Serum antibody responses to Helicobacter pylori and the cagA marker in patients with mucosa-associated lymphoid tissue lymphoma

Helicobacter pylori Strains and Gastric MALT Lymphoma

This article summarizes the main findings concerning Helicobacter pylori associated with gastric MALT lymphoma (GML). Considered together, GML strains based on their virulence factor profile appear to be less virulent than those associated with peptic ulcers or gastric adenocarcinoma. A particular Lewis antigen profile has been identified in GML strains and could represent an alternative adaptive mechanism to escape the host immune response thereby allowing continuous antigenic stimulation of infiltrating lymphocytes.

Neonatal thymectomy favors Helicobacter pylori-promoted gastric mucosa-associated lymphoid tissue lymphoma lesions in BALB/c mice

Neonatal thymectomy in BALB/c mice has been described as a model of gastric mucosa-associated lymphoid tissue (MALT) lymphoma (GML). By using this experimental system, we screened, for the first time to our knowledge, Helicobacter pylori GML-associated strains for their capacity to promote disease. A cohort of BALB/c mice underwent thymectomy at day 3 after birth (d3Tx). Successful thymic ablation was evaluated by the degree of lymphopenia in blood samples collected at 4 weeks of age. d3Tx and non-thymectomized controls were infected with either GML strains (B38 or B47) or control strains (SS1 or TN2GF4). Gastric samples collected at 6, 12, and 18 months after infection were studied for bacteria content, and submitted to histological, immunochemical, molecular, and immunological analyses. Severe gastric inflammation was only observed in d3Tx mice. In these animals, the gastric lamina propria was infiltrated with lymphoid cells organized in follicles composed of B cells with few infiltrating T cells. PCR of D/J IgH gene segments proved the monoclonality of infiltrating B cells, which strongly correlated with the presence of lymphoepithelial lesions. B-cell infiltrates were particularly prominent in mice infected with the B47-GML strain. No pathological changes were detected in noninfected d3Tx mice. We identified new H. pylori isolates adapted to the mouse stomach with high potential of GML development, which is only revealed in hosts rendered lymphopenic by neonatal thymic ablation.

Primary gastric lymphoma pathogenesis and treatment: what has changed over the past 10 years?

Primary gastric (PG) lymphomas are generally non-Hodgkin lymphomas (NHL). They represent 5% of gastric malignancies and show an apparently increasing incidence worldwide. The most common histological subtypes are diffuse large B-cell and marginal zone B-cell NHL of the mucosa-associated lymphoid tissue (MALT)-type. Pathogenesis is often related to Helicobacter pylori infection (HPI). There is still no consensus on the optimal treatment for PG lymphoma. Nowadays surgery is limited to rare cases and radiotherapy--combined or not with chemotherapy--represents an effective therapeutic option ensuring long-term, organ-salvage benefits mainly in aggressive histological subtypes. Additionally, the description of MALT lymphomas has made the situation even more complex, because antibiotics alone can induce lasting remissions in those cases associated with HPI. Consequently, a global therapeutic approach to the cure of PG-NHL has completely changed over the last 10 years: innovative, conservative options to reduce treatment toxicity, thus preventing systemic relapses, have made their appearance and are on the rise.

Evaluation of the association of nine Helicobacter pylori virulence factors with strains involved in low-grade gastric mucosa-associated lymphoid tissue lymphoma

Helicobacter pylori has been associated with the development of two malignant diseases: gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Although the cag pathogenicity island, especially the cagA gene, has been linked with adenocarcinoma, few data concerning H. pylori pathogenic factors involved in low-grade gastric MALT lymphoma are available. The goal of this study was to analyze the prevalence of and correlation between genes coding for seven H. pylori virulence factors (cagA, cagE, vacA, iceA, babA, hopQ, and oipA) and two novel adhesins (sabA and hopZ) by comparing a collection of 43 H. pylori strains isolated from patients with low-grade gastric MALT lymphoma to 39 strains isolated from age-matched patients with gastritis only. Our results show that taken individually, none of the nine genes tested can be considered associated with MALT strains and allow us to conclude that MALT pathogenesis is not linked with more proinflammatory H. pylori strains. We demonstrated that in patients infected with strains harboring the iceA1 allele, sabA functional status, and hopZ "off" status, the odds of developing a MALT lymphoma were 10 times higher. However, the low prevalence of such strains (10 of 43 MALT strains) renders this triple association a low-sensitivity marker for MALT strains. Our data confirmed that H. pylori virulence factors are correlated with one another. If the involvement of H. pylori in MALT lymphoma is well established, the pathomechanism by which gastric lymphoma occurs remains to be identified.

Which test to use to detect Helicobacter pylori infection in patients with low-grade gastric mucosa-associated lymphoid tissue lymphoma?

Helicobacter pylori is involved in the pathogenesis of lymphoma of the gastric mucosa-associated lymphoid tissue (MALT). Because gastric MALT lymphoma is a rare disease, few studies comparing the accuracy of diagnostic tests in this group of patients have been carried out, and only a limited number of tests (essentially histological) were performed. The aim of our study was to compare the results of four different diagnostic methods used to detect H. pylori (histology, culture, polymerase chain reaction, and serology) in a prospective multicenter study. A patient was considered to be H. pylori positive if culture or histology was positive. During the period 1995-2000, a total of 90 patients with low-grade gastric MALT lymphoma were enrolled. Results for the four tests were available for 56 patients (62.2%). Among these patients, the four tests were concordant in 35 cases (62.5%), i.e., were positive in 19 cases (33.9%) and negative in 16 patients (17.8%). Histology (39/40 positive, 97.5%) and serology (38/40 positive, 95.0%) were the most sensitive tests. Polymerase chain reaction (PCR) and culture were positive in 52.5% and 50%, respectively. The cagA gene was detected in 47.4% of the strains.

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) type is closely related to Helicobacter pylori (H. pylori) infection. In vitro studies have demonstrated H. pylori-induced B cell proliferation to be strain dependent. High prevalences of CagA protein and FldA protein have been reported in strains obtained from patients with gastric lymphoma of MALT type. The aims of the present study were to evaluate the prevalence of H. pylori infection and to search for antigenic particularities in 53 patients with 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 type (LGLM) and 16 with diffuse large B-cell lymphoma (DLBCL). They were compared to a group of 162 H. pylori-infected subjects comprising the control group: 111 had gastric or duodenal ulcer (GDU) and 51 nonulcer dyspepsia (NUD). Diagnosis of gastric lymphoma was established on histological examination of endoscopic specimens. Anti-H. pylori antibodies were assayed by third-generation ELISA. Western blot assay was used to detect antibodies against nine antigens (including CagA protein), which were recognized on the basis of their molecular weight.

RESULTS

Of the 53 patients with gastric lymphoma, 45 were H. pylori-positive (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 44.8% (13/29) and 75% (12/16), respectively (p < 0.05). In comparison, the seroprevalence 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 detected 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 was 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 lymphomas in response to H. pylori, virulent strains expressing CagA protein are preferentially associated with DLBCL.