Conversion of US3-encoded protein kinase gene from pseudorabies virus in adiploid gene located within inverted repeats by genetic recombination between the viral genome isomers

The pseudorabies virus (PRV) genome consists of two components, long (U-L) and short (U-S) regions. The U-S region is the only one capable of invertin g itself relative to the U-L region during productive infection, generating two equimolecular isomeric forms of viral DNA. Here we describe a recombin ant virus (gIp2) generated by genetic recombination between pseudorabies vi ral isomers. This recombination event was observed in the parental virus gI S8, which was obtained by insertion of the alpha 4-TK herpes simplex virus type 1 (HSV1) gene. The growth of gIS8 virus in the presence of 5-bromodeox yuridine (BrdU) yielded gIp2. This was generated by nonhomologous recombina tion either between the two viral genomic isomers of gIS8, P and I-US, or b etween the same P isomer using nonhomologous and homologous recombination, with loss of the HSV1 sequences and duplication of the PRV US3-encoded prot ein kinase gene. Virus gIp2 is negative for TM, gI, gE, 11K and 28K and sho ws an in vitro replication capacity in neuronal cells approximately 22 time s lower than that of parental virus gIS8, and similar to that of the Bartha vaccine virus strain in monkey kidney and human neuronal cells. (C) 1999 E lsevier Science B.V. All rights reserved.