Fetal bovine sera (FBS) used to produce vaccines and maintain cell lines is known to be the most common source of Bovine Viral Diarrhea Virus (BVDV) contamination. To investigate whether vaccines and cell lines were contaminated with BVDV, a nested RT-PCR test was used to test for viral genome (sensitivity of the assay @ 0.04 TCID50). Vaccines tested included trivalent measles, mumps, and rubella; five strains of monovalent measles vaccines; oral and inactivated polio vaccines and one experimental vaccine. All vaccines tested were negative for contaminating BVDV RNA, except an experimental vaccine produced in BVDV positive cells.
Cell lines tested including, Vero, MRC-5, WI-38 were positive by RT-PCR for BVDV but negative for the virus when lysates were used to challenge bovine turbinate cells. Passage of these cells in media containing horse serum or irradiated FBS facilitated isolation of cell lines which were negative for BVDV when tested by PCR. In contrast, CHO cells which were RT-PCR positive were shown to be persistently infected with pestivirus. This infection was not cured by passage of the cells in irradiated FBS.