Treatment response in acute/early infection versus advanced AIDS: equivalent first and second phases of HIV RNA decline

Quantifying the Dynamics of HIV Decline in Perinatally Infected Neonates on Antiretroviral Therapy

BACKGROUND

Mathematical modeling has provided important insights into HIV infection dynamics in adults undergoing antiretroviral treatment (ART). However, much less is known about the corresponding dynamics in perinatally infected neonates initiating early ART.

SETTING

From 2014 to 2017, HIV viral load (VL) was monitored in 122 perinatally infected infants identified at birth and initiating ART within a median of 2 days. Pretreatment infant and maternal covariates, including CD4 T cell counts and percentages, were also measured.

METHODS

From the initial cohort, 53 infants demonstrated consistent decline and suppressed VL below the detection threshold (20 copies mL) within 1 year. For 43 of these infants with sufficient VL data, we fit a mathematical model describing the loss of short-lived and long-lived infected cells during ART. We then estimated the lifespans of infected cells and the time to viral suppression, and tested for correlations with pretreatment covariates.

RESULTS

Most parameters governing the kinetics of VL decline were consistent with those obtained previously from adults and other infants. However, our estimates of the lifespan of short-lived infected cells were longer than published values. This difference may reflect sparse sampling during the early stages of VL decline, when the loss of short-lived cells is most apparent. In addition, infants with higher pretreatment CD4 percentage or lower pretreatment VL trended toward more rapid viral suppression.

CONCLUSIONS

HIV dynamics in perinatally infected neonates initiating early ART are broadly similar to those observed in other age groups. Accelerated viral suppression is also associated with higher CD4 percentage and lower VL.

The dynamics of simian immunodeficiency virus after depletion of CD8+ cells

Human immunodeficiency virus infection is still one of the most important causes of morbidity and mortality in the world, with a disproportionate human and economic burden especially in poorer countries. Despite many years of intense research, an aspect that still is not well understood is what (immune) mechanisms control the viral load during the prolonged asymptomatic stage of infection. Because CD8+ T cells have been implicated in this control by multiple lines of evidence, there has been a focus on understanding the potential mechanisms of action of this immune effector population. One type of experiment used to this end has been depleting these cells with monoclonal antibodies in the simian immunodeficiency virus-macaque model and then studying the effect of that depletion on the viral dynamics. Here we review what these experiments have told us. We emphasize modeling studies to interpret the changes in viral load observed in these experiments, including discussion of alternative models, assumptions and interpretations, as well as potential future experiments.

Three-level global resource allocation model for hiv control: A hierarchical decision system approach

Funds from various global organizations, such as, The Global Fund, The World Bank, etc. are not directly distributed to the targeted risk groups. Especially in the so-called third-world-countries, the major part of the fund in HIV prevention programs comes from these global funding organizations. The allocations of these funds usually pass through several levels of decision making bodies that have their own specific parameters to control and specific objectives to achieve. However, these decisions are made mostly in a heuristic manner and this may lead to a non-optimal allocation of the scarce resources. In this paper, a hierarchical mathematical optimization model is proposed to solve such a problem. Combining existing epidemiological models with the kind of interventions being on practice, a 3-level hierarchical decision making model in optimally allocating such resources has been developed and analyzed. When the impact of antiretroviral therapy (ART) is included in the model, it has been shown that the objective function of the lower level decision making structure is a non-convex minimization problem in the allocation variables even if all the production functions for the intervention programs are assumed to be linear.

Acute HIV infection presenting as hemophagocytic syndrome with an unusual serological and virological response to ART

BACKGROUND

HIV clinical presentation in the acute stage is variable and some of its virological and immunological aspects are not completely understood. Most cases of HIV- associated reactive hemophagocytic syndrome have been reported in patients with advanced stages of HIV and to our knowledge, there are only 8 cases in the English literature presenting during acute HIV infection, most in East Asia, being this the first case in a European patient.

