The human immunodeficiency virus type 1 (HIV-1) is the cause of a devastating pandemic. HIV-1 infection leads to the disease AIDS (acquired immunodeficiency syndrome) after several years of clinical latency defined by the occurrence of opportunistic infections. The immune system of the patient is not capable of controlling the virus, not to mention to eliminate the virus. Nowadays, the antiretroviral therapy is very efficient; however, eradication of HIV-1 is currently not feasible. Countless efforts to develop an effective vaccine failed so far. One common cause for development of drug resistance during antiretroviral therapy and these fallibilities of the immune system and vaccine candidates is the rapid adaptability of HIV-1 and the associated high diversity of circulating virus variants world wide and within each patient.