Effect of Epstein-Barr Virus DNA on the Severity of Intestinal Inflammation in a Mouse Model of Acute Colitis

Abstract

Background: Epstein-Barr virus (EBV) infection has been lately associated with inflammatory bowel disease (IBD), which is a collective term for chronic relapsing inflammatory disorders of the gastrointestinal tract with a poorly defined etiopathogenesis. In recent research, our group showed that feeding flies EBV DNA aggravates cellular and humoral innate inflammatory responses in a fruit fly model of gut inflammation. Whether such an exacerbatory role is exhibited by EBV DNA in a complex mammalian system, such as in mice, remains to be investigated. Therefore, the main objective of this study was to determine the effect of EBV DNA on the severity of intestinal inflammation in a murine model of acute colitis.

Methods: To assess the colitogenic potential of Dextran Sodium Sulfate (DSS)-induced colitis in C57BL/6J mice and standardize the optimal DSS concentration for examining the effect of EBV DNA on gut inflammation in subsequent aims, four groups of female C57BL/6J mice were administered 0.5%, 1%, 1.5%, or 2.5% DSS in drinking water for seven days to induce acute colitis. A fifth group served as control and was fed normal drinking water. On day 3, mice were given sterile water by rectal gavage (to control for the route of administration of EBV DNA in this study). All mice were clinically scored on a daily basis for changes in body weight, stool consistency, and fecal blood in assessment of the disease activity index (DAI). On day 7, mice were sacrificed and their colon lengths were measured for macroscopic evaluation of colonic inflammation. The 1.5% DSS concentration was employed in the investigation of the effect of EBV DNA on clinical manifestations and macroscopic inflammatory markers of colitis in the C57BL/6J mouse model of the disease. For this experiment, mouse groups received either 1.5% DSS-containing or normal drinking water for 7 days. Two DSS-treated groups were then rectally administered sterile water or 288 x 103 copies of EBV DNA in sterile water on day 3. Two other normal drinking water-fed groups served as controls and received sterile water or EBV DNA by rectal gavage on day 3. The severity of colitis was evaluated on the basis of the DAI and the colon length shortening that were determined in a similar manner as in the DSS concentration selection protocol.

Results: In the DSS dosage determination experiment, mice-treated with 1.5% DSS in drinking water presented a progressive aggravation of clinical colitis together with a moderately intense DAI and a prominent colon shortening showing statistically significant differences in comparison to the normal water-fed control group, which led us to investigate the effect of EBV DNA on colitis severity using the 1.5% DSS concentration in the C57BL/6J mouse model of the disease. Mouse groups that received DSS alone or EBV DNA in addition to DSS exhibited markedly higher values of body weight loss, DAI, and colon length shortening compared to the normal water-fed control group. Moreover, the increase in the DAI score was significantly more elevated in mice treated with EBV DNA in addition to DSS than in mice treated with DSS alone. In line with the DAI results, mice receiving DSS plus EBV DNA showed a significantly more pronounced reduction in their colon lengths compared to mice receiving DSS alone.

Conclusion: The observed worsening of clinical symptoms and colonic inflammation upon administration of EBV DNA with DSS over treatment with DSS alone indicates that EBV DNA is associated with increased severity of colitis in a mouse model of the disease. These findings merit further investigation to understand the underlying mechanisms and eventually gain insight into potential therapeutic targets that may mitigate inflammatory responses attributed to EBV DNA.