Preventing sexual transmission of HIV

Ex Vivo HIV Infection Model of Cervico-Vaginal and Rectal Tissue

Globally, the most frequent route of HIV transmission is through sexual intercourse. In women, sexual transmission of HIV involves cervical, vaginal, endometrial, and rectal mucosal exposure to the virus. Here we describe technical protocols for ex vivo cervical, vaginal, and rectal tissue infection models and cultures that can be used to assess tissue susceptibility to infection under different conditions as well as the potential antiviral efficacy of a treatment for HIV prevention or cure.

The First 40 Years of AIDS: Promising Programs, Limited Success

HIV-prevention program planning, implementation, and evaluation began in the United States shortly after reports of a mysterious, apparently acquired, immune deficiency syndrome appeared in summer 1981. In San Francisco, New York City, and elsewhere, members of LGBT communities responded by providing accurate information, giving support, and raising money. During the first decade of the AIDS pandemic (1981-1990), social and behavioral scientists contributed by designing theory-based and practical interventions, combining interventions into programs, and measuring impact on behavior change and HIV incidence. In the second decade (1991-2000), federal, state, and local agencies and organizations played a more prominent role in establishing policies and procedures, funding research and programs, and determining the direction of intervention efforts. In the third decade (2001-2010), biomedical interventions were prioritized over behavioral interventions and have dominated attempts in the fourth decade (2011-2020) to integrate biomedical, behavioral, and structural interventions into coherent, efficient, and cost-effective programs to end AIDS.

Cytokine Network and Sexual Human Immunodeficiency Virus Transmission in Men Who Have Sex With Men

BACKGROUND

Seminal human immunodeficiency virus (HIV) transmission from men to their partners remains the main driver of HIV epidemics worldwide. Semen is not merely a carrier of the virus, but also provides an immunological milieu that affects HIV transmission.

METHODS

We collected blood and semen from people with HIV whose epidemiologically linked sexual partners either did or did not acquire HIV. Viral transmission was confirmed by phylogenetic linkage (HIV pol). We measured the concentration of 34 cytokines/chemokines by Luminex in the blood and semen of 21 source partners who transmitted HIV (transmitters) and 22 who did not transmit HIV (nontransmitters) to their sexual partners. Differences between cytokine profiles in transmitters versus nontransmitters were analyzed using the multivariate statistical technique of partial least square discriminant analysis.

RESULTS

The cytokine profile in seminal fluid, but not in peripheral blood, was significantly different between men who have sex with men (MSM) who transmitted HIV and those who did not transmit HIV to their sexual partners (E = 19.77; P < .01). This difference persisted after excluding people with undetectable HIV RNA levels in nontransmitters.

CONCLUSIONS

Seminal cytokine profiles correlated with transmission or nontransmission of HIV from the infected MSM to their partners, independently from seminal viral load. Seminal cytokine spectra might be a contributing determinant of sexual HIV transmission, thus providing new directions for the development of strategies aimed at preventing HIV transmission.

Mucosa: Key Interactions Determining Sexual Transmission of the HIV Infection

In the context of HIV sexual transmission at the genital mucosa, initial interactions between the virus and the mucosal immunity determine the outcome of the exposure. Hence, these interactions have been deeply explored in attempts to undercover potential targets for developing preventative strategies. The knowledge gained has led to propose a hypothetical model for mucosal HIV transmission. Subsequent research studies on this topic further revealed new mechanisms and identified new host-HIV interactions. This review aims at integrating these findings to inform better and update the current model of HIV transmission. At the earliest stage of virus exposure, the epithelial integrity and the presence of antiviral factors are critical in preventing viral entry to the submucosa. However, the virus has been shown to enter to the submucosa in the presence of physical abrasion or via epithelial transmigration using paracellular passage or transcytosis mechanisms. The efficiency of these processes is greater with cell-associated viral inoculums and can be influenced by the presence of viral and immune factors, and by the structure of the exposed epithelium. Once the virus reaches the submucosa, dendritic cells and fibroblasts, as recently described, have been shown in vitro of being capable of facilitating the transfer of viral particles to susceptible cells, leading to viral dissemination, most likely in a trans-infection manner. The presence of activated CD4⁺ T cells in submucosa increases the probability of infection, where the predominant microbiota could be implicated through the modulation of an inflammatory microenvironment. Other factors such as genital fluids and hormones could also play an essential role in HIV transmission. Here, we review the most recent evidence described for mucosal HIV-transmission contributing with the understanding of this phenomenon.

