Drosophila melanogaster as a model system to assess the effect of Epstein-Barr virus DNA on inflammatory gut diseases

Abstract

Background: The Epstein-Barr virus (EBV), also referred to as Human herpesvirus 4 (HHV-4), commonly infects humans and is highly associated with different types of cancer, such as gastric carcinomas, and autoimmune diseases, such as systemic lupus erythematosus. EBV has shown residency in human inflamed gastrointestinal mucosa in patients suffering from inflammation of the digestive tract such as inflammatory bowel disease (IBD); this indicates that this virus potentially plays a role in sustaining inflammation. Our group has previously reported the immune-stimulating capabilities of EBV DNA in Drosophila melanogaster as well as in mammalian immune systems. In flies, we observed increased systemic hemocyte counts and enhanced Immune Deficiency (IMD) pathway activation while pro-inflammatory cytokine levels were increased by EBV administration to mice. Hence, we used the fly as a model system to explore the effect of EBV DNA on intestinal damage. Methods: Adult D. melanogaster flies were fed on 5percent dextran sodium sulfate (DSS) solubilized in 5percent sucrose in the absence or presence of EBV DNA. DSS was used to induce potential damage in fly gut tissues that would then possibly allow EBV DNA to induce alterations. Flies that were fed EBV DNA in the absence of DSS or 5percent sucrose as a vehicle were included as well. To assess the impact of EBV DNA administration on the immune status of the gut, Green Fluorescent Protein (GFP)-expressing hemocytes in the gut were examined as well as GFP-expressing systemic hemocytes. GFP-marked intestinal stem cells (ISCs) and enteroblasts were assessed as indicators of fly midgut regeneration while the relative expression of Diptericin was determined by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) as a marker of IMD pathway activation in the gut. Results: Increased numbers of hemocytes were observed in the hindguts of flies that were administered DSS as compared to the controls; administration of EBV DNA to the DSS-fed flies further increased the levels of hemocytes i