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

Preclinical evaluation of the HIV-1 fusion inhibitor L'644 as a potential candidate microbicide

Topical blockade of the gp41 fusogenic protein of HIV-1 is one possible strategy by which microbicides could prevent HIV transmission, working early against infection, by inhibiting viral entry into host cells. In this study, we examined the potential of gp41 fusion inhibitors (FIs) as candidate anti-HIV microbicides. Preclinical evaluation of four FIs, C34, T20, T1249, and L'644, was performed using cellular and ex vivo genital and colorectal tissue explant models. Increased and sustained activity was detected for L'644, a cholesterol-derivatized version of C34, relative to the other FIs. The higher potency of L'644 was further increased with sustained exposure of cells or tissue to the compound. The activity of L'644 was not affected by biological fluids, and the compound was still active when tissue explants were treated after viral exposure. L'644 was also more active than other FIs against a viral escape mutant resistant to reverse transcriptase inhibitors (RTIs), demonstrating the potential of L'644 to be included as part of a multiactive antiretroviral (ARV) combination-based microbicide. These data support the further development of L'644 for microbicide application.

A mathematical model of comprehensive test-and-treat services and HIV incidence among men who have sex with men in the United States

BACKGROUND

Early diagnosis and treatment of HIV infection and suppression of viral load are potentially powerful interventions for reducing HIV incidence. A test-and-treat strategy may have long-term effects on the epidemic among urban men who have sex with men (MSM) in the United States and may achieve the 5-year goals of the 2010 National AIDS Strategy that include: 1) lowering to 25% the annual number of new infections, 2) reducing by 30% the HIV transmission rate, 3) increasing to 90% the proportion of persons living with HIV infection who know their HIV status, 4) increasing to 85% the proportion of newly diagnosed patients linked to clinical care, and 5) increasing by 20% the proportion of HIV-infected MSM with an undetectable HIV RNA viral load.

METHODS AND FINDINGS

We constructed a dynamic compartmental model among MSM in an urban population (based on New York City) that projects new HIV infections over time. We compared the cumulative number of HIV infections in 20 years, assuming current annual testing rate and treatment practices, with new infections after improvements in the annual HIV testing rate, notification of test results, linkage to care, initiation of antiretroviral therapy (ART) and viral load suppression. We also assessed whether five of the national HIV prevention goals could be met by the year 2015. Over a 20-year period, improvements in test-and-treat practice decreased the cumulative number of new infections by a predicted 39.3% to 69.1% in the urban population based on New York City. Institution of intermediate improvements in services would be predicted to meet at least four of the five goals of the National HIV/AIDS Strategy by the 2015 target.

CONCLUSIONS

Improving the five components of a test-and-treat strategy could substantially reduce HIV incidence among urban MSM, and meet most of the five goals of the National HIV/AIDS Strategy.

Extent of illicit drug use and dependence, and their contribution to the global burden of disease

This paper summarises data for the prevalence, correlates, and probable adverse health consequences of problem use of amphetamines, cannabis, cocaine, and opioids. We discuss findings from systematic reviews of the prevalence of illicit drug use and dependence, remission from dependence, and mortality in illicit drug users, and evidence for acute and chronic effects of illicit drug use. We outline the regional and global distribution of use and estimated health burden from illicit drugs. These distributions are likely to be underestimates because they have not included all adverse outcomes of drug use and exclude those of cannabis--the mostly widely used illicit drug. In high-income countries, illicit drug use contributes less to the burden of disease than does tobacco but a substantial proportion of that due to alcohol. The major adverse health effects of cannabis use are dependence and probably psychotic disorders and other mental disorders. The health-related harms of cannabis use differ from those of amphetamine, cocaine, and opioid use, in that cannabis contributes little to mortality. Intelligent policy responses to drug problems need better data for the prevalence of different types of illicit drug use and the harms that their use causes globally. This need is especially urgent in high-income countries with substantial rates of illicit drug use and in low-income and middle-income countries close to illicit drug production areas.

Episodic HIV Risk Behavior Can Greatly Amplify HIV Prevalence and the Fraction of Transmissions from Acute HIV Infection

A deterministic compartmental model was explored that relaxed the unrealistic assumption in most HIV transmission models that behaviors of individuals are constant over time. A simple model was formulated to better explain the effects observed. Individuals had a high and a low contact rate and went back and forth between them. This episodic risk behavior interacted with the short period of high transmissibility during acute HIV infection to cause dramatic increases in prevalence as the differences between high and low contact rates increased and as the duration of high risk better matched the duration of acute HIV infection. These same changes caused a considerable increase in the fraction of all transmissions that occurred during acute infection. These strong changes occurred despite a constant total number of contacts and a constant total transmission potential from acute infection. Two phenomena played a strong role in generating these effects. First, people were infected more often during their high contact rate phase and they remained with high contact rates during the highly contagious acute infection stage. Second, when individuals with previously low contact rates moved into an episodic high-risk period, they were more likely to be susceptible and thus provided more high contact rate susceptible individuals who could get infected. These phenomena make test and treat control strategies less effective and could cause some behavioral interventions to increase transmission. Signature effects on genetic patterns between HIV strains could make it possible to determine whether these episodic risk effects are acting in a population.

Behavior, intention or chance? A longitudinal study of HIV seroadaptive behaviors, abstinence and condom use

Seroadaptive behaviors have been widely described as preventive strategies among men who have sex with men (MSM) and other populations worldwide. However, causal links between intentions to adopt seroadaptive behaviors and subsequent behavior have not been established. We conducted a longitudinal study of 732 MSM in San Francisco to assess consistency and adherence to multiple seroadaptive behaviors, abstinence and condom use, whether prior intentions predict future seroadaptive behaviors and the likelihood that observed behavioral patterns are the result of chance. Pure serosorting (i.e., having only HIV-negative partners) among HIV-negative MSM and seropositioning (i.e., assuming the receptive position during unprotected anal sex) among HIV-positive MSM were more common, more successfully adhered to and more strongly associated with prior intentions than consistent condom use. Seroconcordant partnerships occurred significantly more often than expected by chance, reducing the prevalence of serodiscordant partnerships. Having no sex was intended by the fewest MSM, yet half of HIV-positive MSM who abstained from sex at baseline also did so at 12 month follow-up. Nonetheless, no preventive strategy was consistently used by more than one-third of MSM overall and none was adhered to by more than half from baseline to follow-up. The effectiveness of seroadaptive strategies should be improved and used as efficacy endpoints in trials of behavioral prevention interventions.

