Antigenic characterization of influenza A (H1N1) viruses recently isolated from pigs and turkeys in France.

The spread of influenza A viruses from one animal reservoir to another forms an important part of the epidemiological study of influenza. The precise characterization of viral antigens by monoclonal antibodies makes possible an interesting immunological approach to the transfer of strains from one reservoir to another.This work has shown that the recent porcine strains in France, Belgium, and Spain are closely related antigenically, and distinct from the A/sw/NJ/8/76 strain. Their prototype is strain A/sw/Fin/2899/82.An avian strain, A/ty/Brit/46/83, which has caused limited epidemics of reduced egg-laying among turkeys, has a haemagglutinin identical with that of strain A/sw/2899/82.This immunological finding, combined with epidemiological information (geographical location and absence of any influenza antibody in turkey farms in previous years), suggests that the transfer of influenza viruses has taken place in the direction from pig to turkey.