An SIR pairwise epidemic model with infection age and demography

The demography and infection age play an important role in the spread of slowly progressive diseases. To investigate their effects on the disease spreading, we propose a pairwise epidemic model with infection age and demography on dynamic networks. The basic reproduction number of this model is derived. It is proved that there is a disease-free equilibrium which is globally asymptotically stable if the basic reproduction number is less that unity. Besides, sensitivity analysis is performed and shows that increasing the variance in recovery time and decreasing the variance in infection time can effectively control the diseases. The complex interaction between the death rate and equilibrium prevalence suggests that it is imperative to correctly estimate the parameters of demography in order to assess the disease transmission dynamics accurately. Moreover, numerical simulations show that the endemic equilibrium is globally asymptotically stable.

Condom Use and its Associated Factors Among Iranian Youth: Results From a Population-Based Study

Background: Given the young structure of Iran’s population and the fact that extramarital sexual relationships are both prohibited by legislation and shunned by society and religion, examining condom use practices among Iranian youth is highly important. The aim of this study was to explore condom use and its correlates among Iranian young adults.

Methods: In a sample of 3,045 individuals aged 19-29 who were recruited from a nation-wide study, we analyzed data from 633 participants who reported a history of extramarital sex. Subjects were asked about their condom use practices during their last penetrative sex. Data were collected through a self-administered questionnaire where the respondents completed the survey on their own and passed it to trained gender-matched interviewers. Multivariable regression models were constructed to report adjusted odds ratios (AOR) along with 95% CI.

Results: Of the 633 participants, 222 (35.1%) reported condom use at last sex. Men reported significantly higher condom use than women (38.5% vs. 25.7%). Having a stable job (AOR = 1.86, 95% CI: 1.01, 3.43), higher knowledge of condom use (AOR = 1.57, 95% CI: 1.03, 2.37) and sexual transmission of HIV (AOR = 1.83, 95% CI: 1.18, 2.85) were positively associated with condom use at last sex. Conversely, experience of sex under the influence of substances (AOR = 0.66, 95% CI: 0.45, 0.94) was significantly associated with reduced odds of condom use at last sex.

Conclusion: This study shows that only one out of every three young adults reported using condoms at last sex. While educational programs are helpful, multi-sectoral approaches (eg, individual-, community-, and structural-level interventions) are required to change sexual behaviours towards safe sex practices and reinforce negotiating condom use among youth.

Penile Immune Activation and Risk of HIV Shedding: A Prospective Cohort Study

Background

Genital immune activation is suspected to modulate local human immunodeficiency virus (HIV) RNA levels and the risk of sexual HIV transmission.

Methods

A prospective, observational cohort study of 221 HIV-infected men undergoing male circumcision (MC) was conducted in Rakai, Uganda. Penile lavage samples collected from the coronal sulcus at baseline and 4 weekly visits after MC were assayed for pro-inflammatory cytokines and HIV RNA. The main analysis was limited to 175 men with detectable HIV plasma viral load (VL > 400 copies/mL; n = 808 visits). The primary exposures of interest were individual and total cytokine detection at the previous postoperative visit. Adjusted prevalence risk ratios (adjPRR) of detectable HIV shedding (VL > 40 copies/mL) were estimated by Poisson regression models with generalized estimating equations and robust variance estimators and included adjustment for plasma HIV VL.

Findings

Among men with a detectable plasma VL, penile HIV shedding was detected at 136 visits (16.8%). Detectable interleukin (IL)-1β (adjPRR = 2.14; 95% confidence interval (CI) = 1.02-4.48), IL-6 (adjPRR = 2.24; 95% CI = 1.28-3.90), IL-8 (adjPRR = 2.42; 95% CI = 1.15-5.08), IL-10 (adjPRR = 2.51; 95% CI = 1.67-3.80), and IL-13 (adjPRR = 1.87; 95% CI = 1.15-3.03) were associated with penile HIV shedding at the subsequent visit. Men with 2-4 (adjPRR = 2.36; 95% CI = 1.08-5.14) and 5-7 (adjPRR = 3.00; 95% CI = 1.28-7.01) detectable cytokines had a greater likelihood of detectable penile HIV shedding at the subsequent visit, compared to men with ≤ 1 detectable cytokine. The total number of detectable cytokines was also associated with a higher penile log10 HIV VL at the subsequent visit among HIV shedders.