Comparisons of HIV-Affected and Non-HIV-Affected Families Over Time

This study compares HIV-affected families and their non-HIV-affected neighbors' behavioral health outcomes and family conflict. To compare two groups from the same neighborhoods at four points over 18 months, mothers with HIV (MLH) (N=167) and their school-age children (age 6 to 20) were recruited from clinical care settings in Los Angeles, CA and neighborhood control mothers (NCM) without HIV (N=204) were recruited from modal neighborhoods. In addition, children living at home who were 12 years and older were recruited. We assessed parenting behaviors, family conflict, mental health, sexual behavior, substance use, and HIV-related health behaviors over time. MLH perceived greater economic insecurity at baseline, less employment, and involvement in romantic relationships. MLH reported more emotional distress and substance use than NCM. MLH, however, reported lowered HIV transmission risk. The random regressions indicated that MLH exhibited higher levels and became significantly less depressed and less anxious over time than their non-HIV-affected neighbors. MLH also reported less initial family violence and conflict reasoning than NCM; violence decreased and conflict increased over time for MLH relative to NCM. Children of MLH decreased their marijuana use but hard drug users of MLH increased their risk, over time, compared to children of NCM. Moreover, children of MLH reported more internalizing behaviors than children of NCM. Even when compared to other families living in the same economically disadvantaged communities, MLH and their children continue to face challenges surrounding family conflict, and key behavioral health outcomes, especially with respect to substance use and mental health outcomes. These families, however, show much resilience and MLH report lowered levels of HIV transmission risk, their children report no greater levels of HIV transmission risk and levels of family violence were lower than reported by families in the same neighborhoods.

Condom-use decision making in the context of hypothetical pre-exposure prophylaxis efficacy among substance-using men who have sex with men: Project MIX

OBJECTIVE

To examine condom-use decision making in the context of hypothetical pre-exposure prophylaxsis (PrEP) efficacy among men who have sex with men who use alcohol and other substances during sex.

METHODS

Substance-using men who have sex with men were recruited in 4 US cities for a behavioral intervention trial. Three groups were defined as follows: men who indicated that to not use a condom for receptive/insertive unprotected anal intercourse (UAI) while using PrEP, PrEP would need to be: (1) "almost always or always" effective (high efficacy); (2) effective "at least half the time or more but not almost always or always" (mid-range efficacy corresponding to recent PrEP trial results); (3) effective "less than half the time" (low efficacy). The mid-range efficacy group was compared with the low-efficacy group (as the reference) and to the-high efficacy group (as the reference).

RESULTS

Among 630 men who never used PrEP, 15.2% were in the mid-range efficacy group for receptive UAI and 34.1% in the mid-range efficacy group for insertive UAI. Scores on difficulty communicating about safer sex while high were significantly higher in the mid-range efficacy group compared with each of the other groups for both receptive and insertive UAI. Men who seemed to be differentiating PrEP use by anal sex role also scored higher on communication difficulties, although scoring lower on condom intentions.

CONCLUSIONS

Communication about safer sex while under the influence of alcohol or other substances and condom intentions are important factors to consider for HIV prevention interventions for PrEP users.

Sex position, marital status, and HIV risk among Indian men who have sex with men: clues to optimizing prevention approaches

A divide exists between categories of men who have sex with men (MSM) in India based on their sex position, which has consequences for the design of novel HIV prevention interventions. We examine the interaction between sex position and other attributes on existing HIV risk including previous HIV testing, unprotected anal intercourse (UAI), and HIV serostatus among MSM recruited from drop-in centers and public cruising areas in the twin cities of Hyderabad and Secunderabad, India. A survey was administered by trained research assistants and minimally invasive HIV testing was performed by finger-stick or oral testing. HIV seropositive MSM underwent CD4+ lymphocyte count measurement. In our sample (n = 676), 32.6% of men were married to women, 22.2% of receptive only participants were married, and 21.9% of men were HIV seropositive. In bivariate analysis, sex position was associated with previous HIV testing, UAI, HIV serostatus, and CD4+ lymphocyte count at diagnosis. In multivariate analysis with interaction terms, dual unmarried men were more likely to have undergone an HIV test than insertive unmarried men (odds ratio [OR] 2.8; 95% confidence interval [CI] 1.2-6.5), a relationship that did not hold among married men. Conversely, dual married men were less likely than insertive married men to engage in UAI (OR 0.3; 95% CI 0.1-0.6), a relationship that did not hold among unmarried men. Further implementation research is warranted in order to best direct novel biologic and behavioral prevention interventions towards specific risk behaviors in this and other similar contexts.

Identifying barriers to HIV testing: personal and contextual factors associated with late HIV testing

Late diagnosis of HIV is associated with increased morbidity, mortality, and health care costs. Despite the availability of HIV testing, persons continue to test late in the course of HIV infection. We used the HIV/AIDS case registry of San Francisco Department of Public Health to identify and recruit 41 persons who developed AIDS within 12 months of their HIV diagnosis to participate in a qualitative and quantitative interview regarding late diagnosis of HIV. Thirty-one of the participants were diagnosed with HIV because of symptomatic disease and 50% of the participants were diagnosed with HIV and AIDS concurrently. Half of the subjects had not been tested for HIV prior to diagnosis. Fear was the most frequently cited barrier to testing. Other barriers included being unaware of improved HIV treatment, free/low cost care, and risk for HIV. Recommendations for health care providers to increase early diagnosis of HIV include routine ascertainment of HIV risk behaviors and testing histories, stronger recommendations for patients to be tested, and incorporating testing into routine medical care. Public health messages to increase testing include publicizing that (1) effective, tolerable, and low cost/free care for HIV is readily available, (2) early diagnosis of HIV improves health outcomes, (3) HIV can be transmitted to persons who engage in unprotected oral and insertive anal sex and unprotected receptive anal intercourse without ejaculation and from HIV-infected persons whose infection is well-controlled with antiretroviral therapy, (4) persons who may be infected based upon these behaviors should be tested following exposure, (5) HIV testing information will be kept private, and (6) encouraging friends and family to get HIV tested is beneficial.

Colorectal microbicide design: triple combinations of reverse transcriptase inhibitors are optimal against HIV-1 in tissue explants

OBJECTIVE

Receptive anal intercourse in both men and women is associated with the highest probability for sexual acquisition of HIV infection. As part of a strategy to develop an effective rectal microbicide, we performed an ex-vivo preclinical evaluation to determine the efficacy and limitation of multiple combinations of reverse transcriptase inhibitors (RTIs).

DESIGN

A nucleotide, PMPA (tenofovir), a nucleoside, FTC (emtricitabine), RTIs and two nonnucleoside RTIs, UC781 and TMC120 (dapivirine), were used in double, triple and quadruple combinations against a panel of CCR5-uing and CXCR4-using clade B HIV-1 isolates and against RTI-escape variants.

METHODS

Indicator cells and colorectal tissue explants were used to assess antiviral activity of drug combinations.

RESULTS

All combinations inhibited the isolates tested in a cellular model and in colorectal explants and produced, for at least one of the compounds, a change in the dose-response curve. Double and triple combinations incrementally augmented activity, even against RTI-escape mutants, whereas quadruple combinations conferred little further advantage.

CONCLUSION

The colorectal explant model may be used to identify the best candidate molecules and their combinations at the preclinical stage. Furthermore, this study demonstrates that combinations based on RTIs with different HIV-1 inhibitory mechanisms have potential as colorectal microbicides.

HIV serosorting among HIV-positive men who have sex with men is associated with increased self-reported incidence of bacterial sexually transmissible infections

BACKGROUND

We aimed to quantify the frequency of HIV serosorting among men who have sex with men (MSM) in Germany, and evaluate the association of serosorting with other sexual risk management approaches (RMA) and with the frequency of bacterial sexually transmissible infections (STI).

METHODS

An anonymous, self-administered questionnaire was distributed through German online sexual networking sites and medical practices in 2006. The analysis was based on 2985 respondents who reported an HIV test result. Based on two questions on RMA, serosorting was classified as tactical (an event-based decision) or strategic (a premeditated search for a seroconcordant partner). The analysis was stratified by HIV serostatus and seroconcordant partnership status.

