The effect of viral exposure of two-cell mouse embryos on their capacity to undergo subsequent cleavage and blastocyst formation in vitro was determined. Exposure to Coxsackie viruses B-4 and B-6, reovirus type 2, influenza virus type A, mouse cytomegalovi-rus, adenovirus type 5, and mouse adenovirus resulted in statistically significant inhibition of blastocyst formation. Development in vitro was unaffected by exposure to ECHO virus type 11, attenuated poliomyelitis virus type 2, parainfluenza virus type 1, mumps, rubella, and herpes simplex viruses types 1 and 2. Blastocyst formation was also unaffected by exposure of embryos to mouse interferon in a concentration 24 units/ml of culture fluid. Coxsackie virus B-4 was recovered from exposed embryos.
Speculation Arrest of cleavage in the preimplantation embryo may be the mechanism by which some maternal viral infections induce reproductive failure. Exposure of embryos to certain viruses, however, fails to interfere with cleavage or blastocyst formation. Further studies are required to determine if these apparently unaffected embryos have sustained occult injury which may result in abnormal development at later stages of gestation.