Biomarkers of immune dysfunction in HIV

HIV infection is characterized by chronic immune system activation and inflammatory cytokine production. This review will highlight recent developments using plasma and cellular biomarkers of immune system activation and dysfunction to predict mortality and opportunistic disease in HIV-infected individuals.

HIV infection results in features characteristic of early aging of the immune system or 'immune senescence', driven by chronic antigen exposure and immune system activation. Microbial translocation of gut bacterial components is associated with chronic immune activation and possibly systemic inflammation. Antiretroviral therapy may not fully normalize this condition. Baseline elevations of certain biomarkers of inflammation or coagulopathy, notably interleukin-6 (IL-6), C-reactive protein (CRP), and D-dimer, have been associated with mortality or opportunistic disease, after adjustment for appropriate variables, in several large randomized clinical trials. It is not known if elevated IL-6 or CRP causes this morbidity and mortality or if they are simply surrogate markers of a global inflammatory state.

Several inflammatory biomarkers appear to add to our ability to predict mortality or opportunistic disease in HIV-infected individuals. Before biomarkers will be useful, it will be necessary to identify interventions that moderate biomarker levels, and then determine if this moderation attenuates disease outcomes.