A cohort observational study evaluating the predictors, incidence, clinical presentation and immunopathogenesis of Immune Reconstitution Syndrome (IRIS) in human immunodeficiency virus (HIV-1) infected patients with CD4 Count less than or equal to 100 cells/microL who are initiating antiretroviral therapy.

Immune reconstitution syndrome (IRIS) is a clinical syndrome that has been described in HIV infected patients after initiation of highly active anti-retroviral therapy (HAART), and is characterized by paradoxical acute worsening of an underlying opportunistic infection or AIDS-defining illness. There is no widely accepted syndromic definition, the pathogenesis of the syndrome is unclear and there is no specific therapy. The syndrome is more common in patients with low CD4+ T cell counts (less than 50 cells/microL) and in those with certain underlying infections (e.g. mycobacterial or cryptococcal infection) and is typically observed when there is evidence of response to HAART and while patients are still at risk for other opportunistic infections (OIs) or AIDS defining illnesses (e.g. pneumocystis jirovecii pneumonia or cytomegalovirus [CMV] retinitis). The incidence of IRIS varies depending on the studied population and is very frequent in developing countries creating significant diagnostic and therapeutic challenges as well as utilization of limited health resources.

DESIGN: International observational cohort study. Participants will be evaluated at baseline and followed according to the protocol follow up schedule after initiation of antiretroviral therapy for a total of two years. Acute symptoms that may be representing manifestations of IRIS will also be evaluated at additional acute care visits if necessary.

DURATION: Enrollment is expected to take 2 years. Each volunteer will be followed for two years with an optional 2-year extension for US participants only. Total duration of the study will be approximately 6-8 years (including the optional extension phase in US).

SAMPLE SIZE: Approximately 500 patients will be recruited over a 2- year period (approximately 100 in US and approximately 400 in Africa). Based on the incidence of IRIS in patients with low CD4 counts (approximately 20-40%), we anticipate strong power (approximately 90%) to identify baseline factors predictive of IRIS.

POPULATION: HIV-l-infected men and women, age greater than or equal to 18 years, antiretroviral therapy (ART)-naive with CD4+ T cell counts less than or equal to 100 cells/mm(3). Participants will be recruited and followed at two sites: the broader Washington DC and Kericho, Kenya, areas.

REGIMEN: Participants will be initiated on ART according to the clinical standard of care. If an OI or other AIDS defining illness is identified prior to or during screening or at any point during the study, they will also be treated according to standard of care.