The Action of Immune Serum on Human Influenza Virus in Vitro

Studies have been conducted on the effect of immune serum upon a strain of human influenza virus (PR8) grown in chick embryo tissue culture medium. The results have demonstrated (a) that when cells are exposed to the action of immune serum of high titer and subsequently washed freely, these cells support the growth of virus as well as cells treated with normal serum; (b) that, in agreement with the results of other workers, when virus is added to cell suspensions before the addition of immune serum of low titer, virus survives in the cells; (c) that when mixtures of immune serum of low titer and virus are added to cells, there is little evidence of survival or multiplication of the virus. Furthermore, when immune serum of high titer is used the virus is inactivated regardless of whether the cells are first exposed to virus or immune serum. Finally, virus mixed with a strong immune serum is inactivated in the absence of cells, as shown by the fact that centrifugation at high speeds of such serum-virus mixtures yields no active virus, whereas normal serum-virus mixtures yield fully active virus.