The AIDS research portfolio at Yerkes National Primate Research Center (YNPRC) has continued to expand as demonstrated by a growth of approximately $12 million dollars (57% increase) in nonhuman primate (NHP) AIDS research grant funding over the past five years. This growth in grant funding is accompanied by a high demand for Indian-origin specific pathogen free (SPF) rhesus macaques as the animal model for this research. YNPRC has maintained a colony of SPF rhesus macaques (previously with U24 support) in order to provide these animals for HIV/AIDS research. This application requests continued support (now a U42 mechanism) to expand the SPF colony by maximizing production. The application includes the Overview; Husbandry and Management Core; the Viral Testing Core; and the MHC Genetic Typing Core. This grant will support a subset of the overall YNPRC SPF colony that derive program income from animal assignment fees and per diems. YNPRC will provide institutional support to cover remaining expenses for this colony as well as the remainder of the SPF colony. Management and Husbandry: To leverage the resources provided by the U42 to maximize production of Indian-origin rhesus monkeys and facilitate allocation of these animals for NIH-funded HIV/AIDS research. Viral Testing: To provide serological and molecular viral diagnostic testing in support of the SPF colony and to maintain a colony free of diseases that impact AIDS-related research at the Yerkes NPRC. In this supplement we propose to develop and implement molecular and serologic methods for detecting SARS-CoV-2 infection and immunity in the SPF rhesus macaque colony at Yerkes National Primate Research Center. MHC Genetic Typing: To provide parentage testing, comprehensive analysis of MHC class I and class II alleles, and to develop new techniques for detailed genetic characterization to support a genetically healthy breeding colony and provide genetic information on animals essential to the animal assignment process in support of AIDS research. In this supplement we propose to define and determine the frequency of distinct ACE2 coding alleles within the YNPRC rhesus macaque breeding colony. Achieving these aims will ensure the Yerkes NPRC SPF breeding program is healthy, providing the necessary animals to support our HIV/AIDS research program using Indian-origin rhesus monkeys. The sustainability of this critical resource to scientists performing preclinical studies using the rhesus monkey model will have a positive, significant impact on the development of treatments to prevent or cure infection from HIV in people.