Helicobacter pylori oipA, vacA and dupA genetic diversity in individual hosts

Helicobacter pylori putative virulence factors can undergo a continuously evolving mechanism as an approach to bacterial adaptation to the host changing environment during chronic infection. oipA, vacA and dupA genetic diversity among isolates from multiple biopsies (niches) from the antrum and corpus of 40 patients was investigated. A set of 229 isolates was examined. Direct DNA sequence analysis of amplified fragments was used to study oipA 'on/off' expression status as well as the presence of C or T insertion in jhp0917 that originates a continuous (jhp0917-jhp0918) dupA gene. vacA alleles were identified by multiplex PCR. Different inter-niches oipA CT repeat patterns were observed in nine patients; in six of these, 'on' and 'off' mixed patterns were found. In three of these nine patients, different vacA alleles were also observed in a single host. Inter-niche dupA differences involved the absence and presence of jhp0917 and/or jhp0918 or mutations in dupA, including those that may originate a non-functional gene, and they were also present in two patients with mixed oipA CT patterns and in another seven patients. Evidence of mixed infection was observed in two patients only. In conclusion, oipA and dupA genes showed similar inter-niche variability, occurring in approximately 1/4 patients. Conversely, vacA allele microevolution seemed to be a less common event, occurring in approximately 1/10 patients, probably due to the mechanism that this gene evolves 'in vivo'.