We previously demonstrated that herpes simplex virus type 1 (HSV-1) preferentially establishes latent infection in monoclonal antibody (MAb) A5-positive ganglionic neurons and that a 2.8-kb portion of the HSV-1 genome, corresponding to the 5 end of the LAT (latency-associated transcript) coding region, is responsible for this phenotype (38, 65). In the current study we carried out further genetic mapping of this latency phenotype and investigated some of the mechanisms that might be responsible. Studies with the chimeric virus HSV-1 17syn؉/LAT2, an HSV-1 virus engineered to express HSV-2 LAT, demonstrated that this virus exhibited an HSV-2 latency phenotype, preferentially establishing latency in MAb KH10-positive neurons. This result is complementary to that previously described for the chimeric virus HSV-2 333/LAT1 and indicate that the HSV-1 latency phenotype can be changed to that of HSV-2 by substitution of a 2. Primary infection with herpes simplex virus (HSV) is characterized by local viral replication at the site of inoculation as well as retrograde axonal transport of the virus to regional sensory ganglia where a latent infection may be established. Sensory ganglia are comprised of a heterogeneous population of neurons, and work in our laboratory has demonstrated that different subpopulations of murine ganglionic neurons have different outcomes of infection with HSV (38,39,65). Of the subpopulations of ganglionic neurons that we have studied, those neurons recognized by monoclonal antibodies (MAbs) A5 (specific for a population of neurons expressing Gal1-4GlcNAc-R epitopes) and KH10 (specific for a different population of ganglionic neurons expressing Gal␣1-3Gal1-4NAc-R epitopes) have the most distinct susceptibility phenotypes (19,22,65). Although all neuronal subpopulations appear to be capable of supporting a productive infection with either HSV type 1 (HSV-1) or HSV-2, as assayed by in situ hybridization for the latency-associated transcripts (LAT), HSV-1 preferentially establishes a latent infection in A5-positive neurons whereas HSV-2 preferentially establishes a latent infection in KH10-positive neurons (38), a pattern that is observed following both ocular and footpad inoculation.In the mouse trigeminal ganglion (TG) MAbs A5 and KH10 recognize functionally distinct neuronal populations. Most A5-positive neurons are immunoreactive for neuropeptides and the high affinity nerve growth factor receptor (and terminate in lamina I and IIa of the dorsal horn of the spinal cord), whereas KH10-positive neurons colabel with the lectin BSL-IB 4 (Bandeiraea simplicifolia isolectin B 4 ), identifying them as a population of small-diameter, peripherin-positive, glial cell line-derived neurotrophic factor-responsive, but vanilloid receptor-negative neurons that terminate largely in lamina IIb of the dorsal horn of the spinal cord (3,19,38,42,52,67). These observations highlight the importance of studying the interaction of HSV with different sensory neuronal subtypes in order to gain a complete understanding ...