Interference with the glycosylation of Semliki Forest virus proteins.

It has been shown that under defined conditions the multiplication of SFV can be inhibited by specific interference with the production of viral glycoproteins. These conditions are: a) Either 0.2 mM dGlc or 2 mM glucosamine in glucose-containing medium, b) lack of any sugar or energy source in the culture medium, c) pyruvate as energy source, late in the infectious cycle. Under these conditions underglycosylated glycoproteins occur, which cannot be used to form physical or infectious particles. It is not yet clear whether the appearance of a heterogeneous population of molecules in the molecular weight range between 50 and 63,000 is due exclusively to different lengths of the carbohydrate side chains, or also due to wrong splitting or partial degradation of the precursor molecules by cellular proteases. Glucosamine seems to act via the accumulation of UDP-N-acetylglucosamine (or a derivative of it), while dGlc is metabolized along the pathway of mannose and acts mainly as an antimetabolite of mannose.