Diversity of the cagA gene of Helicobacter pylori strains from patients with gastroduodenal diseases in the Philippines.

Helicobacter pylori CagA protein is considered a major virulence factor associated with gastric cancer. There are two major types of CagA proteins: the Western and East Asian CagA. The East Asian CagA-positive H. pylori infection is more closely associated with gastric cancer. The prevalence of gastric cancer is quite low in the Philippines, although Philippine populations are considered to originate from an East Asia source. This study investigates the characteristics of the cagA gene and CagA protein in Philippine H. pylori strains and compares them with previously characterized reference strains worldwide. The full-length cagA gene was sequenced from 19 Philippine isolates and phylogenetic relationships between the Philippine and 40 reference strains were analyzed. All Philippine strains examined were cagA positive, and 73.7% (14/19) strains were Western CagA-positive. The phylogenetic tree based on the deduced amino acid sequence of CagA indicated that the Philippine strains were classified into the two major groups of CagA protein: the Western and the East Asian group. These findings suggest that the modern Western influence may have resulted in more Western type H. pylori strains in the Philippines. Therefore, H. pylori-infected Filipinos can be considered to be at a low risk of developing gastric cancer.