Aug
28

H.pylori virulence factor oipA in Asian strains

Helicobacter pylori is a gram-negative bacterium that infects more than half of world’s population. Chronic infection of this bacterium is associated with development of various gastric diseases, such as peptic ulcer, chronic gastritis and gastric cancer.  The outer membrane protein of H. pylori, OipA, has been shown to be closely associated with the Cag-pathogenicity Island (Cag-PAI).  Recently, OipA’s roles in facilitating bacterial adhesion to host epithelial cells, inducing the proinflammatory cytokine IL-8 and association with gastric cancer have been documented.

Before summer, I had created a mutant with the second OipA deleted.

During the summer research, I have completed creation of mutant strains from Asian strains HP98-40 and HP98-19 which have two copies of oipA gene. I used inverse PCR to created a deletion in either first or second OipA site. I also infected AGS cells with my mutant strains and wild types strains to see the differences in triggering interleukin 8 by them. ELISA was performed to analysed interleukin 8 levels in samples. Currently, my data has shown that strains have only one copy of oipA gene would trigger less interleukin 8 in AGS cells, whereas strains have two copies could triggered much more.

Fan,kexin 1

H. pylori 3-D image

 

What’s more, I sequenced both oipA1 &2 in 98-40, and compared their gene. They are only different by two amino acids, which is really similar to each other. Thus, I searched through the H.pylori genome database, and compared all H. pylori strains with duplication of oipA. I found out that all strains’ two oipA copies are totally identical with each other. That might signal an evolution advantage to keep two copies similar in one strain.

Now, I am still working on creating a double deletion of OipA in wild type strain to see whether it still can cause AGS cells to produce interleukin 8. More ELISA will be done after all mutants are created.

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