A field strain of minute virus of mice (MVMm) exhibits age- and strain-specific pathogenesis

The influence of mouse strain, immune competence and age on the pathogenesis of a field strain of minute virus of mice (MVMm) was examined in BALB/c, C3H, C57BL/6 and SCID mice experimentally infected as neonates, weanlings and adults. Sera, bodily excretions and tissues were harvested at 7, 14, 28 and 56 days after inoculation and evaluated by serology, quantitative PCR and histopathology. Seroconversion to recombinant viral capsid protein 2 was consistently observed in all immunocompetent strains of mice, regardless of the age at which they were inoculated, while seroconversion to the viral nonstructural protein 1 was only consistently detected in neonate inoculates. Viral DNA was detected by quantitative PCR in multiple tissues of immunocompetent mice at each time point after inoculation, with the highest levels being observed in neonate inoculates at 7 days after inoculation. In contrast, viral DNA levels in tissues and bodily excretions increased consistently over time in immunodeficient SCID mice, regardless of the age at which they were inoculated, with mortality being observed in neonatal inoculates between 28 and 56 days after inoculation. Overall, productive infection was observed more frequently in immunocompetent mice inoculated as neonates as compared to those inoculated as weanlings or adults, and immunodeficient SCID mice developed persistent, progressive infection, with mortality being observed in mice inoculated as neonates. Importantly, the clinical syndrome observed in experimentally infected SCID neonatal mice recapitulates the clinical presentation reported for the naturally infected immunodeficient NOD µ-chain knockout mice from which MVMm was initially isolated.