Two patterns of persistence of herpes simplex virus DNA sequences in the nervous systems of latently infected mice.

The number of herpes simplex virus (HSV) genome equivalents recovered from latently infected mouse spinal ganglia was compared with the proportion of neurons containing latency-associated transcripts (LATs). Two distinct patterns of HSV persistence were observed, depending on the anatomical location of ganglia with respect to the site of cutaneous inoculation. The location of the bulk of latent viral DNA did not correspond with the highest prevalence of LAT+ neurons. Viral DNA was most abundant in spinal ganglia directly innervating the inoculation site and the amount recovered, which was similar to that found previously in human trigeminal ganglia, suggested that LAT+ neurons each contain hundreds of copies of HSV DNA. In stark contrast, although LAT+ neurons were most abundant in neighbouring ganglia, viral DNA was scarce (approx. 20 copies/LAT+ cell). These data indicate that amplification of HSV DNA sequences is greatest in ganglia previously shown to be associated with viral antigen expression during the productive phase of primary infection.