Influenza A antibodies in Cervine animals.

In the haemagglutination inhibition (HI) test, 20 cervine sera, most of which came from Northern Germany, were treated with receptor destroying enzyme (RDE) and 11 sera were found to contain antibodies against the H1N1 (A/USSR 90/77) and H3N2 (A/Victoria 13/75, A/Texas 1/77) influenza viruses. Only two sera contained antibodies against H3N2 viruses, and seven sera were negative. Evidence of the specificity of influenza antibodies was provided by the following findings: 1) the IgG serum extracts showed the same inhibitory activity of haemagglutinin as the RDE treated sera; 2) addition of protein A led to an increase in the HI titers; 3) in the haemolysis in gel test, some of the HI positive sera formed haemolysis in gel test, some of the HI positive sera formed haemolysis rings of the same diameter as hyperimmune antiinfluenza A (H1N1) serum; and 4) the cervine sera reacted positively in the neuraminidase inhibition (NI) test. It is remarkable that influenza H1N1 antibodies were found in the serum of one cervine before this virus strain appeared in humans.