Replication and virulence of early protein 0 and long latency transcript deficient mutants of the Aujeszky's disease (pseudorabies) virus

Early protein 0 (EP0)-deficient recombinant Aujeszky's disease viruses, Ka- ep0lac and Ba-ep0lac derived from strains Kaplan and Bartha, respectively, were constructed to explore the impact of the mutation on replication, viru lence and latency of the virus. Inactivation of the EP0 gene resulted in a mutation of long latency transcript (Cheung et al., 1991) that is located o n the complementary DNA strand of EP0 and immediate early protein (IE)175 g enes. In infection of immortalized porcine kidney cells, the growth rate an d yield of both EP0(-) mutant strains were significantly smaller than that of wild-type virus. Ka-ep0lac was found to be highly virulent, while Ba-ep0 lac showed an attenuated phenotype in mice. PCR assay and immunohistochemis try showed that the Ba-ep0lac virus was able to establish latency in the mo use trigeminal ganglia. However, latent virus was not able to reactivate in explant reactivation assays. Accordingly, latent Ba-ep0lac has the potenti al to be exploited as vectors for the delivery of foreign genes to the nerv ous system. (C) 2000 Editions scientifiques et medicales Elsevier SAS.