Functional analysis of the p33 and p55 domains of the Helicobacter pylori vacuolating cytotoxin

Abstract

Experimental and epidemiological studies have suggested that the vacuolating cytotoxin (VacA) is an important H. pylori virulence factor that contributes to the development of peptic ulceration and gastric adenocarcinoma. VacA produces a variety of structural and functional changes in eukaryotic cells, many of which are dependent on its ability to form membrane channels. In the absence of a VacA high resolution structure, it has been difficult to analyze VacA structure-function relationships. Thus, one goal of this thesis was to map and characterize VacA functional domains. We describe here the functional characterization of two putative VacA domains (p33 and p55). Collectively, the data generated in this thesis provide strong evidence indicating that both the p33 and p55 functional domains are essential for VacA oligomerization, cell binding, internalization, and vacuolating activity. The second goal of this thesis was to investigate VacA effects on primary human T cells. This study indicates that VacA inhibits activation-induced proliferation of primary human T cells, via a mechanism that requires formation of membrane channels. We propose that the effects of VacA on T cells might contribute to the capacity of H. pylori to evade the adaptive immune response and establish persistent infection.