association between vaccine study participation and receptive UAI with an HIV-positive partner was not significant.

CONCLUSIONS

High-risk sexual behavior was reported by many VAX004 participants and controls. Differences between vaccine trial and control participants in the highest risk per contact behavior, receptive UAI with HIV-positive partners, was partly accounted for by perceived ART use. Partner level data are useful in refining risk assessment, which is important in the evaluation of HIV vaccine and other prevention trials.

Failure to embrace the barrier/condom use message

The objective of this study was to examine the consistency of barrier/condom use among men who have sex with men in the Kansas City metropolitan area. The authors sought to determine if barrier/condom usage patterns were associated with the type of sex act and whether it was insertive or receptive, HIV testing frequency, and number of sexual partners. Data were extracted from a 2003 community health assessment of the gay, lesbian, bisexual, and transgendered community in the metropolitan area. The health assessment instrument was anonymous, self-administered, and distributed at events in that community. Responses from 623 men indicated that consistent use of a barrier/condom was low regardless of the sex act. There was no relationship between barrier/condom usage patterns and HIV testing frequency for any sex act or the number of sex partners, with the exception of anal intercourse. The authors concluded that a different approach is needed to translate the barrier/condom use message into a behavioral response.

Adapting the popular opinion leader intervention for Latino young migrant men who have sex with men

Young Latino migrantmen who have sex with men are at high risk for HIV infection. The Popular Opinion Leader intervention, shown to be effective with White gay men, was adapted by the Farmworker Justice Fund, Inc., for this Latino migrant population. This project, called the Young Latino Promotores, was implemented over a 2-year period by community-based organizations in Vista, California, and McAllen, Texas, with capacity building assistance from the Farmworker Justice Fund, Inc. We report on challenges, preliminary findings, and lessons learned from adapting this intervention.

Unintentional HIV exposures from young men who have sex with men who disclose being HIV-negative

OBJECTIVE

To evaluate the proportion of new sexual partners potentially exposed to HIV from young MSM who disclosed being HIV-negative.

DESIGN

Cross-sectional, observational study of men aged 23-29 years recruited from randomly sampled MSM-identified venues in six US cities.

METHODS

Participants were interviewed and tested for HIV. Analyses were restricted to MSM who reported last testing HIV-negative and having one or more new partners in the prior 6 months.

RESULTS

Of 1701 MSM who reported a total of 11 793 new partners, 1075 (63%) disclosed being HIV-negative to 4253 (36%) new partners before having sex with them for the first time. Of disclosers, 352 (33%) reported last testing HIV-negative > 1 year before their interview and 80 (7%) tested HIV-positive (HIV-infected unaware). By race, 24% of black, 5% of Hispanic, and 3% of white disclosers tested HIV-positive. Of the 4253 new partners, 296 (7%) were partners of the 80 HIV-infected unaware MSM. By race, 22% of new partners of black, 3% of new partners of Hispanic, and 4% of new partners of white MSM, were partners of HIV-infected unaware MSM who disclosed being HIV-negative.

CONCLUSIONS

Many new sex partners may be unintentionally exposed to HIV from young MSM, particularly those who are black and who disclose being HIV-negative based on an earlier test. Young MSM should test for HIV more frequently and consistently use condoms with all partners unless they are in a mutually monogamous relationship in which both partners have tested HIV-negative at least 3 months since their last potential HIV exposure.

On modeling HIV and T cells in vivo: assessing causal estimators in vaccine trials

The first efficacy trials--named STEP--of a T cell vaccine against HIV/AIDS began in 2004. The unprecedented structure of these trials raised new modeling and statistical challenges. Is it plausible that memory T cells, as opposed to antibodies, can actually prevent infection? If they fail at prevention, to what extent can they ameliorate disease? And how do we estimate efficacy in a vaccine trial with two primary endpoints, one traditional, one entirely novel (viral load after infection), and where the latter may be influenced by selection bias due to the former? In preparation for the STEP trials, biostatisticians developed novel techniques for estimating a causal effect of a vaccine on viral load, while accounting for post-randomization selection bias. But these techniques have not been tested in biologically plausible scenarios. We introduce new stochastic models of T cell and HIV kinetics, making use of new estimates of the rate that cytotoxic T lymphocytes--CTLs; the so-called killer T cells--can kill HIV-infected cells. Based on these models, we make the surprising discovery that it is not entirely implausible that HIV-specific CTLs might prevent infection--as the designers explicitly acknowledged when they chose the endpoints of the STEP trials. By simulating thousands of trials, we demonstrate that the new statistical methods can correctly identify an efficacious vaccine, while protecting against a false conclusion that the vaccine exacerbates disease. In addition to uncovering a surprising immunological scenario, our results illustrate the utility of mechanistic modeling in biostatistics.

