Quantifying ongoing HIV-1 exposure in HIV-1-serodiscordant couples to identify individuals with potential host resistance to HIV-1

Upregulation of PTPRC and Interferon Response Pathways in HIV-1 Seroconverters Prior to Infection

Human immunodeficiency virus 1 (HIV-1) exposed seronegative (HESN) individuals may have unique characteristics that alter susceptibility to HIV-1 infection. However, identifying truly exposed HESN is challenging. We utilized stored data and biospecimens from HIV-1 serodifferent couple cohorts, in which couples' HIV-1 exposures were quantified based on unprotected sex frequency and viral load of the partner with HIV-1. We compared peripheral blood gene expression between 15 HESN and 18 seroconverters prior to infection. We found PTPRC (encoding CD45 antigen) and interferon-response pathways had significantly higher expression among individuals who went on to become seropositive and thus may be a signature for increased acquisition risk.

Ensemble clustering of longitudinal bivariate HIV biomarker profiles to group patients by patterns of disease progression

This paper describes an ensemble cluster analysis of bivariate profiles of HIV biomarkers, viral load and CD4 cell counts, which jointly measure disease progression. Data are from a prevalent cohort of HIV positive participants in a clinical trial of vitamin supplementation in Botswana. These individuals were HIV positive upon enrollment, but with unknown times of infection. To categorize groups of participants based on their patterns of progression of HIV infection using both biomarkers, we combine univariate shape-based cluster results for multiple biomarkers through the use of ensemble clustering methods. We first describe univariate clustering for each of the individual biomarker profiles, and make use of shape-respecting distances for clustering the longitudinal profile data. In our data, profiles are subject to either missing or irregular measurements as well as unobserved initiation times of the process of interest. Shape-respecting distances that can handle such data issues, preserve time-ordering, and identify similar profile shapes are useful in identifying patterns of disease progression from longitudinal biomarker data. However, their performance with regard to clustering differs by severity of the data issues mentioned above. We provide an empirical investigation of shape-respecting distances (Fréchet and dynamic time warping (DTW)) on benchmark shape data, and use DTW in cluster analysis of biomarker profile observations. These reveal a primary group of ‘typical progressors,’ as well as a smaller group that shows relatively rapid progression. We then refine the analysis using ensemble clustering for both markers to obtain a single classification. The information from joint evaluation of the two biomarkers combined with ensemble clustering reveals subgroups of patients not identifiable through univariate analyses; noteworthy subgroups are those that appear to represent recently and chronically infected subsets.

Variations in mindfulness associated with the COVID-19 outbreak: Differential effects on cognitive failures, intrusive thoughts and rumination

The lockdown due to the coronavirus outbreak in 2019 (COVID‐19) has caused psychological distress and cognitive discomfort for emerging adults, who have experienced increased rumination, intrusive thoughts and cognitive failures. States of mindfulness and being in the moment can prevent anxiety and fear associated with the lockdown and alleviate ruminative and automatic negative thinking. This longitudinal study investigated the role of mindfulness before and during the COVID‐19 lockdown in protecting a sample of emerging adults from experiencing cognitive failures, intrusive thoughts and rumination and examined how lockdown‐related variables—emotions, socio‐economic status and housing conditions—influenced this mindfulness profile. The results showed overall more cognitive failures and rumination during lockdown, especially in participants whose mindfulness status diminished. However, these signs of cognitive distress remained stable or decreased among participants who reported improved changes in mindfulness. Financial difficulties and a reduced sense of privacy associated with the lockdown predicted lower stability in mindfulness profiles. The state of being fully aware of what is happening in the present moment may be helpful in reducing cognitive discomfort and psychological maladjustment, especially during stressful times such as lockdowns.

Pre-exposure prophylaxis differentially alters circulating and mucosal immune cell activation in herpes simplex virus type 2 seropositive women

OBJECTIVE

Oral tenofovir-based pre-exposure prophylaxis (PrEP) is an important tool for prevention of new HIV infections, which also reduces subclinical herpes simplex virus type 2 (HSV-2) shedding and symptomatic lesions in HIV-negative, HSV-2-seropositive individuals. However, the impact of PrEP on mucosal immunity has not been examined in detail.

