Biochemical analysis of Hyphantria cunea NPV attachment to Spodoptera frugiperda 21 cells.

Binding characteristics of Hyphantria cunea nuclear polyhedrosis virus (HcNPV) to Spodoptera frugiperda 21 (Sf21) cells was determined. The cells displayed an affinity of 0.9 x 10(10) M(-1) with about 8900 binding sites per cell. The biochemical nature of HcNPV-binding sites on the cell surface was also partially elucidated. There were 45 to 49% reductions in HcNPV binding following the pretreatment of cells with three proteases, suggesting the involvement of a cellular protein component in virus binding. Tunicamycin, which inhibits N-linked glycosylation and the expression of some membrane proteins on the cell surface, reduced virus binding suggesting a role for glycoprotein(s) in binding. Treatment of cells with wheat germ agglutinin or neuraminidase did not measurably reduce virus binding, indicating that oligosaccharides containing N-acetylglucosamine or sialic acid are not directly involved in HcNPV attachment. The negative effect of methylamine on HcNPV binding seems to be due to the fact that HcNPV entry via an endocytic pathway is blocked by the increased pH of the endosome. Data on energy inhibitors (sodium azide and dinitrophenol) indicates that HcNPV attachment to Sf21 cells may be closely linked to viral entry via receptor-mediated endocytosis. These findings suggest that the binding site moiety has a glycoprotein component, but that direct involvement of oligosacccharides containing N-acetylglucosamine or sialic acid residues in binding is unlikely, and that HcNPV attachment to Sf21 cells might be via receptor-mediated endocytosis.