The non-human primate models of AIDS, using HIV-2, SHIV, and SIV in macaques, have been used as a complement to ongoing research efforts against the virus. The drug tenofovir has had its efficacy and toxicology evaluated in macaques and found long-term/high-dose treatments had adverse effects not found using short-term/high-dose treatment followed by long-term/low-dose treatment. This finding in macaques was translated into human dosing regimens. Prophylactic treatment with anti-virals has been evaluated in macaques because an introduction of the virus can only be controlled in an animal model. The finding that prophylaxis can be effective at blocking infection has altered the treatment for occupational exposures, such as needle exposures. Such exposures are now followed rapidly with anti-HIV drugs, and this practice has resulted in measurable transient virus infection similar to the NHP model . Similarly, the mother-to-fetus transmission, and its fetal prophylaxis with antivirals such as tenofovir and AZT, has been evaluated in controlled testing in macaques not possible in humans, and this knowledge has guided antiviral treatment in pregnant mothers with HIV. "The comparison and correlation of results obtained in monkey and human studies are leading to a growing validation and recognition of the relevance of the animal model. Although each animal model has its limitations, carefully designed drug studies in nonhuman primates can continue to advance our scientific knowledge and guide future clinical trials."