DESIGN

Here we evaluate paired genital tissue and systemic immune profiles to characterize the immunological effects of PrEP in HIV-negative, HSV-2-seropositive African women sexually exposed to HIV.

METHODS

We compared local and systemic innate and T-cell characteristics in samples collected during PrEP usage and 2 months after PrEP discontinuation.

RESULTS

We found that frequencies of cervical CCR5CD4 cells, regulatory T cells, and tissue macrophages were significantly reduced during PrEP use compared with after PrEP discontinuation. In contrast, peripheral blood CD4 and CD8 T cells expressing markers of activation and trafficking were increased during PrEP usage.

CONCLUSION

Together, our data are consistent with PrEP altering immunity differentially in the female genital tract compared with circulation in HSV-2+ women. Further study including comparison with HSV-2 negative women is needed to define the overall impact and mechanisms underlying these effects. These results point to the critical need to study the human mucosal compartment to characterize immune responses to mucosal infections.

Couple serostatus patterns in sub-Saharan Africa illuminate the relative roles of transmission rates and sexual network characteristics in HIV epidemiology

HIV prevalence has surpassed 30% in some African countries while peaking at less than 1% in others. The extent to which this variation is driven by biological factors influencing the HIV transmission rate or by variation in sexual network characteristics remains widely debated. Here, we leverage couple serostatus patterns to address this question. HIV prevalence is strongly correlated with couple serostatus patterns across the continent; in particular, high prevalence countries tend to have a lower ratio of serodiscordancy to concordant positivity. To investigate the drivers of this continental pattern, we fit an HIV transmission model to Demographic and Health Survey data from 45,041 cohabiting couples in 25 countries. In doing so, we estimated country-specific HIV transmission rates and sexual network characteristics reflective of pre-couple and extra-couple sexual contact patterns. We found that variation in the transmission rate could parsimoniously explain between-country variation in both couple serostatus patterns and prevalence. In contrast, between-country variation in pre-couple or extra-couple sexual contact rates could not explain the observed patterns. Sensitivity analyses suggest that future work should examine the robustness of this result to between-country variation in how heterogeneous infection risk is within a country, or to assortativity, i.e. the extent to which individuals at higher risk are likely to partner with each other.

Concordance of self-reported hormonal contraceptive use and presence of exogenous hormones in serum among African women

OBJECTIVES

Studies that rely on self-report to investigate the relationship between hormonal contraceptive use and HIV acquisition and transmission, as well as other health outcomes, could have compromised results due to misreporting. We determined the frequency of misreported hormonal contraceptive use among African women with and at risk for HIV.

STUDY DESIGN

We tested 1102 archived serum samples from 664 African women who had participated in prospective HIV prevention studies. Using a novel high-performance liquid chromatography-mass spectrometry assay, we quantified exogenous hormones for injectables (medroxyprogesterone acetate or norethisterone), oral contraceptives (OC) (levonorgestrel or ethinyl estradiol) and implants (levonorgestrel or etonogestrel) and compared them to self-reported use.

RESULTS

Among women reporting hormonal contraceptive use, 258/358 (72%) of samples were fully concordant with self-report, as were 642/744 (86%) of samples from women reporting no hormonal contraceptive use. However, 42/253 (17%) of samples from women reporting injectable use, 41/66 (62%) of samples from self-reported OC users and 3/39 (8%) of samples from self-reported implant users had no quantifiable hormones. Among self-reported nonusers, 102/744 (14%) had ≥1 hormone present. Concordance between self-reported method and exogenous hormones did not differ by HIV status.

CONCLUSION

Among African women with and at risk for HIV, testing of exogenous hormones revealed agreement with self-reported contraceptive use for most women. However, unexpected exogenous hormones were identified among self-reported hormonal contraceptive users and nonusers, and an important fraction of women reporting hormonal contraceptive use had no hormones detected; absence of oral contraceptive hormones could be due, at least in part, to samples taken during the hormone-free interval. Misreporting of hormonal contraceptive use could lead to biased results in observational studies of the relationship between contraceptive use and health outcomes.