RESULTS

HIV serosorting patterns were different for HIV-positive and HIV-negative participants. Tactical serosorting ranked second after RMA based on condom use (HIV-positive: 55.1%, HIV-negative: 45.1%; P < 0.001). While the overlap of strategic and tactical HIV serosorting among HIV-positive MSM was substantial (58.0%), HIV-negative strategic and tactical serosorting were more distinct (18.1% overlap). Among HIV-positive and HIV-negative respondents, tactical serosorting was associated with reduced condom use. Compared with respondents using RMA other than serosorting, HIV-positive men reporting serosorting had a three-fold increased risk for bacterial STI (strategic: odds ratio (OR) = 2.62; 95% confidence interval (CI): 1.76-3.89; tactical: OR = 3.19; 95% CI: 2.14-4.75; both for respondents without HIV seroconcordant partners).

CONCLUSIONS

HIV serosorting has emerged as a common RMA among MSM. For HIV-positive MSM, it may contribute to high rates of bacterial STI that may lead to elevated per-contact risks for HIV transmission.

Acceptability of female condom use in money boys compared with other men who have sex with men in Chengdu, China: a comparative study

We conducted a clinical trial to compare sexual behaviours and attitudes regarding female condoms among money boys and other men who have sex with men in Chengdu, China, with a particular focus on factors influencing use of female condoms.

Estimation of HIV Seroprevalence in Colorectal Hospitals by Questionnaire Survey in Korea, 2002-2007

Objectives

The incidence of anal disease is higher among persons with human immunodeficiency virus (HIV) infection than among the general population. We surveyed the status of seroprevalence in colorectal hospitals in Korea.

Methods

The survey was conducted in colorectal hospitals in Korea from November to December 2008. The questionnaire was comprised of six topics about the status of HIV testing in colorectal hospitals. We gathered the data by website (http://hivqa.nih.go.kr/risk) or fax.

Results

Among 774 colorectal hospitals contacted, 109 (14%) hospitals participated in the survey. Among these, 48 hospitals (44%) performed HIV tests in their own hospitals and 11 (23%) took HIV testing by rapid method. The main reason for recommending an HIV test was surgical operation (54%) followed by endoscope (11%) and health checkup (9%). The annual number of HIV tests increased from 58,647 (at 21 hospitals) in 2002 to 246,709 (at 58 hospitals) in 2007. HIV seroprevalence was >3.0 per 10,000 individuals during 2002–2005, decreased to 2.2 per 10,000 individuals in 2006 and rose to 2.8 per 10,000 individuals in 2007.

Conclusions

HIV seroprevalence of colorectal hospitals was more than twice that of general hospitals in Korea. HIV surveillance systems based on colorectal hospitals for HIV/AIDS transmission prevention by early HIV diagnosis are needed.

The cost-effectiveness of a modestly effective HIV vaccine in the United States

BACKGROUND

The recent RV144 clinical trial showed that an ALVAC/AIDSVAX prime-boost HIV vaccine regimen may confer partial immunity in recipients and reduce transmission by 31%. Trial data suggest that efficacy may initially exceed 70% but decline over the following 3.5 years. Estimating the potential health benefits associated with a one-time vaccination campaign, as well as the projected benefits of repeat booster vaccination, may inform future HIV vaccine research and licensing decisions.

METHODS

We developed a mathematical model to project the future course of the HIV epidemic in the United States under varying HIV vaccine scenarios. The model accounts for disease progression, infection transmission, antiretroviral therapy, and HIV-related morbidity and mortality. We projected HIV prevalence and incidence over time in multiple risk groups, and we estimated quality-adjusted life years (QALYs) and costs over a 10-year time horizon. We assumed an exponentially declining efficacy curve fit to trial data, and that subsequent vaccine boosters confer similar immunity. Variations in vaccine parameters were examined in sensitivity analysis.

RESULTS

Under existing HIV prevention and treatment efforts, an estimated 590,000 HIV infections occur over 10 years. One-time vaccination achieving 60% coverage of adults could prevent 9.8% of projected new infections over 10 years (and prevent 34% of new infections in the first year) and cost approximately $91,000/QALY gained relative to the status quo, assuming $500 per vaccination series. Targeted vaccination strategies result in net cost savings for vaccines costing less than $750. One-time vaccination of 60% of all adults coupled with three-year boosters only for men who have sex with men and people who inject drugs could prevent 21% of infections for $81,000/QALY gained relative to vaccination of higher risk sub-populations only. A program attaining 90% vaccination coverage prevents 15% of new HIV cases over 10 years (and approximately 50% of infections in the first year).

CONCLUSIONS

A partially effective HIV vaccine with effectiveness similar to that observed in the RV144 trial would provide large health benefits in the United States and could meet conventionally accepted cost-effectiveness thresholds. Strategies that prioritize key populations are most efficient, but broader strategies provide greater total population health benefit.

Characteristics of HIV epidemics driven by men who have sex with men and people who inject drugs

PURPOSE OF REVIEW

To highlight the latest developments in mathematical transmission modelling of HIV epidemics among men who have sex with men (MSM) and people who inject drugs (PWID).

RECENT FINDINGS

Mathematical approaches have been applied to a wide range of topics in recent HIV research. Epidemiological models have evaluated past and forecasted future trends in prevalence and incidence, evaluated innovative behaviour modification strategies and public health programmes aimed at minimizing risk, and explored the potential impact of various biomedical interventions. MSM have developed new risk reduction strategies which models have deemed to be effective at a population level only in certain settings, such as when there are high rates of HIV testing. Modelling has also indicated that persistent circulation of drug-resistant HIV strains is likely to become an inevitable public health issue in the near future in resource-rich settings among MSM. Models have also recently been used to demonstrate that needle and syringe programmes for harm reduction among PWID are effective and cost-effective.

SUMMARY

Mathematical modelling is particularly amenable to single population groups of concentrated HIV epidemics, such as among MSM and PWID. Models have been utilized to evaluate innovative areas in clinical, biomedical and public health research that cannot be conducted in other population groups. Future directions are likely to include evaluation of specific public health programmes and providing understanding of the importance of specific treatment regimens and incidence and interaction of comorbid conditions associated with HIV.

A cross-sectional assessment of population demographics, HIV risks and human rights contexts among men who have sex with men in Lesotho

Background

Evidence is increasing of high HIV risks among southern African men who have sex with men (MSM). This represents the first study of HIV risks and human rights contexts among MSM in Lesotho.

Methods

Two hundred and fifty-two men who reported ever having anal sex with another man were accrued with snowball sampling and were administered a structured quantitative instrument in October and November 2009.

Results

Of the participants, 96.4% (240/249) were ethnic Basotho with a mean age of 26.3 years (range 18-56), 49.6% (124/250) were currently employed, and 95.2% (238/250) had at least a secondary-level education. Self-reported HIV prevalence was 11.6% (22/190); 54.5% (128/235) reported being tested for HIV in the last year. HIV knowledge was low; only 3.7% (8/212) of MSM knew that receptive anal intercourse was the highest risk for HIV and that a water-based lubricant was most appropriate to use with condoms.

