Abstract – Core B: Viral Testing Core The Viral Testing Core is a critical component for the maintenance of a Specific Pathogen Free (SPF) Indian rhesus macaque (Ind RM) (Macaca mulatta) breeding colony. Rhesus macaques infected with the Simian Immunodeficiency Virus (SIV) are the preferred animal model for AIDS studies and are used to examine many aspects of viral pathogenesis, AIDS vaccine development, and exploratory new systemic and mucosal antiviral therapies, including early events not readily studied in human patients. The presence of certain viruses can confound the results of AIDS-related investigations. SPF colonies have been developed using state-of-the art assays to eliminate animals with simian immunodeficiency virus (SIV), Type D simian retrovirus (SRV) simian T- lymphotropic virus (STLV-1); and herpes B virus (Macacine herpesvirus-1), which is a potential health risk for personnel handling the animals. The goal of the Viral Testing Core is to provide techniques and expertise to assure the continuing SPF status of the Ind RM breeding colony at the Southwest National Primate Research Center (SNPRC). In order to fulfill this goal, the following Specific Aims will be completed: Specific Aim 1: to provide a reliable and sensitive in-house viral screening method. This screening method is intended to produce reliable results in a fast turnaround time. We will continue to use the Charles River Laboratories (CRL) Multiplex Fluorescent ImmunoAssay (FMIA) for serological screening of all animals, which represents one of the current state-of-the-art surveillance techniques. Specific Aim 2: to increase the research value of the SNPRC Ind RM breeding colony by expanding serology testing. The core is ever evolving in the use of state-of-the-art techniques and expanding to detect other pathogens of interest. In recent years, we extended our serology testing to include detection of antibodies against measles virus and Trypanosoma cruzi. Presence of antibodies to measles is used to confirm immune responses to the colony active measles immunization effort. Serological screening for antibodies to the causative agent of Chagas Disease, along with PCR confirmatory testing, is used to 1) assist animal selection; 2) to determine the prevalence of this infection in the NHP colonies; and 3) to improve and evaluate the effectiveness of our pest control system. Finally, SNPRC has recently screened the SPF colony for SARS-CoV-2 by both serology and PCR. Following recommendations developed by the National Primate Research Center Pathogen Detection Working Group, the Viral Testing Core has developed an algorithm that incorporates results from the serological viral screening with both serological and PCR confirmatory assays. Additionally, the Core will continue to participate in activities proposed by the national Breeding Colony Management Consortium (BCMC), which frequently distributes serum panels for proficiency testing among its laboratory members with the i...