AIDS. Promote HIV chemoprophylaxis research, don't prevent it

Compliance With Epidemic Prevention Guidelines Among Wuhan Citizens Under the Stressors of the COVID-19 Pandemic: A Cross-Sectional Multidistrict Comparative Analysis

The current study aims to compare compliance with the COVID-19 prevention guidelines among citizens from 13 districts in Wuhan and to explore the influence of individual-level psychological factors and district-level factors on compliance. A total of 811 participants (52% females) from 13 districts in Wuhan were invited to complete surveys regarding demographics, psychosocial factors and compliance with epidemic prevention guidelines. Individual-level characteristics were combined with district-level measures to create multilevel predictive models of compliance with prevention guidelines, and used the Hierarchical Linear Model (HLM) to analyze the data. Findings revealed that there were significant differences in the compliance of citizens from 13 districts of Wuhan (F = 5.65, P < 0.001). Hierarchical linear model analysis revealed that the risk factors case growth rate, COVID-19-related perceived stress, anxiety, significantly negatively predicted compliance. Hope and conscientiousness significantly positively predicted compliance with prevention guidelines, and the negative predictive effect of anxiety disappeared. Overall, we found significant differences in compliance with prevention guidelines among different districts. Risk factors at the individual level have had a negative impact on individuals’ compliance with prevention guidelines, but this impact can be mitigated by the positive role of personal protective factors such as conscientiousness and hope.

A Mobile Gaming Intervention for Persons on Pre-Exposure Prophylaxis: Protocol for Intervention Development and Randomized Controlled Trial

Background

In the United States, young minority men who have sex with men (MSM) are the most likely to become infected with HIV. Pre-exposure prophylaxis (PrEP) is an efficacious and promising prevention strategy. However, PrEP’s safety and effectiveness can be greatly compromised by suboptimal adherence to treatment. To maximize the positive impact of PrEP, it is necessary to combine its prescription with cost-effective behavioral interventions that promote adherence and decrease HIV risk behaviors. In this project, we developed a theoretically informed app/gaming intervention to engage young MSM in learning information, practicing behaviors, and improving motivation for HIV preventative behaviors and PrEP adherence.

Objective

The goal of this project was to develop and test a cutting-edge, engaging, and entertaining app/gaming intervention for improving adherence to PrEP and building HIV prevention knowledge, skills, and behavior.

Methods

This study was conducted in two phases. In the developmental phase, we conducted qualitative interviews with young MSM (n=20) to guide the development of the gaming intervention. In the randomized controlled trial, we tested the preliminary efficacy of the gaming intervention compared to a comparison condition among young MSM. Subjects were recruited from the University of Mississippi Medical Center HIV/STI testing clinics (n=60).

Results

Institutional review board approval was received in February 2015. Research activities began in June 2015 and are still ongoing.

Conclusions

This app/gaming intervention aimed to improve PrEP adherence and HIV preventative behaviors in young MSM. Engaging young MSM in learning information, practicing behaviors, and improving motivation for increased adherence to PrEP has the potential to decrease HIV seroconversion. It is important to develop interventions that are enjoyable, engaging, and easily incorporated into clinical settings.

Trial Registration

ClinicalTrials.gov RCT02611362; https://tinyurl.com/y65gkuwr

International Registered Report Identifier (IRRID)

DERR1-10.2196/18640

HIV prevention clinical trials' community engagement guidelines: inequality, and ethical conflicts

In 2004 and 2005, the first clinical trials were launched to investigate the use of tenofovir for HIV prevention in Cambodia, Cameroon, Nigeria and Thailand. Controversies erupted over the ethical integrity of the research protocol. We reflect on the events that led to the controversies and identified that scientific and ethical concerns raised by members of local communities at each of these sites were erased by trialists, causing crisis that led to premature shut down the early PrEP trials. In the aftermath of these trials, the World Health Organisation, UNAIDS, and AVAC developed ethics guidelines intended to recognize the concerns as authentic, and developed guidelines to improve researchers’ engagement of communities in biomedical HIV prevention trial design and implementation. Our findings suggest that the ethics guidelines are limited in its ability to address power inequalities that leads to voice erasures and non-recognition of local competencies. Rather the ethical documents enabled trialists to gain a new sense of authority through the interpretations of ethical research conduct enabling trialists regain power that can further entrench inequality and voice erasures. To address concerns with what seems an intractable problem, we suggested models of engagement for off-shored research may be the option.

Protection Efficacy of C5A Against Vaginal and Rectal HIV Challenges in Humanized Mice

Introduction:

In the absence of a vaccine, there is an urgent need for the identification of effective agents that prevent HIV transmission in uninfected individuals. Non-vaccine Biomedical Prevention (nBP) methods, such as topical or systemic pre-exposure prophylaxis (PrEP), are promising strategies to slow down the spread of AIDS.

Methods:

In this study, we investigated the microbicidal efficacy of the viral membrane-disrupting amphipathic SWLRDIWDWICEVLSDFK peptide called C5A. We chose the bone marrow/liver/thymus (BLT) humanized mouse model as vaginal and rectal HIV transmission models.

Results:

We found that the topical administration of C5A offers complete protection against vaginal and rectal HIV challenges in humanized mice. After demonstrating that C5A blocks genital HIV transmission in humanized mice, we examined the molecular requirements for its microbicidal property. We found that the removal of four amino acids on either end of C5A does not diminish its microbicidal efficacy. However, the removal of four amino acids at both the ends, abolishes its capacity to prevent vaginal or rectal HIV transmission, suggesting that the length of the peptide is a critical parameter for the microbicidal activity of C5A. Moreover, we demonstrated that the amphipathicity of the helical peptide as well as its hydrophobic surface represents key factors for the microbicidal activity of C5A in humanized mice.

Conclusion:

With its noncellular cytotoxic activity, its property of neutralizing both HSV and HIV, and its unique mechanism of action that disrupts the stability of the viral membrane, C5A represents an attractive multipurpose microbicidal candidate to be combined with other anti-HIV agents including antiretrovirals.

