Mode of inactivation of influenza virus by tannic acid.

The details of the technique were given previously (Carson and Frisch, 1953) and consisted of the inoculation of standard amounts of influenza A virus (PR8 strain) into the allantoic cavity of 10 day old chick embryos. Thirty minutes later one to two mg of neutralized and filtered tannic acid were introduced and the fluids were harvested, tested for hemagglutination and for infectivity after stated periods of incubation at 37 C. In most of the experiments, hemagglutination was used as the sole indicator for the presence of virus. Although this procedure is admittedly less sensitive than infectivity titers, the two phenomena are related quantitatively (Fazekas de St. Groth and Cairns, 1952). Furthermore, tannic acid does not preferentially destroy either function of the virus (Green, 1948; Carson and Frisch, 1953).