Methamphetamine and sildenafil (Viagra) use are linked to unprotected receptive and insertive anal sex, respectively, in a sample of men who have sex with men

OBJECTIVES

There is evidence that methamphetamine and sildenafil (Viagra) use are associated with sexual risk behaviour among men who have sex with men (MSM). We investigated the association of methamphetamine, sildenafil, and other substance use with unprotected receptive and insertive anal sex among MSM by conducting an encounter specific analysis.

METHODS

Data were from a cross sectional, community based survey of MSM in San Francisco regarding behaviour during their most recent anal sex encounter. Mulitvariate regression analysed independent associations of specific substance use and demographic variables with unprotected anal sex behaviours.

RESULTS

The sample (n = 388) was diverse in race/ethnicity, age, income, education, HIV status, and homosexual/bisexual identification. More than half (53%) reported unprotected anal sex, including insertive (29%) and receptive (37%) during their most recent anal sex encounter; 12% reported unprotected insertive and 17% reported unprotected receptive anal sex with an HIV discordant or unknown partner. Methamphetamine was used by 15% and sildenafil was used by 6% of the men before or during the encounter; 2% used both drugs. In multivariate analysis controlling for demographic factors and other substance use, methamphetamine use was associated with unprotected receptive (odds ratio (OR), 2.03; 95% confidence interval (CI), 1.09 to 3.76) and sildenafil use was associated with unprotected insertive (OR, 6.51; CI, 2.46 to 17.24) anal sex. Effects were stronger with HIV discordant or unknown sex partners specifically.

CONCLUSION

Encounter specific associations of methamphetamine and sildenafil use with unprotected receptive and insertive anal sex, respectively, indicate the importance of assessment specificity and tailoring risk reduction efforts to address certain drugs and sexual behavioural roles among MSM.

Ex vivo culture of human colorectal tissue for the evaluation of candidate microbicides

OBJECTIVES

Establishment of an in vitro model to evaluate rectal safety and the efficacy of microbicide candidates.

DESIGN

An investigation and characterization of human colorectal explant culture for screening candidate microbicides to prevent rectal transmission of HIV-1 infection.

METHODS

Human colorectal explants were cultured at the liquid-air interface on gelfoam rafts. Phenotypic characterization of HIV-1 target cells was performed by fluorescence-activated cell sorter analysis. HIV-1 infection was determined by the measurement of p24 antigen release, viral RNA, and proviral DNA accumulation.

RESULTS

Colorectal explant CD4 T cells expressed higher CCR5 and CXCR4 levels compared with blood. Minor differences between the rectal and sigmoid colon were observed with a trend for slightly higher CCR5 and HLA-DR expression in cells from the sigmoid colon. Favourable culture conditions were established for colorectal tissue. Although tissue structure degenerated with time, CD4: CD8 cell ratios remained constant, and tissue supported productive HIV-1 infection. The ability of candidate microbicides to inhibit R5 HIV-1 infection was evaluated. Polyanion candidates, PRO2000 and dextrin sulphate, provided 99% protection at 1 microg/ml and 1 mg/ml, respectively, equivalent to 1/5000 and 1/40 of the vaginal formulations. The nucleotide reverse transcriptase inhibitor (NRTI) 9-[2-(phosphonomethoxy)propyl]adenine (PMPA) provided protection at concentrations 1000-fold lower (10 microg/ml) than the proposed vaginal formulation (1%). Furthermore, non-NRTI UC-781 and TMC-120 provided greater than 99% inhibition at 3.3 or 0.33 microg/ml, respectively. No products demonstrated toxicity to rectal mucosa at inhibitory concentrations.

CONCLUSION

Colorectal explant culture was shown to be a useful tool for the preclinical evaluation of potential microbicides. The data suggest that rectally applied microbicides might provide protection from HIV-1 transmission.

Greater risk for HIV infection of black men who have sex with men: a critical literature review

HIV rates are disproportionately higher for Black men who have sex with men (MSM) than for other MSM. We reviewed the literature to examine 12 hypotheses that might explain this disparity. We found that high rates of HIV infection for Black MSM were partly attributable to a high prevalence of sexually transmitted diseases that facilitate HIV transmission and to undetected or late diagnosis of HIV infection; they were not attributable to a higher frequency of risky sexual behavior, nongay identity, or sexual nondisclosure, or to reported use of alcohol or illicit substances. Evidence was insufficient to evaluate the remaining hypotheses.Future studies must address these hypotheses to provide additional explanations for the greater prevalence of HIV infection among Black MSM.

