Animal Models
No ideal model exists that can imitate the natural history and pathogenesis of HIV infection and AIDS in the human body, as HIV virus exclusively infects and causes disease in humans. Nonetheless, the data from animal models provides conceptual insights into immune responses elicited by investigational vaccines, and reassurance of safety, guiding preclinical development and the decision to enter into clinical trials in humans.
Non-human primate studies play a leading role in efforts to develop an HIV vaccine.
Scientists are using macaque monkeys infected with simian immunodeficiency virus (SIV), a virus closely related to HIV. This model is useful because SIV in macaques follows a similar disease course to HIV, albeit slowly, and adequate numbers of animals are available. A potential shortcoming is that SIV and HIV, although similar, are different viruses, so that advances made with SIV need to be verified using HIV. Macaques are being used to evaluate a variety of SIV vaccines of the same type as HIV vaccines being developed for humans. Because the monkeys can be challenged with SIV after immunization, the vaccines can be evaluated for their ability to protect from virus infection or disease in the monkeys.
A hybrid virus created by replacing SIV envelope with HIV envelope but retaining the inner core of SIV virus (called SHIVs), replicates acute HIV infection in macaques, and causes rapid disease progression leading to death. Monkeys vaccinated with HIV vaccines are challenged with chimeric SHIV to test the ability of the vaccine to protect from infection with the SHIV viruses.
Scientists are also using a number of different animal models to obtain information that can have application to HIV. Feline immunodeficiency virus (FIV), transgenic mice that contain part of the HIV genome or co-receptors for viral entry, and severe combined immune deficiency (SCID) mice reconstituted with human immune system cells or tissues are some of the animal models being used to study pathogenesis.
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