Bivariate associations of wearing condoms during last intercourse with men include: having easy access to condoms (OR 3.1, 95% CI 1.2-8.5, p < 0.05); being older than 26 years (OR 2.3, 95% CI 1.3-4.2, p < 0.01); knowing that receptive anal intercourse is higher risk than insertive anal intercourse (OR 2.6, 95% CI 1.2-5.9, p < 0.05); wearing condoms with female sexual partners (OR 3.5, 95% 1.4-8.3, p < 0.01); using water-based lubricants (OR 2.8, 95% CI 1.4-5.5, p < 0.01); being less likely to report having been diagnosed with a sexually transmitted infecton (OR 0.21, 95% CI 0.06-0.76, p < 0.05); and being more likely to have been tested for HIV in the last year (OR 2.0, 95% CI 1.2-3.6, p > 0.05).

Human rights abuses were common: 76.2% (170/223) reported at least one abuse, including rape (9.8%, 22/225), blackmail (21.3%, 47/221), fear of seeking healthcare (22.2%, 49/221), police discrimination (16.4%, 36/219), verbal or physical harassment (59.8%, 140/234), or having been beaten (18.9%, 43/228).

Conclusions

MSM in Lesotho are at high risk for HIV infection and human rights abuses. Evidence-based and rights-affirming HIV prevention programmes supporting the needs of MSM should be developed and implemented.

The cost-effectiveness of HIV voluntary counseling and testing in China

China has experienced a dramatic increase in the number of HIV infections. To control the AIDS epidemic, free HIV voluntary counseling and testing has been made available in China. This study compared the cost-effectiveness of this program for 2 populations-the general population and men who have sex with men (MSM), to examine the value for money of this program. A Bernoulli-process model has been used to translate the changes in sexual behaviors to the number of HIV infections averted. Costs are estimated from a societal perspective. The outcomes are measured in terms of the incremental cost per HIV infection averted and the incremental cost per disability-adjusted life-year averted. The study found that the voluntary counseling and testing for the general population is not cost-effective based on the threshold adopted, whereas the same HIV prevention program for MSM is cost-saving. These results suggest that the efficiency of resources used could be substantially improved by appropriately targeting high-risk population groups. Therefore measures should be taken to increase the uptake of this intervention among high-risk groups.

The role of semen in sexual transmission of HIV: beyond a carrier for virus particles

Unprotected sexual intercourse between discordant couples is by far the most frequent mode of HIV-1 (human immunodeficiency virus type 1) transmission being semen the main vector for HIV-1 dissemination worldwide. Semen is usually considered merely as a vehicle for HIV-1 transmission. In this review we discuss recent observations suggesting that beyond being a carrier for virus particles semen markedly influences the early events involved in sexual transmission of HIV through the mucosal barriers.

Using the Internet in Pursuit of Public Sexual Encounters

The current study investigated a subgroup of 112 men who have sex with men who use the Internet in search of partners for sex venue encounters to understand what types of venues they frequent and whether their behaviors are associated with an increased risk of HIV/STI transmission. An initial cluster analysis revealed two patterns of Internet use—low and high frequency—among these men. Although frequency of Internet use to find partners for venue encounters did not cluster with venue attendance, there was a trend among high-frequency Internet users to attend gyms, public bathrooms, and sex clubs more than low-frequency users. Furthermore, high-frequency users attended more venues, preferred venues where multiple partners can be found, and were marginally more likely to engage in unprotected anal sex across venues compared with low-frequency users. Knowing that some venue users initiate venue encounters on the Internet may be useful in targeting appropriate HIV/STI interventions.

Quantifying sexual exposure to HIV within an HIV-serodiscordant relationship: development of an algorithm

BACKGROUND

The risk of acquiring HIV from a single sexual contact varies enormously reflecting biological and behavioural characteristics of both infected and uninfected partners. Accurate information on HIV transmission risk is required to construct evidence-based risk reduction practices for individuals, to direct the provision of prevention strategies at the population level, and enable the definition, quantification and comparison of true exposure in individuals termed 'exposed uninfected' within clinical trials.

METHODS

Following a systematic review of current literature on HIV transmission estimates, an HIV risk score was developed, incorporating weighted risk factors into a Bernoulli mathematical model, allowing quantification of overall risk of HIV acquisition within HIV-serodiscordant partnerships.

RESULTS

The HIV risk score enumerates the relative risk of HIV acquisition from HIV-positive partners incorporating the type and frequency of specific sex acts, the index case HIV plasma viral load and stage of disease, and the presence of genital ulcer disease in either partner and pregnancy, HSV-2 seropositivity, and circumcision status (men only) in the HIV-negative partner.

CONCLUSION

Key determinants of HIV exposure risk can be incorporated into a mathematical model in order to quantify individual relative risks of HIV acquisition. Such a model can facilitate comparisons within clinical trials of exposed uninfected individuals and facilitate interventions to reduce HIV transmission.

Increasing risk behaviour can outweigh the benefits of antiretroviral drug treatment on the HIV incidence among men-having-sex-with-men in Amsterdam

Background

The transmission through contacts among MSM (men who have sex with men) is one of the dominating contributors to HIV prevalence in industrialized countries. In Amsterdam, the capital of the Netherlands, the MSM risk group has been traced for decades. This has motivated studies which provide detailed information about MSM's risk behavior statistically, psychologically and sociologically. Despite the era of potent antiretroviral therapy, the incidence of HIV among MSM increases. In the long term the contradictory effects of risk behavior and effective therapy are still poorly understood.

Methods

Using a previously presented Complex Agent Network model, we describe steady and casual partnerships to predict the HIV spreading among MSM. Behavior-related parameters and values, inferred from studies on Amsterdam MSM, are fed into the model; we validate the model using historical yearly incidence data. Subsequently, we study scenarios to assess the contradictory effects of risk behavior and effective therapy, by varying corresponding values of parameters. Finally, we conduct quantitative analysis based on the resulting incidence data.

Results

The simulated incidence reproduces the ACS historical incidence well and helps to predict the HIV epidemic among MSM in Amsterdam. Our results show that in the long run the positive influence of effective therapy can be outweighed by an increase in risk behavior of at least 30% for MSM.

Conclusion

We recommend, based on the model predictions, that lowering risk behavior is the prominent control mechanism of HIV incidence even in the presence of effective therapy.

Rectal microbicides: can we make them and will people use them?

The results of the CAPRISA 004 and iPrEx HIV prevention studies have demonstrated that topical or systemic use of antiretroviral agents can significantly reduce the risk of HIV acquisition associated with unprotected vaginal or anal sexual intercourse. However, the effect size in these studies was relatively modest and product adherence was generally poor. These observations suggest the need for new approaches to HIV prevention, especially for high risk MSM. Rates of lubricant use are high in MSM practicing receptive anal sex. Consequently, the development of an antiretroviral rectal microbicide gel may provide a safe and effective means of preventing HIV infection with an intervention that is likely to have high acceptability among the target population. The purpose of this article is to describe the challenges and progress in the development of rectal microbicides for HIV prevention.

