Furthermore, increase of cagA copy number up to seven copies from single cagA was reported in a recent experimental H. pylori infection study on human subjects, which was conducted to examine bacterial adaptation during early stages of infection.14 Among the reisolates, some showed loss of ability to induce IL-8 secretion, which was assumed to be due to a mutation in cagE or cagY. This evidence concerns the gene CXCL8 and infection.