CTTN and infection: In contrast to infection of INT 407 cells with a C. jejuni wild-type strain, the C. jejuni ciaD mutant was deficient in maximal phosphorylation of cortactin at the Erk 1/2 phosphorylation sites S405 and S418, as judged by immunoblot analysis with the S418 and S405 phospho-specific antibodies to cortactin (Figure 3C).