[Mechanism mediating HIV replication in infected individuals]

A long asymptomatic period is one of the characteristics of human immunodeficiency virus (HIV). How actively HIV replicates in vivo and what controls viral replication during this period remains to be clarified. Proviral DNA integrated into the cellular DNA of peripheral blood lymphocytes (PBL) is not completely silent, but the viral antigens in PBL are extremely low. Several mechanisms have been proposed to explain the low levels of viral replication: i) the regulatory genes encoded in HIV might control the expression of viral DNA, ii) the majority of the proviruses might be defective, iii) host immune systems such as T cell-mediated HIV-specific cytotoxicity and antibody-dependent cellular cytotoxicity might eliminate infected cells, and iv) CD8+ lymphocytes might suppress spontaneous viral replication in PBL.