Antigenic Properties of HpaA and Omp18, Two Outer Membrane Proteins ofHelicobacter pylori

Abstract

Outer membrane proteins (OMPs) are incorporated into the outer plasma membrane of Helicobacter pylori and are important for, e.g., ion transport, adherence, structural and osmotic stability, and bacterial virulence but may also be antigenic due to their surface exposure. Previous proteome-based approaches with H. pylori lysates determined a strong serological reaction towards two H. pylori OMPs, HpaA (TIGR HP0797) and Omp18 (TIGR HP1125). PCR was used to detect DNA encoding the two proteins, and a positive signal was found in all H. pylori strains tested. Proteins were cloned and expressed in the human kidney cell line HK293 with the QiaExpressionist system with a C-terminal His tag. Only sera from infected persons showed a positive reaction with the recombinant proteins. Recombinant HpaA (rHpaA) and rOmp18 were incubated with human peripheral blood mononuclear cells and induced secretion of interleukin-12 (IL-12) and IL-10 from these cells. To determine the effect on antigen-presenting cells, human blood monocytic and dendritic cells (DCs) were isolated by magnetic cell separation. rOmp18 and rHpaA strongly stimulated major histocompatibility class II and CD83 expression 7-to 10-fold on isolated DCs. rHpaA and rOmp18 failed to stimulate IL-8 secretion from monocytes but increased secretion of IL-12 and IL-10 from DCs significantly. In summary, HpaA and Omp18 are recognized by human dendritic cells and induce their maturation as well as antigen presentation. HpaA and Omp18 of H. pylori thereby appear to have a specific antigenic potential in humans.

Impact of Helicobacter pylori Virulence Factors and Compounds on Activation and Maturation of Human Dendritic Cells

“…Sharma et al demonstrated that IL-8 production by gastric epithelial cells is not solely dependent on the presence of CagA and VacA, but other bacterial constituents are clearly essential (53). H. pylori has a complex structure and harbors several potential immunostimulatory PAMPs (LPS, DNA, and flagellin), as well as outer membrane proteins like HpaA and Omp18 (61). Therefore, it would be surprising if the innate immune response were stringently controlled by the presence or absence of cag PAI and VacA.…”

Helicobacter pylori eradication: Novel therapy for immune thrombocytopenic purpura? A review of the literature

“…Dendritic cells have been observed to extend their lamina podia across an intact epithelium via a paracellular pathway and hence can sample luminal antigen across an intact epithelium. Once dendritic cells bind H. pylori or H. pylori antigens, they can induce an immune response with features of both a Th1 and Th2 response with increased production of both IL-12 (a key cytokine in shifting the immune response from a Th0 to a Th1 response) and IL-10 (a classic Th2 cytokine) [88,89].…”

Helicobacter pyloridirects tolerogenic programming of dendritic cells

“…25,27 We first nonintegrin (DC-SIGN) is the DC surface receptor that binds H. pylori glycans 11,12 and that H. pylori stimulates DCs predominantly through a Toll-like receptor (TLR)-dependent signaling cascade. 13 H. pylori-pulsed DCs (HP-DC) promote a type 1 helper T cell (Th1) response [14][15][16][17][18][19][20] and, as shown more recently, an interleukin (IL)-17-producing helper T cell (Th17) response. 21 Several studies have suggested the immunoregulatory effects of H. pylori on DCs.…”