Polymorphisms of Helicobacter pylori HP0638 reflect geographic origin and correlate with cagA status

Abstract

Since the associations between Helicobacter pylori genotype and disease differ in Asia and the West, we investigated the correlation between HP0638, encoding an outer membrane protein, and potential markers of virulence (cagA, vacA, and iceA). For 109 strains from nine countries, the status of cagA, vacA, and iceA was determined by PCR and/or a line probe assay. We also studied 18 strains from 8 patients (parents and 6 daughters) from a Dutch family and paired strains collected on average 8 years apart from 11 patients. When the HP0638 signal sequences were amplified by PCR and DNA sequence determinations were performed, 89 (96%) of 93 cagA-positive strains had HP0638 in frame, versus none (0%) of 16 cagA-negative strains (P < 0.001). Among strains in which HP0638 was in frame, a six-CT dinucleotide repeat pattern was dominant in Western countries (23 of 33 strains [70%]), while a pattern of three CT repeats with another CT after four T's (3 + 1-CT-repeat pattern) was dominant in East Asia (31 of 46 strains [67%]); however, specific CT repeat patterns did not correlate with clinical outcome. HP0638 phylogenetic trees also showed geographic characters. The HP0638 frame status and CT dinucleotide repeat patterns were identical for 9 of 11 pairs of strains obtained on average 8 years apart from individuals and the 15 strains obtained from the mother and all six daughters. Thus, HP0638 frame status and cagA status are strongly correlated. The CT dinucleotide repeat pattern in the putative HP0638 signal sequence has geographic characters and appears stable in particular patients and families over a period of years. Analysis of HP0638 CT polymorphisms may serve as a new typing system to discriminate H. pylori isolates for epidemiological purposes.

FIG. 1.

Phylogram of H. pylori strains based on the first 150 bp of the HP0638 ORF. Regions from 109 strains were aligned by using GCG Pileup, subjected to phylogenetic analysis by using Paup 4.0b2, and subjected to neighbor-joining analysis based on Kimura’s two-parameter model distance matrices (25). Isolates from East Asia (blue) and western countries (red) segregate into two major branches (A and C). Branch C can be divided into two subbranches (C1 and C2); all strains from African-Americans (AFUSA) are on subbranch C2. vacA s-region allelic types also are shown. Branch B, which is paraphyletic to the other two major branches, is composed of strains from the Indian subcontinent (green).