The immunological reactivity of the surface glycoproteins (gp85) of avian myeloblastosis virus (AMV) and B77 avian sarcoma virus were examined by competition radioimmunoassay. The influence of the protein and carbohydrate portions of the glycoprotein on the antigenic reactivity was investigated by systematic digestions of AMV gp85 with proteases and glycosidases. Digestion of AMV gp85 with trypsin, trypsin and chymotrypsin, or Pronase had no effect on the antigenicity detected in competition radioimmunoassay using rabbit antibody made against AMV gp85. However, digestion of AMV gp85 with a mixture of highly purified glycosidases (neuraminidase, β-galactosidase, β-N-acetylglucosaminidase, and endo-β-N-acetylglucosaminidase) eliminated the reactivity detected in competition radioimmunoassay with the same antisera. The contribution of individual carbohydrates to the reactivity was studied by a sequential digestion of AMV gp85 with various combinations of glycosidases. These studies suggested that removal of sialic residues had no effect on antigenicity and that removal of β-galactose and β-N-acetylglucosamine residues abolished antigenic reactivity. In addition, glycosidase digestion of 125I-labeled AMV gp85 resulted in a decrease of reactivity in direct radioimmunoassay. These results indicate that the immunological reactivity of AMV gp85 depends upon an intact carbohydrate side chain. Digestion of AMV gp85 with proteases and glycosidases, followed by competition radioimmunoassay using antibody prepared against B77 gp85, showed that protease treatment reeulted in a partial loss of antigenic reactivity. Treatment of B77 gp85 with proteases and glycosidases, followed by competition radioimmunoassay using antibody prepared against B77 gp85, showed that protease treatment resulted in a partial loss of antigenic reactivity, while glycosidase treatment resulted in no loss of antigenic reactivity.
|Number of pages||12|
|State||Published - May 1 1978|
Bibliographical noteFunding Information:
We thank Dr. R. Hill and Dr. L. Glasgow for purified glycosidases, Dr. A. Hizi for purified B77 gp85, and Dr. D. P. Bolognesi and Dr. J. Li for anti+@% sera. We are also grateful to Dr. D. P. Bolognesi for generous gifts of reagents and to Dr. T. C. Vanaman for encouragement and helpful discussions. This research was supported by National Cancer Institute Research Grant CA 12323. L.J.V.E. is a recipient of National Science Foundation Graduate Fellowship 3380019.
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