Interpretation

Pro-inflammatory cytokine production had a dose-dependent and temporal association with penile HIV shedding, suggesting that genital immune activation may increase the risk of sexual HIV transmission by driving local HIV replication.

Recent Insights into the HIV/AIDS Pandemic

Etiology, transmission and protection: Transmission of HIV, the causative agent of AIDS, occurs predominantly through bodily fluids. Factors that significantly alter the risk of HIV transmission include male circumcision, condom use, high viral load, and the presence of other sexually transmitted diseases. Pathology/Symptomatology: HIV infects preferentially CD4+ T lymphocytes, and Monocytes. Because of their central role in regulating the immune response, depletion of CD4+ T cells renders the infected individual incapable of adequately responding to microorganisms otherwise inconsequential. Epidemiology, incidence and prevalence: New HIV infections affect predominantly young heterosexual women and homosexual men. While the mortality rates of AIDS related causes have decreased globally in recent years due to the use of highly active antiretroviral therapy (HAART) treatment, a vaccine remains an elusive goal. Treatment and curability: For those afflicted HIV infection remains a serious illness. Nonetheless, the use of advanced therapeutics have transformed a dire scenario into a chronic condition with near average life spans. When to apply those remedies appears to be as important as the remedies themselves. The high rate of HIV replication and the ability to generate variants are central to the viral survival strategy and major barriers to be overcome. Molecular mechanisms of infection: In this review, we assemble new details on the molecular events from the attachment of the virus, to the assembly and release of the viral progeny. Yet, much remains to be learned as understanding of the molecular mechanisms used in viral replication and the measures engaged in the evasion of immune surveillance will be important to develop effective interventions to address the global HIV pandemic.

HIV-Risk Index: Development and Validation of a Brief Risk Index for Hispanic Young People

The prevalence of HIV risk behaviors among young people facilitates the spread of HIV, in particular regarding unsafe sex behavior, although this trend is different within this population. For this reason, identifying the riskier young population is required to prevent HIV infection. The main purpose of this study was to develop and validate a risk index to assess the different sexual HIV risk exposure among Hispanic Young people. For this purpose, 9861 Spanish young people were randomly distributed into two groups (derivation and validation group). According to the results, the factor analyses grouped the nine items of the HIV- risk index into two factors (factor 1, direct sexual risk indicators and factor 2, indirect sexual risk indicators) with an equal structure for men and women by a multi-group confirmatory factor analysis. The variance explained was 54.26 %. Moreover, the Cronbach's alpha coefficient revealed high internal reliability (α = .79) and the convergent validity supported its evidence based on different HIV risk indexes. Therefore, the HIV-risk index seem to be a rigorous and valid measure to estimate HIV risk exposure among young people.

Retrospective analysis of the prevalence of and factors associated with condom use among young HIV-infected women in Cameroon

Objectives:

Young women are more likely to be infected with HIV globally, in sub-Saharan Africa, and in Cameroon. Despite its clear clinical and public health benefits, condom use among HIV-infected women continues to be low. The objective of this study was to describe the prevalence of inconsistent condom use among HIV-infected women in Cameroon and the factors associated with it.

Methods:

We conducted a cross-sectional study of HIV-infected young women aged 17–26 years from three semi-urban HIV clinics in the Northwest Region of Cameroon. This study was a subgroup analysis of a previously reported study on inconsistent condom use in HIV-infected and -uninfected youth. Inconsistent condom use was defined as reporting “sometimes” or “never” to questions regarding frequency of condom use. Logistic regression modeling was used to determine factors associated with inconsistent condom use.

Results:

A total of 84 participants were recruited and submitted completed questionnaires for analysis. Median age was 24 years (interquartile range = 22–25) and the median age at HIV diagnosis was 21 years (interquartile range = 20–23). Fifty percent of the participants reported no prior schooling or only primary school education. Overall, 61/84 (73%) reported inconsistent condom use. After adjusting for potential confounders, education to the secondary school level was protective against inconsistent condom use (odds ratio = 0.19; confidence interval: 0.04–0.95), and having ≥2 pregnancies was associated with inconsistent condom use (odds ratio = 7.52; confidence interval: 1.67–34.00).

