Dynamic Variation of Multiple CagA EPIYA-C Motifs in East-Asian Helicobacter pylori

Abstract

The polymorphic bacterial oncoprotein, CagA bears different types of C-terminal Glu-Pro-Ile- Tyr-Ala (EPIYA) motifs depending on its geographical distribution: ABD type for East-Asian and ABC type for Western H. pylori. The multiple EPIYA-C motifs were associated with a disease severity. Some East-Asian H. pylori isolates carried Western ABC-type CagA. Hence, to gain better understanding, whole genomes of four Korean H. pylori clinical isolates carrying ABC-type CagA were sequenced via Pac-Bio SMRT sequencing technology, and the phylogenetic analysis was performed, which identified that three of four isolates indeed belong to hpEastAsia group with typical East-Asian polymorphism of virulence factors and one is grouped to HpAfrica with typical Western polymorphism. Furthermore, the variation of multiple EPIYA-C motifs in East-Asian H. pylori background was investigated using a Korean clinical isolate, K154, belonging to hpEastAsia but possessing CagA EPIYA-ABCCCC. Due to the sequence homology for CagA multimerization sequence located at the EPIYA-C segment, we predicted the possibility of changing the number of C motifs via homologous recombination. To test this hypothesis, 287 single colonies after culturing 1st generation were screened for the detection of multiple EPIYA-C motifs by PCR-based screening method and further verified by DNA sequencing. Three out of 287 single colony isolates (1%) showed polymorphism in the number of EPIYA-C motifs in vitro: increasing EPIYA-C motifs in five and decreasing EPIYAC motifs in three and even in complete deletion. The mechanism of dynamic change of EPIYAC repeats may play a part in generating an intraspecies diversity in East-Asian H. pylori.