Studies on the glycosylation of flavivirus E proteins and the role of carbohydrate in antigenic structure.

The glycosylation pattern of several flavivirus E proteins as well as the role of carbohydrate in biological functions and the antigenic structure of tick-borne encephalitis (TBE) virus were investigated by the use of specific endoglycosidases. Endoglycosidase F digestion revealed the presence of a single asparagine-linked oligosaccharide side chain in TBE virus (Western and Far Eastern subtype), Louping III virus, Murray Valley encephalitis virus, and Rocio virus. Consistent with published sequence data, the E protein of West Nile virus apparently is not glycosylated at all. Evidence derived from digestion experiments using endoglycosidase H indicates that the tick-borne viruses contain high-mannose type N-linked oligosaccharide side chains, whereas that of the mosquito-borne Murray Valley encephalitis virus and Rocio virus is endoglycosidase H resistant. Complete deglycosylation of TBE virus by endoglycosidase F did not impair infectivity and HA activity. Carbohydrate does not seem to play a major role in the antigenic structure of the TBE virus glycoprotein since the reactivity of the native virus and the deglycosylated virus was identical when analyzed with monoclonal as well as polyclonal immune sera.