Accelerated immune senescence and HIV-1 infection.

A recent consensus has emerged regarding the association between chronic immune activation and poor outcome in HIV-1 infection. However, its basis remains unclear. Accumulating evidence suggests that the cells of the immune system may have a limited replicative lifespan in vivo. In this context, persistent activation during chronic HIV infection may lead to an exhaustion of immune resources. This may occur at two levels: Clonal and Global. Some HIV-1-specific CD8+ T-cells start expressing the senescence marker CD57 soon after primary infection. Persistently activated HIV-1-specific T-cell clones may eventually reach stages of replicative senescence and disappear, resulting in the specific loss of CD8+ T-cell populations important to control viral replication. In addition, HIV-1 infected individuals are characterized by the accumulation of highly differentiated CD8+ and CD4+ T-cells overtime. Together with the decline of T-cell renewal capacities, this may reflect a general ageing of the lymphocyte population. Similar observations have been done in HIV non-infected elderly individuals, which suggests that premature immunosenescence occurs in HIV-1 infection, as a result of persistent immune activation.