A STUDY OF 2 MUTANT STRAINS OF PSEUDORABIES VIRUS (PRV) UNABLE TO EXPRESS THYMIDINE KINASE (TK) FUNCTION

Two mutant strains of pseudorabies virus (PRV) were selected from the virulent 86/27V virus treated with chemical drugs. The viruses, named 6A1 and 6C2, respectively, appeared to be unable to express thymidine kinase function, as demonstrated by the autoradiography test. They sho wed a reduced virulence for some susceptible animal species (chickens, mice, rabbits, calves, lambs and piglets) and virus was isolated spor adically. The mutant viruses appeared to be able to protect animals ag ainst infection with the virulent strain of PRV. At gross, as well as at histological examination, no lesions in apparatus, system and tissu es were detected in pigs inoculated with 6A1 and 6C2 viruses. By contr ast, rabbits treated with 6C2 mutant strain presented lymphomononuclea ted cuffs, microgliosis, and neuronophagia in some areas of the brain. This focal spreading, together with the absence of neuronal necrosis and intranuclear inclusions, suggest an infection induced by a modifie d strain of PRV.