CASE PRESENTATION

We report a case of a European Caucasian 27- year old woman with a primary HIV- infection presenting with extremely low CD4+ T cell count who developed a haemophagocytic syndrome after starting ART and in whom we documented a very unusual serological and virological response, characterized by an impaired HIV- antibody production and a 12 month time frame to reach an undetectable viral load, despite no evidence of resistance.

CONCLUSIONS

This case report apart from describing an unusual clinical presentation of an acute HIV infection as hemophagocytic syndrome provides useful information that might contribute for understanding some subtle issues in acute HIV infection, namely the dynamics of virological and immunological aspects after antiretroviral therapy initiation.

Molecular clock of HIV-1 envelope genes under early immune selection

Background

The molecular clock hypothesis that genes or proteins evolve at a constant rate is a key tool to reveal phylogenetic relationships among species. Using the molecular clock, we can trace an infection back to transmission using HIV-1 sequences from a single time point. Whether or not a strict molecular clock applies to HIV-1’s early evolution in the presence of immune selection has not yet been fully examined.

Results

We identified molecular clock signatures from 1587 previously published HIV-1 full envelope gene sequences obtained since acute infection in 15 subjects. Each subject’s sequence diversity linearly increased during the first 150 days post infection, with rates ranging from \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.54 \times 10^{ - 5}$$\end{document}1.54×10-5 to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3.91 \times 10^{ - 5}$$\end{document}3.91×10-5 with a mean of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.69 \times 10^{ - 5}$$\end{document}2.69×10-5 per base per day. The rate of diversification for 12 out of the 15 subjects was comparable to the neutral evolution rate. While temporal diversification was consistent with evolution patterns in the absence of selection, mutations from the founder virus were highly clustered on statistically identified selection sites, which diversified more than 65 times faster than non-selection sites. By mathematically quantifying deviations from the molecular clock under various selection scenarios, we demonstrate that the deviation from a constant clock becomes negligible as multiple escape lineages emerge. The most recent common ancestor of a virus pair from distinct escape lineages is most likely the transmitted founder virus, indicating that HIV-1 molecular dating is feasible even after the founder viruses are no longer detectable.

Conclusions

The ability of HIV-1 to escape from immune surveillance in many different directions is the driving force of molecular clock persistence. This finding advances our understanding of the robustness of HIV-1’s molecular clock under immune selection, implying the potential for molecular dating.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0269-6) contains supplementary material, which is available to authorized users.

HIV-1-Specific CD8 T Cells Exhibit Limited Cross-Reactivity during Acute Infection

Prior work has demonstrated that HIV-1-specific CD8 T cells can cross-recognize variant epitopes. However, most of these studies were performed in the context of chronic infection, where the presence of viral quasispecies makes it difficult to ascertain the true nature of the original antigenic stimulus. To overcome this limitation, we evaluated the extent of CD8 T cell cross-reactivity in patients with acute HIV-1 clade B infection. In each case, we determined the transmitted founder virus sequence to identify the autologous epitopes restricted by individual HLA class I molecules. Our data show that cross-reactive CD8 T cells are infrequent during the acute phase of HIV-1 infection. Moreover, in the uncommon instances where cross-reactive responses were detected, the variant epitopes were poorly recognized in cytotoxicity assays. Molecular analysis revealed that similar antigenic structures could be cross-recognized by identical CD8 T cell clonotypes mobilized in vivo, yet even subtle differences in a single TCR-accessible peptide residue were sufficient to disrupt variant-specific reactivity. These findings demonstrate that CD8 T cells are highly specific for autologous epitopes during acute HIV-1 infection. Polyvalent vaccines may therefore be required to provide optimal immune cover against this genetically labile pathogen.

SPMM: estimating infection duration of multivariant HIV-1 infections

MOTIVATION

Illustrating how HIV-1 is transmitted and how it evolves in the following weeks is an important step for developing effective vaccination and prevention strategies. It is currently possible through DNA sequencing to account for the diverse array of viral strains within an infected individual. This provides an unprecedented opportunity to pinpoint when each patient was infected and which viruses were transmitted.

