Helicobacter pylori and gastric lymphoma: High seroprevalence of CagA in diffuse large B-cell lymphoma but not in low-grade lymphoma of mucosa-associated lymphoid tissue type

OBJECTIVE: Gastric lymphoma of mucosa-associated lymphoid tissue (MALT) typ e is closely related to Helicobacter pylori (H. pylori) infection. In vitro studies have demonstrated H. pylori-induced B cell proliferation to be str ain dependent. High prevalences of CagA protein and FldA protein have been reported in strains obtained from patients with gastric lymphoma of MALT ty pe. The aims of the present study were to evaluate the prevalence of H. pyl ori infection and to search for antigenic particularities in 53 patients wi th primary gastric lymphoma in comparison with a group of infected patients with benign disease. METHODS: Of the 53 patients. 37 presented with low-grade lymphoma of MALT t ype (LGLM) and 16 with diffuse large B-cell lymphoma (DLBCL). They were com pared to a group of 162 H. pylori-infected subjects comprising the control group: 111 had gastric or duodenal ulcer (GDU) and 51 nonulcer dyspepsia (N UD). Diagnosis of gastric lymphoma was established on histological examinat ion of endoscopic specimens. Anti-H. pylori antibodies were assayed by thir d-generation ELISA. Western blot assay was used to detect antibodies agains t nine antigens (including CagA protein). which were recognized on the basi s of their molecular weight. RESULTS: Of the 53 patients with gastric lymphoma. 45 were H. pylori-positi ve (85%), of these. 25 (56.5%) had anti-CagA antibodies. The prevalence of H. pylori seropositivity was 78% (29/37) in LGLM and 100% (16/16) in DLBCL. The prevalence of CagA seropositivity in H. pylori-positive patients was 4 4.8% (13/29) and 75% (12/16), respectively (p < 0.05). In comparison, the s eroprevalence of CagA was 77.4% (86/111) in GDU patients and 43.1% (22/53) in NUD patients. The prevalence of antibodies to other antigenic proteins d etected with Helicoblot 2.0 (19.5kd, 30kd, 35kd, VacA, HSPb, Urease A, and Urease B) did not differ among the groups except for 35kd protein, which wa s significantly higher (p < 0.01) in GDU than in NUD and in LGLM (76.6% vs 49% and 46.7%). CONCLUSION: These findings suggest that in patients who develop gastric lym phomas in response to H. pylori, virulent strains expressing CagA protein a re preferentially associated with DLBCL. (C) 2001 by Am. Coll. of Gastroent erology.