Comparative Study of Pathology of Various Organs of Rhesus and Cynomolgus Nonhuman Primates Exposed to Two Different Doses of Acute Total-body Radiation

The rhesus macaque (Macaca mulatta) is the primary nonhuman primate (NHP) model used for the development of radiation medical countermeasures (MCMs), but due to the limited supply of rhesus macaques that has resulted from their need in other high priority medical research areas, alternative animal models for MCM development have been sought. The cynomolgus macaque (Macaca fascicularis) is less well characterized and less commonly used, but represents another quite viable, large animal NHP model for investigating MCMs. We have investigated the nature of injuries within selected organ systems induced by two potentially lethal doses (5.8 and 6.5 Gy) of ionizing radiation delivered as a total-body exposure to both rhesus and cynomolgus NHPs. Results suggest that the injuries within organs with strong self-renewing capacities (gastrointestinal and lymphohematopoietic systems) were comparable between the two NHP species, although the severity of the injuries differed. By contrast, the nature and seriousness of noted tissue pathologies were more comparable for other tissues with more limited self-renewal. In aggregate, however, the observed radiation-associated pathologies in various organs appeared to be more prominent within cynomolgus NHPs and hence, were somewhat more sensitive to the radiation exposures compared to rhesus NHPs.