RESULTS

Here we develop a mathematical tool for early HIV-1 evolution within a subject whose infection originates either from a single or multiple viral variants. The shifted Poisson mixture model (SPMM) provides a quantitative guideline for segregating viral lineages, which in turn enables us to assess when a subject was infected. The infection duration estimated by SPMM showed a statistically significant linear relationship with that by Fiebig laboratory staging (P = 0.00059) among 37 acutely infected subjects. Our tool provides a functional approach to understanding early genetic diversity, one of the most important parameters for deciphering HIV-1 transmission and predicting the rate of disease progression.

AVAILABILITY AND IMPLEMENTATION

SPMM, webserver, is available at http://www.hayounlee.org/web-tools.html.

CONTACT

hayoun@usc.edu

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Prevalence and risk factors of HIV and syphilis, and knowledge and risk behaviors related to HIV/AIDS among men who have sex with men in Chongqing, China

High HIV prevalence and incidence burdens have been reported in men who have sex with men (MSM) in Chongqing, China. We aimed to estimate the prevalence of HIV and other sexually transmitted infections (STIs), to appraise the knowledge and risk behaviors related to HIV/AIDS among MSM, and to analyze the possible causes of deviation between behavior and knowledge to make better strategies. We recruited 617 MSM from February to July in 2008 by using a respondent-driven sampling (RDS) method in Chongqing, China. Through the collection of questionnaire-based data and biological testing results from all objects, we launched a cross-sectional survey. STATA/SE was used for data analysis by frequency, ANOVA, rank sum test and logistic regression models. MSM with syphilis (OR=4.16, 95%CI: 2.35-7.33, P<0.0001) were more likely to be HIV infected. Being a company employee (OR=3.64, 95%CI: 1.22-10.08, P<0.0001) and having bought male for sex (OR=3.52, 95%CI: 1.10-11.32, P < 0.034) were associated with a higher probability of syphilis. MSM with younger age, higher education and greater monthly income had a higher mean knowledge score. MSM who had HIV testing had a higher mean knowledge score than those who never had. Students, venues for finding sex partners by Internet and homosexuals in MSM had a higher mean knowledge score compared to other occupations, venues for finding sex partners and sexual orientation. There is an urgent need for delivery of barrier and biomedical interventions with coordinated behavioral and structural strategies to improve the effect of HIV interventions among MSM.

Illustration of a measure to combine viral suppression and viral rebound in studies of HIV therapy

Viral load is an important tool for assessing antiretroviral treatment efficacy. However, the most common viral load end point, virologic failure, may be flawed. We illustrate an alternative end point that estimates the average time patients spent suppressed before rebound in the AIDS Clinical Trials Group A5095 trial. Patients averaged 644 days suppressed in the 3-drug arm and 686 days suppressed in the 4-drug arm, for a difference of 42 days in favor of the 4-drug regimen (95% confidence interval: -11 to 96). These results agree with results using virologic failure as the end point but better emphasize the separate suppression and rebound processes.

Anti-APOBEC3G activity of HIV-1 Vif protein is attenuated in elite controllers

HIV-1-infected individuals who control viremia to below the limit of detection without antiviral therapy have been termed elite controllers (EC). Functional attenuation of some HIV-1 proteins has been reported in EC. The HIV-1 accessory protein Vif (virion infectivity factor) enhances viral infectivity through anti-retroviral factor apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3G (APOBEC3G) degradation; however, little is known regarding Vif function in EC. Here, the anti-APOBEC3G activities of clonal, plasma HIV RNA-derived Vif sequences from 46 EC, 46 noncontrollers (NC), and 44 individuals with acute infection (AI) were compared. Vesicular stomatitis virus glycoprotein (VSV-G)-pseudotyped viruses were generated by cotransfecting 293T cells with expression plasmids encoding patient-derived Vif, human APOBEC3G, VSV-G, and a vif/env-deficient luciferase-reporter HIV-1 proviral DNA clone. Viral stocks were used to infect 293T cells, and Vif anti-APOBEC3G activity was quantified in terms of luciferase signal. On average, the anti-APOBEC3G activities of EC-derived Vif sequences (median log10 relative light units [RLU], 4.54 [interquartile range {IQR}, 4.30 to 4.66]) were significantly lower than those of sequences derived from NC (4.75 [4.60 to 4.92], P < 0.0001) and AI (4.74 [4.62 to 4.94], P < 0.0001). Reduced Vif activities were not associated with particular HLA class I alleles expressed by the host. Vif functional motifs were highly conserved in all patient groups. No single viral polymorphism could explain the reduced anti-APOBEC3G activity of EC-derived Vif, suggesting that various combinations of minor polymorphisms may underlie these effects. These results further support the idea of relative attenuation of viral protein function in EC-derived HIV sequences.

