期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：20
页码：7727-7732
DOI：10.1073/pnas.0401528101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Recent evidence indicates that the secreted Helicobacter pylori vacuolating toxin (VacA) inhibits the activation of T cells. VacA blocks IL-2 secretion in transformed T cell lines by suppressing the activation of nuclear factor of activated T cells (NFAT). In this study, we investigated the effects of VacA on primary human CD4+ T cells. VacA inhibited the proliferation of primary human T cells activated through the T cell receptor (TCR) and CD28. VacA-treated Jurkat T cells secreted markedly diminished levels of IL-2 compared with untreated cells, whereas VacA-treated primary human T cells continued to secrete high levels of IL-2. Further experiments indicated that the VacA-induced inhibition of primary human T cell proliferation was not attributable to VacA effects on NFAT activation or IL-2 secretion. We show here that VacA suppresses IL-2-induced cell-cycle progression and proliferation of primary human T cells without affecting IL-2-dependent survival. Through the analysis of a panel of mutant VacA proteins, we demonstrate that VacA-mediated inhibition of T cell proliferation requires an intact N-terminal hydrophobic region necessary for the formation of anion-selective membrane channels. Remarkably, we demonstrate that one of these mutant VacA proteins [VacA-{Delta}(6-27)] abrogates the immunosuppressive actions of wild-type VacA in a dominant-negative fashion. We suggest that VacA may inhibit the clonal expansion of T cells that have already been activated by H. pylori antigens, thereby allowing H. pylori to evade the adaptive immune response and establish chronic infection.
