Helicobacter pylori VacA Activates NF‐κB in T Cells via the Classical but not Alternative Pathway

Background: Helicobacter pylori secretes vacuolating cytotoxin (VacA) that damages the gastric epithelium by erosion and loosening of tight junctions. VacA has also immunosuppressive effects, inhibiting interleukin (IL)-2 secretion by interference with the T cell receptor/IL-2 signaling pathway. This study investigated the effect of VacA on gene expression of T cells. Materials and methods:  Gene expression profile of a T cell line, Jurkat, was analyzed by the cDNA microarray technique after VacA challenge. The expression of specific mRNAs was assessed by reverse transcription-polymerase chain reaction. Interleukin (IL)-8 concentrations in culture supernatants and cell surface expression of CD69 were measured by enzyme-linked immunosorbent assay and flow cytometry, respectively. We evaluated nuclear factor-κB (NF-κB) activation in Jurkat cells challenged with VacA by luciferase assay, electrophoretic mobility shift assay, and Western blot analysis. Results:  VacA produced two or greater fold up-regulation of expression of 60 genes. Most of these genes were associated with signal transduction, regulation of gene expression, apoptosis, and inflammation. Up-regulation of four genes (IL8, IL2RA, ICAM1, and CD69) was confirmed. The supernatants of cells incubated with VacA showed significantly higher secretion levels of IL-8 than those incubated without VacA. VacA also induced the cell surface expression of CD69. Since microarray analysis indicated NF-κB was involved in the transcriptional activation of the above genes, we examined NF-κB signaling pathway. VacA activated NF-κB via classical but not alternative pathway. Conclusions:  VacA has two paradoxical effects on T cells, immunosuppression, and proinflammatory effects. The latter is mediated by NF-κB activation.