Analysis of a pair of END+ and END- viruses derived from the same bovine viral diarrhea virus stock reveals the amino acid determinants in Npro responsible for inhibition of type I interferon production.

The Exaltation of Newcastle disease virus (END) phenomenon is induced by the inhibition of type I interferon in pestivirus-infected cells in vitro, via proteasomal degradation of cellular interferon regulatory factor (IRF)-3 with the property of the viral autoprotease protein N(pro). Reportedly, the amino acid residues in the zinc-binding TRASH motif of N(pro) determine the difference in characteristics between END-phenomenon-positive (END(+)) and END-phenomenon-negative (END(-)) classical swine fever viruses (CSFVs). However, the basic mechanism underlying this function in bovine viral diarrhea virus (BVDV) has not been elucidated from the genomic differences between END(+) and END(-) viruses using reverse genetics till date. In the present study, comparison of complete genome sequences of a pair of END(+) and END(-) viruses isolated from the same virus stock revealed that there were only four amino acid substitutions (D136G, I2623V, D3148G and D3502Y) between two viruses. Based on these differences, viruses with and without mutations at these positions were generated using reverse genetics. The END assay, measurements of induced type I interferon and IRF-3 detection in cells infected with these viruses revealed that the aspartic acid at position 136 in the zinc-binding TRASH motif of N(pro) was required to inhibit the production of type I interferon via the degradation of cellular IRF-3, consistently with CSFV.

Methods to select suitable fetal bovine serum for use in quality control assays for the detection of adventitious viruses from biological products.

Production of biological products, especially vaccines, usually requires materials derived from animals, and there are always risks that animal pathogens derived from these materials could contaminate the final products. Detection of adventitious agents is performed by quality control tests. In these biological assays, animal derived materials are also used and another problem arises, as fetal bovine serum (FBS) is used as an ingredient in tissue culture media. FBS contaminated with bovine viral diarrhea virus (BVDV) or other bovine pathogens, as well as antibodies against these pathogens may lead to false results in quality control assays. In this study, in order to determine the actual status of commercial FBS, we performed quality tests on various FBS samples. As a result, in 28 of 49 FBS samples (57.1%), pestivirus genes were detected by pan-pestivirus reverse transcription-polymerase chain reaction assay. Furthermore, two samples contained infectious BVDV. Neutralizing antibodies against BVDVs were detected in 48 of 49 samples (97.6%) by the virus neutralization test based on the serum-dilution or virus-dilution methods. Antibodies against other bovine pathogens were detected rarely in these samples. From our results, we recommend methods to select FBS that are focused on detection of BVDV and neutralizing antibodies against BVDV.

Characterization of Staphylococcus aureus strains isolated from bovine mastitis in Japan.

Fifty-three strains of Staphylococcus aureus isolated from cows affected with mastitis from 21 prefectures in Japan were characterized by phenotypic and genotypic methods. Thirty-three (62.3%) strains showed biotype K-beta+CV:A, coagulase type VI, and sensitivity to bovine phages of group III or IV. These 33 strains could be subdivided into two groups on the basis of the production of staphylococcal enterotoxins (SEs) and on toxic shock syndrome toxin-1 (TSST-1). By pulsed-field gel electrophoresis, the 16 SEC- and TSST-1-producing strains showed similar patterns that differed by only a few fragments, suggesting that they were genetically closely related. Fifteen of 17 non SEC-producing strains which did not produce any other SEs and TSST-1 were genetically different from the SEC-producing strains and showed genetic diversity.