Reactivation of Simian Varicella Virus in Rhesus Macaques after CD4 T Cell Depletion

Abstract

Rhesus macaques intrabronchially inoculated with simian varicella virus (SVV), the counterpart of human varicella-zoster virus (VZV), developed primary infection with viremia and rash, which resolved upon clearance of viremia, followed by the establishment of latency. To assess the role of CD4 T cell immunity in reactivation, monkeys were treated with a single 50-mg/kg dose of a humanized monoclonal anti-CD4 antibody; within 1 week, circulating CD4 T cells were reduced from 40 to 60% to 5 to 30% of the total T cell population and remained low for 2 months. Very low viremia was seen only in some of the treated monkeys. Zoster rash developed after 7 days in the monkey with the most extensive CD4 T cell depletion (5%) and in all other monkeys at 10 to 49 days posttreatment, with recurrent zoster in one treated monkey. SVV DNA was detected in the lung from two of five monkeys, in bronchial lymph nodes from one of the five monkeys, and in ganglia from at least two dermatomes in three of five monkeys. Immunofluorescence analysis of skin rash, lungs, lymph nodes, and ganglia revealed SVV ORF63 protein at the following sites: sweat glands in skin; type II cells in lung alveoli, macrophages, and dendritic cells in lymph nodes; and the neuronal cytoplasm of ganglia. Detection of SVV antigen in multiple tissues upon CD4 T cell depletion and virus reactivation suggests a critical role for CD4 T cell immunity in controlling varicella virus latency. IMPORTANCE Reactivation of latent VZV in humans can result in serious neurological complications. VZV-specific cell-mediated immunity is critical for the maintenance of latency. Similar to VZV in humans, SVV causes varicella in monkeys, establishes latency in ganglia, and reactivates to produce shingles. Here, we show that depletion of CD4 T cells in rhesus macaques results in SVV reactivation, with virus antigens found in zoster rash and SVV DNA and antigens found in lungs, lymph nodes, and ganglia. These results suggest the critical role of CD4 T cell immunity in controlling varicella virus latency. KEYWORDS CD4 T cell depletion, animal model, simian varicella virus reactivation V aricella-zoster virus (VZV) causes chickenpox (varicella) in children, becomes latent in ganglia, and reactivates decades later to produce shingles (zoster) in the elderly due to the decline of VZV-specific T cells important in maintaining virus latency (1). Reactivation of latent VZV is associated with serious neurological complications, including postherpetic neuralgia (the most common cause of suicide in the elderly), characterized by the persistence of pain for more than 3 months after zoster (2). VZV reactivation can result in vasculopathy (3) and giant cell arteritis, which causes primary systemic vasculitis, leading to blindness and stroke, and other multisystem diseases that can occur without rash (4-6). Persistent inflammation, with the predominance of T cells and macrophages, is seen for RESULTSPrimary SVV infection in rhesus macaques and establishment of latency. Five Indian rhesus macaques, ...

Current In Vivo Models of Varicella-Zoster Virus Neurotropism

“…SVV reactivation was confirmed by the presence of SVV antigens in multiple tissues and virus DNA in lung and lymph nodes. Although the reason for the contrasting results in the two studies [132,133] is unclear, both studies suggest an important role for CD4 T-cell immunity in controlling varicella virus latency. Together, despite being an expensive model, SVV infection in NHP continues to be an extremely valuable animal model, expanding our understanding of the mechanisms of neurotropism and pathogenesis of varicella virus.…”

“…At 7–14 dpi, a robust adaptive immune response develops, characterized by the presence of both binding and neutralizing antibodies and the detection of antigen-specific CD4 and CD8 central and effector memory T-cells in both BAL and PBMC samples [79,113,114,123,128,129]. Studies using the RM model clearly indicate a critical role for CD4 T-cell immunity in resolution of acute SVV infection [130] and the establishment of latency [131], as well as reactivation [132,133]. As early as 3 dpi, SVV probably traffics to the ganglia by hematogenous transport.…”

“…However, within 1–2 months after a stressful event (moving the monkeys to a different room), SVV DNA was detected in whole blood in some of the CD4-depleted and CD8-depleted monkeys, in the absence of a zoster rash [133]. More recently, clinical reactivation of latent SVV was shown in RM after CD4-depletion, in which circulating CD4 T-cells were reduced by more than half within a week and remained low for two months; a zoster rash was seen in one animal with the most extensive CD4-depletion at seven days post-treatment and in the other treated RM at 10–40 days post-treatment, with recurrent zoster observed in one animal [132]. Although the untreated control retained normal CD4 levels, it also developed zoster.…”

Simian Varicella Virus DNA in Saliva and Buccal Cells After Experimental Acute Infection in Rhesus Macaques

“…Quantitative real-time polymerase chain reaction (qPCR)— SVV copy number was measured by real-time qPCR performed on the salivary and buccal DNA (3.5 μl per reaction) and PBMC DNA (100 ng per reaction) with TaqMan ® 7900, using fluorescence-based amplification (Applied Biosystems, Inc, Life Technologies, Grand Island, NY). Primers and Taqman probes specific for the SVV open reading frame (ORF) 61 were used for real-time qPCR as described (Cohrs et al., 2008) and have been our lab standard for all SVV diagnostics (Mahalingam et al., 2007, 2010; Traina-Dorge et al., 2015, 2019). Briefly, final concentrations of primers and probes in PCR were 500 and 250 nM, respectively.…”

“…Following acute SVV infection, the virus establishes latency and later reactivates to produce zoster (Mahalingam et al., 2007, 2010; James et al., 2014; Traina-Dorge et al., 2014). As such, the SVV infection in NHP has been an extremely valuable animal model to further study the pathobiology and neurotropism of VZV showing virus entering ganglia before the appearance of primary rash; viral transport is via both hematogenous and non-hematogenous routes, critical gene expression, and cell signaling changes associated with disease; tropism of ganglionic, epithelial, and T lymphocytes (Mahalingam et al., 2001; Ouwendijk et al., 2013; Traina-Dorge et al., 2015, 2019; Arnold et al., 2016).…”