DIFFERENTIATION BETWEEN GLYCOPROTEIN-III GENE-DELETED VACCINE AND WILD-TYPE STRAINS OF PSEUDORABIES VIRUS BY POLYMERASE CHAIN-REACTION (PCR)

One of the attenuated and genetically recombinant modified-live viral (MLV) vaccine strains currently used contains a deletion in its glycoprotein III (gIII) gene, while prototypic wild-type pseudorabies (WT-PR) viruses contain an intact gIII gene. A polymerase chain reaction (PCR) system differentiating, based on this difference, between the vaccine virus and prototypic WT-PR viruses was investigated. This PCR system utilized two consecutive stages. Primers for the first-stage PCR were designed so as to amplify of DNA fragments lengths in respect to the vaccine and WT-PR viruses. The second-stage PCR amplification for improving the sensitivity and specificity and for confirming of the sites deleted from the first-stage PCR products produced an all-or-none result: internal DNA fragments were derived from only WT-PR viruses but not from the vaccine virus. These PCR-amplified fragment length polymorphisms clearly distinguished the vaccine virus from WT-PR viruses. The vaccine and WT-PR viruses in mixtures were each identified in this PCR system. This PCR system may permit rapid and sensitive detection of PR viral gIII gene, analysis of the genotype of PR virus isolates, and also examination of the isolates for purity and identity.