Prevention of vaginal and rectal HIV transmission by antiretroviral combinations in humanized mice

With more than 7,000 new HIV infections daily worldwide, there is an urgent need for non-vaccine biomedical prevention (nBP) strategies that are safe, effective, and acceptable. Clinical trials have demonstrated that pre-exposure prophylaxis (PrEP) with antiretrovirals (ARVs) can be effective at preventing HIV infection. In contrast, other trials using the same ARVs failed to show consistent efficacy. Topical (vaginal and rectal) dosing is a promising regimen for HIV PrEP as it leads to low systematic drug exposure. A series of titration studies were carried out in bone marrow/liver/thymus (BLT) mice aimed at determining the adequate drug concentrations applied vaginally or rectally that offer protection against rectal or vaginal HIV challenge. The dose-response relationship of these agents was measured and showed that topical tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) can offer 100% protection against rectal or vaginal HIV challenges. From the challenge data, EC50 values of 4.6 μM for TDF and 0.6 μM for FTC for HIV vaginal administration and 6.1 μM TDF and 0.18 μM for FTC for rectal administration were obtained. These findings suggest that the BLT mouse model is highly suitable for studying the dose-response relationship in single and combination ARV studies of vaginal or rectal HIV exposure. Application of this sensitive HIV infection model to more complex binary and ternary ARV combinations, particularly where agents have different mechanisms of action, should allow selection of optimal ARV combinations to be advanced into pre-clinical and clinical development as nBP products.

From subjects to relations: Bioethics and the articulation of postcolonial politics in the Cambodia Pre-Exposure Prophylaxis trial

Controversies about global clinical trials, particularly HIV trials, tend to be framed in terms of ethics. In this article, I explore debates about ethics in the Cambodia Pre-Exposure Prophylaxis trial, which was designed to test the safety and efficacy of tenofovir as a prevention for HIV infection. Bringing together studies of public participation in science with studies of bioethics, I show how activists around the Cambodian Pre-Exposure Prophylaxis trial circulated and provoked debates about standards of research ethics, as opposed to research methodology. This postcolonial bioethics was configured through the circulation of and debate about ethics guidelines, and historically and culturally specific relations of vulnerability and responsibility between foreigners and Cambodians and between Cambodian leaders and Cambodian subjects. I argue that this shift in the object of ethical concern, from the experimental human subject to the relation between subjects and researchers, illustrates how a postcolonial field of articulation reformulates classical bioethics.

Southern African guidelines on the safe use of pre-exposure prophylaxis in persons at risk of acquiring HIV-1 infection

The Southern African HIV Clinicians Society published its first set of oral pre-exposure prophylaxis (PrEP) guidelines in June 2012 for men who have sex with men (MSM) who are at risk of HIV infection. With the flurry of data that has been generated in PrEP clinical research since the first guideline, it became evident that there was a need to revise and expand the PrEP guidelines with new evidence of safety and efficacy of PrEP in several populations, including MSM, transgender persons, heterosexual men and women, HIV-serodiscordant couples and people who inject drugs. This need is particularly relevant following the World Health Organization (WHO) Consolidated Treatment Guidelines released in September 2015. These guidelines advise that PrEP is a highly effective, safe, biomedical option for HIV prevention that can be incorporated with other combination prevention strategies in Southern Africa, given the high prevalence of HIV in the region. PrEP should be tailored to populations at highest risk of HIV acquisition, whilst further data from studies in the region accrue to guide optimal deployment to realise the greatest impact regionally. PrEP may be used intermittently during periods of perceived HIV acquisition risk, rather than continually and lifelong, as is the case with antiretroviral treatment. Recognition and accurate measurement of potential risk in individuals and populations also warrants discussion, but are not extensively covered in these guidelines.

Saying 'No' to PrEP research in Malawi: what constitutes 'failure' in offshored HIV prevention research?

Between 2004 and 2005, the first multi-sited clinical trial tested whether an existing, marketed antiretroviral drug, Tenofovir (TDF), could prevent HIV transmission. Referred to as pre-exposure prophylaxis (PrEP), most of these trial sites prematurely closed down. Two sites located in Cambodia and Cameroon received international media attention. But little attention was drawn to sites in Malawi and Nigeria, where university ethicists and research scientists extensively debated PrEP. This article focuses on events that took place in Malawi where there was a prolonged dispute over the scientific rationales of PrEP and not trial specific ethics referred to as 'bioethics'. Specifically, the article discusses debates pertaining to three PrEP trial protocols that were refused ethics approval in Malawi between 2004 and 2009. It is argued that HIV science debates in Malawi are embedded in postcolonial politics--geopolitical histories and state and household economic dispossessions that have created the structural possibilities for Malawi to become an offshore destination for HIV clinical research. As such, ethics in this case does not pertain to trial or bioethical 'failures'. Rather, ethics is located at the scale of imperial relations that give rise to multiple, often invisible, research concerns and constraints.

Cultural conundrums: the ethics of epidemiology and the problems of population in implementing pre-exposure prophylaxis

The impending implementation of pre-exposure prophylaxis (PrEP) has prompted complicated bioethical and public health ethics concerns regarding the moral distribution of antiretroviral medications (ARVs) to ostensibly healthy populations as a form of HIV prevention when millions of HIV-positive people still lack access to ARVs globally. This manuscript argues that these questions are, in part, concerns over the ethics of the knowledge production practices of epidemiology. Questions of distribution, and their attendant cost-benefit calculations, will rely on a number of presupposed, and therefore, normatively cultural assumptions within the science of epidemiology specifically regarding the ability of epidemiologic surveillance to produce accurate maps of HIV throughout national populations. Specifically, ethical questions around PrEP will focus on who should receive ARVs given the fact that global demand will far exceed supply. Given that sexual transmission is one of the main modes of HIV transmission, these questions of 'who' are inextricably linked to knowledge about sexual personhood. As a result, the ethics of epidemiology, and how the epidemiology of HIV in particular conceives, classifies and constructs sexual populations will become a critical point of reflection and contestation for bioethicists, health activists, physicians, nurses, and researchers in the multi-disciplinary field of global health. This paper examines how cultural conundrums within the fields of bioethics and public health ethics are directly implicated within the ethics of PrEP, by analyzing the problems of population inaugurated by the construction of the men who have sex with men (MSM) epidemiologic category in the specific national context of South Africa.

Pre-exposure prophylaxis of HIV: A right way to go or a long way to go?

Antiretroviral drugs are being tried as candidates for the pre-exposure prophylaxis (PrEP) against HIV for a considerable period, due to their potential for immediate inhibition of viral replication. Discrepancies in the findings called for a critical review of the relevant efforts and their outcomes. A systematic literature search identified 143 eligible articles of which only 5 reported complete findings while another 11 were still on-going. Observed moderate efficacy and good safety profile seemed to identify PrEP as a promising step for minimizing the spread of HIV to relatively unaffected population and controlling the epidemic among high risk population groups. But the duration of this efficacy was found to depend heavily on the availability, adherence and other related issues like cost, political commitment, ethical consideration etc. To prevent potential cultural and behavioral modifications, proper pre-administration counseling also seemed critical for the success of PrEP as a cost-effective intervention with adequate coverage.

