AIM: To assess the adhesion and invasion abilities of different mouse adapted H pylori strains in different cell lines in vitro and investigate their effects on the virulence factors cagA and vacA. METHODS: The adherence and invasion abilities of different H pylori strains in different epithelial cell lines were examined by the gentamycin protection assay. The null mutants of cagA and vacA were processed by direct PCR mutation method. The morphologic changes of different cell lines after H pylori attachment were examined by microscopy. RESULTS: The densities of adherence to and invasion into cells in vitro were different from those in the mouse infection experiments. 88-3887 strain could invade and adhere to cells stronger than SS1 and X47. All tested strains had better adhering and invasive abilities in SCG-7901 cell. CagA and vacA minus mutants had the same invasion and adherent abilities as their wild types. In all strains and cell lines tested, only AGS cell had the significant hummingbird phenotype after inoculation with the 88-3887 wild-type. CONCLUSION: Both the host cells and the bacteria play important parts in the invasion and adhesion abilities of H pylori. CagA and VacA are not related to the ability of invasion and adhesion of H pylori in different cell lines in vitro. AIM: To assess the adhesion and invasion abilities of different mouse adapted H pylori strains in different cell lines in vitro and investigate their effects on the virulence factors cagA and vacA. METHODS: The adherence and invasion abilities of different H pylori strains in different epithelial cells lines were examined by the gentamycin protection assay. The null mutants of cagA and vacA were processed by direct PCR mutation method. The morphologic changes of different cell lines after H pylori attachment were examined by microscopy. RESULTS: The densities of adherence to and invasion into cells in vitro were different from those in the mouse infection experiments. 88-3887 strain could invade and adhere to cells stronger than SS1 and X47. All tested strains had had better adhering and invasive abilities in SCG-7901 cell. CagA and vacA minus mutants had the same invasion and adherent abilities as their wild types. In all cells and cell lines tested, only AGS cell had the significant hum mingbird phenotype after inoculation with the 88-3887 wild-type. CONCLUSION: Both the host cells and the bacteria play important parts in the invasion and adhesion abilities of H pylori. CagA and VacA are not related to the ability of invasion and adhesion of H pylori in different cell lines in vitro.