Search for evidence of a viral aetiology for inflammatory bowel disease

The aetiology of the inflammatory bowel diseases. Crohn's disease, and ulcerative colitis, is still obscure. A viral aetiology has been proposed, based in part on reports that filtrates prepared from tissues of patients with inflammatory bowel disease induce cytopathic effects in tissue culture cells. Our attempts to culture viruses in many cell lines from filtrates prepared from the tissue of 95 patients have been negative, except for one case in which cytomegalovirus was isolated from the tissue of a Crohn's disease patient. Our studies confirm previous reports that intestinal tissue filtrates induce cytopathic effects in inoculated cell cultures, but the effect we observed is non-specific; cytopathic effects were induced in most cell lines tested and with similar frequency irrespective of whether the intestinal filtrates were prepared from Crohn's disease patients, ulcerative colitis patients, or non-inflammatory bowel disease controls. Electron microscopy studies of tissue culture cells exhibiting cytopathic effects have not revealed virus particles. Characterisation of the cytopathic effect inducing factor showed that it was incapable of serial passage in tissue culture, too small to be a conventional virus, resistant to inactivation by ultraviolet light, and heat stable. Our results suggest that the observed cytopathic effect was caused by a non-replicating cytotoxic factor, or factors, released from intestinal tissues of both inflammatory bowel disease and non-inflammatory bowel disease patients.