Setting the bar high or setting up to fail? Interpretations and implications of the EXPLORE Study (HPTN 015)

Controlled studies show that HIV risk reduction counseling significantly increases condom use, reduces unprotected sex and prevents sexually transmitted infections. Nevertheless, without evidence of reducing HIV incidence, these interventions are generally discarded. One trial, the EXPLORE study, was designed to test whether ten sessions of risk reduction counseling could impact HIV incidence among men who have sex with men in six US cities. Based on epidemiologic models to define effective HIV vaccines, a 35 % reduction in HIV incidence was set a priori as the benchmark of success in this behavioral intervention trial. Results demonstrated a significant effect of the intervention, with more than a 35 % reduction in HIV incidence observed during the initial 12-18 months following counseling. Over an unprecedented 48-month follow-up, however, the effect of counseling on HIV incidence declined to 18 %. The current review examined how the scientific literature has thus far judged the outcomes of the EXPLORE study as well as the policy implications of these judgments. We identified 127 articles that cited the EXPLORE study since its publication. Among articles that discuss the HIV incidence outcomes, 20 % judged the intervention effective and 80 % judged the intervention ineffective. The overwhelmingly negative interpretation of the EXPLORE study outcomes is reflected in public policies and prevention planning. We conclude that using a vaccine standard to define success led to a broad discrediting of the benefits of behavioral counseling and, ultimately, adversely impacted policies critical to the field of HIV prevention.

Legal and ethical values in the resolution of research-related disputes: how can IRBS respond to participant complaints?

Under US federal regulations, participants providing informed consent must receive information regarding whom to contact in case of a research-related injury or complaint. Although informed consent processes routinely direct participants to contact institutional review boards (IRBs) with questions or concerns, there has been little empirical study of the ways in which IRBs act to resolve participants' research-related complaints. This article explores available literature on participant complaints, considers the responsibilities of IRBs in dispute resolution, and outlines a research agenda. As a case study, this review considers disputes arising from HIV/AIDS research, focusing on novel issues arising from biomedical HIV prevention trials.

Pre-exposure prophylaxis for the prevention of HIV infection in high risk populations: a meta-analysis of randomized controlled trials

BACKGROUND

Nearly ten randomized controlled trials (RCTs) of pre-exposure prophylaxis (PrEP) have been completed or are ongoing worldwide to evaluate the effectiveness of PrEP in HIV transmission among HIV-uninfected high risk populations. The purpose of this study was to evaluate the role of PrEP to prevent HIV transmission through a Mata-analysis.

METHODS

A comprehensive computerized literature search was carried out in PubMed, EMbase, Ovid, Web of Science, Science Direct, Wan Fang, CNKI and related websites to collect relevant articles (from their establishment date to August 30, 2013). The search terms were "pre-exposure prophylaxis", "high risk population", "HIV infection", "reduction", "relative risk" and "efficacy". We included any RCT assessing PrEP for the prevention of HIV infection in high risk populations. Interventions of the studies were continuously daily or intermittent doses of single or compound antiretrovirals (ARVs) before HIV exposure or during HIV exposure. A meta-analysis was conducted using Stata 10.0. A random-effects method was used to calculate the pooled relative risk (RR) and 95% confidence intervals (CI) for all studies included.

RESULTS

Seven RCTs involving 14,804 individuals in high risk populations were eligible for this study. The number of subjects in the experimental groups was 8,195, with HIV infection rate of 2.03%. The number of subjects in the control groups was 6,609, with HIV infection rate of 4.07%. The pooled RR was 0.53 (95% CI = 0.40 ∼ 0.71, P<0.001). The re-analyzed pooled RR were 0.61 (95% CI = 0.48 ∼ 0.77, P<0.001), 0.49 (95% CI = 0.38 ∼ 0.63, P<0.001), respectively, by excluding the largest study or two studies without statistical significance. Publication bias analysis revealed a symmetry funnel plot. The fail-safe number was 1,022.

CONCLUSION

These results show that PrEP is an effective strategy for reducing new HIV infections in high risk populations.

Acceptability of PrEP for HIV prevention among women at high risk for HIV

OBJECTIVE

To assess the acceptability of a daily pill for prevention of HIV acquisition among 400 Ghanaian women in the oral tenofovir disoproxil fumarate (TDF) clinical trial.

METHODS

Structured questionnaires were conducted with women enrolled in the trial at enrollment and at each of the 12 monthly follow-up visits. Growth curve analysis was used to examine adherence patterns over time. Qualitative interviews were carried out with a subsample of the clinical trial population, and thematic analysis was applied to these data.

RESULTS

Overall, acceptability of the pill was good. Adherence remained > 82% throughout the 12-month trial. Consistent access to the pill and study assignment were both associated with adherence. Most reported problems diminished over time as women became accustomed to the pill and developed strategies to incorporate pill taking into their daily routines.

CONCLUSIONS

If daily preexposure prophylaxis (PrEP) for HIV is found to be efficacious and has as few physical side effects as TDF, acceptability of this method among women in the study population may not be problematic. However, future studies must develop better acceptability measures, in order to more fully address the relationship among adherence, safety, and effectiveness.

Mucosal HIV-1 transmission and prevention strategies in BLT humanized mice

Clinical trials testing microbicides and related biomedical interventions to block HIV transmissions have produced contradictory results and to date it is unclear why. Further elucidation of the molecular basis of mucosal HIV transmission and extensive pharmacokinetic and pharmacodynamic analyses are essential to implementing effective prevention strategies. Animal models are of critical importance to this effort and bone marrow-liver-thymus (BLT) humanized mice have recently emerged as a powerful small animal research platform for in vivo efficacy evaluation of mucosal and parenteral HIV-1 prevention interventions. The availability of this validated system for the pre-clinical evaluation of HIV-1 prevention approaches will accelerate the implementation of the best candidate interventions into clinical trials.

