Nepali rhesus monkeys are genetically similar to animals native to India—good news for scientists faced with a continued shortage of these important research subjects.

For more than half a century, rhesus macaques (Macaca mulatta) of Indian origin have been the nonhuman primate (NHP) model of choice for biomedical and behavioral research. Studies using these monkeys have led to many medical advances, including the development of rabies and polio vaccines and the discovery of the Rh factor in blood. In recent years, the rhesus macaque's susceptibility to HIV-like viruses has made these animals an important model for studying HIV/AIDS. Due in part to India's 1978 ban on the exportation of NHPs for use in research, a scarcity of Indian macaques has led some researchers to opt for rhesus macaques of Chinese origin as substitutes, despite reports of genetic differences and variations in disease progression between animals from both countries.

Now, in a paper published in the June issue of the American Journal of Primatology, Randall C. Keyes of the University of Washington (Seattle) and colleagues suggest that Nepal-derived animals may be a better stand-in. The researchers collected blood from rhesus macaques living in Kathmandu, Nepal, and used the samples in mitochondrial and genomic DNA analyses. A comparison of the sequence results with those previously obtained from macaques of Indian and Chinese origin revealed that macaques of Nepali origin were more genetically similar to animals of Indian origin than to those from China. Keyes's group also looked for similarities in major histocompatibility complex (MHC) alleles, which have important implications for immune function and disease progression, and found that the Nepali monkeys expressed class I MHC alleles common in animals of Indian origin but absent from their Chinese counterparts.

Keyes's group acknowledges that these results are based on analyses of a small, isolated population of animals, but, as they write in the American Journal of Primatology, “its geographic location within the country and previous opportunities for migration (gene flow) to and from the surrounding areas suggest that this population may be a representative sample of Nepali rhesus macaques.”

The use of monkeys from Nepal may help ease the demand for Indian macaques, allowing researchers to continue work originally begun with the Indian monkeys. The use of these animals in research would not affect the naturally occurring populations, because the Wildlife Framing, Breeding and Research Working Policy, enacted by the Nepal government in 2003, mandates that only captive-bred monkeys can be used in research.