IMPLICATIONS

Research studies investigating associations between hormonal contraceptive use and HIV should consider validating self-reported use by objective measures; because both overreporting and underreporting of use occur, potential misclassification based on self-report could lead to biased results in directions that cannot be easily predicted.

Anal Intercourse Among Female Sex Workers in Côte d'Ivoire: Prevalence, Determinants, and Model-Based Estimates of the Population-Level Impact on HIV Transmission

Current evidence suggests that anal intercourse (AI) during sex work is common in sub-Saharan Africa, but there have been few studies in which the contribution of heterosexual AI to human immunodeficiency virus (HIV) epidemics has been investigated. Using a respondent-driven sampling survey of female sex workers (FSWs; n = 466) in Abidjan, Côte d'Ivoire, in 2014, we estimated AI prevalence and frequency. Poisson regressions were used to identify AI determinants. Approximately 20% of FSWs engaged in AI during a normal week (95% confidence interval: 15, 26). Women who performed AI were generally younger, had been selling sex for longer, were born in Côte d'Ivoire, and reported higher sex-work income, more frequent sex in public places, and violence from clients than women not reporting AI. Condom use was lower, condom breakage/slippage more frequent, and use of water-based lubricants was less frequently reported for AI than for vaginal intercourse. Using a dynamic transmission model, we estimated that 22% (95% credible interval: 11, 37% of new HIV infections could have been averted among FSWs during 2000-2015 if AI had been substituted for vaginal intercourse. Despite representing a small fraction of all sex acts, AI is an underestimated source of HIV transmission. Increasing availability and uptake of condoms, lubricants, and pre-exposure prophylaxis for women engaging in AI could help mitigate HIV risk.

Whole genome sequencing of extreme phenotypes identifies variants in CD101 and UBE2V1 associated with increased risk of sexually acquired HIV-1

Host genetic variation modifying HIV-1 acquisition risk can inform development of HIV-1 prevention strategies. However, associations between rare or intermediate-frequency variants and HIV-1 acquisition are not well studied. We tested for the association between variation in genic regions and extreme HIV-1 acquisition phenotypes in 100 sub-Saharan Africans with whole genome sequencing data. Missense variants in immunoglobulin-like regions of CD101 and, among women, one missense/5' UTR variant in UBE2V1, were associated with increased HIV-1 acquisition risk (p = 1.9x10-4 and p = 3.7x10-3, respectively, for replication). Both of these genes are known to impact host inflammatory pathways. Effect sizes increased with exposure to HIV-1 after adjusting for the independent effect of increasing exposure on acquisition risk.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00194519; NCT00557245.

Changing Dynamics of HIV Transmission in Côte d'Ivoire: Modeling Who Acquired and Transmitted Infections and Estimating the Impact of Past HIV Interventions (1976-2015)

INTRODUCTION

Understanding the impact of past interventions and how it affected transmission dynamics is key to guiding prevention efforts. We estimated the population-level impact of condom, antiretroviral therapy (ART), and prevention of mother-to-child transmission activities on HIV transmission and the contribution of key risk factors on HIV acquisition and transmission.

METHODS

An age-stratified dynamical model of sexual and vertical HIV transmission among the general population, female sex workers (FSW), and men who have sex with men was calibrated to detailed prevalence and intervention data. We estimated the fraction of HIV infections averted by the interventions, and the fraction of incident infections acquired and transmitted by different populations over successive 10-year periods (1976-2015).

RESULTS

Overall, condom use averted 61% (95% credible intervals: 56%-66%) of all adult infections during 1987-2015 mainly because of increased use by FSW (46% of infections averted). In comparison, ART prevented 15% (10%-19%) of adult infections during 2010-2015. As a result, FSW initially (1976-1985) contributed 95% (91%-97%) of all new infections, declining to 19% (11%-27%) during 2005-2015. Older men and clients mixing with non-FSW are currently the highest contributors to transmission. Men who have sex with men contributed ≤4% transmissions throughout. Young women (15-24 years; excluding FSW) do not transmit more infections than they acquired.