Protection against rectal transmission of an emtricitabine-resistant simian/human immunodeficiency virus SHIV162p3M184V mutant by intermittent prophylaxis with Truvada

Daily preexposure prophylaxis (PrEP) with Truvada (emtricitabine [FTC] and tenofovir disoproxil fumarate [TDF]) is a novel HIV prevention strategy recently found to reduce HIV incidence among men who have sex with men. We used a macaque model of HIV transmission to investigate if Truvada maintains prophylactic efficacy against an FTC-resistant isolate containing the M184V mutation. Five macaques received a dose of Truvada 3 days before exposing them rectally to the simian/human immunodeficiency virus mutant SHIV162p3(M184V), followed by a second dose 2 h after exposure. Five untreated animals were used as controls. Virus exposures were done weekly for up to 14 weeks. Despite the high (>100-fold) level of FTC resistance conferred by M184V, all five treated animals were protected from infection, while the five untreated macaques were infected (P = 0.0008). Our results show that Truvada maintains high prophylactic efficacy against an FTC-resistant isolate. Increased susceptibility to tenofovir due to M184V and other factors, including residual antiviral activity by FTC and/or reduced virus fitness due to M184V, may all have contributed to the observed protection.

Generation and mucosal transmissibility of emtricitabine- and tenofovir-resistant SHIV162P3 mutants in macaques

Transmission of drug-resistant HIV has been widely documented. We generated tenofovir (TFV)- and emtricitabine (FTC)-resistant SHIV162P3 mutants that can be used to investigate the transmission efficiency of drug-resistant viruses and their impact on the efficacy of pre-exposure prophylaxis. Both SHIV162p3(M184V) and SHIV162p3(K65R) replicated in vitro at high titers. Drug resistance profiles were similar to those seen in HIV. Virus infectivity to virion particle ratios were 4- and 10-fold lower in SHIV162p3(M184V) and SHIV162p3(K65R), compared to a concurrently generated WT SHIV162p3, respectively. Mucosal transmissibility studies using a repeat low-dose macaque model of rectal and vaginal transmission showed that both mutants were able to efficiently infect macaques only after the dose was increased to adjust for fitness reductions due to K65R and M184V. Our results in limited number of macaques suggest that the reduction in fitness due to M184V and K65R decreases virus transmissibility, and identify in vitro infectivity parameters that associate with mucosal transmissibility.

Preexposure chemoprophylaxis for HIV prevention in men who have sex with men

BACKGROUND

Antiretroviral chemoprophylaxis before exposure is a promising approach for the prevention of human immunodeficiency virus (HIV) acquisition.

METHODS

We randomly assigned 2499 HIV-seronegative men or transgender women who have sex with men to receive a combination of two oral antiretroviral drugs, emtricitabine and tenofovir disoproxil fumarate (FTC-TDF), or placebo once daily. All subjects received HIV testing, risk-reduction counseling, condoms, and management of sexually transmitted infections.

RESULTS

The study subjects were followed for 3324 person-years (median, 1.2 years; maximum, 2.8 years). Of these subjects, 10 were found to have been infected with HIV at enrollment, and 100 became infected during follow-up (36 in the FTC-TDF group and 64 in the placebo group), indicating a 44% reduction in the incidence of HIV (95% confidence interval, 15 to 63; P=0.005). In the FTC-TDF group, the study drug was detected in 22 of 43 of seronegative subjects (51%) and in 3 of 34 HIV-infected subjects (9%) (P<0.001). Nausea was reported more frequently during the first 4 weeks in the FTC-TDF group than in the placebo group (P<0.001). The two groups had similar rates of serious adverse events (P=0.57).

CONCLUSIONS

Oral FTC-TDF provided protection against the acquisition of HIV infection among the subjects. Detectable blood levels strongly correlated with the prophylactic effect. (Funded by the National Institutes of Health and the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT00458393.).

Antiretroviral therapy as HIV prevention: status and prospects

As antiretroviral treatment of HIV infection has become increasingly accessible, attention has focused on whether these drugs can used for prevention because of increased tolerability of newer medications, decreased cost, and the limitations of other approaches. We review the status of antiretroviral HIV prevention, including chemoprophylaxis, as well as the effects of treatment of infected individuals on prevention. It is possible that the life-saving agents that have transformed the natural history of AIDS can be a critical component of HIV prevention efforts, but their ultimate role in affecting HIV transmission dynamics remains to be defined.

Preexposure prophylaxis and predicted condom use among high-risk men who have sex with men

OBJECTIVES

Preexposure prophylaxis (PREP) is an emerging HIV prevention strategy; however, many fear it may lead to neglect of traditional risk reduction practices through behavioral disinhibition or risk compensation.

METHODS

Participants were 180 HIV-negative high-risk men who have sex with men recruited in New York City, who completed an Audio Computer Assisted Self Interview-administered survey between September 2007 and July 2009. Bivariate and multivariate logistic regression models were used to predict intention to use PREP and perceptions that PREP would decrease condom use.

RESULTS

Almost 70% (n = 124) of participants reported that they would be likely to use PREP if it were at least 80% effective in preventing HIV. Of those who would use PREP, over 35% reported that they would be likely to decrease condom use while on PREP. In multivariate analyses, arousal/pleasure barriers to condom use significantly predicted likelihood of PREP use (odds ratio = 1.71, P < 0.05) and risk perception motivations for condom use significantly predicted decreased condom use on PREP (odds ratio = 2.48, P < 0.05).

DISCUSSION

These data provide support for both behavioral disinhibition and risk compensation models and underscore the importance of developing behavioral interventions to accompany any wide-scale provision of PREP to high-risk populations.

Antiretroviral agents used by HIV-uninfected persons for prevention: pre- and postexposure prophylaxis

Prophylactic use of antimicrobial agents and microbicides has been proven for many infections, including surgical, gastrointestinal, upper respiratory, and meningococcal infections. Antiretroviral therapy for pregnant women prevents mother-to-child transmission of human immunodeficiency virus (HIV), which has become rare in settings where access to therapy is widespread. Postexposure prophylaxis after needlestick injury or significant sexual exposure is recommended on the basis of animal studies and case-control observational studies, although use of these interventions is limited to those who recognize exposure, have access, and have the power to use the interventions. Clinical trials are evaluating whether regular or preexposure use of antiretroviral therapy provides additional protection for persons at high risk of infection who are also offered standard prevention care, including HIV testing, counseling, condoms, and management of sexually transmitted infections. Trials are evaluating topical or oral use. Concerns have arisen with regard to optimal dosing strategies, costs, access, drug resistance, risk behavior, and the role of communities. Future implementation, if warranted, will be guided by the results of clinical trials in progress and engagement of communities exposed to HIV.

