RECENT DEVELOPMENTS IN LATENCY AND RECOMBINATION OF AUJESZKYS-DISEASE(PSEUDORABIES) VIRUS

Latency is a characteristic and fascinating part of the biology of alp haherpesvirinae, including ADV. Tissue explantation, blot hybridizatio n, in situ hybridization and more recently PCR are the experimental me thods used to demonstrate that latent infections consistently occur in ganglionic neurons and, at a lower level, in tonsillar and possibly o ther cells. In vivo reactivation of ADV, resulting in shedding of viru lent ADV, has been demonstrated experimentally following administratio n of high doses of corticosteroids. To determine the influence of vacc ination with currently used gene deleted vaccines on field virus laten cy load, it is essential to use quantitative latency detection methods , We have developed chemiluminescence-based quantitative PCR assays sp ecific for gG and gE, and are currently using these to determine field virus latency loads in tissues of pigs vaccinated with one of several gene deleted vaccines. Recombination between ADV strains has been dem onstrated both in vitro and in vivo and has raised concerns about the generation of gene deleted virulent ADV strains. Recent studies in a m ouse model have shown that high concentrations of both strains have to be present at the same anatomical site for recombination to take plac e. This led to the conclusion that ongoing ADV eradication programs, b ased upon the use of gene deleted vaccines and differential serologica l testing, are not likely to be threatened by recombination between vi rulent ADV and gene deleted vaccine strains. (C) 1997 Elsevier Science B.V.