HIV pathogenesis: knowledge gained after two decades of research.

Great progress has been made in our understanding of HIV since its initial discovery about 20 years ago. The ability of HIV to infect CD4+ lymphocytes and a wide variety of other cells in the body is appreciated, as is its role in immunologic, gastrointestinal, and brain disorders. HIV enters cells via the CD4 molecule, chemokine co-receptors (CXCR4, CCR5), and other cell-surface proteins. Several accessory virus-associated genes (e.g., Rev, Tat, Nef) have uncovered unique pathways that can also be observed in normal cells. Recently, the discovery of natural cellular resistant factors (APOBEC3G and TRIM5a) has provided avenues for novel antiviral therapies. Studies of long-term survivors have given insight into immune responses that control HIV and can prevent infection. Neutralizing antibodies and CD8+ cell cytotoxic responses, as well as plasmacytoid dendritic cells and CD8+ cell non-cytotoxic antiviral responses, are adaptive and innate immune activities mediating this anti-HIV effect. HIV vaccine studies have indicated that conventional approaches do not work against this integrated intracellular parasite. While much has been learned about HIV, more details are needed about its infection cycle and its pathologic effects in the body. The past 20 years have yielded important information on HIV/AIDS that should lead to effective anti-HIV therapies and a vaccine.