Advances in the prevention of heterosexual transmission of HIV/AIDS among women in the United States

Despite recent advances in testing and treatment, the incidence of HIV/AIDS in the United States has remained stagnant with an estimated 56,300 new infections every year. Women account for an increasing proportion of the epidemic. The vulnerability of women to HIV stems from both increased biologic susceptibility to heterosexual transmission and also the social, economic, and structural disadvantages they often confront. This review describes the main reasons for the increased vulnerability of U.S. women to HIV transmission with particular emphasis on specific highrisk groups including: non-Hispanic blacks, women who use drugs, women with a history of incarceration, and victims of intimate partner violence. Although behavioral approaches to HIV prevention may be effective, pragmatic implementation is often difficult, especially for women who lack sociocultural capital to negotiate condoms with their male partners. Recent advances in HIV prevention show promise in terms of female-initiated interventions. These notably include female condoms, non-specific vaginal microbicides, and antiretroviral oral and vaginal pre-exposure prophylaxis. In this review, we will present evidence in support of these new female-initiated interventions while also emphasizing the importance of advocacy and the political support for these scientific advances to be successful.

HIV seroadaptation among individuals, within sexual dyads, and by sexual episodes, men who have sex with men, San Francisco, 2008

"Seroadaptation" comprises sexual behaviors to reduce the risk of HIV acquisition and transmission based on knowing one's own and one's sexual partners' serostatus. We measured the prevalence of seroadaptive behaviors among men who have sex with men (MSM) recruited through time-location sampling (TLS) across three perspectives: by individuals (N = 1207 MSM), among sexual dyads (N = 3746 partnerships), and for sexual episodes (N = 63,789 episodes) in the preceding six months. Seroadaptation was more common than 100% condom use when considering the consistent behavioral pattern of individuals (adopted by 39.1% vs. 25.0% of men, respectively). Among sexual dyads 100% condom use was more common than seroadaptation (33.1% vs. 26.4%, respectively). Considering episodes of sex, not having anal intercourse (65.0%) and condom use (16.0%) were the most common risk reduction behaviors. Sex of highest acquisition and transmission risks (unprotected anal intercourse with a HIV serodiscordant or unknown status partner in the riskier position) occurred in only 1.6% of sexual episodes. In aggregate, MSM achieve a high level of sexual harm reduction through multiple strategies. Detailed measures of seroadaptive behaviors are needed to effectively target HIV risk and gauge the potential of serosorting and related sexual harm reduction strategies on the HIV epidemic.

Minimal impact of circumcision on HIV acquisition in men who have sex with men

BACKGROUND

Men who have sex with men (MSM) are disproportionately affected by HIV. The proven efficacy of circumcision in reducing the risk of HIV acquisition among African heterosexual males has raised the question of whether this protective effect may extend to MSM populations. We examined the potential impact of circumcision on an HIV epidemic within a population of MSM.

METHODS

A mathematical model was developed to simulate HIV transmission in an MSM population. The model incorporated both circumcision and seropositioning, and was used to predict the reduction in HIV prevalence and incidence as a result of the two interventions. Estimates for the time required to achieve these gains were also calculated.

RESULTS

We derive simple formulae for the decrease in HIV prevalence with increased circumcision. Our model predicts that if an initially uncircumcised MSM population in a developed country with a baseline HIV prevalence of 10% underwent universal circumcision, HIV incidence would only be reduced to 95% of pre-intervention levels and HIV prevalence to 9.6% after 20 years. In the longer term, our model predicts that prevalence would only decrease from 10% to 6%, but this would take several generations to achieve. The effectiveness of circumcision increases marginally with higher degrees of seropositioning.

CONCLUSIONS

The results of these calculations suggest that circumcision as a public health intervention will not produce a substantial decrease in HIV prevalence or incidence among MSM in the near future, and only modest reductions are achievable in the long-term.

Estimating the risk of HIV transmission from homosexual men receiving treatment to their HIV-uninfected partners

OBJECTIVE

To determine how the risk of HIV transmission from homosexual men receiving antiretroviral treatment is related to patterns of patient monitoring and condom use.

METHODS

A stochastic mathematical simulation model was developed of cohorts of men in the Netherlands who have sex with men (MSM), defining the parameters of the model using observational cohort data. The model incorporates viral load trends during first-line treatment, patient monitoring and different scenarios for the way in which condom use may depend on recent viral load measurements. The model does not include the effect of sexually transmitted infections on HIV transmission.

RESULTS

For MSM receiving treatment, the risk of transmitting HIV to their long-term partner is 22% (uncertainty interval: 9-37%) if condoms are never used. With incomplete use (in 30% of sex acts) the risk is reduced slightly, to 17% (7-29%). However, the risk is as low as 3% (0.2-8%) when men receiving treatment use condoms only 6 months beyond their last undetectable viral load measurement. The risk is further reduced when 3 months is the time period beyond which condoms are used.

CONCLUSIONS

When condom use by HIV-infected men receiving combination treatment with antiretroviral agents is based on their last viral load measurement, the transmission risk is much lower than with incomplete condom use. The key message for patients is that although always using condoms during treatment is the best way to protect partners from the risk of HIV transmission, when such use cannot be achieved, the second best strategy is to use condoms whenever the last undetectable viral load was measured more than 3 months ago.

HIV is inactivated after transepithelial migration via adult oral epithelial cells but not fetal epithelial cells

Oral transmission of human immunodeficiency virus (HIV) in adult populations is rare. However, HIV spread across fetal/neonatal oropharyngeal epithelia could be important in mother-to-child transmission. Analysis of HIV transmission across polarized adult and fetal oral epithelial cells revealed that HIV transmigrates through both adult and fetal cells. However, only virions that passed through the fetal cells - and not those that passed through the adult cells - remained infectious. Analysis of expression of anti-HIV innate proteins beta-defensins 2 and 3, and secretory leukocyte protease inhibitor in adult, fetal, and infant oral epithelia showed that their expression is predominantly in the adult oral epithelium. Retention of HIV infectivity after transmigration correlated inversely with the expression of these innate proteins. Inactivation of innate proteins in adult oral keratinocytes restored HIV infectivity. These data suggest that high-level innate protein expression may contribute to the resistance of the adult oral epithelium to HIV transmission.

The cost-effectiveness and population outcomes of expanded HIV screening and antiretroviral treatment in the United States

BACKGROUND

Although recent guidelines call for expanded routine screening for HIV, resources for antiretroviral therapy (ART) are limited, and all eligible persons are not currently receiving treatment.

OBJECTIVE

To evaluate the effects on the U.S. HIV epidemic of expanded ART, HIV screening, or interventions to reduce risk behavior.

DESIGN

Dynamic mathematical model of HIV transmission and disease progression and cost-effectiveness analysis.

DATA SOURCES

Published literature.

TARGET POPULATION

High-risk (injection drug users and men who have sex with men) and low-risk persons aged 15 to 64 years in the United States.

TIME HORIZON

Twenty years and lifetime (costs and quality-adjusted life-years [QALYs]).

PERSPECTIVE

Societal.

INTERVENTION

Expanded HIV screening and counseling, treatment with ART, or both.

OUTCOME MEASURES

New HIV infections, discounted costs and QALYs, and incremental cost-effectiveness ratios.

RESULTS OF BASE-CASE ANALYSIS

One-time HIV screening of low-risk persons coupled with annual screening of high-risk persons could prevent 6.7% of a projected 1.23 million new infections and cost $22,382 per QALY gained, assuming a 20% reduction in sexual activity after screening. Expanding ART utilization to 75% of eligible persons prevents 10.3% of infections and costs $20,300 per QALY gained. A combination strategy prevents 17.3% of infections and costs $21,580 per QALY gained.

