T-Cell Infiltration Correlates with CXCL10 Expression in Ganglia of Cynomolgus Macaques with Reactivated Simian Varicella Virus

Abstract

Ganglia of monkeys with reactivated simian varicella virus (SVV) contained more CD8 than CD4 T cells around neurons. The abundance of CD8 T cells was greater less than 2 months after reactivation than that at later times and correlated with that of CXCL10 RNA but not with those of SVV protein or open reading frame 61 (ORF61) antisense RNA. CXCL10 RNA colocalized with T-cell clusters. After SVV reactivation, transient T-cell infiltration, possibly mediated by CXCL10, parallels varicella zoster virus (VZV) reactivation in humans. Varicella zoster virus (VZV) causes varicella (chickenpox) and becomes latent in ganglia, producing zoster (shingles) upon reactivation. Because VZV infects only humans, studies of virus latency and reactivation have been restricted to autopsy tissues. Analyses of ganglia obtained after death from individuals with recent zoster revealed lymphocytic infiltration (1, 2), possibly mediated by antigenic stimuli or chemokines, including CXCL10 (3). VZV-specific T cells have not been identified in human ganglia latently infected with VZV (4, 5). Simian varicella virus (SVV) infection in monkeys closely resembles VZV infection in humans (6). Earlier, we demonstrated reactivation of latent SVV in immunosuppressed monkeys (7). Herein, we extended those studies by examining ganglia containing reactivated SVV for infiltrating T cells. Four cynomolgus macaques (GP02, -04, -06, and -07) were naturally infected with SVV (7). Ten to 14 days later, all monkeys developed varicella ( Fig. 1). At 4 months postinfection, monkeys were immunosuppressed with tacrolimus, resulting in a 34% reduction in mean white blood cell counts at 6 weeks posttreatment (7). Monkeys GP02, -06, and -07 developed zoster at 23, 3, and 10 days, respectively, after starting tacrolimus. Monkeys were euthanized at monthly intervals post-tacrolimus treatment (Fig. 1). Detection of SVV glycoproteins in lungs and multiple ganglia in monkey GP04, which did not develop skin rash, confirmed subclinical reactivation (7).Immunohistochemical analysis of consecutive ganglion tissue sections from these monkeys and from an uninfected control monkey (CTRL) for CD3, CD4 and CD8 expression showed that SVV reactivation was associated with T-cell infiltration, mostly CD8 T cells, in ganglia along the entire neuraxis (Fig. 2). T cells were dispersed throughout ganglia. T-cell clusters, of both CD4 and CD8 T cells, were occasionally detected adjacent to neurons ( Fig. 2A). Rare granzyme B ϩ (grB) cells, not restricted to T-cell clusters, were observed in ganglia from all monkeys ( Fig. 2A), suggesting that ganglion-infiltrating T cells did not encounter their cognate antigen (8). Ganglion-infiltrating CD8 T cells in zoster patients are also predominantly grB negative (9).We analyzed 11 to 19 ganglia from each monkey to determine the number of T cells per neuron. The number of ganglionic neurons counted in sections from each anatomical level of the neuraxis ranged from 657 to 3,991 (Table 1). Ganglia obtained from monkey GP02, euthanized at 4 days post-...

Acute Simian Varicella Virus Infection Causes Robust and Sustained Changes in Gene Expression in the Sensory Ganglia

“…As previously reported for ganglion explants experimentally infected with VZV (6) and ganglia collected from acutely infected AGMs (14), we saw an upregulation of CXCL10 in the ganglia at 7 dpi. CXCL10 is a chemokine that can be produced by neurons, astrocytes, and oligodendrocytes (145) and binds the receptor CXCR3 on memory T cells and NK cells to induce their migration to the site of infection (146).…”

“…Previous studies have shown a role for T cells in VZV and SVV dissemination (14,28,29). To determine whether T cells infiltrate the ganglia early after SVV infection in rhesus macaques, we digested DRG-T, DRG-C, and DRG-LS collected 3, 7, 10, 14, and 100 dpi and analyzed the isolated lymphocytes using flow cytometry and antibodies directed against CD4, CD8, CD28, CD95, and CCR7 in order to delineate naive and memory T cell subsets as well as CD20, CD27, and IgD to delineate naive and memory B cell subsets as recently described (19).…”

“…Intrabronchial infection of rhesus macaques (RM) with the closely related simian varicella virus (SVV) recapitulates hallmarks of primary VZV infection, including the appearance of varicella, the development of cellular and humoral immunity, and establishment of latency in sensory ganglia (10). Moreover, as described for VZV, SVV can reactivate during episodes of immune suppression and stress (11)(12)(13), and this reactivation is accompanied by the upregulation of CXCL10 and T cell infiltration (14). Recent studies using African green monkeys (AGMs) inoculated with SVV-enhanced green fluorescent protein (EGFP) have shown that SVV infects T cells that infiltrate the ganglia during acute infection 9 dpi (15).…”

Molecular mechanisms of varicella zoster virus pathogenesis

“…DRG xenografts can be used to investigate VZV–neuron interactions, but axonal transport to skin cannot be examined in this model, and stimuli of viral reactivation from latency have not been explored. By contrast, simian varicella virus (SVV) can be studied in the natural non-human primate host 99,100 and has been used to investigate reactivation that is associated with immunosuppression 84 . The SVV model avoids the need to acquire human tissue to make xenografts, which is a limitation of the SCID model, but genetic dissimilarities between SVV and VZV are likely to lead to differences in pathogenesis in their native hosts.…”

Simian Varicella Virus Is Present in Macrophages, Dendritic Cells, and T Cells in Lymph Nodes of Rhesus Macaques after Experimental Reactivation

“…In rhesus macaques, intrabronchial inoculation with SVV produces varicella, followed by the establishment of latency (5) and virus reactivation after X-irradiation (6,7). At the time of SVV reactivation in CM, expression of CXCL10 (a chemokine which recruits activated T cells and NK cells) correlates with transient T cell infiltration in ganglia (8). In the study described here, we determined if a combination of irradiation and treatment with prednisone and tacrolimus induces reactivation of SVV in latently infected rhesus macaques to study the distribution of reactivated SVV in ganglionic and nonganglionic tissues.…”