Immunohistochemical analysis of primary sensory neurons latently infected with herpes simplex virus type 1

Abstract

We characterized the populations of primary sensory neurons that become latently infected with herpes simplex virus (HSV) following peripheral inoculation. Twenty-one days after ocular inoculation with HSV strain KOS, 81% of latency-associated transcript (LAT)-positive trigeminal ganglion (TG) neurons coexpressed SSEA3, 71% coexpressed Trk(A) (the high-affinity nerve growth factor receptor), and 68% coexpressed antigen recognized by monoclonal antibody (MAb) A5; less than 5% coexpressed antigen recognized by MAb KH10. The distribution of LAT-positive, latently infected TG neurons contrasted sharply with (i) the overall distribution of neuronal phenotypes in latently infected TG and (ii) the neuronal distribution of viral antigen in productively infected TG. Similar results were obtained following ocular and footpad inoculation with KOS/62, a LAT deletion mutant in which the LAT promoter is used to drive expression of the Escherichia coli lacZ gene. Thus, although all neuronal populations within primary sensory ganglia appear to be capable of supporting a productive infection with HSV, some neuronal phenotypes are more permissive for establishment of a latent infection with LAT expression than others. Furthermore, expression of HSV LAT does not appear to play a role in this process. These findings indicate that there are marked differences in the outcome of HSV infection among the different neuronal populations in the TG and highlight the key role that the host neuron may play in regulating the repertoire of viral gene expression during the establishment of HSV latent infection.

FIG. 1

Representative examples of KOS/62-infected TG tissue sections stained by dual immunofluorescence to identify neuronal subpopulations expressing β-Gal or HSV antigen. At 3 days p.i., HSV antigen expression (A and B) can be seen colocalizing to KH10- and CGRP-immunoreactive neurons (A′ and B′, respectively). At 7 days p.i., β-Gal expression (C and D) can be seen colocalizing to Trk_A- and A5-immunoreactive neurons (C′ and D′ respectively). Magnification bar represents 100 μm.

FIG. 2

Representative examples of KOS-infected TG tissue sections, 21 days p.i., assayed by FISH for LAT (A to G) and immunoperoxidase for specific neuronal subpopulations (A′ to G′). Panels A′ to G′ are examples of neurons labeled with Trk_A, CGRP, b-NOS, SP, KH10, A5, and SSEA3 antisera, respectively. Magnification bar represents 100 μm.