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Infection and Immunity, December 2006, p. 6839-6846, Vol. 74, No. 12
0019-9567/06/$08.00+0     doi:10.1128/IAI.00991-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Dual Roles of Helicobacter pylori NapA in Inducing and Combating Oxidative Stress{triangledown}

Ge Wang, Yang Hong, Adriana Olczak, Susan E. Maier, and Robert J. Maier*

Department of Microbiology, University of Georgia, Athens, Georgia 30602

Received 22 June 2006/ Returned for modification 2 August 2006/ Accepted 28 September 2006

Neutrophil-activating protein (NapA) has been well documented to play roles in human neutrophil recruitment and in stimulating host cell production of reactive oxygen intermediates (ROI). A separate role for NapA in combating oxidative stress within H. pylori was implied by studies of various H. pylori mutant strains. Here, physiological analysis of a napA strain was the approach used to assess the iron-sequestering and stress resistance roles of NapA, its role in preventing oxidative DNA damage, and its importance to mouse colonization. The napA strain was more sensitive to oxidative stress reagents and to oxygen, and it contained fourfold more intracellular free iron and more damaged DNA than the parent strain. Pure, iron-loaded NapA bound to DNA, but native NapA did not, presumably linking iron levels sensed by NapA to DNA damage protection. Despite its in vitro phenotype of sensitivity to oxidative stress, the napA strain showed normal (like that of the wild type) mouse colonization efficiency in the conventional in vivo assay. By use of a modified mouse inoculation protocol whereby nonviable H. pylori is first inoculated into mice, followed by (live) bacterial strain administration, an in vivo role for NapA in colonization efficiency could be demonstrated. NapA is the critical component responsible for inducing host-mediated ROI production, thus inhibiting colonization by the napA strain. An animal colonization experiment with a mixed-strain infection protocol further demonstrated that the napA strain has significantly decreased ability to survive when competing with the wild type. H. pylori NapA has unique and separate roles in gastric pathogenesis.

* Corresponding author. Mailing address: Department of Microbiology, 815 Biological Sciences Building, University of Georgia, Athens, GA 30602. Phone: (706) 542-2323. Fax: (706) 542-2674. E-mail: rmaier{at}uga.edu.

{triangledown} Published ahead of print on 9 October 2006.

Editor: J. N. Weiser

Infection and Immunity, December 2006, p. 6839-6846, Vol. 74, No. 12
0019-9567/06/$08.00+0     doi:10.1128/IAI.00991-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



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