Persistence of a T Cell Infiltrate in Human Ganglia Years After Herpes Zoster and During Post-herpetic Neuralgia

Abstract

Varicella-zoster virus (VZV) is a human herpesvirus which causes varicella (chicken pox) during primary infection, establishes latency in sensory ganglia, and can reactivate from this site to cause herpes zoster (HZ) (shingles). A major complication of HZ is a severe and often debilitating pain called post-herpetic neuralgia (PHN) which persists long after the resolution of the HZ-associated rash. The underlying cause of PHN is not known, although it has been postulated that it may be a consequence of immune cell mediated damage. However, the nature of virus-immune cell interactions within ganglia during PHN is unknown. We obtained rare formalin fixed paraffin embedded sections cut from surgically excised ganglia from a PHN-affected patient years following HZ rash resolution. VZV DNA was readily detected by qPCR and regions of immune infiltration were detected by hematoxylin and eosin staining. Immunostaining using a range of antibodies against immune cell subsets revealed an immune cell response comprising of CD4⁺ and CD8⁺ T cells and CD20⁺ B cells. This study explores the immune cell repertoire present in ganglia during PHN and provides evidence for an ongoing immune cell inflammation years after HZ.

Keywords: ganglia; herpes zoster (HZ); immune cell; post-herpetic neuralgia (PHN); varicella-zoster virus.

FIGURE 1

Histology of human ganglia during post-herpetic neuralgia (PHN) and herpes zoster (HZ). Representative images of hematoxylin and eosin staining ganglion sections from PHN ganglia sample 1 (A) and sample 2 (B) showing infiltrates of small round immune-like cells (arrows). Ganglion sections from a case of active HZ (C), and control ganglia sample 1 (D) and 2 (E).

FIGURE 2

Immunohistochemical detection of VZV antigens in human ganglia from patients experiencing herpes zoster. Representative images of ganglionic sections from PHN1 (A) and PHN2 (B), HZ (C), and CON1 (D), as well as a positive control section of infected human fibroblasts stained (F) with an anti-VZV IE63 specific antibody. Isotype control antibodies were also applied to a HZ ganglion section (E). Bound primary antibodies were visualized using DAB substrate, and sections were counterstained with Azure B.

FIGURE 3

Characterization of the immune response within human ganglia during herpes zoster and post-herpetic neuralgia. (A) Representative images are shown for PHN1, HZ, and CON1. Primary antibodies used were specific for CD3, CD4, CD8, and CD20, and were detected using Alexa Fluor fluorescent conjugated antibodies (red). Sections were counterstained with DAPI (blue). All PHN sections were co-stained with all immune cell antibodies, HZ and CON1 with CD3 with an antibody specific for the satellite cell marker S100 (green). (B) The number of positive cells per square millimeter for each immune cell marker examined was determined for at least two independent stains and the average is shown.