Transplacental transmission of polyoma virus in mice.

When pregnant mice were inoculated on day 1 of gestation with polyoma, some of them exhibited total resorption or reduced litter size, the extent depending on the dose of virus. Virus was detected in 4 out of 11 mouse embryo fibroblast (MEF) cultures made from infected mothers. After maternal infection on day 5 or 10 of gestation, virus titers of up to 10(7) 50% tissue culture infectious doses (TCID50)/g of fetus were found in all pools of fetuses tested 5 days later, with the titers falling by day 6. Hemagglutination-inhibiting antibodies against polyoma appeared in maternal serum by day 6 and rose to a maximum by day 14. Immunoglobulin G class antibodies were detected by day 7, with titers rising rapidly to a maximum at day 14. After maternal infection later in gestation (day 15), one out of three litters of newborn mice was found to have 10(5) TCID50 polyoma virus per g in pooled kidney samples.