Systemic administration of antiretrovirals prior to exposure prevents rectal and intravenous HIV-1 transmission in humanized BLT mice

Successful antiretroviral pre-exposure prophylaxis (PrEP) for mucosal and intravenous HIV-1 transmission could reduce new infections among targeted high-risk populations including discordant couples, injection drug users, high-risk women and men who have sex with men. Targeted antiretroviral PrEP could be particularly effective at slowing the spread of HIV-1 if a single antiretroviral combination were found to be broadly protective across multiple routes of transmission. Therefore, we designed our in vivo preclinical study to systematically investigate whether rectal and intravenous HIV-1 transmission can be blocked by antiretrovirals administered systemically prior to HIV-1 exposure. We performed these studies using a highly relevant in vivo model of mucosal HIV-1 transmission, humanized Bone marrow/Liver/Thymus mice (BLT). BLT mice are susceptible to HIV-1 infection via three major physiological routes of viral transmission: vaginal, rectal and intravenous. Our results show that BLT mice given systemic antiretroviral PrEP are efficiently protected from HIV-1 infection regardless of the route of exposure. Specifically, systemic antiretroviral PrEP with emtricitabine and tenofovir disoproxil fumarate prevented both rectal (Chi square = 8.6, df = 1, p = 0.003) and intravenous (Chi square = 13, df = 1, p = 0.0003) HIV-1 transmission. Our results indicate that antiretroviral PrEP has the potential to be broadly effective at preventing new rectal or intravenous HIV transmissions in targeted high risk individuals. These in vivo preclinical findings provide strong experimental evidence supporting the potential clinical implementation of antiretroviral based pre-exposure prophylactic measures to prevent the spread of HIV/AIDS.

Resistance and viral subtypes: how important are the differences and why do they occur?

PURPOSE OF REVIEW

The global HIV-1 pandemic has evolved to include 11 subtypes and 34 circulating recombinant forms. Our knowledge of HIV-1 response to antiretroviral drugs and emergent drug resistance has, however, been limited to subtype B infections circulating in Europe and North America, with little comparative information on non-B subtypes representing approximately 90% of worldwide epidemics. This review summarizes publications in the past year that highlight intersubtype differences influencing viral susceptibility to antiretroviral drugs and emergent drug resistance.

RECENT FINDINGS

Cumulative findings from clinical studies suggest that antiretroviral therapy will be of benefit in the overall treatment of non-B subtype infections, and result in drug-resistance profiles comparable to those observed for subtype B infections. Nevertheless, the 10-15% sequence diversity in the Pol region contributes to intersubtype differences in response to particular nucleoside and non-nucleoside analogues, as well as protease inhibitors. Distinct signature mutations and mutational pathways are identified for specific non-B subtypes. The implications of subtype on clinical outcome and interpretative algorithms are described.

SUMMARY

Understanding intersubtype differences in drug resistance is important in optimizing treatment strategies in resource-poor settings. Hopefully, this may assist in the design of prophylactic approaches to prevent HIV-1 horizontal and vertical HIV-1 transmission.

HIV preexposure prophylaxis in the United States: impact on lifetime infection risk, clinical outcomes, and cost-effectiveness

BACKGROUND

The combination of tenofovir and emtricitabine shows promise as HIV preexposure prophylaxis (PrEP). We sought to forecast clinical, epidemiologic, and economic outcomes of PrEP, taking into account uncertainties regarding efficacy, the risks of developing drug resistance and toxicity, behavioral disinhibition, and drug costs.

METHODS

We adapted a computer simulation of HIV acquisition, detection, and care to model PrEP among men who have sex with men and are at high risk of HIV infection (i.e., 1.6% mean annual incidence of HIV infection) in the United States. Base-case assumptions included 50% PrEP efficacy and monthly tenofovir-emtricitabine costs of $753. We used sensitivity analyses to examine the stability of results and to identify critical input parameters.

RESULTS

In a cohort with a mean age of 34 years, PrEP reduced lifetime HIV infection risk from 44% to 25% and increased mean life expectancy from 39.9 to 40.7 years (21.7 to 22.2 discounted quality-adjusted life-years). Discounted mean lifetime treatment costs increased from $81,100 to $232,700 per person, indicating an incremental cost-effectiveness ratio of $298,000 per quality-adjusted life-year gained. Markedly larger reductions in lifetime infection risk (from 44% to 6%) were observed with the assumption of greater (90%) PrEP efficacy. More-favorable incremental cost-effectiveness ratios were obtained by targeting younger populations with a higher incidence of infection and by improvements in the efficacy and cost of PrEP.

CONCLUSIONS

PrEP could substantially reduce the incidence of HIV transmission in populations at high risk of HIV infection in the United States. Although it is unlikely to confer sufficient benefits to justify the current costs of tenofovir-emtricitabine, price reductions and/or increases in efficacy could make PrEP a cost-effective option in younger populations or populations at higher risk of infection. Given recent disappointments in HIV infection prevention and vaccine development, additional study of PrEP-based HIV prevention is warranted.

A macaque model of HIV-1 infection

The lack of a primate model that utilizes HIV-1 as the challenge virus is an impediment to AIDS research; existing models generally employ simian viruses that are divergent from HIV-1, reducing their usefulness in preclinical investigations. Based on an understanding of species-specific variation in primate TRIM5 and APOBEC3 antiretroviral genes, we constructed simian-tropic (st)HIV-1 strains that differ from HIV-1 only in the vif gene. We demonstrate that such minimally modified stHIV-1 strains are capable of high levels of replication in vitro in pig-tailed macaque (Macaca nemestrina) lymphocytes. Importantly, infection of pig-tailed macaques with stHIV-1 results in acute viremia, approaching the levels observed in HIV-1-infected humans, and an ensuing persistent infection for several months. stHIV-1 replication was controlled thereafter, at least in part, by CD8+ T cells. We demonstrate the potential utility of this HIV-1-based animal model in a chemoprophylaxis experiment, by showing that a commonly used HIV-1 therapeutic regimen can provide apparently sterilizing protection from infection following a rigorous high-dose stHIV-1 challenge.

Antiretroviral pre-exposure prophylaxis (PrEP) for preventing HIV in high-risk individuals

BACKGROUND

Twenty-five years into the global HIV/AIDS epidemic, infection rates remain alarmingly high, with over 4 million people becoming infected every year. There is a need for HIV prevention strategies that are more effective. Oral antiretroviral pre-exposure prophylaxis (PrEP) in high-risk individuals may be a reliable tool in preventing the transmission of HIV.

OBJECTIVES

To evaluate the risk reduction and side effects of antiretroviral chemoprophylaxis in preventing HIV infection in high-risk individuals

SEARCH STRATEGY

We conducted electronic searches of MEDLINE (1980 through June 2008); the Cochrane Central Register of Controlled Trials (March 2008); EMBASE (June 2008); and AIDSearch (June 2008). We also searched the WHO International Clinical Trials Registry Platform in June 2008 for ongoing or prospective trials.

