Adherence and invasion of mouse-adapted H pylori in different epithelial cell lines

Abstract

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.

Figure 1

Levels of adherence and invasion of H pylori in different cell lines. Bacteria were added to AGS cell monolayer at an MOI of 100 for 5 h at 37°C in a humidified atmosphere with 5% CO₂. Data were obtained by adherence and invasiveness assays in three independent experiments and are expressed as CFU per well of AGS cells. The left side 3 refrangible lines indicate the ability of the adherence in 3 different cell lines. The right sides indicate the invasiveness ability in the 3 cell lines. Values represent the mean CFU of viable bacteria recovered per well of a 24-well tissue culture tray.

Figure 2

Images showing morphologic changes induced by H pylori attachment. After co-culture of the bacteria with different cells for 5 h, the monolayer AGS cells were washed with PBS and the images were captured by microscopic Olympus BX51. A: AGS cell; B: The hummingbird/scattering appearance of AGS after being attached with 88-3887 wild-type, 5 h; C: AGS with H pylori 88-3887 cagA minus mutant (88-3887 cagA::cam), 5 h.