Abstract
A close relationship between haemolytic and fusion activities of Sendai virus has been argued (Hosaka, 1962, 1970; Okada, 1958). A decrease in fusion activity of Sendai virus and Newcastle disease virus (NDV) after single passage in tissue culture cells has also been reported (Hosaka, 1962; Young & Ash, 1970).
Sendai virus (L Sendai) recovered from L cells after single passage of Sendai virus previously grown in eggs (egg Sendai) had a higher density and was apparently lacking in both infectivity for L cells and haemolytic activity (Ishida & Homma, 1960, 1961). These defective properties of L Sendai were shown to be due to the masking of sites, as a mild treatment of L Sendai with trypsin markedly restored both activities (Homma, 1971, 1972).
We have now made a comparative study of the effect of trypsin on the restoration of the fusion and haemolytic activities and on the infectivity for L cells.