Distribution and phenotype of Epstein-Barr virus-infected cells in inflammatory bowel disease

Abstract

Little is known about Epstein-Barr virus (EBV) infection of colon mucosa, particularly in inflammatory bowel diseases. Crohn's disease and ulcerative colitis are thought to differ in T-helper lymphocyte composition and cytokine secretion patterns. Some of the implicated cytokines are growth factors for EBV-infected cells. We examined colon mucosa for differences in the distribution and phenotype of EBV-infected cells. Colon tissues with Crohn's disease (n = 31) or ulcerative colitis (n = 25) and controls (n = 60) were characterized by in situ hybridization and immunohistology for six EBV gene products as indicators of latent and replicative EBV infection. The cells were additionally phenotyped by combined detection of the EBV transcripts and B- or T-cell antigens. B lymphocytes predominated as the site of latent EBV infection in the colon and were most numerous in ulcerative colitis. In active ulcerative colitis, EBV-positive lymphocytes accumulated under and within the epithelium and displayed evidence for replicative infection. The patterns of mucosal EBV gene expression indicate local impairment of virus-specific T-cell responses in active ulcerative colitis. Detection of EBV may help to discriminate between active ulcerative colitis and other inflammatory bowel diseases. Colon mucosa is a potential site of EBV replication and may be relevant for EBV transmission.

Figure 1.

Detection of EBER-positive cells (arrows) in the lamina propria (A), in the neighborhood to a fissural ulcer (B), and in the periphery of a lymphoid follicle (C) in specimens with Crohn’s disease and in the stroma of an adenocarcinoma of the colon (D) by in situ hybridization using [³⁵S]-labeled anti-sense RNA probes. The relative density of EBER-positive cells per section area is low. Autoradiographic exposure time, 4 days; original magnifications, ×50 (A–C) and ×75 (D).

Figure 2.

EBV gene expression and phenotype of EBV-infected cells in cases of ulcerative colitis. A small proportion of subepithelial and intraepithelial infected lymphocytes express the early lytic cycle gene products BZLF1 protein (A) and BHLF1 transcript (B) detected by immunohistology with the antibody BZ.1 or an oligonucleotide probe, respectively. The colon mucosa displays flattened epithelium with reduced numbers of goblet cells and a leukocyte infiltrate containing polymorphonuclear cells in the crypt lumen. A proportion of EBER-positive cells (red signal) display CD20 expression detectable by immunohistology (brown cytoplasmic and membrane signal) indicating the B-lymphoid nature of these infected cells (C and D). Note the subepithelial distribution of many EBER-positive lymphocytes and the presence of one infected cell (arrow) in the crypt lumen (C) as well as a mitotic figure in an EBER-positive cell (arrow; D). When detection of EBER and IgLC transcripts is combined, the majority of EBV-infected cells can be identified as B-lymphocytes with polytypic IgLC expression pattern: ∼50% of EBER-positive cells are labeled by the IgLC-κ probe (E), although a small proportion of EBER-positive cells does not display IgLC expression even after extended autoradiographic exposure time (F). Two EBER- and IgLC-positive cells are marked by arrows (F). Autoradiographic exposure time, 14 days (E) and 24 days (F). Original magnifications, ×120 (A and B), ×60 (D), ×75 (C, E, F).