Characterization of rabies glycoprotein expressed in yeast

The rabies virus surface glycoprotein was synthesized in Saccharomyces cerevisiae using an expression vector which contains an inducible promoter from the copper metallothionein gene. The rabies G protein was also expressed constitutively in yeast when cloned under control of the triose dehydrogenase promoter. Polypeptides of 65-68 kDa, which migrated at the same molecular weight as authentic viral rabies G protein species, were synthesized by yeast transformants as detected by immunoblotting with rabies specific antiserum. In addition, these polypeptides were immunoprecipitated with several rabies G-specific monoclonal antibodies which neutralize virus infectivity. The recombinant rabies G proteins were glycosylated and associated with membranes in yeast. When injected into guinea pigs, yeast extracts containing the rabies G protein protected animals from lethal rabies virus challenge when administered intramuscularly. However, the same material did not protect mice from a lethal rabies intracerebral challenge.