Investigation of pseudorabies virus DNA and RNA in trigeminal ganglia and tonsil tissues of latently infected swine.

Pseudorabies virus (PRV) nucleic acids in the trigeminal ganglia and tonsils of swine latently infected with the virus were analyzed. By use of DNA-polymerase chain reaction (PCR), 14 of 14 trigeminal ganglia and 12 of 14 tonsils were positive for PRV genomes. By use of RNA-PCR, RNA containing the large latency transcript splice junction were detected in 4 of 4 trigeminal ganglia and 4 of 5 tonsils. In general, results of both PCR procedures indicated that the amounts of PRV DNA and RNA per microgram of cellular nucleic acids were higher in trigeminal ganglia than in tonsils. Identification of peripheral tissues that harbor latent PRV is an important asset for PRV research. The presence of large latency transcript in tonsil tissues, in the absence of virus replication, is a critical characteristic, which indicates that the tonsil is a site of PRV latency. For diagnostic purposes, animals need not be euthanatized to obtain their nervous tissue to determine latency; instead, tonsil biopsy specimens could be obtained from live animals for analysis. For pathogenesis, studies, multiple specimens obtained sequentially from the same animal would be available for examination for the duration of the experiment.