Virology, immunology, and clinical course of HIV infection

Human immunodeficiency virus (HIV), the cause of AIDS, was the second retrovirus to be associated with human diseases. The unique life cycle of retroviruses involves reverse transcription of their RNA to DNA, which is incorporated into their host's genes. HIV, despite its small genome, contains multiple structural and regulatory genes, the latter controlling the rate of viral replication. Experimental vaccines are aimed at inhibiting binding of HIV to host cells. Azidothymidine (AZT) and other nucleoside analogues inhibit the reverse transcriptase enzyme. HIV induces profound and specific immunosuppression by depleting helper lymphocytes that bear the cluster determinant 4 (CD4, formerly T4). The clinical course of HIV infection is mainly determined by the number of CD4 lymphocytes in the blood. A comprehensive, multidisciplinary approach to patient management can reduce the adverse medical, psychosocial, and economic impact of AIDS.