Correlation between Herpes Simplex Virus Type 1 Rate of Reactivation from Latent Infection and the Number of Infected Neurons in Trigeminal Ganglia

Abstract

The presence of wild-type herpes simplex virus type 1 (HSV-1) and several latency associated transcript (LAT) region mutants within the trigeminal ganglia (TG) of latently infected mice was examined. A combination of methods including conventionalin situhybridization to detect viral LAT and anin situDNA polymerase chain reaction (PCR) to detect viral DNA was used. These data show that, for all virus strains in which a comparison was possible, the population of neurons expressing detectable levels of LAT was approximately one-third the total number of viral DNA-containing cells. In addition,in situPCR analysis revealed that mutants such as 17ΔSty, 17ΔBstE, and 17ΔS/N, which contain deletions within the LAT locus which do not affect the kinetics of viral reactivation from explanted murine TG, are present in as many neurons as wild-type virus. This was true regardless of the ability to induce accumulation of intact 2.0-kb LAT. On the other hand, mutant 17ΔN/H, which contains a deletion removing the LAT promoter and surrounding genomic region and reactivates slowly from explanted TG, was present in only one-sixth as many neurons as wild-type virus. These data show that detection of mutants unable to synthesize or accumulate 2.0-kb LAT (such as 17ΔN/H) is possible within situDNA PCR and that the slow reactivation phenotype of 17ΔN/H correlates with a reduced number of HSV DNA-containing neurons.