Identification of a new segment involved in cagA 3' region variation of Helicobacter pylori.

The cagA 3' region shows marked variation among Helicobacter pylori strains. Two segments of 102 bp and 57 bp are reportedly responsible for this variation. We analysed the cagA 3' region in 70 H. pylori strains using polymerase chain reaction and sequencing. We found that another segment, namely beta segment, was also involved in the variation of this region. The beta segment was 105 bp long and located between the aforementioned two segments. Six genotypes were identified based on the structure of the cagA 3' region. No relationship was found between these genotypes and the clinical outcomes or vacA genotypes. The numbers of tyrosine phosphorylation sites within the cagA 3' region varied among strains, but this was not related to the cagA genotypes. Our data suggest that the cagA 3' region is significantly variable. It appears that the variation of the cagA 3' region might contribute to the modification of virulence.