INVIVO STUDIES WITH AN ORPHAN PARVOVIRUS OF MICE

A virus antigenically related to, but distinct from, minute virus of m ice was assessed for infectivity in neonatal and weanling random-bred mice and was equally infectious for both age groups. The virus, design ated a mouse ''orphan'' parvovirus (OPV), was also localized in tissue s of experimentally infected random-bred, inbred, and immunodeficient mice by in situ hybridization. Hybridization signal was seen in exocri ne and endocrine pancreas, abdominal lymph nodes, mesentery, intestine , and sporadically in other tissues of Sencar, C3H, and DBA mice inocu lated as infants. In adult BALB/c severe combined immunodeficient (sci d) mice, signal was seen in lung, liver, spleen, lymph nodes, and inte stine but not in pancreas. Transmission of OPV by Sencar mice inoculat ed as infants was intermittent, whereas transmission by Sencar mice in oculated as weanlings was consistent during the first 2 weeks both by direct contact and by exposure to soiled bedding. The longest duration of transmission was 6 weeks among mice inoculated as infants. The res ults implicate a role for urinary, fecal, and perhaps respiratory excr etion of virus, depending on host genotype and route of virus exposure . They also suggest that evaluation of pancreatic and immune function during acute infection is warranted.