Detection and elimination of adventitious agents in continuous cell lines

The National Veterinary Services Laboratories (NVSL) routinely monitors continuous cell lines (CCL's) used for veterinary biologicals and diagnostic virology. All veterinary biologicals produced in CCL's must follow the master seed concept which limits the use of the master seed CCL to up to 20 passages beyond the passage level characterized and deposited at NVSL. All CLL's are evaluated for the presence of adventitious agents such as mycoplasma, bovine viral diarrhea virus, and other bacteria and viruses. Previously, CCLs were evaluated for tumorigenicity by the Syrian hamster cheek pouch method; however, this procedure has now been eliminated. The adventitious agents most frequently detected in CCL's have been bovine viral diarrhea virus and mycoplasma. Our laboratory has consistently found that the source of bovine viral diarrhea contamination of CCLs has been the use of contaminated fetal bovine cell culture enrichment serum. Gamma irradiation at 2.5-3.5 megarads at -40 degrees C of carefully screened fetal bovine serum has been used in the Diagnostic Virology Laboratory for over 10 years. If the irradiated serum is used at a final concentration of 10 percent, there is no untoward effect on cell susceptibility for virus propagation or cell culture growth. Gamma irradiation has also been demonstrated to be a very efficient inactivator of mycoplasma. Specific conditions utilized by our laboratory to preserve fetal bovine serum cell culture growth factors while eliminating adventitious bovine viral diarrhea virus will be presented.