Herpes Simplex Virus Type 1 Infects Enteric Neurons and Triggers Gut Dysfunction via Macrophage Recruitment

Abstract

Herpes Simplex Virus type 1 (HSV-1), a neurotropic pathogen widespread in human population, infects the enteric nervous system (ENS) in humans and rodents and causes intestinal neuromuscular dysfunction in rats. Although infiltration of inflammatory cells in the myenteric plexus and neurodegeneration of enteric nerves are common features of patients suffering from functional intestinal disorders, the proof of a pathogenic link with HSV-1 is still unsettled mainly because the underlying mechanisms are largely unknown. In this study we demonstrated that following intragastrical administration HSV-1 infects neurons within the myenteric plexus resulting in functional and structural alterations of the ENS. By infecting mice with HSV-1 replication-defective strain we revealed that gastrointestinal neuromuscular anomalies were however independent of viral replication. Indeed, enteric neurons exposed to UV-inactivated HSV-1 produced monocyte chemoattractant protein-1 (MCP-1/CCL2) to recruit activated macrophages in the longitudinal muscle myenteric plexus. Infiltrating macrophages produced reactive oxygen and nitrogen species and directly harmed enteric neurons resulting in gastrointestinal dysmotility. In HSV-1 infected mice intestinal neuromuscular dysfunctions were ameliorated by in vivo administration of (i) liposomes containing dichloromethylene bisphosphonic acid (clodronate) to deplete tissue macrophages, (ii) CCR2 chemokine receptor antagonist RS504393 to block the CCL2/CCR2 pathway, (iii) Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) and AR-C 102222 to quench production of nitrogen reactive species produced via iNOS. Overall these data demonstrate that HSV-1 infection makes enteric neurons recruit macrophages via production of a specific chemoattractant factor. The resulting inflammatory reaction is mandatory for intestinal dysmotility. These findings provide insights into the neuro-immune communication that occurs in the ENS following HSV-1 infection and allow recognition of an original pathophysiologic mechanism underlying gastrointestinal diseases as well as identification of novel therapeutic targets.

Intestinal Dysmotility Syndromes following Systemic Infection by Flaviviruses

“…Although viral infection is a postulated cause of human dysmotility disorders, causality has not been proven. Our findings are consistent with recent studies in mice (Brun et al, 2018; Khoury-Hanold et al, 2016) demonstrating that infection of the ENS by HSV can induce acute GI dysmotility, although Khoury-Hanold et al described toxic megacolon and Brun et al showed intestinal dysmotility was due to infiltrating macrophages. In comparison, WNV RNA persisted in the bowel of surviving animals, and this was associated with chronic delays in GI transit times.…”

“…Multiple herpesviruses ( e.g ., herpes simplex virus 1 (HSV-1), varicella-zoster virus, and Epstein Barr virus) also can infect the ENS of humans or experimentally infected animals (Brun et al, 2010; Chen et al, 2011; Debinski et al, 1997; Khoury-Hanold et al, 2016). Analysis of GI tract tissues from human patients with achalasia (Facco et al, 2008; Villanacci et al, 2010) and experimentally infected animals (Brun et al, 2010; Brun et al, 2018) showed infection-induced inflammation of enteric ganglia and immune cell infiltration of the myenteric plexus ganglia and muscularis propria, suggesting a possible immune-mediated pathogenesis of GI dysmotility disorders.…”

Herpes Simplex Virus Type 1 Engages Toll Like Receptor 2 to Recruit Macrophages During Infection of Enteric Neurons

“…Several studies have reported the involvement of TLR2 in anti-HSV-1 response ( Sørensen et al, 2008 ; Zolini et al, 2014 ) but no data are available about the role of TLR2 in controlling HSV-1 infection and replication in the ENS. We previously reported that HSV-1 retains infectivity following IG inoculum in WT mice ( Brun et al, 2018 ). By comparing WT and TLR2 ko mice we found that HSV-1 infected the ENS of both animal strains ( Figure 1A ).…”

“…HSV-1 strain SC16 was propagated on Vero cells (ATCC ® CCL81 TM , American Type Culture Collection, VA, United States), as previously described ( Brun et al, 2018 ). Vero cells were maintained in Dulbecco’s Modified Eagle’s Medium (DMEM) supplemented with 10% heat-inactivated fetal bovine serum (FBS) and penicillin/streptomycin 1% (all from Gibco), at 5% CO 2 and 37°C.…”

“…We recently reported that HSV-1 persistently infects the enteric nervous system (ENS) and engages a local immune response causing gut neuromuscular abnormalities ( Brun et al, 2010 ; Brun et al, 2018 ). In this study, we tested the hypothesis that TLR2-dependent signals in enteric neurons orchestrate immune cells recruitment and mediate HSV-1 induced neuronal damage.…”