Alcohol and sexual HIV risk behavior among problem drinking men who have sex with men: An event level analysis of timeline followback data

While heavy drinking among men who have sex with men (MSM) has been shown to be associated with an increase in sexual risk taking, a temporal relationship between drinking and an increase in subsequent HIV risk behaviors among adult samples has been less obvious. This study used an event level analysis to examine this relationship among HIV negative problem drinking MSM. Within subjects analyses show a higher probability of unprotected anal intercourse after drinking. Post-hoc analyses of within subjects data indicate that drinking increases risk taking when engaging in receptive anal intercourse but not for insertive anal intercourse. Findings from this study support evidence that drinking is a factor that increases risk taking among HIV negative problem drinking MSM, particularly for receptive anal intercourse.

Transmission Behaviors of Recently HIV-Infected Men Who Have Sex With Men

OBJECTIVES

Analyze postdiagnosis behaviors of recently HIV-infected men who have sex with men (MSM).

METHODS

Recently HIV-infected MSM were interviewed at 6 weeks (n = 153) and 3 months (n = 113) after diagnosis. Behaviors from baseline to follow-up were compared; multivariate logistic regression identified associations between baseline characteristics and behavior at follow-up.

RESULTS

At follow-up, MSM reported a significantly lower mean of partners (7.9 vs. 5.2) and lower means of 1-time (1.9 vs. 0.8), unknown (3.7 vs. 2.6), and acquaintance (1.1 vs. 0.5) partners than at baseline. In multivariate analyses, unprotected anal intercourse (UAI) with the last partner at follow-up was more likely if the last partner at baseline was a main partner (odds ratio [OR] = 2.94, 95% confidence interval [CI]: 1.04 to 8.33) or HIV-positive partner (OR = 3.36, 95% CI: 1.27 to 8.88) but less likely if, at follow-up, the last partner was HIV-negative (OR = 0.28, 95% CI: 0.08 to 1.00) or of unknown HIV status (OR = 0.23, 95% CI: 0.08 to 0.71), the participant had a history of nonconsensual sex (OR = 0.25, 95% CI: 0.09 to 0.72), or the participant had more than 1 partner (OR = 0.28, 95% CI: 0.09 to 0.86). More than 1 partner at follow-up was associated with no main partner at baseline or follow-up (OR = 2.76, 95% CI: 1.12 to 6.78), more partners in the last 12 months (OR = 1.02, 95% CI: 1.01 to 1.04), and UAI with the last partner (OR = 0.36, 95% CI: 0.14 to 0.90).

CONCLUSIONS

After diagnosis, some but not all recently HIV-infected MSM reduced risky sexual behavior permitting potential HIV transmission.

Molecular analysis of HIV strains from a cluster of worker infections in the adult film industry, Los Angeles 2004

OBJECTIVES

In April 2004, 13 susceptible women were exposed to a single acutely HIV-1-infected man while employed to perform various sex acts for the production of adult films; three women were subsequently found to have acquired HIV infection (23% attack rate). As part of the investigation of this infection cluster, we evaluated whether viral strains collected from infected individuals were significantly related.

METHODS

We determined nucleotide sequences from the C2V3C3 and gp41 region of env and the p17 region of gag in viruses from the three infected individuals from whom specimens were available. We then compared these sequences phylogenetically to comparable sequences from available reference strains. Genotypic and phenotypic antiretroviral drug resistance was determined for plasma virus from the male index case and one female contact at a separate commercial laboratory.

RESULTS

The env and gag sequences of the HIV strains from the male index case and two of the infected women were 100% similar. Genotyping of the male index case's virus identified 12 mutations, which represented known naturally occurring polymorphisms in the subtype B consensus sequence that are not associated with antiretroviral drug resistance. Genotyping of the virus from the female contact identified 10 mutations, all of which were shared by the virus from the male index case. Phenotyping demonstrated that both viruses were susceptible to all antiretroviral drugs tested.

CONCLUSION

Molecular and virological data strongly support the epidemiological conclusion that these women were infected with an identical strain of HIV through occupational exposure to an individual with an acute HIV infection.

