S100A8 and infection: For this purpose, and in order to study CagA expression inside the epithelial cells through an infection, rather than transfection system, a series of H. pylori isogenic mutants based on P12 reference strain were produced, expressing CagA protein with varying numbers of phosphorylation-functional (EPIYA-C) and phosphorylation-deficient EPIFA motifs, while keeping the CM motifs intact.