FACTORS AFFECTING THE ASSAY OF BOVINE TYPE-I INTERFERON ON BOVINE EMBRYONIC LUNG-CELLS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 41  (4) , 552-556
Abstract
One preparation of interferon (IF) on 7 day old bovine embryonic lung cultures free of bovine viral diarrhea virus had titers ranging from 20-10,240 in plaque-reduction tests using bovine vesicular stomatitis virus. Factors believed to contribute to this variation were investigated. Although titers differed on different cell strains, different passages and on cultures of different ages, variations between the 2 assays definitely could not be established as a function of these factors. IF titers on low passage cultures were usually lower than were titers on subsequent passages of the same cell strain. Calf serum in the diluent for IF reduced the titer one or two 2-fold dilutions. Over the range of 7-24 h contact of IF with bovine embryonic lung cultures, the titer decreased steadily and was 1 2-fold dilution less at 24 h than it was at 7 h. Latent viruses were not found in cultures by EM. Treatment of cultures with a noncytopathogenic strain of bovine viral diarrhea virus almost eliminated the effect of IF. Naturally occurring production of IF was not a major problem. While IF was on the cells, the pH of IF had a pronounced effect on the titer and may have been responsible for the variation observed with different passages, different cell strains, use of cultures of different ages and use of calf serum in the diluent. Interferon at a low pH had a titer three or four 2-fold dilutions less than did the IF at a high pH.

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