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

Binding characteristics of Hyphantria cunea nuclear polyhedrosis virus (HcN PV) to Spodoptera frugiperda 21 (Sf21) cells was determined. The cells disp layed an affinity of 0.9 x 10(10) M-1 with about 8900 binding sites per cel l. The biochemical nature of HcNPV-binding sites on the cell surface was al so partially elucidated. There were 45 to 49% reductions in HcNPV binding f ollowing the pretreatment of cells with three proteases, suggesting the inv olvement of a cellular protein component in virus binding. Tunicamycin, whi ch inhibits N-linked glycosylation and the expression of some membrane prot eins on the cell surface, reduced virus binding suggesting a role for glyco protein(s) in binding. Treatment of cells with wheat germ agglutinin or neu raminidase did not measurably reduce virus binding, indicating that oligosa ccharides containing N-acetylglucosamine or sialic acid are not directly in volved in HcNPV attachment. The negative effect of methylamine on HcNPV bin ding 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 cel ls may be closely linked to viral entry via receptor-mediated endocytosis. These findings suggest that the binding site moiety has a glycoprotein comp onent, but that direct involvement of oligosacccharides containing N-acetyl glucosamine or sialic acid residues in binding is unlikely, and that HcNPV attachment to Sf21 cells might be via receptor-mediated endocytosis.