Inhibition of passive hemagglutination- a sensitive test for host antigen detection and evaluation of virus purity.

: Inhibition of passive hemagglutination (IPHA) proved to be a very sensitive and specific reaction for immunochemical detection and dosage of host antigens or proteins impurifying various virus suspensions. Thus, IPHA is able to detect bovine serum albumin amounts of 0.05 mug/ml, and chorio-allantoic membrane antigens at a concentration of 0.35 mug/ml. The estimation of the ratio between specific activity (hemagglutinating (HA) titer in the case of influenza A0PR8 virus) and the amount of host proteins (evaluated by IPHA) is recommended as a criterion of virus purity. In the case of highly purified virus suspensions this criterion is more reliable than the presently used ratio between HA titer and total protein amount (estimated by Lowry's reaction).