RESULTS OF SENSITIVITY ANALYSIS

With no reduction in sexual activity, expanded screening prevents 3.7% of infections. Earlier ART initiation when a CD4 count is greater than 0.350 × 10(9) cells/L prevents 20% to 28% of infections. Additional efforts to halve high-risk behavior could reduce infections by 65%.

LIMITATION

The model of disease progression and treatment was simplified, and acute HIV screening was excluded.

CONCLUSION

Expanding HIV screening and treatment simultaneously offers the greatest health benefit and is cost-effective. However, even substantial expansion of HIV screening and treatment programs is not sufficient to markedly reduce the U.S. HIV epidemic without substantial reductions in risk behavior.

PRIMARY FUNDING SOURCE

National Institute on Drug Abuse, National Institutes of Health, and Department of Veterans Affairs.

Racial/Ethnic differences in seroadaptive and serodisclosure behaviors among men who have sex with men

We examined racial/ethnic differences in reported seroadaptive and serodisclosure behaviors among the partnerships of MSM recruited for a cross-sectional survey using time-location sampling (TLS) in San Francisco during 2007-2008. The sample (N = 1,199) consisted of 12.2% Asian/Pacific Islander (API), 52.4% White, 6.8% Black, 20.2% Latino, and 8.5% of "other" race/ethnicity. Pure serosorting was most common (about 20%) among HIV-negative men while seropositioning was most used (about 15%) by HIV-positive men. Reported seroadaptive behaviors did not differ significantly across races/ethnicities among both HIV-negative and HIV-positive men. However, HIV-positive Black and Latino men were significantly more likely to report no preventive, seroadaptive behavioral strategy (i.e., unprotected insertive anal intercourse with unknown status or serodiscordant partners). Among men who reported engaging in seroadaptive behaviors, they reported not discussing HIV status with a third of their partners-a major concern in that lack of disclosure undermines the effectiveness and means to practice serosorting. Partnerships of API and Black men were least likely to involve serodisclosure behaviors. Our study confirms that seroadaptive behaviors are common preventive strategies reported by MSM of all races/ethnicities, and does not find strong evidence that racial/ethnic differences in seroadaptive behaviors are enhancing disparities in HIV prevalence. The implications are that condom promotion and safe sex messages are not the only prevention measures adopted by MSM and that public health professionals should be well aware of current trends within the MSM community in order to better assist HIV prevention efforts.

The cost-effectiveness and population outcomes of expanded HIV screening and antiretroviral treatment in the United States

BACKGROUND

Although recent guidelines call for expanded routine screening for HIV, resources for antiretroviral therapy (ART) are limited, and all eligible persons are not currently receiving treatment.

OBJECTIVE

To evaluate the effects on the U.S. HIV epidemic of expanded ART, HIV screening, or interventions to reduce risk behavior.

DESIGN

Dynamic mathematical model of HIV transmission and disease progression and cost-effectiveness analysis.

DATA SOURCES

Published literature.

TARGET POPULATION

High-risk (injection drug users and men who have sex with men) and low-risk persons aged 15 to 64 years in the United States.

TIME HORIZON

Twenty years and lifetime (costs and quality-adjusted life-years [QALYs]).

PERSPECTIVE

Societal.

INTERVENTION

Expanded HIV screening and counseling, treatment with ART, or both.

OUTCOME MEASURES

New HIV infections, discounted costs and QALYs, and incremental cost-effectiveness ratios.

RESULTS OF BASE-CASE ANALYSIS

One-time HIV screening of low-risk persons coupled with annual screening of high-risk persons could prevent 6.7% of a projected 1.23 million new infections and cost $22,382 per QALY gained, assuming a 20% reduction in sexual activity after screening. Expanding ART utilization to 75% of eligible persons prevents 10.3% of infections and costs $20,300 per QALY gained. A combination strategy prevents 17.3% of infections and costs $21,580 per QALY gained.

RESULTS OF SENSITIVITY ANALYSIS

With no reduction in sexual activity, expanded screening prevents 3.7% of infections. Earlier ART initiation when a CD4 count is greater than 0.350 × 10(9) cells/L prevents 20% to 28% of infections. Additional efforts to halve high-risk behavior could reduce infections by 65%.

LIMITATION

The model of disease progression and treatment was simplified, and acute HIV screening was excluded.

CONCLUSION

Expanding HIV screening and treatment simultaneously offers the greatest health benefit and is cost-effective. However, even substantial expansion of HIV screening and treatment programs is not sufficient to markedly reduce the U.S. HIV epidemic without substantial reductions in risk behavior.

PRIMARY FUNDING SOURCE

National Institute on Drug Abuse, National Institutes of Health, and Department of Veterans Affairs.

Male circumcision for HIV prevention: current research and programmatic issues

Randomized controlled trials in sub-Saharan Africa have shown that adult male circumcision reduces the risk of HIV acquisition in men by about 60%. In this article, we review recent data on the association of male circumcision and HIV/sexually transmitted infection in men and women. This includes a summary of data showing some evidence of an effect of male circumcision against genital ulcer disease, HSV-2 infection, human papillomavirus and Trichomonas vaginalis, but not Chlamydia trachomatis or Neisseria gonorrhoea in men. Longitudinal studies among HIV discordant couples suggest that male circumcision may provide some direct long-term benefit to women, which may start after complete wound healing. Circumcision may also protect against HIV acquisition in men who have sex with men (MSM) and those who practice unprotected anal intercourse (either exclusively or predominantly), although these data are not consistent. To date, there is little evidence from the few studies available of either unsafe practices or reported increases in risky behaviour, or adverse changes in sexual satisfaction and function. As countries in southern and eastern Africa scale up services, operational research will likely be useful to iteratively improve programme delivery and impact while identifying the best methods of integrating safe male circumcision services into HIV prevention strategies and strengthening health systems.

HIV transmission risk among serodiscordant couples: a retrospective study of former plasma donors in Henan, China

OBJECTIVES: To estimate the HIV incidence and assess the behavioral, clinical, and quality-of-life risk factors for HIV transmission among serodiscordant couples from Henan Province, China. METHODS: Between January 2006 and December 2008, initially seronegative spouses were tested for HIV at six month intervals. Retrospectively identified subjects were interviewed through face-to-face questionnaire. Cox proportional-hazards model was used to assess the relationship between risk factors and HIV seroconversion. RESULTS: Out of 1927 couples, 84 (4.3%) seroconversions occurred, representing a seroconversion rate of 1.71 per 100 person-years. Seroconversion rates increased over time. Not always using condoms (RR=8.42; 95% CI, 4.83-14.67), sexual activity ≥ 4 times per month (RR=5.24; 95% CI, 2.55-10.77), not switching anti-retroviral treatment regimen (RR=1.99; 95% CI, 0.85-4.65), and a quality of life score <12 on the psychological domain (RR=2.33; 95% CI, 1.21-4.48) were associated with increased risk of seroconversion. Seventy one percent of index spouses were on ART. There was no association between rate of HIV seroconversion and last recorded CD4 cell count level of the index spouse. CONCLUSIONS: Effective HIV prevention interventions targeting discordant couples should focus on sustaining health education, increasing psychosocial support services, and increasing medication adherence monitoring.