Conclusion:

There is a high prevalence of inconsistent condom use among young HIV-infected women in Cameroon, which appears to be associated with lower levels of educational attainment and higher parity. Further larger studies assessing the factors associated with poor condom use in this population are warranted and may inform public health policy in resource-limited settings with high HIV prevalence.

Tracking the luminal exposure and lymphatic drainage pathways of intravaginal and intrarectal inocula used in nonhuman primate models of HIV transmission

Over 80% of sexual HIV-1 transmissions originate from a single viral variant, but the underlying basis for this transmission bottleneck remains to be elucidated. Nonhuman primate models of mucosal virus transmission allow opportunities to gain insight into the basis of this mucosal bottleneck. We used simulated inocula consisting of either non-infectious vital dye or contrast dye with non-invasive magnetic resonance imaging (MRI) to visualize mucosal exposure and passive lymphatic drainage patterns following vaginal and rectal exposures in Indian origin rhesus macaques. Results revealed a limited overall distance of dye coverage from the anal verge following 1 ml (n = 8) intrarectally administered, which greatly increased with a 3 ml (n = 8) volume. Intravaginal dye exposure using 2 ml revealed complete coverage of the mucosa of the vagina and ectocervix, however dye was not detectable in the endocervix, uterus, fallopian tubes or ovaries in nuliparous sexually mature rhesus macaques (n = 9). In addition, following submucosal and intranodal injections of vital dye or MRI contrast dye in the rectum (n = 9), or distal and proximal vagina (n = 4), the lymphatic drainage pathways were identified as first the internal then common iliac chain followed by para-aortic lymph nodes. Drainage from the distal descending colon (n = 8) was via the para-colonic lymph nodes followed by the inferior mesenteric and para-aortic lymph nodes. Analysis after vaginal challenge with infectious SIVmac239 followed by euthanasia at day 3 revealed a pattern of viral dissemination consistent with the imaging results. These results provide insights into potential patterns of viral dissemination that can help guide efforts to better elucidate the earliest events of virus transmission and potential intervention strategies.

Innate Immunity in Simian Immunodeficiency Virus Infection

The past decade has seen the emergence of innate immunity as a mature field. The study of innate immunity has had a significant impact on the concepts of HIV immunity, pathogenesis, and vaccines. In this chapter, basic concepts of innate immunity at the anatomical, cellular, and molecular levels will be introduced from the perspective of their interplay with HIV and simian immunodeficiency virus (SIV). An emphasis will be placed on studies using SIV/non-human primate (NHP) models that shape current models of HIV pathogenesis. Finally, studies modulating the innate system in vivo in NHPs will be discussed.

Using nonhuman primates to model HIV transmission

PURPOSE OF REVIEW

One of the major obstacles in fully understanding HIV transmission comes from the impracticality of studying transmission in humans. Because of this encumbrance, the early phases of HIV transmission and systemic dissemination are poorly understood. In order to fully comprehend these critical steps in HIV infection, animal models must be devised to accurately reflect HIV's mode of action. This review seeks to highlight the essential nature of modelling HIV transmission in nonhuman primates (NHPs).

RECENT FINDINGS

Recently, it was discovered that HIV infection is established in newly infected recipients by a single or few transmitted/founder variants. This has reshaped how animal modelling is conducted with researchers currently recapitulating a physiologically relevant, low-titre infection. Pertinent animal models have been established for the most common routes of infection, including rectal, vaginal and penile transmission; models for intravenous and oral transmission are still in developmental stages.

SUMMARY

These limited dose models now accurately reflect HIV transmission in humans and provide a realistic experimental platform for vaccine development and other intervention strategies that can be used to inform vaccine development in humans. Using information obtained in NHP and human trials, it is conceivable to envision effective prevention modalities in the near future.

