[Immunovirologic markers of the risk of influenza A H3N2 among swine]

Abstract

A seroepidemiological survey using the radial haemolysis test has been performed on a representative sampling of the pig herds in Brittany. Since 1978, Influenza A H3N2 strains spread in that reservoir giving subclinical infections. We detected antibodies directed against the Influenza prototypes isolated during the human outbreaks from 1973 to 1977. Only one H3N2 virus was isolated in 1980: its antigenic structure was in agreement with the previous serological data. In 1984 outbreaks of swine Influenza A H3N2 occurred. The isolated viruses carried an hemagglutinin antigenically identical to the one of the 1980's strain but the neuraminidase looked clearly different. When studying the specific immune response of the young animals to the influenza infection, it appeared that the hemagglutinin of the 1984's viruses antigenically varied from the 1980's ones in about 2/3 of all the animals. With monoclonal antibodies anti N3 and N2 of the human prototypes we confirmed the data obtained in using the post infection ferret antisera. Monoclonal antibodies directed against the swine H3N2 1984 viruses are in preparation. We have no precise information so far on the mechanism of the antigenic variations.