Evaluation of the anti-East Asian CagA-specific antibody for CagA phenotyping.

The determination of the cagA genotype is generally based on sequencing the variable 3' region of the cagA gene. In a previous study, we successfully generated an anti-East Asian CagA-specific antibody (anti-EAS Ab) immunoreactive only with the East Asian CagA and not with the Western CagA. In a small number of Japanese patients, anti-EAS Ab appeared to be a useful tool for phenotyping CagA immunohistochemically. The present study was conducted to validate the anti-EAS Ab immunohistochemistry method in a larger number of patients from Vietnam and Thailand. A total of 385 Vietnamese and Thais were recruited. Helicobacter pylori status was determined by a combination of three methods, including culture, histology, and immunohistochemistry with anti-H. pylori antibody. The sensitivity, specificity, and accuracy of the anti-EAS Ab immunohistochemistry method for the diagnosis of CagA phenotype were calculated based on the results of the cagA sequencing as the gold standard. The sensitivity, specificity, and accuracy of our immunohistochemistry method were 96.7%, 97.9%, and 97.1%, respectively. Moreover, anti-EAS Ab was not cross-reactive with noninfected gastric mucosa. In conclusion, immunohistochemistry with anti-EAS Ab appears to be a good method for determination of CagA phenotype.

Analysis of virulence factors of Helicobacter pylori isolated from a Vietnamese population.

BACKGROUND: The incidence of gastric cancer differs among countries in Asia, and it has been suggested that virulence factors associated with Helicobacter pylori are partly responsible. The aim of this study was to investigate several genetic factors regarded as virulence or molecular epidemiologic markers in H. pylori isolates from Vietnamese subjects. RESULTS: The cagA, vacA and cag right-end junction genotypes of 103 H. pylori strains from Vietnam (54 from Hanoi and 49 from Ho Chi Minh) were determined by PCR and sequencing. Three types of deletion in the region located upstream of the cagA Glu-Pro-Ile-Tyr-Ala (EPIYA) repeat region were identified: the 39-bp deletion type, the 18-bp deletion type, and the no-deletion type. The majority of strains studied (77%; 80/103) had the 18-bp deletion irrespective of geographical location in the country or clinical outcome. All of the 39-bp and 18-bp deletion-type strains possessed the East Asian type cagA repeat region. The type II cag right-end junction genotype was predominant (84%). The vacA m1 genotype was significantly more common in strains isolated in Hanoi, where the incidence of gastric cancer is higher, than in strains from Ho Chi Minh. CONCLUSION: Pre-EPIYA-region typing of the cagA gene could provide a new genetic marker of H. pylori genomic diversity. Our data support the hypothesis that vacA m1 is closely associated with gastric carcinogenesis.