IMPORTANCE

HIV-1 elite controllers (EC) are rare individuals who are able to control plasma viremia to undetectable levels without antiretroviral therapy. Understanding the pathogenesis and mechanisms underpinning this rare phenotype may provide important insights for HIV vaccine design. The EC phenotype is associated with beneficial host immunogenetic factors (such as HLA-B*57) as well as with functions of attenuated viral proteins (e.g., Gag, Pol, and Nef). In this study, we demonstrated that HIV-1 Vif sequences isolated from EC display relative impairments in their ability to counteract the APOBEC3G host restriction factor compared to Vif sequences from normal progressors and acutely infected individuals. This result extends the growing body of evidence demonstrating attenuated HIV-1 protein function in EC and, in particular, supports the idea of the relevance of viral factors in contributing to this rare HIV-1 phenotype.

Conceptualizing a Human Right to Prevention in Global HIV/AIDS Policy

Given current constraints on universal treatment campaigns, recent advances in public health prevention initiatives have revitalized efforts to stem the tide of HIV transmission. Yet, despite a growing imperative for prevention-supported by the promise of behavioral, structural and biomedical approaches to lower the incidence of HIV-human rights frameworks remain limited in addressing collective prevention policy through global health governance. Assessing the evolution of rights-based approaches to global HIV/AIDS policy, this review finds that human rights have shifted from collective public health to individual treatment access. While the advent of the HIV/AIDS pandemic gave meaning to rights in framing global health policy, the application of rights in treatment access litigation came at the expense of public health prevention efforts. Where the human rights framework remains limited to individual rights enforced against a state duty bearer, such rights have faced constrained application in framing population-level policy to realize the public good of HIV prevention. Concluding that human rights frameworks must be developed to reflect the complementarity of individual treatment and collective prevention, this article conceptualizes collective rights to public health, structuring collective combination prevention to alleviate limitations on individual rights frameworks and frame rights-based global HIV/AIDS policy to assure research expansion, prevention access and health system integration.

Surveillance of transmitted antiretroviral drug resistance among HIV-1 infected women attending antenatal clinics in Chitungwiza, Zimbabwe

The rapid scale-up of highly active antiretroviral therapy (HAART) and use of single dose Nevirapine (SD NVP) for prevention of mother-to-child transmission (pMTCT) have raised fears about the emergence of resistance to the first line antiretroviral drug regimens. A cross-sectional study was conducted to determine the prevalence of primary drug resistance (PDR) in a cohort of young (<25 yrs) HAART-naïve HIV pregnant women attending antenatal clinics in Chitungwiza, Zimbabwe. Whole blood was collected in EDTA for CD4 counts, viral load, serological estimation of duration of infection using the BED Calypte assay and genotyping for drug resistance. Four hundred and seventy-one women, mean age 21 years; SD: 2.1 were enrolled into the study between 2006 and 2007. Their median CD4 count was 371cells/µL; IQR: 255–511 cells/µL. Two hundred and thirty-six samples were genotyped for drug resistance. Based on the BED assay, 27% were recently infected (RI) whilst 73% had long-term infection (LTI). Median CD4 count was higher (p<0.05) in RI than in women with LTI. Only 2 women had drug resistance mutations; protease I85V and reverse transcriptase Y181C. Prevalence of PDR in Chitungwiza, 4 years after commencement of the national ART program remained below WHO threshold limit (5%). Frequency of recent infection BED testing is consistent with high HIV acquisition during pregnancy. With the scale-up of long-term ART programs, maintenance of proper prescribing practices, continuous monitoring of patients and reinforcement of adherence may prevent the acquisition and transmission of PDR.

