The pathogenic potential of Helicobacter pullorum: possible role for the type VI secretion system.
BACKGROUND
Helicobacter pullorum is a putative enterohepatic pathogen that has been associated with hepatobiliary and gastrointestinal diseases in chickens and in humans. The pathogenic potential of H. pullorum NCTC 12826 was investigated.


METHODS
Adherence and gentamicin protection assays and scanning electron microscopy were performed to quantitate and visualise H. pullorum adherence and invasion. Proteomics coupled with mass spectrometry was employed to characterise the secretome of H. pullorum.


RESULTS
Helicobacter pullorum was able to adhere to the Caco-2 intestinal epithelial cell line with a mean attachment value of 1.98 ± 0.16% and invade Caco-2 cells with a mean invasion value of 0.25 ± 0.02%. The in vitro adherence and invasion assays were confirmed with scanning electron microscopy, which showed that H. pullorum can adhere to host cells through flagellum-microvillus interaction and invade causing a membrane-ruffling effect. One hundred and thirty-seven proteins were identified, of which 33 were bioinformatically predicted to be secreted. Further functional classifications revealed six putative virulence and colonisation factors, which included cell-binding factor 2, flagellin, secreted protein Hcp, valine-glycine repeat protein G, a type VI secretion protein, and a protease. Protein threading of H. pullorum Hcp and subsequent 3D-Blast searches revealed structural similarities between Hcp and endocytic vesicle coat proteins, suggesting the type VI secretion system of H. pullorum may interact with endocytic vesicles.


CONCLUSIONS
This study has shown that H. pullorum has the ability to adhere to and invade human cells and secrete factors that may contribute to the pathogenic potential of H. pullorum.
School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia.
Andrea
A
Sirianni
Nadeem O
NO
Kaakoush
Mark J
MJ
Raftery
Hazel M
HM
Mitchell
D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000502:physiology*; D018938:Caco-2 Cells; D002645:Chickens; D002966:Clathrin / Q000378:metabolism; D004847:Epithelial Cells / Q000382:microbiology*; D005407:Flagella / Q000378:metabolism; D005839:Gentamicins / Q000378:metabolism; D016998:Helicobacter / Q000472:pathogenicity* / Q000502:physiology*; D006801:Humans; D007422:Intestines / Q000166:cytology / Q000382:microbiology*; D013058:Mass Spectrometry; D040901:Proteomics; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism
D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D002966:Clathrin; D005839:Gentamicins; D037521:Virulence Factors