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

Abstract

Primary infection with varicella-zoster virus (VZV), a neurotropic alphaherpesvirus, results in varicella. VZV establishes latency in the sensory ganglia and can reactivate later in life to cause herpes zoster. The relationship between VZV and its host during acute infection in the sensory ganglia is not well understood due to limited access to clinical specimens. Intrabronchial inoculation of rhesus macaques with simian varicella virus (SVV) recapitulates the hallmarks of VZV infection in humans. We leveraged this animal model to characterize the host-pathogen interactions in the ganglia during both acute and latent infection by measuring both viral and host transcriptomes on days postinfection (dpi) 3, 7, 10, 14, and 100. SVV DNA and transcripts were detected in sensory ganglia 3 dpi, before the appearance of rash. CD4 and CD8 T cells were also detected in the sensory ganglia 3 dpi. Moreover, lung-resident T cells isolated from the same animals 3 dpi also harbored SVV DNA and transcripts, suggesting that T cells may be responsible for trafficking SVV to the ganglia. Transcriptome sequencing (RNA-Seq) analysis showed that cessation of viral transcription 7 dpi coincides with a robust antiviral innate immune response in the ganglia. Interestingly, a significant number of genes that play a critical role in nervous system development and function remained downregulated into latency. These studies provide novel insights into host-pathogen interactions in the sensory ganglia during acute varicella and demonstrate that SVV infection results in profound and sustained changes in neuronal gene expression. IMPORTANCEMany aspects of VZV infection of sensory ganglia remain poorly understood, due to limited access to human specimens and the fact that VZV is strictly a human virus. Infection of rhesus macaques with simian varicella virus (SVV), a homolog of VZV, provides a robust model of the human disease. Using this model, we show that SVV reaches the ganglia early after infection, most likely by T cells, and that the induction of a robust innate immune response correlates with cessation of virus transcription. We also report significant changes in the expression of genes that play an important role in neuronal function. Importantly, these changes persist long after viral replication ceases. Given the homology between SVV and VZV, and the genetic and physiological similarities between rhesus macaques and humans, our results provide novel insight into the interactions between VZV and its human host and explain some of the neurological consequences of VZV infection. V aricella-zoster virus (VZV) is a neurotropic alphaherpesvirus and the causative agent of varicella (chickenpox) (1). VZV establishes latency in the sensory ganglia and can reactivate later in life to cause herpes zoster (shingles), a painful disease that affects almost 1 million individuals in the United States alone (2). VZV is transmitted through the inhalation of virus-laden saliva droplets or by direct contact with the infectious fluid from vesicles...

Simian varicella virus causes robust transcriptional changes in T cells that support viral replication

“…As described for VZV, we and others have demonstrated that SVV primarily infects T cells that traffic to the ganglia as early as 3 days postinfection (Ouwendijk et al, 2013;Arnold et al, 2016a). Moreover, we showed that T cells isolated from the broncho-alveolar lavage (BAL) during acute infection supported SVV replication (Arnold et al, 2016a). These data firmly establish the importance of T cells in SVV pathogenesis making this model ideal for investigating how VZV infection alters T cell behavior and function.…”

“…This model mimics the key characteristics of VZV infection including the development of varicella, cellular and humoral immune responses, the establishment of latency in sensory ganglia, and reactivation (Messaoudi et al, 2009;Mahalingam et al, 2010;Mahalingam et al, 2007;Kolappaswamy et al, 2007). As described for VZV, we and others have demonstrated that SVV primarily infects T cells that traffic to the ganglia as early as 3 days postinfection (Ouwendijk et al, 2013;Arnold et al, 2016a). Moreover, we showed that T cells isolated from the broncho-alveolar lavage (BAL) during acute infection supported SVV replication (Arnold et al, 2016a).…”

Robust gene expression changes in the ganglia following subclinical reactivation in rhesus macaques infected with simian varicella virus

“…We also compared changes in gene expression in ganglia collected from animals that experienced a reactivation event and those that did not relative to ganglia collected from naïve animals (Arnold et al , 2016). Overall, we detected 967 DEGs (403 up-regulated, 325 down-regulated) in ganglia from animals that did not have a reactivation and 1200 DEGs (641 up-regulated, 559 down-regulated) in the ganglia from animals that did.…”

“…Recent studies from our lab have shown a down-regulation of neuronal genes during acute infection (Arnold et al , 2016), therefore we compared the DEGs detected after acute SVV infection (100 dpi) and those detected after SVV reactivation. Only 48 common DEGs were identified, most of which were down-regulated after both acute infection and reactivation.…”

“…Analysis of differentially expressed genes (DEGs) was performed with the GLM method from the edgeR package (Anders et al , 2013; Robinson et al , 2010)(SRP097695). For comparison to naïve ganglia, we leveraged RNASeq data from our recent publication (SRP072525, (Arnold et al , 2016)). In all analyses, differentially expressed genes (DEGs) were defined as those with a fold change ≥2, a false discovery rate (FDR) ≤0.05 and a median RPKM value ≥5.…”