Differences in the biological phenotype of low-yielding (L) and high-yielding (H) variants of swine influenza virus A/NJ/11/76 are associated with their different receptor-binding activity

摘要

Growth properties of low (L-) and high (H-)-yielding strains of A/sw/NJ/11/76 influenzavirus were compared in embryonated chicken eggs and MDCK cells. Binding affinities of the strains from membrane fractions prepared from cells of chick embryo allantoic membrane, MDCK and swine tracheal cells and for soluble sialic acid containing macromolecules and monovalent sialosides, were also compared. The progeny of the L variant remained predominantly cell associated in infected MDCK cells and eggs so thataccumulation of the L stain in allantoic or culture fluid is slowed compared to the H variant. Examination of the infectious foci formed in MDCK cell monolayers and on allantoic membrane showed that L variant spreads predominantly from cell to cell while spread of H variant is associated with the release of virus progeny into solution and then rapid distribution over the cell monolayer by conventional flow of the liquid. Binding affinity of L variant was higher for cellular membranes, gangliosides andsialyglycoproteins. The affinity for the monovalent sialic acid compounds was comparable. L variant bound strongly to dextran sulfate, unlike the H variant. These results suggest that previously reported differences for the L and H phenotypes could be explained by the higher binding affinity of the L variant to the surface of target cells and that this is due mainly to increased electrostatic interactions.