Helicobacter pylori VacA activates NF-kappaB in T cells via the classical but not alternative pathway

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.

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-kappaB (NF-kappaB) activation in Jurkat cells challenged with VacA by luciferase assay, electrophoretic mobility shift assay, and Western blot analysis.

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-kappaB was involved in the transcriptional activation of the above genes, we examined NF-kappaB signaling pathway. VacA activated NF-kappaB via classical but not alternative pathway.

VacA has two paradoxical effects on T cells, immunosuppression, and proinflammatory effects. The latter is mediated by NF-kappaB activation.