Carbohydrate-induced conformational changes strongly modulate the antigenicity of coronavirus TGEV glycoproteins S and M.
The carbohydrate composition and the immunoreactivity of the S and M glycoproteins of the coronavirus TGEV were studied at different stages of their maturation. The biosynthesis of S and M was analyzed in the presence of tunicamycin and monensin. The effect of treatment with endoglycosidases H and F and glycopeptidase F on the precursors and mature forms of S and M were also examined. Species 175K and 29K were characterized as high mannose forms of S and M, respectively, and species 220K and 30-36K as complex type glycosylated forms of these two proteins. M was present mainly as a 29K species in mature virions whereas the 175K form of S was not detected, thus implying that the two proteins undergo Golgi modifications at a far different efficiency. Anti-S and -M monoclonal antibodies were examined for their reactivity towards polypeptide species either treated with endo H or produced in the presence of tunicamycin. It was found that (i) among the four major antigenic sites previously defined (Delmas et al., 1986), only site C (amino acids 363 to 371) was notably expressed by the unglycosylated S polypeptide 155K, whereas the three other sites were dependent upon core-glycosylation, (ii) three of the four anti-M mAbs tested did not recognize the unglycosylated M polypeptide 26K. These data led us to conclude that co-translational, but not terminal glycosylation is an essential requirement for both acquisition and maintenance of the antigenicity of TGEV glycoproteins.
Delmas
B
B
Laboratoire de Virologie et d'Immunologie Moléculaires, Institut National de la Recherche Agronomìque, Jouy-en-Josas, France.
Laude
H
H
D000818:Animals; D000911:Antibodies, Monoclonal; D000956:Antigens, Viral / Q000737:chemistry; D002241:Carbohydrates / Q000737:chemistry; D003332:Coronaviridae / Q000737:chemistry / Q000276:immunology*; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology*; D006026:Glycoside Hydrolases; D006031:Glycosylation; D011487:Protein Conformation; D014764:Viral Proteins / Q000737:chemistry / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000956:Antigens, Viral; D002241:Carbohydrates; D006023:Glycoproteins; D014764:Viral Proteins; D006026:Glycoside Hydrolases