Efficacy of NNRTI-based antiretroviral therapy initiated during acute HIV infection

OBJECTIVE

Characterize responses to non-nucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral treatment (ART) initiated during acute HIV infection (AHI).

DESIGN

This was a prospective, single-arm evaluation of once-daily, co-formulated emtricitabine/tenofovir/efavirenz initiated during AHI.

METHODS

The primary endpoint is the proportion of responders with HIV RNA less than 200 copies/ml by week 24. We examined time to viral suppression and CD8 cell activation in relation to baseline participant characteristics. We compared time to viral suppression and viral dynamics using linear mixed-effects models between acutely infected participants and chronically infected controls.

RESULTS

Between January 2005 and May 2009, 61 AHI participants were enrolled. Of participants whose enrollment date allowed 24 and 48 weeks of follow-up, 47 of 51 (92%) achieved viral suppression to less than 200 copies/ml by week 24, and 35 of 41 (85.4%) to less than 50 copies/ml by week 48. The median time from ART initiation to suppression below 50 copies/ml was 93 days (range 14-337). Higher HIV RNA levels at ART initiation (P = 0.02), but not time from estimated date of infection to ART initiation (P = 0.86), were associated with longer time to viral suppression. The median baseline frequency of activated CD8+CD38+HLA-DR+ T cells was 67% (range 40-95), and was not significantly associated with longer time to viral load suppression (P = 0.15). Viremia declined to less than 50 copies/ml more rapidly in AHI than chronically infected participants. Mixed-model analysis demonstrated similar phase I HIV RNA decay rates between acute and chronically infected participants, and more rapid viral decline in acutely infected participants in phase II.

CONCLUSION

Once-daily emtricitabine/tenofovir/efavirenz initiated during AHI achieves rapid and sustained HIV suppression during this highly infectious period.

CD8 T-cell proliferative capacity is compromised in primary HIV-1 infection

Understanding the correlates of immunity that control HIV-1 infection is imperative to our understanding of HIV-1 disease and vaccine development. HIV-1-specific cytotoxic T lymphocytes are fundamental to the control of viremia; however, which T-cell repertoire components enact this control remains unclear. We hypothesize that polyfunctional HIV-1-specific CD8 T cells capable of viral control are present in most patients early in infection and these cells are distinguished by their ability to secrete interleukin (IL)-2 and proliferate. We examined HIV-1-specific CD8 T-cell proliferation and cytokine secretion in primary HIV-1 infection (PHI) using known HIV-1 cytotoxic T-cell epitopes to exclude CD4 bystander effect. We found that only a subset of patients with PHI demonstrated "CD4-independent" CD8 proliferation ex vivo. The remainder of the patients lacked HIV-1-specific CD8 T cells with proliferative capacity, even after the addition of exogenous IL-2. Among the proliferators, IL-2 production from the total HIV-specific CD8 T-cell population correlated with proliferation. Surprisingly, though, we did not routinely detect both IL-2 secretion and proliferative capacity from the same antigen-specific CD8 T cells. Thus, there are distinct and heterogeneous populations of CD8 T cells, phenotypically characterized by either proliferation or IL-2 secretion and few with dual capacity. Generation of these responses may be an important measure of HIV-1 control but are not universal after PHI. Furthermore, the heterogeneity of this population suggests that a simple measure of an effective vaccine response remains elusive.

