HIV Infection, AIDS and Vaccines

HIV (human immunodeficiency virus) is a retrovirus that infects CD4+ T cells of the human immune system. If the infection is not treated, these cells are destroyed, resulting in an acquired immunodeficiency, i.e., “AIDS” (acquired immunodeficiency syndrome). HIV owns a reverse transcriptase enzyme to convert its RNA into DNA, which is then integrated into the human genome – then undetectable by the immune system. Today, sexual transmission is the major route of HIV infection, while parenteral transmission (sharing needles among drug addicts; rarely blood transfusion) and perinatal transmission are also possible. Acute HIV infection is accompanied by infectious mononucleosis-like symptoms (fevers, rash, lymphadenopathy, sore throat, fatigue), followed by a chronic asymptomatic stage, with viral replication at low levels, followed years later by AIDS, characterized by a plethora of possible opportunistic infections and cancers that result from T-cell deficiency and finally in death within about 2–3 years. Antiretroviral treatment (ART) includes 6 main classes of medicines that affect different steps of viral activities. While no cure is possible, ART – and particularly “Highly active antiretroviral therapy” (HAART) – has made HIV infections a chronic disease and therapy also results in a reduction of transmission. A large variety of vaccine candidates have been assessed – including phase 3 studies – but for many reasons, none of them have been successful to date.