At three days post-infection, a timepoint prior to T-repeat length extension (Supplementary Fig. 2e), levels of bacterial colonization and Cxcl2 mRNA in the stomach were found to be significantly increased for the Δhpnc4160-hpnc4170 strain compared to wild-type, whereas those of the Δhpnc4160-hpnc4170/pHel2-hpnc4160 strain were equivalent to wild-type (Fig. 4a, b). This evidence concerns the gene CXCL2 and infection.