Differential mucosal susceptibility in HIV-1 transmission and infection

HIV infection occurs primarily through mucosal surfaces, indicating that protection at mucosal sites may be crucial in prevention and treatment. The host innate and adaptive immune elements provide a level of protection, which differs between mucosal compartments, and appears to be most successful in the oral environment, where transmission is rare. In addition to the distinct oral mucosal architecture and cellular constituents, oral fluids, unlike other mucosal secretions, are rarely a vehicle for HIV infection. Multiple soluble factors may contribute to this antiviral activity, including neutralizing antibodies, secretory leukocyte protease inhibitor (SLPI), antiviral peptides such as defensins and cystatins, glycoproteins including thrombospondin and lactoferrin, and complement components. Understanding the antiviral activities of these and other potential resistance factors is becoming increasingly important in attempts to design treatments in the era of HAART resistance. In this regard, the mechanism of anti-HIV action of SLPI has recently been further elucidated by the discovery of its binding protein/receptor, which plays a key role in the infection of macrophages and may consequently be a novel therapeutic target. Continued elucidation of the unique features of mucosal HIV immunology is essential for understanding HIV pathogenesis and for developing effective vaccines and therapeutics.

(C2) Saliva, breast milk, and mucosal fluids in HIV transmission

The oral environment has received various amounts of attention in association with HIV infection and pathogenesis. Since HIV infection occurs through mucosal tissue, oral factors-including tissue, fluids, and compartments-are of interest in furthering our understanding of the diagnosis, infectivity, transmission, and pathogenesis of disease. This report reviews: (1) HIV testing and diagnoses with oral fluids; (2) post-natal acquisition of HIV in association with breast-feeding from HIV-positive mothers; and (3) oral sex and HIV transmission. In the first, we examine how oral fluids are used to detect HIV infection and review current consensus on the role of salivary molecules as markers for immunosuppression. Second, lactation-associated HIV acquisition is reviewed, with special consideration of emerging issues associated with the impact of anti-retroviral therapies. Last, we consider current data on the risk of HIV infection in association with oral sex. Investigation of these diverse topics has a common goal: understanding how HIV presents in the oral environment, with an aim to rapid and accessible HIV diagnosis, and improved prevention and treatment of infection.

Risk factors for HIV infection among men who have sex with men

OBJECTIVES

Risk factors for HIV acquisition were examined in a recent cohort of men who have sex with men (MSM).

DESIGN

A longitudinal analysis of 4295 HIV-negative MSM enrolled in a randomized behavioral intervention trial conducted in six US cities.

METHODS

MSM were enrolled and assessed for HIV infection and risk behaviors semi-annually, up to 48 months.

RESULTS

In multivariate analysis, men reporting four or more male sex partners, unprotected receptive anal intercourse with any HIV serostatus partners and unprotected insertive anal intercourse with HIV-positive partners were at increased risk of HIV infection, as were those reporting amphetamine or heavy alcohol use and alcohol or drug use before sex. Some depression symptoms and occurrence of gonorrhea also were independently associated with HIV infection. The attributable fractions of high number of male partners, use of alcohol or drugs before sex, and unprotected receptive anal intercourse with unknown status partners and the same with presumed negative partners accounted for 32.3, 29.0, 28.4 and 21.6% of infections, respectively.

CONCLUSIONS

The challenge is to develop strategies to identify men in need. Interventions are needed to help men reduce their number of sexual partners, occurrences of unprotected anal intercourse, alcohol or drug use before sex and address other mental health issues.

Changing patterns of sexual behaviour in the era of highly active antiretroviral therapy

PURPOSE OF REVIEW

To describe changing patterns of sexual behaviour in the era of highly active antiretroviral therapy among gay/bisexual men in Europe, Canada, USA and Australia.

RECENT FINDINGS

While there has been a substantial increase in high-risk sexual behaviour among gay men since 1996, this now appears to be levelling off in some cities. Overall the empirical evidence does not support the suggestion that taking highly active antiretroviral therapy or having an undetectable viral load leads to risky sexual behaviour among people with HIV. Nor can HIV treatment optimism alone explain the recent increase in high-risk sexual behaviour. Since 1996, an increasing number of gay men have begun to use the Internet to look for sexual partners. By serosorting on the Internet, HIV-positive men are more likely to meet online, rather than off-line, other HIV-positive men for unprotected sex. While serosorting does not present a risk of HIV transmission to an uninfected person, it does present a risk of other sexually transmitted infections and co-infection with resistant virus for HIV-positive men themselves. This review also explores emerging behaviours such as barebacking and strategic positioning as well as the role of crystal meth and Viagra.

SUMMARY

The review reminds us of the complexity of human and sexual behaviour. Among gay men, sexual behaviour in the era of highly active antiretroviral therapy has been characterized by risk reduction and stabilization as well as increasing risk. These changing patterns provide a new challenge as well as new opportunities for HIV prevention.