Non-specific inhibitors of influenza viruses in normal sera

The presence of non-specific inhibitors in immune influenza sera may falsify the antibody pattern as shown by the haemagglutination-inhibition test, and it is consequently often necessary to pre-treat sera in order to inactivate these inhibitors. A number of different methods are in use for this purpose. It was therefore thought useful to compare the efficacy of the various methods with different representative influenza strains and normal sera from eight animal species and acute-phase human sera. Tests were carried out with simple heating at 56 degrees C, the use of receptor-destroying enzyme, the use of potassium periodate, and two methods involving the use of trypsin. No one technique was found to be universally applicable for all types of serum against all strains, and further testing with larger numbers of sera is advocated. It is felt that a combination of potassium periodate and trypsin with a change in concentration and times of action may be found advantageous.