Serodiscordance and disclosure among HIV-positive pregnant women in the Southwestern United States

The prevalence of HIV-positive pregnant women in relationships with HIV-negative men in the United States is unclear. The purpose of this study was to calculate the prevalence of HIV-positive pregnant women with a serodiscordant (HIV-negative) partner within a single clinic population, assess disclosure of their HIV status, and examine factors associated with disclosure. All HIV-positive pregnant women who received prenatal care at the Harris County Hospital District Women's Program at Northwest Health Center in Houston TX between 1/1/2006 and 4/1/2011 were identified. Data were obtained from electronic medical records. Prevalence of serodiscordance and disclosure was calculated, and predictors of disclosure were evaluated. We identified 212 HIV-positive pregnant women. About 40% had a serodiscordant partner, and 34% had a partner with an unknown HIV status. Disclosure occurred in over 90% of women with a serodiscordant partner and in 68% of women with partners whose HIV status was unknown. Among pregnant women who knew their HIV status prior to the current pregnancy and had a serodiscordant partner, 92% reported disclosing their status prior to conception. Our data indicated that serodiscordant relationships are common in our clinic population. Suboptimal disclosure rates were observed, especially among women who have a partner with an unknown HIV status. Further research is needed to evaluate the prevalence of serodiscordance and disclosure in other United States populations.

Women-specific HIV/AIDS services: identifying and defining the components of holistic service delivery for women living with HIV/AIDS

Introduction

The increasing proportion of women living with HIV has evoked calls for tailored services that respond to women's specific needs. The objective of this investigation was to explore the concept of women-specific HIV/AIDS services to identify and define what key elements underlie this approach to care.

Methods

A comprehensive review was conducted using online databases (CSA Social Service Abstracts, OvidSP, Proquest, Psycinfo, PubMed, CINAHL), augmented with a search for grey literature. In total, 84 articles were retrieved and 30 were included for a full review. Of these 30, 15 were specific to HIV/AIDS, 11 for mental health and addictions and four stemmed from other disciplines.

Results and discussion

The review demonstrated the absence of a consensual definition of women-specific HIV/AIDS services in the literature. We distilled this concept into its defining features and 12 additional dimensions (1) creating an atmosphere of safety, respect and acceptance; (2) facilitating communication and interaction among peers; (3) involving women in the planning, delivery and evaluation of services; (4) providing self-determination opportunities; (5) providing tailored programming for women; (6) facilitating meaningful access to care through the provision of social and supportive services; (7) facilitating access to women-specific and culturally sensitive information; (8) considering family as the unit of intervention; (9) providing multidisciplinary integration and coordination of a comprehensive array of services; (10) meeting women “where they are”; (11) providing gender-, culture- and HIV-sensitive training to health and social care providers; and (12) conducting gendered HIV/AIDS research.

Conclusions

This review highlights that the concept of women-specific HIV/AIDS services is a complex and multidimensional one that has been shaped by diverse theoretical perspectives. Further research is needed to better understand this emerging concept and ultimately assess the effectiveness of women-specific services on HIV-positive women's health outcomes.

Predictors of HIV Sexual Risk Behavior among Men Who Have Sex with Men, Men Who Have Sex with Men and Women, and Transgender Women

Men who have sex with men, men who have sex with men and women, and transgender women are at high risk for HIV infection. This study seeks to clarify which known HIV risk factors (partner type, sex location, serodiscordance, multiple sex partners, substance use during sex) contribute to engagement in high-risk (unprotected receptive anal) sex in each population. Data collected from June 2005 through June 2008 indicate all three populations display different HIV sexual risk profiles. The data suggest that HIV-prevention interventions should be individually tailored to address the specific needs of these three highly vulnerable and impacted populations.

Dilemma of concepts and strategies for the prevention of spread of HIV in relation to human behavior, law and human rights

The new prevalence data regarding the estimated global number of human immunodeficiency virus positive (HIV+) cases, i.e., including people who are either aware or unaware of their HIV infection in 2010, lead many to wonder why the increase in incidence has reached today's unprecedented level and escalated within such a short time. This, in spite of prevention campaigns in countries affected by HIV/acquired immune deficiency syndrome (AIDS) with their urgent messages aimed at preventing HIV transmission by promoting changes in individual's behavior. This article analyzes the background of the prevention strategies, in particular their political, social and legal concepts in terms of human rights, and reveals traits of human behavior not considered thus far. A radical reappraisal is necessary, at social and legislative levels, as well as options additional to current concepts. When ethical issues come up, they become blamed for outmoded moralistic positions. However, ignoring the reality has led to dire consequences from prioritizing individual human rights over society's collective need to prevent the spread of HIV.

