Characterization of flgK gene and FlgK protein required for H. pylori colonization--from cloning to clinical relevance.
OBJECTIVE
To characterize the role of flgK and its protein product in H. pylori colonization.


METHODS
The PCR cloning method identified the flgK gene. An isogenic flgK mutant was constructed by gene replacement and confirmed by Southern blot analysis and PCR analysis. The recombinant FlgK protein (r-FlgK) was purified. Electron microscopy (EM) was applied to demonstrate the flagella of H. pylori. An in vitro motility test was assessed in semisolid medium. The densities of H. pylori colonization with either the wild-type strain or its flgK mutant were compared among BALB/c mice with or without pre-immunization with r-FlgK. The serological responses to r-FlgK were analyzed for 70 clinical patients with different densities of H. pylori colonization.


RESULTS
From a duodenal ulcer strain, the flgK gene was cloned and it contained 1821 bp, with a 95.7% identity to the published sequences. No flagella were observed under EM for the mutant strain, which had a loss of motility. H. pylori density was lower in the BALB/c mice inoculated by the mutant or with pre-immunization with r-FlgK compared to unimmunized mice or mice inoculated by the wild-type strain (P<0.05). In the H. pylori-infected patients, the serological responses to r-FlgK were uniformly low in titer.


CONCLUSIONS
FlgK encoded by flgK is important for flagella formation and H. pylori motility. Deficiency in FlgK or an enhanced serological response to r-FlgK can interfere with H. pylori colonization. FlgK of H. pylori could be a novel target for vaccination.
Wu
Jiunn-Jong
JJ
Department of Medical Technology, National Cheng Kung University Hospital, 138 Sheng Li Road, Tainan 70428, Taiwan, China.
Sheu
Bor-Shyang
BS
Huang
Ay-Huey
AH
Lin
Shin-Ting
ST
Yang
Hsiao-Bai
HB
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D003001:Cloning, Molecular; D005408:Flagellin / Q000276:immunology; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011446:Prospective Studies; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; C088595:FlgK protein, Bacteria; D005408:Flagellin; C067138:flaA protein, bacteria