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SUMMARYThe replication of flaviviruses results in the secretion of four virus-coded proteins into the extracellular environment. Three of these proteins, E, C and M (or pre-M), are found in purified virions. A fourth virus-specified extracellular protein which was not present in either the slowly sedimenting haemagglutinin particles or in virions is described. The relationship of this protein to the intracellular NSI polypeptide was investigated along with its similarity to the soluble complement-fixing antigen (SCF) reported for mosquito-borne flaviviruses. The difference in the Mr of NS1 and SCF is the result of additional glycosylation of SCF, mostly by the addition of fucose molecules. The synthesis orE and NS1 is sequential but their secretion is simultaneous, suggesting a role for NS1 in virion protein transport or virion release.

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SUMMARYTick-borne encephalitis virus codes for two major immunogenic polypeptides, one of which is the major virion envelope protein E, and the other, NV3, does not have a designated function at present. The intracellular forms of both the E and NV3 polypeptides contain at least four types of sugar residues, i.e. galactose, glucosamine, fucose and mannose. The only glycoprotein in the extracellular virion particles is E. Experiments performed in the presence of tunicamycin have demonstrated that most of these sugars are N-linked. The kinetics of synthesis of E and NV3 have been studied and both show a distinct lag period between initiation of protein synthesis and the appearance of either protein.

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