CONCLUSIONS

Early increases in condom use, mainly by FSW, have substantially reduced HIV transmission. Clients of FSWs and older men have become the main source of transmission, whereas young women remain at increased risk. Strengthening prevention and scaling-up of ART, particularly to FSW and clients of female sex workers, is important.

Preventing HIV infection without targeting the virus: how reducing HIV target cells at the genital tract is a new approach to HIV prevention

For over three decades, HIV infection has had a tremendous impact on the lives of individuals and public health. Microbicides and vaccines studies have shown that immune activation at the genital tract is a risk factor for HIV infection. Furthermore, lower level of immune activation, or what we call immune quiescence, has been associated with a lower risk of HIV acquisition. This unique phenotype is observed in highly-exposed seronegative individuals from different populations including female sex workers from the Pumwani cohort in Nairobi, Kenya. Here, we review the link between immune activation and susceptibility to HIV infection. We also describe a new concept in prevention where, instead of targeting the virus, we modulate the host immune system to resist HIV infection. Mimicking the immune quiescence phenotype might become a new strategy in the toolbox of biomedical methods to prevent HIV infection. Clinical trial registration on clinicaltrial.gov: #NCT02079077.

Population-level impact of an accelerated HIV response plan to reach the UNAIDS 90-90-90 target in Côte d'Ivoire: Insights from mathematical modeling

BACKGROUND

National responses will need to be markedly accelerated to achieve the ambitious target of the Joint United Nations Programme on HIV/AIDS (UNAIDS). This target aims for 90% of HIV-positive individuals to be aware of their status, for 90% of those aware to receive antiretroviral therapy (ART), and for 90% of those on treatment to have a suppressed viral load by 2020, with each individual target reaching 95% by 2030. We aimed to estimate the impact of various treatment-as-prevention scenarios in Côte d'Ivoire, one of the countries with the highest HIV incidence in West Africa, with unmet HIV prevention and treatment needs, and where key populations are important to the broader HIV epidemic.

METHODS AND FINDINGS

An age-stratified dynamic model was developed and calibrated to epidemiological and programmatic data using a Bayesian framework. The model represents sexual and vertical HIV transmission in the general population, female sex workers (FSW), and men who have sex with men (MSM). We estimated the impact of scaling up interventions to reach the UNAIDS targets, as well as the impact of 8 other scenarios, on HIV transmission in adults and children, compared to our baseline scenario that maintains 2015 rates of testing, ART initiation, ART discontinuation, treatment failure, and levels of condom use. In 2015, we estimated that 52% (95% credible intervals: 46%-58%) of HIV-positive individuals were aware of their status, 72% (57%-82%) of those aware were on ART, and 77% (74%-79%) of those on ART were virologically suppressed. Reaching the UNAIDS targets on time would avert 50% (42%-60%) of new HIV infections over 2015-2030 compared to 30% (25%-36%) if the 90-90-90 target is reached in 2025. Attaining the UNAIDS targets in FSW, their clients, and MSM (but not in the rest of the population) would avert a similar fraction of new infections (30%; 21%-39%). A 25-percentage-point drop in condom use from the 2015 levels among FSW and MSM would reduce the impact of reaching the UNAIDS targets, with 38% (26%-51%) of infections averted. The study's main limitation is that homogenous spatial coverage of interventions was assumed, and future lines of inquiry should examine how geographical prioritization could affect HIV transmission.

CONCLUSIONS

Maximizing the impact of the UNAIDS targets will require rapid scale-up of interventions, particularly testing, ART initiation, and limiting ART discontinuation. Reaching clients of FSW, as well as key populations, can efficiently reduce transmission. Sustaining the high condom-use levels among key populations should remain an important prevention pillar.