Biomarkers of HIV replication

PURPOSE OF REVIEW

Viremia provides a biomarker for HIV-1 replication in various tissues. The purpose of this review is to discuss the relationship between viremia and viral replication at a theoretical level and to review recent advances in understanding this relationship, particularly in the context of highly active antiretroviral therapy (HAART).

RECENT FINDINGS

Recent studies have focused on understanding the extremely low level of residual viremia that can be detected in patients on HAART. The two major explanations for this residual viremia are that it represents ongoing cycles of replication that continue despite HAART or that it represents release of virus from stable reservoirs. The recent finding that intensification of HAART does not further reduce residual viremia supports that latter hypothesis. Direct sequence analysis of the residual viremia has provided new insights into the complex relationship between residual viremia and viral reservoirs.

SUMMARY

In patients with untreated HIV-1 infection, the level of viremia is a direct indication of the level of viral replication and a predictor of the rate of CD4 depletion. However, when viral replication is suppressed by HAART, the level of residual viremia is to a large extent an indication of virus release from stable viral reservoirs.

Antiretroviral therapy initiated soon after HIV diagnosis as standard care: potential to save lives?

In 2008, an estimated 33.4 million people were infected with human immunodeficiency virus (HIV) and ~4 million people were receiving antiretroviral therapy (ART). However, in 2007, an estimated 6.7 million people were in need of ART under the current World Health Organization guidelines, and 2.7 million more people became infected with HIV. Most of those not currently eligible for ART will become eligible within the next decade, making the current treatment strategy unsustainable. The development of cheaper, less toxic, and more potent antiretrovirals over the past decade has made it possible to consider novel strategies of arresting the HIV/AIDS epidemic. Evidence is growing that ART can be used to prevent HIV transmission and that earlier initiation of treatment is beneficial for those infected with HIV. A mathematical model predicts that by testing whole communities annually and treating all who are infected immediately, up to 7.2 million AIDS-related deaths could be prevented in the next 40 years, long-term funding required to fight the HIV epidemic could be reduced, and, most importantly, control of the HIV/ AIDS epidemic could be regained within 1–2 years of full-scale implementation of the strategy. We discuss the development of the concept of ART for the prevention of HIV transmission and the modeled impact that a test-and-treat strategy could have on the HIV epidemic, and consequently argue that a field trial should be carried out to confirm model parameters, highlight any practical problems, and test the model’s predictions.

Impaired replication capacity of acute/early viruses in persons who become HIV controllers

Human immunodeficiency virus type 1 (HIV-1) controllers maintain viremia at <2,000 RNA copies/ml without antiretroviral therapy. Viruses from controllers with chronic infection were shown to exhibit impaired replication capacities, in part associated with escape mutations from cytotoxic-T-lymphocyte (CTL) responses. In contrast, little is known about viruses during acute/early infection in individuals who subsequently become HIV controllers. Here, we examine the viral replication capacities, HLA types, and virus sequences from 18 HIV-1 controllers identified during primary infection. gag-protease chimeric viruses constructed using the earliest postinfection samples displayed significantly lower replication capacities than isolates from persons who failed to control viremia (P = 0.0003). Protective HLA class I alleles were not enriched in these early HIV controllers, but viral sequencing revealed a significantly higher prevalence of drug resistance mutations associated with impaired viral fitness in controllers than in noncontrollers (6/15 [40.0%] versus 10/80 [12.5%], P = 0.018). Moreover, of two HLA-B57-positive (B57(+)) controllers identified, both harbored, at the earliest time point tested, signature escape mutations within Gag that likewise impair viral replication capacity. Only five controllers did not express "protective" alleles or harbor viruses with drug resistance mutations; intriguingly, two of them displayed typical B57 signature mutations (T242N), suggesting the acquisition of attenuated viruses from B57(+) donors. These data indicate that acute/early stage viruses from persons who become controllers have evidence of reduced replication capacity during the initial stages of infection which is likely associated with transmitted or acquired CTL escape mutations or transmitted drug resistance mutations. These data suggest that viral dynamics during acute infection have a major impact on HIV disease outcome.

