The mannosidase inhibitors 1-deoxymannojirimycin and swainsonine have no effect on the biosynthesis and infectivity of Rous sarcoma virus.

The effects of inhibitors, which interfere with oligosaccharide trimming by blocking mannosidases, on the processing and export of the viral glycoproteins of Rous sarcoma virus (RSV), have been studied. 1-Deoxymannojirimycin (DIM) prevents removal of mannose residues from the Man9 (GlcNAc)2 oligosaccharide whereas swainsonine (SW) blocks at a later stage resulting in the formation of so-called hybrid oligosaccharides. Under a regime of these inhibitors, proteolytic cleavage of the viral glycoprotein precursor can still occur to yield aberrant glycoprotein products, gp75DIM/gp30DIM and gp80SW/gp30SW. Virus particles carrying these aberrant viral glycoproteins are released from inhibitor-treated cultures in normal amounts and these virions are fully infectious. Thus blocking oligosaccharide trimming at the stages described here or, using different inhibitors, at different stages as described previously (J. V. Bosch and R. T. Schwarz, Virology 132, 95-109 (1984)), does not have any influence on the infectivity of Rous sarcoma virus.