Definition:

The human immunodeficiency virus (HIV) is a lentivirus (a subgroup of retrovirus) that causes HIV infection and over time acquired immunodeficiency syndrome (AIDS). Two types of HIV has been characterized. HIV-1 is the most virulent and pathogenic strain. Worldwide, the predominant virus is HIV-1. The relatively uncommon HIV-2 type is concentrated in West Africa and is rarely found elsewhere. Infection with HIV occurs by transfer of blood, semen, and breast milk. The identification of HIV as the causative agent of AIDS catalyzed efforts to develop antiviral agents. The licenced anti-HIV drugs fall into some categories: reverse transcriptase inhibitors (NRTIs and NNRTIs), integrase inhibitors, protease inhibitors (PIs), fusion inhibitors (FIs), and coreceptor inhibitors. The advent of highly active antiretroviral therapy (HAART) as the standard of care for the treatment of HIV infection was seminal in reducing the morbidity and mortality associated with HIV infection and progression to AIDS. Combination antiretroviral therapy dramatically suppresses HIV replication and reduces the plasma HIV-1 viral load, resulting in significant reconstitution of the immune system. Genetic susceptibility to HIV infection and AIDS progression is variable among individuals and populations, and in part genetically determined. Genetic variants of genes encoding HIV co-receptors and their chemokine ligands have been described, and some of these variants were associated with resistance to HIV infection and/or disease progression.