Dynamic sex roles among men who have sex with men and transmissions from primary HIV infection

BACKGROUND

Previous studies estimating the fraction of transmissions from persons with primary HIV have not focused on the effects of switching sex role in male homosexual populations. Such behavioral fluctuations can increase the contribution of primary HIV in the overall population.

METHODS

We modeled HIV transmission with 8 compartments defined by 4 behavioral groups, with different anal-insertive and anal-receptive combinations, and 2 stages of infection. We explored the effects of fluctuating behavioral categories on endemic prevalence and the fraction of transmissions from primary HIV. We varied transition rates to develop the theory on how behavioral fluctuation affects infection patterns, and we used the transition rates in a Netherlands cohort to assess overall effects in a real setting.

RESULTS

The dynamics of change in behavior-group status over time observed in the Netherlands cohort amplifies the prevalence of infection and the fraction of transmissions from primary HIV, resulting in the highest proportions of transmissions being from people with primary HIV. Fluctuation between dual- or receptive-role periods and no-anal-sex periods mainly determines this amplification. In terms of the total transmissions, the dual-role risk group is dominant. Fluctuation between insertive and receptive roles decreases the fraction of transmissions from primary HIV, but such fluctuation is infrequently observed.

CONCLUSION

The fraction of transmissions from primary HIV is considerably raised by fluctuations in insertive and receptive anal sex behaviors. This increase occurs even when primary HIV or later infection status does not influence risk behavior. Thus, it is not simply biology but also behavior patterns and social contexts that determine the fraction of transmissions from primary HIV. Moreover, each primary HIV transmission has a larger population effect than each later infection transmission because the men to whom one transmits from primary HIV carry on more chains of transmissions than the men to whom one transmits later in infection. Reducing transmissions from primary HIV should be a primary focus of HIV control efforts.

HIV testing among bisexual men in the United States

Little is known about HIV testing among bisexual men in the United States. Existing studies lack adequate representation, multivariate analytical strategies, and measurement of bisexuality indicators. To address these limitations, this study used the National Survey of Family Growth (N = 3,875). Sexual behavior and identity measures compared bisexual and other men along HIV testing history, reasons for testing, and recency of testing. Multivariate analyses adjusted for sociodemographic and risk factors that covary with testing. Bisexually active men were significantly less likely than homosexually active men to ever test, and they tested less often to know their HIV serostatuses. Bisexual identification decreased the odds of testing among bisexually active men but not others. Findings suggest that bisexual behavior and identity interact to decrease men's likelihoods of HIV testing. Interventions must recognize the potentially mediating roles of bisexual identity and behavior as well as risk factors that increase bisexual men's susceptibility to HIV infection.

HIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention

BACKGROUND

The human immunodeficiency virus (HIV) infectiousness of anal intercourse (AI) has not been systematically reviewed, despite its role driving HIV epidemics among men who have sex with men (MSM) and its potential contribution to heterosexual spread. We assessed the per-act and per-partner HIV transmission risk from AI exposure for heterosexuals and MSM and its implications for HIV prevention.

METHODS

Systematic review and meta-analysis of the literature on HIV-1 infectiousness through AI was conducted. PubMed was searched to September 2008. A binomial model explored the individual risk of HIV infection with and without highly active antiretroviral therapy (HAART).

RESULTS

A total of 62,643 titles were searched; four publications reporting per-act and 12 reporting per-partner transmission estimates were included. Overall, random effects model summary estimates were 1.4% [95% confidence interval (CI) 0.2-2.5)] and 40.4% (95% CI 6.0-74.9) for per-act and per-partner unprotected receptive AI (URAI), respectively. There was no significant difference between per-act risks of URAI for heterosexuals and MSM. Per-partner unprotected insertive AI (UIAI) and combined URAI-UIAI risk were 21.7% (95% CI 0.2-43.3) and 39.9% (95% CI 22.5-57.4), respectively, with no available per-act estimates. Per-partner combined URAI-UIAI summary estimates, which adjusted for additional exposures other than AI with a 'main' partner [7.9% (95% CI 1.2-14.5)], were lower than crude (unadjusted) estimates [48.1% (95% CI 35.3-60.8)]. Our modelling demonstrated that it would require unreasonably low numbers of AI HIV exposures per partnership to reconcile the summary per-act and per-partner estimates, suggesting considerable variability in AI infectiousness between and within partnerships over time. AI may substantially increase HIV transmission risk even if the infected partner is receiving HAART; however, predictions are highly sensitive to infectiousness assumptions based on viral load.

CONCLUSIONS

Unprotected AI is a high-risk practice for HIV transmission, probably with substantial variation in infectiousness. The significant heterogeneity between infectiousness estimates means that pooled AI HIV transmission probabilities should be used with caution. Recent reported rises in AI among heterosexuals suggest a greater understanding of the role AI plays in heterosexual sex lives may be increasingly important for HIV prevention.

Stigma and sexual health risk in HIV-positive African American young men who have sex with men

Understanding the multiple forms of stigma experienced by young HIV-positive African American men who have sex with men and how they relate to sexual risk behaviors is essential to design effective HIV prevention programs. This study of 40 African American young MSM found that 90% of those surveyed experienced sexual minority stigma, 88% experienced HIV stigma, and 78% experienced dual stigma. Sexual minority stigma was characterized by experiences of social avoidance, and HIV stigma, by shame. Individuals with high HIV stigma were significantly more likely to engage in unprotected sex while high or intoxicated. Associations between stigma and sexual practices were examined; youth endorsing higher levels of sexual minority stigma engaged in less insertive anal intercourse. Individuals endorsing more HIV stigma reported more receptive anal intercourse. These findings support the development of stigma-informed secondary prevention interventions for African American HIV-positive young MSM.

Prevention of HIV infection for people who inject drugs: why individual, structural, and combination approaches are needed

HIV can spread rapidly between people who inject drugs (through injections and sexual transmission), and potentially the virus can pass to the wider community (by sexual transmission). Here, we summarise evidence on the effectiveness of individual-level approaches to prevention of HIV infection; review global and regional coverage of opioid substitution treatment, needle and syringe programmes, and antiretroviral treatment; model the effect of increased coverage and a combination of these three approaches on HIV transmission and prevalence in injecting drug users; and discuss evidence for structural-level interventions. Each intervention alone will achieve modest reductions in HIV transmission, and prevention of HIV transmission necessitates high-coverage and combined approaches. Social and structural changes are potentially beneficial components in a combined-intervention strategy, especially when scale-up is difficult or reductions in HIV transmission and injection risk are difficult to achieve. Although further evidence is needed on how to optimise combinations of interventions in different settings and epidemics, we know enough now about which actions are effective: the challenge is to deliver these well and to scale.

Modeling HIV vaccines in Brazil: assessing the impact of a future HIV vaccine on reducing new infections, mortality and number of people receiving ARV

Background

The AIDS epidemic in Brazil remains concentrated in populations with high vulnerability to HIV infection, and the development of an HIV vaccine could make an important contribution to prevention. This study modeled the HIV epidemic and estimated the potential impact of an HIV vaccine on the number of new infections, deaths due to AIDS and the number of people receiving ARV treatment, under various scenarios.

