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Abstract
After incubation for 1 hr at 37° with caseinase C (a purified fraction of actinomycetin), the neuraminidase activity of concentrated purified influenza virus pr 8 suspension was unchanged, whereas its infectivity and haemagglutinating activity were considerably decreased. After 4 hr, infectivity and haemagglutinating activity were still more decreased and most of the neuraminidase activity was destroyed. The ability to fix complement in the presence of specific antibodies was slightly decreased, whereas the ability to neutralize haemagglutination-inhibiting antibodies was not affected.
Influenza virus pr 8 suspension treated with enzyme caseinase C contained material sedimentable by centrifugation for 1 hr at 31,000 g and material which remained in the supernatant fluid under these conditions. Both materials fixed complement in the presence of control pr 8 virus antiserum. The ability of control pr 8 virus suspension to neutralize haemagglutination-inhibiting antibodies and its ability to react with strain-specific complement-fixing antibodies were related to material sedimentable by centrifugation for 1 hr at 31,000 g. Treatment of PR8 virus suspension by caseinase C destroyed its ability to produce antibody-fixing complement in the presence of control influenza virus pr 8. But this treatment did not suppress ability to produce specific haemagglutination-inhibiting antibodies. Following this treatment of pr 8 virus a new antigenic activity was shown: the antiserum to enzyme-treated virus not only fixed complement in the presence of enzyme-treated pr 8 virus, but also in the presence of enzyme-treated Asian virus. Material which fixed complement in the presence of antiserum to enzyme-treated virus was sedimentable from enzyme-treated pr 8 virus suspension by centrifugation at 31,000 g.
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