Prevalence of Seropositivity to CagA and VacA in Helicobacter pylori Infected Korean Patients Using Commercial Western Blot Kit ( Helicoblot 2.0TM )

Kang, Jin Kyung; Park, In Suh; Chung, Jae Bock; Park, Hyo Jin; Lee, Yong Chan; Kim, P S; Moon, Young Myoung

Abstract

BACKGROUND AND AIMS: Seropositivity to CagA and/or VacA has been implicated in the pathogenesis of peptic ulcers. Korea is well known with high incidence of gastric cancer and Helicobacter pylori infection. However, most studies to evaluate CagA and VacA phenotype in Korea have been performed in limited cases and have showed inconsistent results. Some of these differences may be explained by variation in methods, geographic factors and socioeconomic factors. We evaluated the prevalence of seropositivity to CagA and VacA in different disease entities by using a commercial Western blot kit (Helicoblot 2.0TM, Genelabs Diagnostics, Singapore). This kit allows rapid visualization of full serologic profiles of various antigens which belong to H. pylori and standardization for international cornparisons.
METHODS
For 117 consecutive patients (72 nonulcer dyspepsia, 23 gastric ulcers and 22 duodenal ulcers, histology, rapid urease test (CLOTM Delta- West, Western Australia) and ELISA test (GAPTM test, BIORAD, Millan, Italy) were performed. From each patient, serum was collected and western blot assay was performed. Patients are considered as H. pylori positive if two of above tests were positive.
RESULTS
CagA and VacA were positive in 88.5% and 50.0% of H. pylori infected patients. All the VacA positive patients expressed CagA positivity while only 56.5% of CagA positive patients showed VacA positivity. Reactivities to CagA and VacA were not significantly different according to different types of disease. Comparison of western blot assay with ELISA test showed decrease in specificity of both tests after the age of 50 (76.0% vs 42.9%, 80.0% vs 42.9% respectively, p<0.05).
CONCLUSIONS
Reactivity of the H. pylori positive sera to western blot assay differs according to disease entities. Serologic profiles to CagA and VacA show no significant association with peptic ulceration in Korean patients with H. pylori infection. In addition, the western blot assay shows poor and limited specificity in old patients.