The effectiveness of trypsin treatment to remove Sendai virus adhering to the zona pellucida of mouse preimplantation embryos.

The standard washing and trypsin treatment procedures to remove viruses adhering to the zona pellucida (ZP) were evaluated. Mouse embryos at the early blastocyst stage were exposed to Sendai virus, and then washed or treated with trypsin. Even after washing or trypsin treatment, Sendai virus was detected in the twelfth and final wash. The virus was still shown to adhere to the ZP by immunofluorescence assay. The embryos developed into expanded blastocysts following 24 hours of in vitro culture. Viral antigen was clearly demonstrated in the cells forming the expanded blastocysts, indicating that viral replication occurred in these cells. The present results suggest that the standard washing or trypsin treatment are not sufficient to remove Sendai virus adhering to the ZP of mouse embryos.