SPECIFICITY OF THE N1 AND N2 SIALIDASE SUBTYPES OF HUMAN INFLUENZA-A VIRUS FOR NATURAL AND SYNTHETIC GANGLIOSIDES

Sialyl-linkage specificity of sialidases of the human influenza A viru s strains, A/Aichi/2/68 (H3N2) and A/PR/8/34 (H1N1) were studied using natural and synthetic gangliosides. The sialidase of the A/Aichi/2/68 strain hydrolyzed the terminal Neu5Ac alpha 2-3Gal sequence but not t he Neu5Ac alpha 2-3 linkage on the inner Gal of GM1a, which is a gangl ioside that has the gangliotetraose chain (Gal beta 1-3GalNAc beta 1-4 -(Neu5Ac alpha 2-3) Gal beta 1-4Glc beta 1-Cer). The sialidase hydroly zed the Neu5Ac on the inner Gal of GM2, which had a shorter gangliotri ose chain. GM4, which had the shortest chain (Neu5Ac alpha 2-3Gal beta 1-Cer) of the gangliosides, had a lower substrate specificity. The N1 and N2 sialidase subtypes of the human influenza A virus had no signi ficant variation in their substrate specificity for the gangliosides. Analysis of 11 synthetic gangliosides, which contained various ceramid e or sialic acid moieties, demonstrated that A/Aichi/2/68 (H3N2) siali dase recognized the ceramide and sialic acid moiety and the length and structure of the sialyl sugar chain.