Helicobacter pylori colonize the stomachs of approximately 50% of the world’s population. The prevalence of infection ranges from 25% in developed countries to more than 90% in developing countries. In spite of this high prevalence, only a small percentage of infected individuals develop peptic ulcer disease, of which H pylori plays an important role in the pathogenesis. The cytotoxin-associated gene (cagA) and vacuolating cyto-toxin gene (vacA) are among the important factors in the pathogenesis of peptic ulcer disease. These genes encode for CagA and VacA proteins, which stimulate antibody formation in infected patients. The association of such antibodies with an increased risk of developing peptic ulcer diseases is controversial. Investigators from developed countries have found a significant association between the prevalence of CagA antibodies and duodenal ulcer. However, other studies, particularly those from developing countries, have shown no such association.
Several tests have been used to diagnose H pylori infection; these are divided into biopsy-based tests (CLO, culture, histology, polymerase chain reaction) and nonbiopsy-based tests (serology, urea breath test) (20). Serological tests are noninvasive and are used to detect immunoglobulin (Ig) G, IgA and IgM antibodies in the sera of H pylori-infected subjects. The ELISA test is the most widely used test for the detection of such antibodies in epidemiological studies. Immunoblot assay enables the detection of antibodies against specified H pylori antigens, such as CagA and VacA antigens. The aim of the present study was to detect H pylori antibodies in symptomatic and asymptomatic subjects by the ELISA test, and to determine the prevalence of anti-CagA antibodies and other H pylori-specific antigens in both groups by immunoblotting.