HIV-1-Neutralizing IgA Detected in Genital Secretions of Highly HIV-1-Exposed Seronegative Women on Oral Preexposure Prophylaxis

Although nonhuman primate studies have shown that simian immunodeficiency virus/simian-human immunodeficiency virus (SIV/SHIV) exposure during preexposure prophylaxis (PrEP) with oral tenofovir can induce SIV immunity without productive infection, this has not been documented in humans. We evaluated cervicovaginal IgA in Partners PrEP Study participants using a subtype C primary isolate and found that women on PrEP had IgA with higher average human immunodeficiency virus type 1 (HIV-1)-neutralizing magnitude than women on placebo (33% versus 7%; P = 0.008). Using a cutoff of ≥90% HIV-1 neutralization, 19% of women on-PrEP had HIV-1-neutralizing IgA compared to 0% of women on placebo (P = 0.09). We also estimated HIV-1 exposure and found that the proportion of women with HIV-1-neutralizing IgA was associated with the level of HIV-1 exposure (P = 0.04). Taken together, our data suggest that PrEP and high levels of exposure to HIV may each enhance mucosal HIV-1-specific humoral immune responses in sexually exposed but HIV-1-uninfected individuals.

IMPORTANCE

Although there is not yet an effective HIV-1 vaccine, PrEP for at-risk HIV-1-uninfected individuals is a highly efficacious intervention to prevent HIV-1 acquisition and is currently being recommended by the CDC and WHO for all individuals at high risk of HIV-1 acquisition. We previously demonstrated that PrEP use does not enhance peripheral blood HIV-1-specific T-cell responses in HIV-exposed individuals. Here, we evaluate for cervicovaginal HIV-neutralizing IgA responses in genital mucosal secretions of HIV-exposed women, which is likely a more relevant site than peripheral blood for observation of potentially protective immune events occurring in response to sexual HIV-1 exposure for various periods. Furthermore, we assess for host response in the context of longitudinal quantification of HIV-1 exposure. We report that HIV-neutralizing IgA is significantly correlated with higher HIV-1 exposure and, furthermore, that there are more women with HIV-1-neutralizing IgA in the on-PrEP group than in the placebo group.

kmlShape: An Efficient Method to Cluster Longitudinal Data (Time-Series) According to Their Shapes

BACKGROUND

Longitudinal data are data in which each variable is measured repeatedly over time. One possibility for the analysis of such data is to cluster them. The majority of clustering methods group together individual that have close trajectories at given time points. These methods group trajectories that are locally close but not necessarily those that have similar shapes. However, in several circumstances, the progress of a phenomenon may be more important than the moment at which it occurs. One would thus like to achieve a partitioning where each group gathers individuals whose trajectories have similar shapes whatever the time lag between them.

METHOD

In this article, we present a longitudinal data partitioning algorithm based on the shapes of the trajectories rather than on classical distances. Because this algorithm is time consuming, we propose as well two data simplification procedures that make it applicable to high dimensional datasets.

RESULTS

In an application to Alzheimer disease, this algorithm revealed a "rapid decline" patient group that was not found by the classical methods. In another application to the feminine menstrual cycle, the algorithm showed, contrarily to the current literature, that the luteinizing hormone presents two peaks in an important proportion of women (22%).

Risk Factors for HIV Acquisition in a Prospective Nairobi-Based Female Sex Worker Cohort

With two million new HIV infections annually, ongoing investigations of risk factors for HIV acquisition is critical to guide ongoing HIV prevention efforts. We conducted a prospective cohort analysis of HIV uninfected female sex workers enrolled at an HIV prevention clinic in Nairobi (n = 1640). In the initially HIV uninfected cohort (70 %), we observed 34 HIV infections during 1514 person-years of follow-up, i.e. an annual incidence of 2.2 % (95 % CI 1.6-3.1 %). In multivariable Cox Proportional Hazard analysis, HIV acquisition was associated with a shorter baseline duration of sex work (aHR 0.76, 95 % CI 0.63-0.91), minimum charge/sex act (aHR 2.74, 0.82-9.15, for low vs. intermediate; aHR 5.70, 1.96-16.59, for high vs. intermediate), N. gonorrhoeae infection (aAHR 5.89, 95 % CI 2.03-17.08), sex with casual clients during menses (aHR 6.19, 95 % CI 2.58-14.84), Depo Provera use (aHR 5.12, 95 % CI 1.98-13.22), and estimated number of annual unprotected regular partner contacts (aHR 1.004, 95 % CI 1.001-1.006). Risk profiling based on baseline predictors suggested that substantial heterogeneity in HIV risk is evident, even within a key population. These data highlight several risk factors for HIV acquisition that could help to re-focus HIV prevention messages.

