Vertical transmission of murine gammaherpesvirus 68 in mice.

The mouse infected with murine gammaherpesvirus 68 (MHV-68) is accepted animal model for investigation of pathogenesis, oncogenesis, immunology and molecular biology of gammaherpesviruses in their natural host. However, little is known about the host range, epidemiology and pathogenesis of this natural pathogen of free-living murid rodents. Therefore we addressed the question of transplacental transmission of MHV-68 from pregnant Balb/c mice chronically infected with the virus to their fetuses and shedding of the virus by breast milk from chronically infected mothers to their offspring. The mothers were positive to infectious virus and viral antigen in various organs but mainly in the spleen and peritoneal *macrophages. Virus-neutralizing serum antibodies, and leukocyte count with a proportion of atypical lymphocytes were increasing to elevated values with the time of infection. The chronic infection resulted in premature termination of pregnancy or reduced number and size of newborns due to their retarded development. Out of 10 infected pregnant mice just one died and another developed a tumor. All these results confirm the vertical transmission of MHV-68 in mice, teratogenicity of the virus and the virus shedding by breast milk.