Characterization and immunogenicity of the CagF protein of the cag pathogenicity island of Helicobacter pylori.

Helicobacter pylori infection causes severe gastroduodenal diseases in humans. Its virulence is strongly increased by the presence of the cag pathogenicity island (cag PAI). It has been shown that CagA, a major antigen in humans, is translocated to the host cell via a secretion system encoded by the cag PAI. The roles of many of the proteins encoded within the cag PAI are not known. Here we report on the cloning and expression of CagF, one of those proteins. We show that CagF is associated to the outer membrane of H. pylori G27 and that the protein is always expressed with electrophoretic mobility variations among the 20 strains tested here. We have also found that natural infection with H. pylori is able to induce antibodies against CagF.