Alternative effector-function profiling identifies broad HIV-specific T-cell responses in highly HIV-exposed individuals who remain uninfected

The characterization of host immune responses to human immunodeficiency virus (HIV) in HIV controllers and individuals with high exposure but seronegativity to HIV (HESN) is needed to guide the development of effective preventive and therapeutic vaccine candidates. However, several technical hurdles severely limit the definition of an effective virus-specific T-cell response. By using a toggle-peptide approach, which takes HIV sequence diversity into account, and a novel, boosted cytokine staining/flow cytometry strategy, we here describe new patterns of T-cell responses to HIV that would be missed by standard assays. Importantly, this approach also allows detection of broad and strong virus-specific T-cell responses in HESN individuals that are characterized by a T-helper type 1 cytokine-like effector profile and produce cytokines that have been associated with potential control of HIV infection, including interleukin 10, interleukin 13, and interleukin 22. These results establish a novel approach to improve the current understanding of HIV-specific T-cell immunity and identify cellular immune responses and individual cytokines as potential markers of relative HIV resistance. As such, the findings also help develop similar strategies for more-comprehensive assessments of host immune responses to other human infections and immune-mediated disorders.

HIV-1 specific IgA detected in vaginal secretions of HIV uninfected women participating in a microbicide trial in Southern Africa are primarily directed toward gp120 and gp140 specificities

Background

Many participants in microbicide trials remain uninfected despite ongoing exposure to HIV-1. Determining the emergence and nature of mucosal HIV-specific immune responses in such women is important, since these responses may contribute to protection and could provide insight for the rational design of HIV-1 vaccines.

Methods and Findings

We first conducted a pilot study to compare three sampling devices (Dacron swabs, flocked nylon swabs and Merocel sponges) for detection of HIV-1-specific IgG and IgA antibodies in vaginal secretions. IgG antibodies from HIV-1-positive women reacted broadly across the full panel of eight HIV-1 envelope (Env) antigens tested, whereas IgA antibodies only reacted to the gp41 subunit. No Env-reactive antibodies were detected in the HIV-negative women. The three sampling devices yielded equal HIV-1-specific antibody titers, as well as total IgG and IgA concentrations. We then tested vaginal Dacron swabs archived from 57 HIV seronegative women who participated in a microbicide efficacy trial in Southern Africa (HPTN 035). We detected vaginal IgA antibodies directed at HIV-1 Env gp120/gp140 in six of these women, and at gp41 in another three women, but did not detect Env-specific IgG antibodies in any women.

Conclusion

Vaginal secretions of HIV-1 infected women contained IgG reactivity to a broad range of Env antigens and IgA reactivity to gp41. In contrast, Env-binding antibodies in the vaginal secretions of HIV-1 uninfected women participating in the microbicide trial were restricted to the IgA subtype and were mostly directed at HIV-1 gp120/gp140.

Variants in host viral replication cycle genes are associated with heterosexual HIV-1 acquisition in Africans

Supplemental Digital Content is Available in the Text.

Objective:

We evaluated genetic variants in 51 candidate genes encoding proteins that interact with HIV-1 during the virus life cycle for association with HIV-1 outcomes in an African cohort.

Methods:

Using a nested case–control study within a cohort of heterosexual HIV-1–serodiscordant couples, we genotyped 475 haplotype-tagging single-nucleotide polymorphisms (tagSNPs) and 18 SNPs previously associated with HIV-1 transmission and/or progression (candidate SNPs) in 51 host genes. We used logistic and Cox proportional hazard regression with adjustment for sex, age, and population stratification to detect SNP associations with HIV-1 acquisition, plasma HIV-1 set point, and a composite measure of HIV-1 disease progression. Significant thresholds for tagSNP, but not candidate SNP, associations were subjected to Bonferroni correction for multiple testing.

