Pathogenesis, natural history, and classification of HIV infection

Much has been learned about the pathogenesis and natural history of AIDS over the past decade. The causative agent is now known to be a human retrovirus that selectively infects CD4 lymphocytes and monocyte/macrophages. The structure, genetic composition, and major proteins of HIV have been identified, and its basic pathophysiology defined. Antibody tests have been developed to screen for HIV infection, and antiretroviral agents devised for its treatment. The viral and host factors that protect against HIV infection and modulate its course, once established, remain to be clarified. HIV infection produces a chronic disease characterized by a primary syndrome, clinical latency period, and manifestations of increasing immunosuppression. It encompasses a wide clinical spectrum ranging from the absence of symptoms to the presence of life-threatening opportunistic diseases. Clinical and laboratory predictors of disease progression have been identified. Neither of the published classification systems for HIV has gained widespread acceptance by the medical community. Staging of patients based on the management implications of their CD4 lymphocyte count is perhaps of greatest practical value to the clinician.