In vivo CD8+ T-cell suppression of siv viremia is not mediated by CTL clearance of productively infected cells

The CD8+ T-cell is a key mediator of antiviral immunity, potentially contributing to control of pathogenic lentiviral infection through both innate and adaptive mechanisms. We studied viral dynamics during antiretroviral treatment of simian immunodeficiency virus (SIV) infected rhesus macaques following CD8+ T-cell depletion to test the importance of adaptive cytotoxic effects in clearance of cells productively infected with SIV. As previously described, plasma viral load (VL) increased following CD8+ T-cell depletion and was proportional to the magnitude of CD8+ T-cell depletion in the GALT, confirming a direct relationship between CD8+ T-cell loss and viral replication. Surprisingly, first phase plasma virus decay following administration of antiretroviral drugs was not slower in CD8+ T-cell depleted animals compared with controls indicating that the short lifespan of the average productively infected cell is not a reflection of cytotoxic T-lymphocyte (CTL) killing. Our findings support a dominant role for non-cytotoxic effects of CD8+ T-cells on control of pathogenic lentiviral infection and suggest that cytotoxic effects, if present, are limited to early, pre-productive stages of the viral life cycle. These observations have important implications for future strategies to augment immune control of HIV.

The recognition and elimination of infected host cells by CD8+ T-lymphocytes is held to be a key component of the immune response against viral pathogens. However, this basic tenet of viral immunology may not hold true for HIV and the related SIV. In the current work, we eliminated CD8+ T-cells by treating simian immunodeficiency virus (SIV) infected macaques with a CD8-depleting monoclonal antibody then treated the animals with antiretroviral drugs and measured virus levels. Viral levels fell just as fast for the animals with or without CD8+ T-cells, implying that survival of infected cells producing SIV was not impacted by the presence or absence of CD8+ T-cells. Virus obtained after CD8+ T-cell depletion showed changes in the types of sequences in a viral protein (Nef) that is expressed early after infection of a cell but not in a viral protein (Gag) that is expressed later. These findings suggest CD8+ T-cells have a limited ability to kill cells already expressing SIV but instead may be restricted to non-killing mechanisms or to targeting cells during earlier stages of infection before virus production begins. Understanding and overcoming the factors that prevent CD8+ T-cells from effectively eliminating infected cells producing virus could advance HIV vaccine efforts.

Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model

BACKGROUND

Roughly 3 million people worldwide were receiving antiretroviral therapy (ART) at the end of 2007, but an estimated 6.7 million were still in need of treatment and a further 2.7 million became infected with HIV in 2007. Prevention efforts might reduce HIV incidence but are unlikely to eliminate this disease. We investigated a theoretical strategy of universal voluntary HIV testing and immediate treatment with ART, and examined the conditions under which the HIV epidemic could be driven towards elimination.

METHODS

We used mathematical models to explore the effect on the case reproduction number (stochastic model) and long-term dynamics of the HIV epidemic (deterministic transmission model) of testing all people in our test-case community (aged 15 years and older) for HIV every year and starting people on ART immediately after they are diagnosed HIV positive. We used data from South Africa as the test case for a generalised epidemic, and assumed that all HIV transmission was heterosexual.

FINDINGS

The studied strategy could greatly accelerate the transition from the present endemic phase, in which most adults living with HIV are not receiving ART, to an elimination phase, in which most are on ART, within 5 years. It could reduce HIV incidence and mortality to less than one case per 1000 people per year by 2016, or within 10 years of full implementation of the strategy, and reduce the prevalence of HIV to less than 1% within 50 years. We estimate that in 2032, the yearly cost of the present strategy and the theoretical strategy would both be US$1.7 billion; however, after this time, the cost of the present strategy would continue to increase whereas that of the theoretical strategy would decrease.

INTERPRETATION

Universal voluntary HIV testing and immediate ART, combined with present prevention approaches, could have a major effect on severe generalised HIV/AIDS epidemics. This approach merits further mathematical modelling, research, and broad consultation.