Pertussis Toxin Exploits Host Cell Signaling Pathways Induced by Meningitis-Causing E. coli K1-RS218 and Enhances Adherence of Monocytic THP-1 Cells to Human Cerebral Endothelial Cells

Helicobacter pylori Neutrophil-Activating Protein Directly Interacts with and Activates Toll-like Receptor 2 to Induce the Secretion of Interleukin-8 from Neutrophils and ATRA-Induced Differentiated HL-60 Cells

Helicobacter pylori neutrophil-activating protein (HP-NAP)-induced production of reactive oxygen species (ROS) by neutrophils and monocytes is regulated by pertussis toxin (PTX)-sensitive G proteins, whereas HP-NAP-induced cytokine secretion by monocytes is mediated by Toll-like receptor 2 (TLR2). However, it is unclear whether TLR2 participates in HP-NAP-induced cytokine secretion by neutrophils. Here, all-trans retinoic acid (ATRA)-induced differentiated HL-60 cells were first employed as a neutrophil model to investigate the molecular mechanisms underlying neutrophil responses to HP-NAP. HP-NAP-induced ROS production in ATRA-induced differentiated HL-60 cells is mediated by the PTX-sensitive heterotrimeric G protein-dependent activation of extracellular signal-regulated kinase 1/2 and p38-mitogen-activated protein kinase, which is consistent with the findings reported for human neutrophils. Next, whether TLR2 participated in HP-NAP-induced secretion of interleukin-8 (IL-8) was investigated in neutrophils and ATRA-induced differentiated HL-60 cells. In both cells, TLR2 participated in HP-NAP-induced IL-8 secretion but not HP-NAP-induced ROS production. Interestingly, PTX-sensitive G proteins also contributed to the HP-NAP-induced secretion of IL-8 from neutrophils and the differentiated HL-60 cells. Our ELISA-based binding assay further revealed the competitive binding of Pam₃CSK₄, a TLR2 agonist, and HP-NAP to TLR2, which suggests the presence of specific and direct interactions between HP-NAP and TLR2. Thus, HP-NAP directly interacts with and activates TLR2 to induce IL-8 secretion in neutrophils and ATRA-induced differentiated HL-60 cells.

Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections

Well-adapted pathogens have evolved to survive the many challenges of a robust immune response. Defending against all host antimicrobials simultaneously would be exceedingly difficult, if not impossible, so many co-evolved organisms utilize immunomodulatory tools to subvert, distract, and/or evade the host immune response. Bordetella spp. present many examples of the diversity of immunomodulators and an exceptional experimental system in which to study them. Recent advances in this experimental system suggest strategies for interventions that tweak immunity to disrupt bacterial immunomodulation, engaging more effective host immunity to better prevent and treat infections. Here we review advances in the understanding of respiratory pathogens, with special focus on Bordetella spp., and prospects for the use of immune-stimulatory interventions in the prevention and treatment of infection.