Methods and Findings

The historical HIV prevalence was modeled using Spectrum and projections were made from 2010 to 2050 to study the impact of an HIV vaccine with 40% to 70% efficacy, and 80% coverage of adult population, specific groups such as MSM, IDU, commercial sex workers and their partners, and 15 year olds. The possibility of disinhibition after vaccination, neglecting medium- and high-risk groups, and a disease-modifying vaccine were also considered. The number of new infections and deaths were reduced by 73% and 30%, respectively, by 2050, when 80% of adult population aged 15–49 was vaccinated with a 40% efficacy vaccine. Vaccinating medium- and high-risk groups reduced new infections by 52% and deaths by 21%. A vaccine with 70% efficacy produced a great decline in new infections and deaths. Neglecting medium- and high-risk population groups as well as disinhibition of vaccinated population reduced the impact or even increased the number of new infections. Disease-modifying vaccine also contributed to reducing AIDS deaths, the need for ART and new HIV infections.

Conclusions

Even in a country with a concentrated epidemic and high levels of ARV coverage, such as Brazil, moderate efficacy vaccines as part of a comprehensive package of treatment and prevention could have a major impact on preventing new HIV infections and AIDS deaths, as well as reducing the number of people on ARV. Targeted vaccination strategies may be highly effective and cost-beneficial.

Youth-specific considerations in the development of preexposure prophylaxis, microbicide, and vaccine research trials

Preventing HIV infection in adolescents and young adults will require a multimodal targeted approach, including individual-directed behavioral risk reduction, community-level structural change, and biomedical interventions to prevent sexual transmission. Trials testing biomedical interventions to prevent HIV transmission will require special attention in this population due to the unique psychosocial and physiologic characteristics that differentiate them from older populations. For example, microbicide research will need to consider acceptability, dosing requirements, and coinfection rates that are unique to this population. Preexposure prophylaxis studies also will need to consider potential unique psychosocial issues such as sexual disinhibition and acceptability as well as unique pharmacokinetic parameters of antiretroviral agents. Vaccine trials also face unique issues with this population, including attitudes toward vaccines, risks related to false-positive HIV tests related to vaccine, and different immune responses based on more robust immunity. In this article, we will discuss issues around implementing each of these biomedical prevention modalities in trials among adolescents and young adults to help to guide future successful research targeting this population.

Methamphetamine use among newly diagnosed HIV-positive young men in North Carolina, United States, from 2000 to 2005

Background

Methamphetamine (MA) is a new arrival to the Southeastern United States (US). Incidence of HIV is also increasing regionally, but data are limited regarding any association between this trend and MA use. We examined behavioral data from North Carolina (NC) residents newly diagnosed with HIV, collected by the Department of Health between 2000-2005.

Principal Findings

Among 1,460 newly diagnosed HIV-positive young men, an increasing trend was seen from 2000-2005 in MA use (p = 0.01, total n = 20). In bivariate analyses, users of MA had significantly greater odds of reporting other substance use, including alcohol, powder or crack cocaine, marijuana, and methylenedioxymethamphetamine (MDMA, “ecstasy”). They were also more likely to have reported sexual activity while traveling outside NC; sex with anonymous partners; and previous HIV testing. In a predictive model, MA use had a negative association with nonwhite race, and strong positive associations with powder cocaine, “ecstasy,” or intravenous drug use and being a university student.

Conclusions

Similar to trends seen in more urban parts of the US, MA use among newly diagnosed, HIV-positive young men is increasing in NC. These data are among the first to demonstrate this relationship in a region with a burgeoning epidemic of MA use. Opportunities exist for MA-related HIV risk-reduction interventions whenever young men intersect the healthcare system.

Semen-mediated enhancement of HIV infection is donor-dependent and correlates with the levels of SEVI

Background

HIV-1 is usually transmitted in the presence of semen. We have shown that semen boosts HIV-1 infection and contains fragments of prostatic acid phosphatase (PAP) forming amyloid aggregates termed SEVI (semen-derived enhancer of viral infection) that promote virion attachment to target cells. Despite its importance for the global spread of HIV-1, however, the effect of semen on virus infection is controversial.

Results

Here, we established methods allowing the meaningful analysis of semen by minimizing its cytotoxic effects and partly recapitulating the conditions encountered during sexual HIV-1 transmission. We show that semen rapidly and effectively enhances the infectivity of HIV-1, HIV-2, and SIV. This enhancement occurs independently of the viral genotype and coreceptor tropism as well as the virus producer and target cell type. Semen-mediated enhancement of HIV-1 infection was also observed under acidic pH conditions and in the presence of vaginal fluid. We further show that the potency of semen in boosting HIV-1 infection is donor dependent and correlates with the levels of SEVI.

Conclusions

Our results show that semen strongly enhances the infectivity of HIV-1 and other primate lentiviruses and that SEVI contributes to this effect. Thus, SEVI may play an important role in the sexual transmission of HIV-1 and addition of SEVI inhibitors to microbicides may improve their efficacy.

Acceptability of UC781 gel as a rectal microbicide among HIV-uninfected women and men

We studied the overall acceptability of UC781 gel formulation when applied rectally. Ten women and twenty-six men, all HIV-uninfected, were enrolled in a Phase 1, randomized, blinded, placebo-controlled safety and acceptability study of the vaginal microbicide gel UC781 applied rectally. Participants were randomized to three groups: 0.1% UC781 gel, 0.25% UC781 gel, or a placebo gel. Acceptability was assessed using structured questionnaires and qualitative in-depth interviews. After using UC781 gel rectally for seven consecutive days, participants’ reports suggest that a UC781 gel formulation is highly acceptable and comparable to a placebo gel. The gels received favorable ratings overall and on attributes such as color, smell and consistency. All of the participants reported high intentions to use a gel like the one they used in this study. Acceptability research is essential in early phases of microbicide development to identify potential problems, understand user preferences, and introduce changes if needed.

27 years of the HIV epidemic amongst men having sex with men in the Netherlands: an in depth mathematical model-based analysis

BACKGROUND

There has been increasing concern about a resurgent epidemic of HIV-1 amongst men having sex with men in the Netherlands, which has parallels with similar epidemics now occurring in many other countries.

METHODS

A transmission model applicable to HIV-1 epidemics, including the use of antiretroviral therapy, is presented in a set of ordinary differential equations. The model is fitted by maximum likelihood to national HIV-1 and AIDS diagnosis data from 1980 to 2006, estimating parameters on average changes in unsafe sex and time to diagnosis. Robustness is studied with a detailed univariate sensitivity analysis, and a range of hypothetical scenarios are explored for the past and next decade.

RESULTS

With a reproduction number around the epidemic threshold one, the HIV-1 epidemic amongst men having sex with men in the Netherlands is still not under control. Scenario analysis showed that in the absence of antiretroviral therapy limiting infectiousness in treated patients, the epidemic could have been more than double its current size. Ninety percent of new HIV transmissions are estimated to take place before diagnosis of the index case. Decreasing time from infection to diagnosis, which was 2.5 years on average in 2006, can prevent many future infections.

CONCLUSIONS

Sexual risk behaviour amongst men having sex with men who are not aware of their infection is the most likely factor driving this epidemic.