Antigenic Relationships of Swine Influenza Virus

SUMMARY: Antigenic comparisons of six strains of swine influenza virus with three strains of human influenza A virus were made by the agglutination-inhibition technique. The strains were also compared in regard to inhibition by normal sera, rate of elution from red cells, pathogenicity for mice, and other properties. All swine strains were significantly different from human strains. Four American swine strains formed a fairly homogeneous group, but were less closely related to two strains recovered in the United Kingdom. The findings are briefly discussed in terms of the relationship between human and swine influenza.