ABSTRACT
Fetal bovine serum (FBS) used in cell culture may be contaminated with viruses, among them bovine viral diarrhea virus (BVDV) affecting the production of biological reagents and the results of diagnosis. The filtration process used in the preparation of commercial FBS abrogates most viral agents that may be present in raw FBS, but BVDV may pass through the filters because of its small size and its pleomorphism. While detection of bovine herpes virus-1 and parainfluenza-3 (PI-3) is determined by observation of the cytopathic effect, and also by hemadsorption in the case of PI-3, the most frequently isolated BVDV is non cytopathic, and infects cells without morphological alterations, inducing problems that arise after several cell generations. Batches of raw and processed FBS were analyzed. Frequencies of BVDV detection in raw serum in Argentina were similar to those published for USA. By conventional methods for BVDV detection, only 2 of 20 commercial batches of FBS had BVDV. Using cell cultures maintained with high concentrations of the serum under study for at least 2 weeks, with detection of viral antigen by indirect immunofluorescence, the percentage of BVDV detection was 80. This method shows that most lots of commercial FBS contain BVDV. RT-PCR allows faster detection of the viral genome, but it must be validated, as it does not show viral replication. To eliminate the problem of BVDV contamination in FBS, only gamma irradiated FBS is used in our laboratory.
Subject(s)
Animals , Cattle , Blood , Diarrhea Viruses, Bovine Viral/isolation & purification , Culture MediaABSTRACT
The word "prion" was created in 1982 to name the etiological agent of the transmissible spongiform encephalopathies (TSE), a group of degenerative diseases affecting central nervous system of man and animals, including bovine spongiform encephalopathy (BSE) and variant Creutzfeldt-Jakob disease (vCJD). Prions present two isoforms: PrPC, cellular or normal, which exists in all vertebrates and is sensitive to detergents and proteases, and PrPSc, disease associated, partially resistant. The molecular weight of both PrPC and PrPSc is 30-35 kD; after treatment with detergents and proteases PrPSc originates PrP27-30 (27-30 kD). PrPC is also denominated PrPsens, and PrPSc is PrPres. PrPSc and PrP27-30 cause disease. PrPC presents polymorphisms specifically associated with some TSE. The "prion hypothesis" says that PrPSc transmits its characteristic resistance to PrPC through conformational changes, and accumulation of the protein, without involvement of nucleic acids, causes disease. Most of the hypothesis has been demonstrated with transgenic mice, computer models and recombinant proteins, but the existence of strains of the TSE agents has not been explained. The description of similar mechanisms of propagation of protein conformational properties in Saccharomyces cereviseae has extended the meaning of the prion definition. Although the transmission of conformational changes between PrPC and PrPSc was experimentally shown, the pathogenesis of the TSE remains unknown. The relationship between BSE and vCJD is mentioned.