Antigenic comparison of swine influenza virus isolates

Abstract
Cross hemagglutination inhibition (HI) and neuraminidase inhibition (NI) tests demonstrated strong antigenic relationship between A/Swine/Wisconsin/1/73 (SW/73) and A/Swine/Shope/15/31 (SW/31) influenza viruses. An eightyone fold purification of virus was achieved by adsorption and elution followed by differential ultracentrifugation and sedimentation through linear sucrose gradient. Radio-immunoassay using purified125I labeled viral antigens revealed antigenic variation between the two virus isolates. Neuraminidase of both viruses had pH optima between 6.5 and 7.0, and SW/31 enzyme was relatively more heat stable than SW/73.