Results:

We evaluated 491 HIV-1–infected and 335 HIV-1–uninfected individuals for 493 SNPs, 459 of which passed quality control filters. Candidate SNP PPIA rs8177826 and tagSNP SMARCB1 rs6003904 were significantly associated with HIV-1 acquisition risk (odds ratio = 0.14, P = 0.03, and odds ratio = 2.11, P_corr = 0.01, respectively). Furthermore, the TT genotype for CCR5 rs1799988 was associated with a mean 0.2 log₁₀ copies per milliliter lower plasma HIV-1 RNA set point (P = 0.04). We also identified significant associations with HIV-1 disease progression for variants in FUT2 and MBL2.

Conclusions:

Using a targeted gene approach, we identified variants in host genes whose protein products interact with HIV-1 during the virus replication cycle and were associated with HIV-1 outcomes in this African cohort.

The rise and fall of HIV in high-prevalence countries: a challenge for mathematical modeling

Several countries with generalized, high-prevalence HIV epidemics, mostly in sub-Saharan Africa, have experienced rapid declines in transmission. These HIV epidemics, often with rapid onsets, have generally been attributed to a combination of factors related to high-risk sexual behavior. The subsequent declines in these countries began prior to widespread therapy or implementation of any other major biomedical prevention. This change has been construed as evidence of behavior change, often on the basis of mathematical models, but direct evidence for behavior changes that would explain these declines is limited. Here, we look at the structure of current models and argue that the common “fixed risk per sexual contact" assumption favors the conclusion of substantial behavior changes. We argue that this assumption ignores reported non-linearities between exposure and risk. Taking this into account, we propose that some of the decline in HIV transmission may be part of the natural dynamics of the epidemic, and that several factors that have traditionally been ignored by modelers for lack of precise quantitative estimates may well hold the key to understanding epidemiologic trends.

Toll-like receptor polymorphism associations with HIV-1 outcomes among sub-Saharan Africans

OBJECTIVE

We evaluated Toll-like receptors (TLRs) single nucleotide polymorphisms (SNPs) for associations with HIV-1 acquisition, set-point and disease progression in African couples.

METHODS

Seven candidate and 116 haplotype-tagging SNPs (tagSNPs) were genotyped in 504 HIV-1 infected cases, and 343 seronegative controls.

RESULTS

TLR9 1635A/G was associated with reduced HIV-1 acquisition among HIV-seronegative controls with high but not low HIV-1 exposure (odds ratio [OR] = 0.7; P = .03 and OR = 0.9, P = .5, respectively). TLR7 rs179012 and TLR2 597C/T reduced set-point; the latter modified by time since HIV-1 acquisition. TLR8 1A/G reduced disease progression.

CONCLUSIONS

TLR SNPs impact HIV-1 outcomes with epidemiologic factors modifying these relationships.

Differential regulatory T cell activity in HIV type 1-exposed seronegative individuals

The potential role of conventional and regulatory T cells (Tregs) in protection from HIV-1 infection remains unclear. To address this question, we analyzed samples from 129 HIV-1-exposed seronegative individuals (HESN) from an HIV-1-serodiscordant couples cohort. To assess the presence of HIV-specific T cell responses and Treg function, we measured the proliferation of T cells in response to HIV-1 peptide pools in peripheral blood mononuclear cells (PBMCs) and PBMCs depleted of Tregs. We identified HIV-specific CD4(+) and CD8(+) T cell responses and, surprisingly, the overall CD4(+) and CD8(+) T cell response rate was not increased when Tregs were removed from cell preparations. Of the 20 individuals that had HIV-1-specific CD4(+) T cell responses, only eight had Tregs that could suppress this proliferation. When compared with individuals whose Tregs could suppress HIV-1-specific CD4(+) T cell proliferation, individuals with Tregs unable to suppress showed a trend toward increased T cell activation and Treg frequency and a significant increase in HIV-1-specific production of microphage inflammatory protein-1β (MIP-1β) by CD4(+) T cells, autocrine production of which has been shown to be protective in terms of HIV-1 infection of CD4(+) T cells.