Adhesion and invasion of HEp-2 cells by wild type IP32953 and defined mutants. (A) adhesion, (B) invasion (C) adhesion with pYV cured strains, using differential staining assay. Wild type (IPWT) was compared to insertional mutants of ifp (IPΔIFP) and inv (IPΔINV), an ifp and inv double mutant (IPΔIFPΔINV) and an ifp mutant with complemented ifp (IPΔIFPpIFP), by setting IPWT values to 100%. Strains cured of pYV are marked with "c". Data was pooled from assays performed in triplicate on at least three independent occasions with statistical analysis by unpaired t-test and statistically significant results designated by *. ** indicates p value of <0.005, *** indicates p value of <0.0005. (D) Presence of invasin at 28°C and 37°C after 15 hours incubation detected by western blotting with anti-invasin monoclonal antibody.