Inhibitory Effect of Cow's Milk on Influenza Virus Hemagglutination.

Abstract

Raw skim milk inhibits hemagglutination by PR8 and swine influenza viruses, the inhibitory effect being about 50 times as great against heated virus as against unheated virus (swine influenza) under standard conditions. Standard inhibition titers of individual milks from 8 cows ranged from 2600 to 6400, with a mean of 5100. The mechanism of inhibition is based on a reaction between inhibitor and virus. Pasteurization of skim milk (30 min. at 71[degree]C) both reduces the conventional titer and alters the behavior of the inhibitor at the endpoint. The inhibitor, which occurs in the whey and can be purified about 20 times (relative to skim milk) by salting out at half saturation with (NH4)2SO4, appears to be destroyed by unheated virus but not by heated virus. In this and in other respects the inhibitor in milk resembles the inhibitors in normal serum, egg white and certain other biological fluids. This resemblance and the relative uniformity of inhibition titers of individual samples indicate that the inhibitor is a characteristic component of milk, possibly the mucoprotein lactomucin, rather than a specific antibody.