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Infect. Immun., Apr 1997, 1181-1188, Vol 65, No. 4
BE Dunn, NB Vakil, BG Schneider, MM Miller, JB Zitzer, T Peutz and SH Phadnis
Helicobacter pylori is a spiral, gram-negative bacterium which causes
chronic gastritis and plays a critical role in peptic ulcer disease,
gastric carcinoma, and gastric lymphoma. H. pylori expresses significant
urease activity which is an essential virulence factor. Since a significant
fraction of urease activity is located on the surface of the bacterium, the
urease molecule is a logical choice as an antigen for a vaccine; currently
recombinant urease apoenzyme is being tested as a vaccine in phase II
clinical trials. We have recently demonstrated that urease and HspB (a
homolog of the GroEL heat shock protein) become associated with the surface
of H. pylori in vitro in a novel manner: these cytoplasmic proteins are
released by bacterial autolysis and become adsorbed to the surface of
intact bacteria, reflecting the unique characteristics of the outer
membrane. To determine if similar mechanisms are operative in vivo, we
determined the ultrastructural locations of urease and HspB within bacteria
present in human gastric biopsies. Our results demonstrate that both urease
and HspB are located within the cytoplasm of all bacteria examined in human
gastric biopsies. Interestingly, a significant proportion of the bacteria
examined also possessed variable amounts of surface-associated urease and
HspB antigen (from 5 to 50% of the total antigenic material), indicating
that in vivo, H. pylori has surface characteristics which enable it to
adsorb cytoplasmic proteins. This is consistent with our altruistic
autolysis model in which H. pylori uses genetically programmed bacterial
autolysis to release urease and other cytoplasmic proteins which are
subsequently adsorbed onto the surface of neighboring viable bacteria.
These observations have important implications regarding pathogenesis and
development of vaccines for H. pylori.
Copyright © 1997, American Society for Microbiology
Localization of Helicobacter pylori urease and heat shock protein in human gastric biopsies
Department of Pathology, Medical College of Wisconsin, Milwaukee, USA.
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