Identifying and characterizing recently transmitted viruses

PURPOSE OF REVIEW

Improvements in sequencing approaches and robust mathematical modeling have dramatically increased information on viral genetics during acute infection with HIV and simian immunodeficiency virus, providing unprecedented insight into viral transmission and viral/immune interactions.

RECENT FINDINGS

Overall viral genetic diversity is reduced significantly during mucosal transmission. Remarkably, in the vast majority of sexual transmissions, this diversity is reduced to a single viral variant that establishes the initial productive clinical infection. By identifying and enumerating transmitted/founder viruses, researchers can begin to define the characteristics that are necessary and sufficient for successful viral replication within a new host.

SUMMARY

Acute HIV infection is a critical window of opportunity for vaccine and therapeutic intervention. New sequencing technologies and mathematical modeling of transmission and early evolution have provided a clearer understanding of the number of founder viruses that establish infection, the rapid generation of diversity in these viruses and the subsequent evasion of host immunity. The information gained by identifying transmitted viruses, monitoring the initial host responses to these viruses and then identifying mechanisms of viral escape could provide better strategies for vaccine development, preexposure prophylaxis, microbicides, or other therapeutic interventions.

Weighing the gold in the gold standard: challenges in HIV prevention research

OBJECTIVE(S)

Few HIV prevention interventions have been evaluated in randomized controlled trials (RCTs). We examined design, implementation, and contextual considerations that may limit detection of a positive or adverse effect in HIV prevention trials.

DESIGN

A systematic review of late phase RCTs for prevention of sexual transmission of HIV that randomly allocated intervention and comparison groups; evaluated interventions to prevent sexual transmission in nonpregnant populations; and reported HIV incidence as the primary or secondary outcome.

METHODS

PubMed/MEDLINE, other electronic databases, and electronic conference proceedings of recent HIV/AIDS-related conferences were searched to identify published or unpublished trials meeting the inclusion criteria. Descriptive, methodological, and contextual factors were abstracted from each trial.

RESULTS

The review included 37 HIV prevention RCTs reporting on 39 unique interventions. Only six RCTs, all evaluating biomedical interventions, demonstrated definitive effects on HIV incidence. Five of the six RCTs significantly reduced HIV infection: all three male circumcision trials, one trial of sexually transmitted infection treatment and care, and one vaccine trial. One microbicide trial of nonoxynol-9 gel produced adverse results. Lack of statistical power, poor adherence, and diluted versions of the intervention in comparison groups may have been important issues for the other trials that demonstrated 'flat' results.

CONCLUSION

Almost 90% of HIV prevention trials had 'flat' results, which may be attributable to trial design and/or implementation. The HIV prevention community must not only examine evidence from significant RCTs, but must also examine flat trials and address design and implementation issues that limit detection of an effect.

Gender, sex, and HIV: how well are we addressing the imbalance?

PURPOSE OF REVIEW

Heightened interest in sex and gender differences in HIV warrant a review of the status of current understanding of their determinants and progress in addressing them.

RECENT FINDINGS

The proportion of women among people living with HIV continues to increase in most countries; however, women are proportionately more likely to be on antiretroviral treatment than are men. Inadequate representation of women in clinical trials is compounding the dearth of information on sex-based differences in response to life prolonging antiretroviral medication. Progress in addressing gender inequalities and inequities, though incremental, is too slow to reach Millennium Development Goal 6 of halting and reversing the HIV epidemic by 2015. Structural determinants, such as food insufficiency, poverty, decreased access to credit, and inequitable inheritance practices, continue to act with social gender norms to shape the increased risk of exposure to HIV that women and adolescent girls face in many settings.

SUMMARY

Special measures should be taken to overcome barriers and facilitate enrolment and retention of women in biomedical HIV prevention and treatment trials. Law reform, economic empowerment, gender transformative work, and political mobilization are needed if women and men are to share the power, influence, rights, responsibilities, and opportunities that can create resilience to HIV.

Evolution and molecular epidemiology of subtype C HIV-1 in Zimbabwe

OBJECTIVE

To investigate the origins and evolutionary history of subtype C HIV-1 in Zimbabwe in a context of regional conflict and migration.

DESIGN

HIV-1C pol sequence datasets were generated from four sequential cohorts of antenatal women in Harare, Zimbabwe sampled over 15 years (1991-2006).

