[Animal AIDS models].

In human immunodeficiency virus (HIV) infections, host immune responses fail to control viral replication and allow persistent HIV infection, resulting in AIDS progression. Analyses in animal AIDS models as well as in HIV-infected individuals are essential for understanding the mechanism of viral replication in vivo and disease progression. HIV-mediated AIDS progression is seen only in humans, and simian immunodeficiency virus (SIV) infection in macaque monkeys is currently considered as the best model for these analyses. Furthermore, studies on replication of HIV, SIV, and HIV-SIV chimeric viruses in humans and macaques may contribute to elucidation of the mechanism for viral tropism.