Basic-Alimentary TractHerpes Simplex Virus Type 1 Infection of the Rat Enteric Nervous System Evokes Small-Bowel Neuromuscular Abnormalities

Background & AimsInfectious agents, such as neurotropic viruses, are proposed to disrupt the enteric neuromuscular system, leading to dysmotility, although the mechanisms are unknown. Our purpose was to assess whether herpes simplex virus type-1 (HSV-1) establishes an enteric-neuronal infection and induces gut dysmotility.MethodsRats were inoculated with HSV-1 intranasally and after 4 weeks intragastrically. After 1-10 weeks, infection was determined by molecular analysis whereas neuromuscular function was evaluated by pharmacologic/electrical stimulation of longitudinal ileal segments and by gastrointestinal transit and by [3H]acetylcholine release measurements. Inflammation in the neuromuscular layer was assessed by myeloperoxidase and cytokine levels and by anti-CD3+ immunohistochemistry.ResultsAfter 1-10 weeks of intragastric inoculation, HSV-1 latency-associated messenger RNA transcripts were detected in the brain and in ileal neurons with no signs of illness or histologic gut abnormalities. By using a recombinant HSV-1 carrying the lacZ gene, HSV-1 virions were localized in myenteric ganglia by in situ X-gal staining. Interleukin-2 and IFN-γ levels were increased significantly 1 and 6 weeks after inoculation. CD3+ cells were found around the myenteric ganglia 6 weeks after inoculation. Smooth muscle responses to carbachol, CaCl2, and gut transit were increased significantly after 1 and 6 weeks, whereas KCl- and electrical field stimulation-mediated contractions were modified significantly only 1-2 weeks after HSV-1 administration. The release of [3H]acetylcholine was reduced significantly in ileum segments after 1 and 6 weeks.ConclusionsAfter intragastric inoculation, HSV-1 establishes a latent infection in the rat myenteric ganglia, which leads to gut dysmotility.