Two novel rat parvoviruses, RPV1 and RPV2, have recently been identified by the applicant's laboratory. These viruses are genetically different from each other and from other known rodent parvoviruses. Preliminary evidence indicates that infections with these viruses are highly prevalent throughout laboratory rat colonies, and that rats remain persistently infected. Although infections with other persistent or latent viruses and particularly parvoviruses, are known to alter the host's physiology and immune responses, the effect of these novel rat parvoviruses on rats is unknown. However, there is concern that laboratory rats infected with these viruses may exhibit altered host responses, which may compromise or invalidate their use as animal models in biomedical research investigations. The long-term goal of this project, therefore, is to elucidate and minimize the potential effects of infections with these novel parvoviruses on animal-based research. Three Specific Aims will be pursued: 1) sensitive and specific diagnostic assays will be used to determine prevalence of infection in laboratory rat colonies and to identify rats free of the viruses; 2) the pathogenesis of RPV infection, the mode of transmission, and the effect of infections on specific immune responses will be determined to provide information about the potential adverse effects of RPV infections on the outcome or interpretation of research studies that utilize infected rats as models; and 3) the viruses will be characterized at the molecular level to gain insights into the viral determinants that play a role in disease pathogenesis and host range. The results of the proposed studies will provide information that will directly and immediately benefit the scientific community by developing diagnostic techniques to detect infections with these novel parvoviruses, identifying rats free of the confounding effects of RPV infection, and by determining the potential adverse effects of RPV infections on prior, current, and future research investigations.