Eight strains of influenza virus were titrated as plaque-forming units in both monolayers and suspensions of chick embryo cells. In the absence of trypsin, satisfactory plaques were formed only by the A/WSN strain of virus. When trypsin was included in the overlay medium of cell monolayers, all the influenza virus strains tested produced plaques, and the plaque infectivities of all but one strain were close to the egg infectivities. Using cells suspended in agar in the presence of trypsin, four strains gave plaque infectivities indistinguishable from egg infectivities, two strains formed plaques with rather low efficiency and two strains did not produce plaques. Plaque formation was also enhanced by pronase or subtilisin. A preliminary investigation was made of the mode of action of trypsin.


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  1. Belton F. C., Garriock D. J. 1972; A semiautomatic method for the production of primary ceil suspensions. Journal o f Applied Chemistry and Biotechnology 22:335–341
    [Google Scholar]
  2. Came P. E., Pascale E., Shimonaski G. 1968; Effect of pancreatin on plaque formation by influenza viruses. Archiv für gesamte Virusforschung 23:346–352
    [Google Scholar]
  3. Schild G. C., Mccahon D., Kendal A. P. 1970; Immunological and structural studies on a recombinant influenza A virus. In Biology of Large RNA Viruses638–654 Edited by Barry R. D., Mahy B. W. J. London and New York: Academic Press;
    [Google Scholar]
  4. Spendlove R. S., Schaffer F. L. 1965; Enzymatic enhancement of infectivity of reovirus. Journal of Bacteriology 89:597–602
    [Google Scholar]
  5. Tobita K., Kilbourne E. D. 1974; Genetic recombination for antigenic markers of antigenically different strains of influenza B virus. Journal of Virology 13:347–352
    [Google Scholar]

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