Effects of Rauscher leukemia virus infection on BALB/c mouse embryos

The effects of Rauscher leukemia virus (R-MuLV) infection on BALB/c mouse embryos were described. In mice infected with R-MuLV 12 days before mating, there were no embryos 8 days after possible conception, whereas in those infected either 8 days or 1 day before mating, pregnancy was established. The most striking effect of R-MuLV infection on the microscopic properties of the embryos was vast "apoptosis" in the mesoderm. The XC test with trypsinized embryo cells showed numerous polykaryons, which suggested that active leukemia virus was present in the embryonal tissue. Indirect immunofluorescence studies with specific rabbit antiserum to R-MuLV demonstrated the presence of virus antigens in the embryonal tissue. Vast immunofluorescence was also found in trophoblastic cells and embryonal membranes. We concluded that R-MuLV in BALB/c mice was transmitted from mother to embryo through the placenta and thereby caused excessive cell death, especially in the mesoderm.