Reciprocal productive and restrictive virus-cell interactions of immunosuppressive and prototype strains of minute virus of mice

Viral and cellular factors responsible for parvovirus target cell specificity have been examined for two serologically indistinguishable strains of the minute virus of mice which infect mouse cells of dissimilar differentiated phenotype. Both the prototype strain and the immunosuppressive strain grow in and form plaques on monolayers of simian virus 40-transformed human fibroblasts, a finding that has allowed the comparison of several aspects of their virus-host cell interactions. Although closely related by antigenic and genomic criteria, both the prototype strain and the immunosuppressive strain are restricted for lytic growth in each other's murine host cell, that is, in T cells and fibroblasts, respectively. The host range of each virus variant appears to be specified by a genetic determinant that is stably inherited in the absence of selection. In the restrictive virus-host interaction lytic growth is limited to a small or, in some cases, undetectable subset of the host cell population, and the majority of the infected cells remain viable, continuing to grow at the normal rate without expressing viral antigens. The susceptible host cell phenotype is dominant in T lymphocyte x fibroblast fusion hybrids, implying that different cell types express different developmentally regulated virus helper functions that can only be exploited by the virus variant that carries the appropriate strain-specific determinant.