SELECTION CRITERIA

Randomized controlled trials that evaluated the effects of any antiretroviral agent in preventing HIV infection in high-risk individuals

DATA COLLECTION AND ANALYSIS

Data concerning outcomes, details of the interventions, and other study characteristics were extracted by two independent authors using a standardized data extraction form. The information gathered from each included trial were location of the trial, date, publication status, demographics of participants (e.g. age, gender, risk behaviour), exposure modality, type of antiretroviral drug used, duration of drug use, and outcomes. Relative risk with a 95% confidence interval (CI) was used as the measure of effect. Only one trial met our inclusion criteria, so we did not perform a meta-analysis.

MAIN RESULTS

One randomised controlled trial met the criteria for the review, although it was not completed as planned. The trial did not have the statistical power to answer questions about the efficacy of antiretroviral PrEP for HIV prevention in the assessed risk group.

AUTHORS' CONCLUSIONS

Presently there is no reliable evidence to support the use of any antiretroviral agent for HIV chemoprophylaxis.The value of chemoprophylaxis for HIV prevention cannot be assessed on the basis of the included trial. The result was not statistically significant and, moreover, the trial was not completed as planned; therefore, the use of antiretroviral agents for HIV chemoprophylaxis cannot be recommended at present. To assess the value of antiretroviral agents for HIV chemoprophylaxis, we advocate well-conducted trials with the statistical power to answer questions about PrEP efficacy and safety in various populations and risk groups. These trials also should evaluate other important issues of concern, such as drug safety, adherence, drug resistance, and the effect of PrEP on risk behaviour.

Partnering for Care in HIV Prevention Trials

QUALITATIVE CASE STUDIES WERE conducted at seven international sites conducting HIV prevention research in Africa, Asia, and the Americas to identify strategies for ensuring that health needs of research participants identified in the course of research are adequately addressed. Key factors were identified that contribute to the balance between direct care and healthcare referrals at a research site, as well as the overall quality of the healthcare made available to research participants. The case studies exemplify the concept of "moral negotiation" in research (Weijer & LeBlanc, 2006), that is, a process where researchers and sponsors negotiate with increasingly empowered local communities and host countries to achieve meaningful and substantive benefits from biomedical research for all stakeholders.

Modeling the impact of HIV chemoprophylaxis strategies among men who have sex with men in the United States: HIV infections prevented and cost-effectiveness

BACKGROUND AND OBJECTIVE

HIV chemoprophylaxis may be a future prevention strategy to help control the global epidemic of HIV/AIDS. Safety and efficacy trials of two agents are currently underway. We assess the expected number of HIV cases prevented and cost-effectiveness of a hypothetical HIV chemoprophylaxis program among men who have sex with men in a large US city.

DESIGN AND METHODS

We developed a stochastic compartmental mathematical model using HIV/AIDS surveillance data to simulate the HIV epidemic and the impact of a 5-year chemoprophylaxis program under varying assumptions for epidemiological, behavioral, programmatic and cost parameters. We estimated program effectiveness and costs from the perspective of the US healthcare system compared with current HIV prevention practices. The main outcome measures were number of HIV infections prevented and incremental cost per quality-adjusted life-years saved.

RESULTS

A chemoprophylaxis program targeting 25% of high-risk men who have sex with men in New York City could prevent 780 (4%) to 4510 (23%) of the 19 510 HIV infections predicted to occur among all men who have sex with men in New York City in 5 years. More than half of prevented infections would be among those not taking chemoprophylaxis but who benefit from reduced HIV prevalence in the community. Under base-case assumptions, incremental cost was US$ 31 970 per quality-adjusted life-years saved. The program was cost-effective under most variations in efficacy, mechanism of protection and adherence.

CONCLUSION

HIV chemoprophylaxis among high-risk men who have sex with men in a major US city could prevent a significant number of HIV infections and be cost-effective.

The impact of pre-exposure prophylaxis (PrEP) on HIV epidemics in Africa and India: a simulation study

BACKGROUND

Pre-exposure prophylaxis (PrEP) is a promising new HIV prevention method, especially for women. An urgent demand for implementation of PrEP is expected at the moment efficacy has been demonstrated in clinical trials. We explored the long-term impact of PrEP on HIV transmission in different HIV epidemics.

METHODOLOGY/PRINCIPAL FINDINGS

We used a mathematical model that distinguishes the general population, sex workers and their clients. PrEP scenarios varying in effectiveness, coverage and target group were modeled in the epidemiological settings of Botswana, Nyanza Province in Kenya, and Southern India. We also studied the effect of condom addition or condom substitution during PrEP use. Main outcome was number of HIV infections averted over ten years of PrEP use. PrEP strategies with high effectiveness and high coverage can have a substantial impact in African settings. In Southern India, by contrast, the number of averted HIV infections in different PrEP scenarios would be much lower. The impact of PrEP may be strongly diminished or even reversed by behavioral disinhibition, especially in scenarios with low coverage and low effectiveness. However, additional condom use during low coverage and low effective PrEP doubled the amount of averted HIV infections.

CONCLUSIONS/SIGNIFICANCE

The public health impact of PrEP can be substantial. However, this impact may be diminished, or even reversed, by changes in risk behavior. Implementation of PrEP strategies should therefore come on top of current condom campaigns, not as a substitution.

The spread, treatment, and prevention of HIV-1: evolution of a global pandemic

The most up-to-date estimates demonstrate very heterogeneous spread of HIV-1, and more than 30 million people are now living with HIV-1 infection, most of them in sub-Saharan Africa. The efficiency of transmission of HIV-1 depends primarily on the concentration of the virus in the infectious host. Although treatment with antiviral agents has proven a very effective way to improve the health and survival of infected individuals, as we discuss here, the epidemic will continue to grow unless greatly improved prevention strategies can be developed and implemented. No prophylactic vaccine is on the horizon. However, several behavioral and structural strategies have made a difference--male circumcision provides substantial protection from sexually transmitted diseases, including HIV-1, and the application of antiretroviral agents for prevention holds great promise.

Antiretroviral therapy for prevention of HIV infection: new clues from an animal model

The authors discuss the implications of a new study in macaques of antiretroviral pre-exposure prophylaxis regimens.

Prevention of rectal SHIV transmission in macaques by daily or intermittent prophylaxis with emtricitabine and tenofovir

BACKGROUND

In the absence of an effective vaccine, HIV continues to spread globally, emphasizing the need for novel strategies to limit its transmission. Pre-exposure prophylaxis (PrEP) with antiretroviral drugs could prove to be an effective intervention strategy if highly efficacious and cost-effective PrEP modalities are identified. We evaluated daily and intermittent PrEP regimens of increasing antiviral activity in a macaque model that closely resembles human transmission.