METHODS

One hundred and seventy-seven HIV-1C pol sequences were obtained from four successive cohorts in Zimbabwe. Maximum-likelihood methods were used to explore phylogenetic relationships between Zimbabwean HIV-1C sequences and subtype C strains from other regions. A Bayesian coalescent-based framework was used to estimate evolutionary parameters for HIV-1C in Zimbabwe, including origin and demographic growth patterns.

RESULTS

Zimbabwe HIV-1C pol demonstrated increasing sequence divergence over the 15-year period. Nearly all Zimbabwe sequences clustered phylogenetically with subtype C strains from neighboring countries. Bayesian evolutionary analysis indicated a most recent common ancestor date of 1973 with three epidemic growth phases: an initial, slow phase (1970s) followed by exponential growth (1980s), and a linearly expanding epidemic to the present. Bayesian trees provided evidence for multiple HIV-1C introductions into Zimbabwe during 1979-1981, corresponding with Zimbabwean national independence following a period of socio-political instability.

CONCLUSION

The Zimbabwean HIV-1C epidemic likely originated from multiple introductions in the late 1970s and grew exponentially during the 1980s, corresponding to changing political boundaries and rapid population influx from neighboring countries. The timing and phylogenetic clustering of the Zimbabwean sequences is consistent with an origin in southern Africa and subsequent expansion. HIV-1 sequence data contain important epidemiological information, which can help focus treatment and prevention strategies in light of more recent political volatility in Zimbabwe.

Repeated rectal SHIVSF162P3 exposures do not consistently induce sustained T cell responses prior to systemic infection in the repeat-low dose preclinical macaque model

The macaque model of repeated SHIV exposures is increasingly used as a preclinical tool to evaluate biomedical HIV intervention strategies. It is unclear whether multiple virus exposures induce immune responses in macaques, as documented in uninfected individuals repeatedly exposed to HIV. We here address whether repeated, rectal SHIV(SF162P3) exposures lead to systemic T cell activation in 12 rhesus macaques, and whether this is associated with increased infection resistance. Eight macaques became systemically infected after 2-7 exposures, three macaques were less susceptible (infection after 10-12 exposures), and one macaque remained uninfected after 14 exposures. PBMCs were retrospectively monitored for increases in T cell activation by analyzing the proportion of CD8(+) T cells, recently activated or proliferated T cells (markers CD38, Ki67), a marker for cytotoxicity (granzyme B), or T cell-produced plasma cytokines (IFN-gamma, RANTES, IL-2). Repeated virus exposures did not induce sustained, potent, or diverse T cell responses prior to systemic infection. Some changes occurred in the analyzed parameters during repeated virus exposures, but similar T cell activities were also observed in five SHIV-unexposed control macaques. Thus, we found no evidence that delayed infection or resistance to infection was associated with systemic, long-lasting, protective T cell responses to repeated rectal virus exposures. Our results provide further insights into the repeat exposure macaque model. We find that this model can be used for testing biomedical prevention strategies without concern of eliciting a systemic vaccination effect.

Human immunodeficiency virus type 1 is trapped by acidic but not by neutralized human cervicovaginal mucus

To reliably infect a primate model for human immunodeficiency virus (HIV), approximately 10,000-fold more virus must be delivered vaginally than intravenously. However, the vaginal mechanisms that help protect against HIV are poorly understood. Here, we report that human cervicovaginal mucus (CVM), obtained from donors with normal lactobacillus-dominated vaginal flora, efficiently traps HIV, causing it to diffuse more than 1,000-fold more slowly than it does in water. Lactobacilli acidify CVM to pH approximately 4 by continuously producing lactic acid. At this acidic pH, we found that lactic acid, but not HCl, abolished the negative surface charge on HIV without lysing the virus membrane. In contrast, in CVM neutralized to pH 6 to 7, as occurs when semen temporarily neutralizes the vagina, HIV maintained its native surface charge and diffused only 15-fold more slowly than it would in water. Thus, methods that can maintain both a high lactic acid content and acidity for CVM during coitus may contribute to both vaginal and penile protection by trapping HIV before it can reach target cells. Our results reveal that CVM likely plays an important but currently unappreciated role in decreasing the rate of HIV sexual transmission.

