Receptor Specificity of Influenza A Viruses Correlates with the Agglutination of Erythrocytes from Different Animal Species

Abstract

Despite their uniform ability to bind to oligosaccharide-containing terminal sialic acids, influenza A viruses show differences in receptor specificity. To test whether agglutination of erythrocytes from different animal species could be used to assess the receptor specificity of influenza A viruses, we determined the agglutinating activities of a range of virus strains, including those with known receptor specificities, using erythrocytes from seven animal species. All equine and avian viruses, including those known to recognizeN-acetyl andN-glycolyl sialic acid linked to galactose by the α2,3 linkage (NeuAcα2,3Gal and NeuGcα2,3Gal), agglutinated erythrocytes from all of the animal species tested (chickens, ducks, guinea pigs, humans, sheep, horses, and cows). The human viruses, including those known to preferentially recognize NeuAcα2,6Gal, agglutinated all but the horse and cow erythrocytes. Fluorescence-activated cell sorting analysis of erythrocytes using linkage-specific lectins [Sambucus nigraagglutinin for sialic acid (SA)α2,6Gal andMaackia amurensisagglutinin for SAα2,3Gal] showed that both cow and horse erythrocytes contain a large amount of SAα2,3Gal-, but virtually no SA2,6Gal-specific lectin-reactive oligosaccharides on the cell surface, while human and chicken erythrocytes contained both types of oligosaccharides. Considering that the majority (>93%) of sialic acid in horse and cow erythrocytes is of theN-glycolyl type, our results suggest that viruses able to agglutinate these erythrocytes (i.e., avian and equine viruses) recognize NeuGcα2,3Gal. These findings also show that agglutinating assays with erythrocytes from different animal species would be useful in characterizing the receptor specificity of influenza A viruses.