METHODS AND FINDINGS

We used a repeat-exposure macaque model with 14 weekly rectal virus challenges. Three drug treatments were given once daily, each to a different group of six rhesus macaques. Group 1 was treated subcutaneously with a human-equivalent dose of emtricitabine (FTC), group 2 received orally the human-equivalent dosing of both FTC and tenofovir-disoproxil fumarate (TDF), and group 3 received subcutaneously a similar dosing of FTC and a higher dose of tenofovir. A fourth group of six rhesus macaques (group 4) received intermittently a PrEP regimen similar to group 3 only 2 h before and 24 h after each weekly virus challenge. Results were compared to 18 control macaques that did not receive any drug treatment. The risk of infection in macaques treated in groups 1 and 2 was 3.8- and 7.8-fold lower than in untreated macaques (p = 0.02 and p = 0.008, respectively). All six macaques in group 3 were protected. Breakthrough infections had blunted acute viremias; drug resistance was seen in two of six animals. All six animals in group 4 that received intermittent PrEP were protected.

CONCLUSIONS

This model suggests that single drugs for daily PrEP can be protective but a combination of antiretroviral drugs may be required to increase the level of protection. Short but potent intermittent PrEP can provide protection comparable to that of daily PrEP in this SHIV/macaque model. These findings support PrEP trials for HIV prevention in humans and identify promising PrEP modalities.

Antiretroviral pre-exposure prophylaxis prevents vaginal transmission of HIV-1 in humanized BLT mice

BACKGROUND

Worldwide, vaginal transmission now accounts for more than half of newly acquired HIV-1 infections. Despite the urgency to develop and implement novel approaches capable of preventing HIV transmission, this process has been hindered by the lack of adequate small animal models for preclinical efficacy and safety testing. Given the importance of this route of transmission, we investigated the susceptibility of humanized mice to intravaginal HIV-1 infection.

METHODS AND FINDINGS

We show that the female reproductive tract of humanized bone marrow-liver-thymus (BLT) mice is reconstituted with human CD4+ T and other relevant human cells, rendering these humanized mice susceptible to intravaginal infection by HIV-1. Effects of HIV-1 infection include CD4+ T cell depletion in gut-associated lymphoid tissue (GALT) that closely mimics what is observed in HIV-1-infected humans. We also show that pre-exposure prophylaxis with antiretroviral drugs is a highly effective method for preventing vaginal HIV-1 transmission. Whereas 88% (7/8) of BLT mice inoculated vaginally with HIV-1 became infected, none of the animals (0/5) given pre-exposure prophylaxis of emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF) showed evidence of infection (Chi square = 7.5, df = 1, p = 0.006).

CONCLUSIONS

The fact that humanized BLT mice are susceptible to intravaginal infection makes this system an excellent candidate for preclinical evaluation of both microbicides and pre-exposure prophylactic regimens. The utility of humanized mice to study intravaginal HIV-1 transmission is particularly highlighted by the demonstration that pre-exposure prophylaxis can prevent intravaginal HIV-1 transmission in the BLT mouse model.

Can the new humanized mouse model give HIV research a boost

The "BLT mouse" holds promise for the preclinical evaluation of microbicides and antiretroviral prophylaxis regimens.

A history of AIDS: looking back to see ahead

Since breaking onto the scene 26 years ago, HIV has proven an indefatigable foe. Over 60 million people have been infected with this retrovirus, and 25 million have already died of AIDS. HIV infection is hitting the hardest in the developing world 1. Tragically, 1600 babies continue to acquire HIV every day from their infected mothers. Over 12 million children have also been orphaned by AIDS, and this number will likely double by 2010. With these sobering statistics as a backdrop, this feature traces the history of the devastating HIV/AIDS pandemic and offers a view for what the future may hold.

Pregnancy prevention practices among women with multiple partners in an HIV prevention trial

BACKGROUND

Women enrolled in microbicide and pre-exposure prophylaxis (PrEP) HIV prevention trials are not allowed to continue use of study products when pregnant because of fetal safety concerns. High pregnancy rates among women in trials can undermine statistical measures of safety and effectiveness.

METHODS

Women enrolled in a PrEP trial in Ghana, Nigeria, and Cameroon had an overall pregnancy rate of 52 per 100 person-years of observation. In-depth interviews were conducted with 67 women who were asked to describe any changes made in their pregnancy prevention practices after enrolling in the trial.

RESULTS

Most women (n = 44, 65%) reported changing pregnancy prevention practices after enrolling in the trial. Twice as many reported using condoms for pregnancy prevention after enrollment (n = 56, 84%) than before (n = 27, 40%). Cluster analysis identified site-specific patterns. Nigerian women tended to report using condoms for dual protection before and after trial enrollment. Cameroonian women tended to rely on natural methods before and after trial enrollment. Ghanaian women tended to switch from hormonal methods to condoms.

CONCLUSIONS

The role of condoms in HIV prevention trials must not be diminished. Their use-effectiveness for contraception is likely too low for microbicide and PrEP trial needs, however. HIV prevention trials with women should be appropriately staffed to provide effective contraceptive counseling and, if needed, direct provision of contraceptives. This must be done without undermining women's reproductive rights.

Potential impact of antiretroviral chemoprophylaxis on HIV-1 transmission in resource-limited settings

Background

The potential impact of pre-exposure chemoprophylaxis (PrEP) on heterosexual transmission of HIV-1 infection in resource-limited settings is uncertain.

Methodology/Principle Findings

A deterministic mathematical model was used to simulate the effects of antiretroviral PrEP on an HIV-1 epidemic in sub-Saharan Africa under different scenarios (optimistic, neutral and pessimistic) both with and without sexual disinhibition. Sensitivity analyses were used to evaluate the effect of uncertainty in input parameters on model output and included calculation of partial rank correlations and standardized rank regressions. In the scenario without sexual disinhibition after PrEP initiation, key parameters influencing infections prevented were effectiveness of PrEP (partial rank correlation coefficient (PRCC) = 0.94), PrEP discontinuation rate (PRCC = −0.94), level of coverage (PRCC = 0.92), and time to achieve target coverage (PRCC = −0.82). In the scenario with sexual disinhibition, PrEP effectiveness and the extent of sexual disinhibition had the greatest impact on prevention. An optimistic scenario of PrEP with 90% effectiveness and 75% coverage of the general population predicted a 74% decline in cumulative HIV-1 infections after 10 years, and a 28.8% decline with PrEP targeted to the highest risk groups (16% of the population). Even with a 100% increase in at-risk behavior from sexual disinhibition, a beneficial effect (23.4%–62.7% decrease in infections) was seen with 90% effective PrEP across a broad range of coverage (25%–75%). Similar disinhibition led to a rise in infections with lower effectiveness of PrEP (≤50%).