Fourteen million women with limited options: HIV/AIDS and highly effective reversible contraception in sub-Saharan Africa

An estimated 14 million women in sub-Saharan Africa are HIV infected and these women deserve access to evidence-based family planning services. Increasing contraceptive use in HIV-infected women can reduce the numbers of unintended pregnancies and thus reduce maternal death and vertical transmission of HIV. A delicate balance exists between risks associated with pregnancy and any theoretical risks of acquiring, transmitting or worsening HIV attributable to using a contraceptive. This commentary reviews interactions between hormonal, intrauterine and barrier contraception in HIV-infected women, with a focus on sub-Saharan Africa. Unfortunately, the evidence on these interactions to guide family planning providers is limited and more research in this area is urgently needed.

Women facing HIV. Key question on women with HIV infection: Italian consensus workshop

A panel of leading Italian specialists in infectious diseases, obstetrics and gynaecology met in a national consensus workshop on women facing HIV to review critical aspects and discuss recommendations for selected key questions on four issues: (1) women and highly active antiretroviral therapy (HAART): access to care and adherence to therapy, side effects and drug-drug interaction; (2) HIV-infected pregnant women: prevention of mother to child transmission; (3) desire for children among women living with HIV: assisted reproduction; (4) sexually transmitted diseases and genital disturbances. The method of a nominal group meeting was used, and recommendations were graded for their strength and quality of evidence using a system based on the one adopted by the Infectious Diseases Society of America. Main conclusions are summarized and critically discussed, and some of the most recent data supporting recommendations are provided.

Behavioural strategies to reduce HIV transmission: how to make them work better

This paper makes five key points. First is that the aggregate effect of radical and sustained behavioural changes in a sufficient number of individuals potentially at risk is needed for successful reductions in HIV transmission. Second, combination prevention is essential since HIV prevention is neither simple nor simplistic. Reductions in HIV transmission need widespread and sustained efforts, and a mix of communication channels to disseminate messages to motivate people to engage in a range of options to reduce risk. Third, prevention programmes can do better. The effect of behavioural strategies could be increased by aiming for many goals (eg, delay in onset of first intercourse, reduction in number of sexual partners, increases in condom use, etc) that are achieved by use of multilevel approaches (eg, couples, families, social and sexual networks, institutions, and entire communities) with populations both uninfected and infected with HIV. Fourth, prevention science can do better. Interventions derived from behavioural science have a role in overall HIV-prevention efforts, but they are insufficient when used by themselves to produce substantial and lasting reductions in HIV transmission between individuals or in entire communities. Fifth, we need to get the simple things right. The fundamentals of HIV prevention need to be agreed upon, funded, implemented, measured, and achieved. That, presently, is not the case.

Rethinking the heterosexual infectivity of HIV-1: a systematic review and meta-analysis

Studies of cumulative HIV incidence suggest that cofactors such as genital ulcer disease, HIV disease stage, and male circumcision influence HIV transmission; however, the heterosexual infectivity of HIV-1 is commonly cited as a fixed value (approximately 0.001, or one transmission per 1000 contacts). We sought to estimate transmission cofactor effects on the heterosexual infectivity of HIV-1 and to quantify the extent to which study methods have affected infectivity estimates. We undertook a systematic search (up to April 27, 2008) of PubMed, Web of Science, and relevant bibliographies to identify articles estimating the heterosexual infectivity of HIV-1. We used meta-regression and stratified random-effects meta-analysis to assess differences in infectivity associated with cofactors and study methods. Infectivity estimates were very heterogeneous, ranging from zero transmissions after more than 100 penile-vaginal contacts in some serodiscordant couples to one transmission for every 3.1 episodes of heterosexual anal intercourse. Estimates were only weakly associated with study methods. Infectivity differences, expressed as number of transmissions per 1000 contacts, were 8.1 (95 % CI 0.4-15.8) when comparing uncircumcised to circumcised susceptible men, 6.0 (3.3-8.8) comparing susceptible individuals with and without genital ulcer disease, 1.9 (0.9-2.8) comparing late-stage to mid-stage index cases, and 2.5 (0.2-4.9) comparing early-stage to mid-stage index cases. A single value for the heterosexual infectivity of HIV-1 fails to reflect the variation associated with important cofactors. The commonly cited value of 0.001 was estimated among stable couples with low prevalences of high-risk cofactors, and represents a lower bound. Cofactor effects are important to include in epidemic models, policy considerations, and prevention messages.

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.