(and host cell) proteins that assist with replication. The three main enzymes are reverse transcriptase, protease, and integrase. The envelope contains proteins that allow the virus to attach to and enter its main target cells in the body: the CD4+ T lymphocyte (also known as CD4+ T cell or CD4 cell) and the macrophage. The CD4+ T lymphocyte is a critical element in or-chestrating the normal immune response to a wide range of infectious agents. Once inside the CD4+ cell, the virus replicates. Early in this process, HIV viral RNA is transcribed to double stranded DNA by the virus’ reverse transcriptase enzyme. This newly produced viral DNA is integrated into the DNA of the host’s CD4+ T lymphocyte and becomes known as “proviral DNA.” As infection depletes CD4+ cells, the immune system becomes compromised and the person develops AIDS; this process typically occurs over the course of years in an otherwise normal adult. When the immune system becomes debilitated to the point of the AIDS, the person can develop a range of opportunistic infections (OI), like tuberculosis, pneumocystosis, cryptococcus, toxoplasmosis, and certain cancers, like Kaposi’s sarcoma and lymphoma.
An HIV-infected person is categorized as having AIDS when the CD4+ white blood cell count drops to below 200 cells/mm3 (normal counts vary significantly but typically range between around 500 and 1500 cells/mm3) or when he or she develops opportunistic infections or cancers. The complete criteria for diagnosing AIDS may be found in the December 1992 Morbidity and Mortality Weekly Report article (Centers for Disease Control and Prevention, 1992).
While there is no cure for HIV or AIDS, treatment is now available. This includes antibiotics to prevent and treat OIs and specific antiretroviral (ARV) therapy to control HIV viral replication itself. In resource-rich countries where ARVs have been available and affordable for several years, HIV infection has ceased to be considered an automatic death sentence. With carefully managed therapy and a motivated patient, HIV infection is a serious but treatable chronic disease that does not necessarily preclude additional decades of good quality life.
The use of antiretroviral therapy for HIV infection has become complex as more has been learned about the virus and its ever-changing response to therapeutics and about patient factors affecting therapy. The goals of therapy are to inhibit viral replication while minimizing toxicities and side effects associated with the available drugs. This inhibition of virus replication permits restoration of the immune system. Viral eradication from the host genome is not achievable; thus a cure for HIV is not yet possible. By using an appropriate antiretroviral treatment regimen it is