VACCINATION AGAINST RABIES - CONSTRUCTION AND CHARACTERIZATION OF SAG2, A DOUBLE AVIRULENT DERIVATIVE OF SAD(BERN)

A double avirulent mutant was isolated from the SAD(Bern) strain of ra bies virus by two successive selection steps using neutralizing anti-g lycoprotein monoclonal antibodies. Both mutations affect the triplet c oding for amino acid 333 of the glycoprotein. The resulting virus, cal led SAG2, has a glutamate coded by GAA in position 333 instead of an a rginine. This new codon differs by two nucleotides from all the argini ne triplets. SAG2 is avirulent in adult mice by intracerebral and intr amuscular routes and it protects mice against a challenge by the CVS s train. This double mutant is still avirulent after three successive pa ssages in suckling mouse brain or after ten successive cycles of multi plication in cell culture. Because it is protective and genetically st able, SAG2 represents an improvement on SAG1 which is already used for oral vaccination of foxes in Switzerland and France. It could also be a candidate for oral vaccination of dogs against rabies.