Submitted to: Agri Practice
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 1996
Publication Date: N/A
Interpretive Summary: The economic impact of pseudorabies virus (PRV) on the swine industry in the United States has been estimated to be $60 million annually. This includes costs of disease control, such as vaccination and quarantine, as well as losses due to clinical disease. Swine that survive initial exposure become latently-infected carriers of PRV. Latent viruses sometimes reactivate from dormancy and replicate, and infectious viruses are disseminated to susceptible animals. The latency-reactivation cycle is believed to be the primary way by which PRV survives in the swine population. All current PRV vaccines are capable of the establishment of, and reactivation from, latency. This work uncovered two viral genes, the early protein 0 (EP0) and large latency transcript (LLT) genes, that are important for the pathogenesis of PRV and have potential for use in vaccine development.
Technical Abstract: A double mutant of pseudorabies virus (EL-beta) with deletions in the latency and early protein 0 genes was examined. The results demonstrated that EL-beta is attenuated for replication in tissue culture cells and in swine. In comparison with InFh-infected pigs, EL-beta-infected swine shed significantly less virus and EL-beta was not reactivated from latency by dexamethasone treatment. Furthermore, EL-beta could induce solid protection in animals without causing noticeable clinical signs at low dosages. Mutations in these genes can be engineered into current vaccine viruses which will further reduce their virulence while inducing protective immunity in swine. These new vaccine candidates are expected to exhibit lower ability to reactivate from latency and reduced spreading to susceptible animals. A safer pseudorabies virus vaccine will aid in the eventual eradication of the virus and benefit the swine industry.