Conclusions/Significance

Mathematical modeling supports the potential public health benefit of PrEP. Approximately 2.7 to 3.2 million new HIV-1 infections could be averted in southern sub-Saharan Africa over 10 years by targeting PrEP (having 90% effectiveness) to those at highest behavioral risk and by preventing sexual disinhibition. This benefit could be lost, however, by sexual disinhibition and by high PrEP discontinuation, especially with lower PrEP effectiveness (≤50%).

Practice brief: adolescents and HIV clinical trials: ethics, culture, and context

One quarter of HIV infections globally occur among young people 15 to 24 years of age, and more than half of all new infections are in people younger than 25 years. Clearly, there is a need to identify and implement effective HIV prevention strategies among at-risk teens. Some of the most effective options for slowing the epidemic are biomedical, and several promising methods are in development, including microbicides, vaccines, and preexposure prophylaxis (PREP, or the daily use of antiretrovirals to prevent the acquisition of HIV). There is widespread reluctance to enroll minors in such biomedical prevention trials because of concerns about vulnerability related to physical maturity, experiential maturity, and diminished autonomy as well as legal and social challenges that vary across and within nations. However, excluding minors from trials misses an important opportunity to evaluate the effectiveness, acceptability, and safety of innovative interventions under the best conditions for identifying and resolving potential problems. The challenges of including minors in HIV prevention trials are highlighted through the example of one rural South African community that has been particularly devastated by the HIV epidemic.

Ethical issues in the NIMH Collaborative HIV/STD Prevention Trial

OBJECTIVE

To develop decision rules regarding key ethical dimensions in scientific protocols for the National Institute for Mental Health (NIMH) Collaborative HIV/STD Prevention Trial taking place in five countries (China, India, Peru, Russia, and Zimbabwe).

DESIGN

Countries had HIV rates from 27 to 0.1%, the standard of care varied from access to antiretroviral drugs to no availability, and the reporting of sexually transmitted diseases (STD) to government agencies was mandatory in some countries and not in others. These variations presented challenges when developing decision rules that could be uniformly adopted across countries and simultaneously follow the ethical principles of beneficence, respect, and justice.

METHODS

We used several strategies to identify and resolve ethical dilemmas for this international HIV prevention trial. First, we identified key principles, especially those derived for clinical therapeutic, biomedical preventive, or device trials. We convened a 'workgroup on protecting human participants' and charged them with identifying and implementing optimal procedures for ensuring the ethical and equitable treatment of participants and making recommendations to minimize physical, psychological, and social harm to the participants. Each site had a community advisory board, essential in identifying local ethical issues and possible resolutions to them. The NIMH established a data safety and monitoring board with ultimate responsibility for adjudicating ethical dilemmas and decisions. The protocols were deliberated thoroughly by the Trial steering committee, and approved by nine United States and five in-country institutional review boards.

RESULTS

We summarize the decision rules adopted to resolve the ethical dilemmas identified. Especially important were the translation of clinical trials principles for a behavioral intervention trial, strategies for ensuring confidentiality and informed consent, dilemmas relating to partner notification of sexually transmitted infections including HIV, minimizing the risks of social harm, establishing community partnerships, ensuring equity among United States and in-country principal investigators, and building capacity for additional research.

CONCLUSION

We document our processes and decisions, and their underlying rationales, and hope they contribute to the development of further thinking and practice regarding the ethics of social and behavioral HIV and STD prevention trials in resource-poor settings.

HIV-1 subtype C viruses rapidly develop K65R resistance to tenofovir in cell culture

BACKGROUND

Genotypic diversity among HIV-1 subtypes and circulating recombinant forms (CRF) may lead to distinct pathways to drug resistance. This study evaluated subtype-related differences in the development of resistance in culture to tenofovir.

METHODS

Genotyping determined nucleotide diversity among subtypes. Representative subtype B, C, CRF1_AE, CRF2_AG, G, and HIV-2 isolates were selected for resistance to tenofovir, lamivudine and didanosine in cell culture. Phenotypic assays determined the effects of the K65R substitution in reverse transcriptase (RT) on drug susceptibility.

RESULTS

Subtype C isolates show unique polymorphisms in RT codons 64 (AAG-->AAA), 65 (AAA-->AAG), and 66 (AAA-->AAG), absent in other subtypes. The K65R mutation (AAG-->AGG) arose with tenofovir by week 12 in four subtype C selections. In contrast, no tenofovir resistance arose in four subtype B (> 34-74 weeks), one each of CRF2_AG and G (> 30-33 weeks), and three HIV-2 (> 27-28 weeks) selections. K65R appeared after 55 and 73 weeks in two CRF1_AE selections with tenofovir. In contrast, times to the appearance of M184V with lamivudine pressure (weeks 8-14) did not vary among subtypes. Selective didanosine pressure resulted in the appearance of M184V and L74V after 38 weeks in two of four subtype C selections. The K65R transitions in subtype C and other subtypes (AGG and AGA) conferred similar 6.5-10-fold resistance to tenofovir and five to 25-fold cross-resistance to each of abacavir, lamivudine, and didanosine, while not affecting zidovudine susceptibility.

CONCLUSION

Tenofovir -based regimens will need to be carefully monitored in subtype C infections for the possible selection of K65R.

Microbicides and other topical strategies to prevent vaginal transmission of HIV

The HIV epidemic is, by many criteria, the worst outbreak of infectious disease in history. The rate of new infections is now approximately 5 million per year, mainly in the developing world, and is increasing. Women are now substantially more at risk of infection with HIV than men. With no cure or effective vaccine in sight, a huge effort is required to develop topical agents (often called microbicides) that, applied to the vaginal mucosa, would prevent infection of these high-risk individuals. We discuss the targets for topical agents that have been identified by studies of the biology of HIV infection and provide an overview of the progress towards the development of a usable agent.

Enrolling women into HIV preventive vaccine trials: an ethical imperative but a logistical challenge

Mills and colleagues argue that the challenge of enrolling women into HIV vaccine trials must be overcome in order for trials to be considered ethical, valid, and generalizable.