Pathogenicity of fibroblast- and lymphocyte-specific variants of minute virus of mice.

We tested two strains of the minute virus of mice (MVM) for pathogenic effects and patterns of infection in laboratory mice. The two strains differ in their ability to infect differentiated cultured cells: the prototype virus, MVMp, infects only fibroblasts, while its variant, MVMi, is restricted to lymphocytes. We find that neither strain has any demonstrable effects on the T-cell function of mice infected as adults. In contrast, MVMi, but not MVMp, is able to induce a runting syndrome accompanied by mild immune deficiencies upon the infection of newborn mice. After neonatal infection, MVMi spreads to many organs, and the presence of viral replicative form DNA is evident in nucleic acid hybridization experiments. In contrast, replication of MVMp can be detected only by the seroconversion of infected animals. Newborn mice that grow abnormally as a result of MVMi infection also have low circulating antibody titers to the virus. This phenomenon may be a consequence of the lymphotropism of MVMi.