Latent HIV-1 persists in resting memory CD4+ T cells, even in patients receiving highly active antiretroviral therapy (HAART). It has been unclear how stable this latent reservoir is and whether its persistence reflects replenishment by low-level viremia. Here we show that even in treated patients who have had no detectable viremia for as long as 7 years, the reservoir decays so slowly (t(1/2) = 44 months) that eradication is unlikely.

Combination therapy for HIV-1 infection can reduce plasma virus to undetectable levels, indicating that prolonged treatment might eradicate the infection. However, HIV-1 can persist in a latent form in resting CD4+ T cells. We measured the decay rate of this latent reservoir in 34 treated adults whose plasma virus levels were undetectable. The mean half-life of the latent reservoir was very long (43.9 months). If the latent reservoir consists of only 1 x 10(5) cells, eradication could take as long as 60 years. Thus, latent infection of resting CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective anti-retroviral therapy.

Competing events can preclude the event of interest from occurring in epidemiologic data and can be analyzed by using extensions of survival analysis methods. In this paper, the authors outline 3 regression approaches for estimating 2 key quantities in competing risks analysis: the cause-specific relative hazard ((cs)RH) and the subdistribution relative hazard ((sd)RH). They compare and contrast the structure of the risk sets and the interpretation of parameters obtained with these methods. They also demonstrate the use of these methods with data from the Women's Interagency HIV Study established in 1993, treating time to initiation of highly active antiretroviral therapy or to clinical disease progression as competing events. In our example, women with an injection drug use history were less likely than those without a history of injection drug use to initiate therapy prior to progression to acquired immunodeficiency syndrome or death by both measures of association ((cs)RH = 0.67, 95% confidence interval: 0.57, 0.80 and (sd)RH = 0.60, 95% confidence interval: 0.50, 0.71). Moreover, the relative hazards for disease progression prior to treatment were elevated ((cs)RH = 1.71, 95% confidence interval: 1.37, 2.13 and (sd)RH = 2.01, 95% confidence interval: 1.62, 2.51). Methods for competing risks should be used by epidemiologists, with the choice of method guided by the scientific question.

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BackgroundCombination antiretroviral therapy (ART) has significantly increased survival among HIV-positive adults in the United States (U.S.) and Canada, but gains in life expectancy for this region have not been well characterized. We aim to estimate temporal changes in life expectancy among HIV-positive adults on ART from 2000–2007 in the U.S. and Canada.MethodsParticipants were from the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD), aged ≥20 years and on ART. Mortality rates were calculated using participants' person-time from January 1, 2000 or ART initiation until death, loss to follow-up, or administrative censoring December 31, 2007. Life expectancy at age 20, defined as the average number of additional years that a person of a specific age will live, provided the current age-specific mortality rates remain constant, was estimated using abridged life tables.ResultsThe crude mortality rate was 19.8/1,000 person-years, among 22,937 individuals contributing 82,022 person-years and 1,622 deaths. Life expectancy increased from 36.1 [standard error (SE) 0.5] to 51.4 [SE 0.5] years from 2000–2002 to 2006–2007. Men and women had comparable life expectancies in all periods except the last (2006–2007). Life expectancy was lower for individuals with a history of injection drug use, non-whites, and in patients with baseline CD4 counts <350 cells/mm3.ConclusionsA 20-year-old HIV-positive adult on ART in the U.S. or Canada is expected to live into their early 70 s, a life expectancy approaching that of the general population. Differences by sex, race, HIV transmission risk group, and CD4 count remain.

Background-The optimal time for the initiation of antiretroviral therapy for asymptomatic patients with human immunodeficiency virus (HIV) infection is uncertain.

9The Women's Interagency HIV Study (WIHS) is an ongoing long-term observational study of 3,772 women who are either infected with human immunodeficiency virus (HIV) or considered to be at risk for acquiring HIV. Since 1994, the WIHS (pronounced like "wise") has developed a large database and specimen repository that serve as resources for WIHS investigators as well as for nonaffiliated researchers working on HIVrelated or HIV coinfection issues. The purpose of this report is to update researchers on the progress of the WIHS and to provide information on WIHS resources, the methods by which they were obtained, and background for any new potential researchers interested in conducting collaborative research through shared use of these resources. BACKGROUND

To understand the high variability of the asymptomatic interval between primary human immunodeficiency virus type 1 (HIV-1) infection and the development of AIDS, we studied the evolution of the C2-V5 region of the HIV-1 env gene and of T-cell subsets in nine men with a moderate or slow rate of disease progression. They were monitored from the time of seroconversion for a period of 6 to 12 years until the development of advanced disease in seven men. Based on the analysis of viral divergence from the founder strain, viral population diversity within sequential time points, and the outgrowth of viruses capable of utilizing the CXCR4 receptor (X4 viruses), the existence of three distinct phases within the asymptomatic interval is suggested: an early phase of variable duration during which linear increases (∼1% per year) in both divergence and diversity were observed; an intermediate phase lasting an average of 1.8 years, characterized by a continued increase in divergence but with stabilization or decline in diversity; and a late phase characterized by a slowdown or stabilization of divergence and continued stability or decline in diversity. X4 variants emerged around the time of the early- to intermediate-phase transition and then achieved peak representation and began a decline around the transition between the intermediate and late phases. The late-phase transition was also associated with failure of T-cell homeostasis (defined by a downward inflection in CD3+ T cells) and decline of CD4+ T cells to ≤200 cells/μl. The strength of these temporal associations between viral divergence and diversity, viral coreceptor specificity, and T-cell homeostasis and subset composition supports the concept that the phases described represent a consistent pattern of viral evolution during the course of HIV-1 infection in moderate progressors. Recognition of this pattern may help explain previous conflicting data on the relationship between viral evolution and disease progression and may provide a useful framework for evaluating immune damage and recovery in untreated and treated HIV-1 infections.