Bordetella adenylate cyclase toxin differentially modulates toll-like receptor-stimulated activation, migration and T cell stimulatory capacity of dendritic cells.

Irena Adkins,Jiri Masin,Jana Kamanova,Barbora Chladkova,Marek Kovar,Kingston H G Mills,Ladislav Bumba,Hana Janova,Ludmila Tuckova,Jakub Tomala,Aneta Kocourkova,Padraig J Ross,Martina Svedova,Radek Spisek,Peter Sebo,Daniela Flavia Hozbor

doi:10.1371/journal.pone.0104064

Abstract

Adenylate cyclase toxin (CyaA) is a key virulence factor of the whooping cough agent Bordetella pertussis. The toxin targets CD11b-expressing phagocytes and delivers into their cytosol an adenylyl cyclase (AC) enzyme that subverts cellular signaling by increasing cAMP levels. In the present study, we analyzed the modulatory effects of CyaA on adhesive, migratory and antigen presenting properties of Toll-like receptor (TLR)-activated murine and human dendritic cells (DCs). cAMP signaling of CyaA enhanced TLR-induced dissolution of cell adhesive contacts and migration of DCs towards the lymph node-homing chemokines CCL19 and CCL21 in vitro. Moreover, we examined in detail the capacity of toxin-treated DCs to induce CD4+ and CD8+ T cell responses. Exposure to CyaA decreased the capacity of LPS-stimulated DCs to present soluble protein antigen to CD4+ T cells independently of modulation of co-stimulatory molecules and cytokine production, and enhanced their capacity to promote CD4+CD25+Foxp3+ T regulatory cells in vitro. In addition, CyaA decreased the capacity of LPS-stimulated DCs to induce CD8+ T cell proliferation and limited the induction of IFN-γ producing CD8+ T cells while enhancing IL-10 and IL-17-production. These results indicate that through activation of cAMP signaling, the CyaA may be mobilizing DCs impaired in T cell stimulatory capacity and arrival of such DCs into draining lymph nodes may than contribute to delay and subversion of host immune responses during B. pertussis infection.

Highlights

Despite extensive vaccination programs, pertussis called whooping cough, remains the least controlled vaccine-preventable infectious disease and represents a significant health burden worldwide, accounting for as many as 300 000 deaths per year [1]
Prior to analyzing the effect of CyaA on immunostimulatory activities of Toll-like receptor (TLR)-stimulated dendritic cells (DCs), we first examined the impact of exposure to low CyaA concentration (10 ng/ml) on viability of murine bone-marrow derived DCs (BMDCs) and human monocyte-derived DCs (MDDCs)
These effects were mediated by CyaA-induced cAMP signaling, since the enzymatically inactive CyaA-AC2 did not affect cell viability of untreated, or LPS-treated MDDCs and BMDCs, respectively

Summary

Introduction

Pertussis called whooping cough, remains the least controlled vaccine-preventable infectious disease and represents a significant health burden worldwide, accounting for as many as 300 000 deaths per year [1]. The currently observed significant upsurge of pertussis incidence in the most developed countries raises substantial prospective concern about evolution of whooping cough epidemiology [2]. This highly contagious disease is caused by the Gram-negative coccobacilli Bordetella pertussis and B. parapertussis that adhere to ciliated epithelial cells of human nasopharynx and trachea. The adenylate cyclase toxin (CyaA) is a key virulence factor of B. pertussis that subverts host defense [4]. The C-terminal RTX hemolysin (Hly) moiety (,1306 residues) mediates CyaA toxin binding to myeloid phagocytic cells via the aMb2 integrin, known as CD11b/CD18, complement receptor 3 (CR3), or Mac-1) [7]. CyaA-induced efflux of K+ ions from the host cell was, shown to activate the NALP3 inflammasome and promote IL-1b release from LPSprimed dendritic cells (DCs) [9]

Objectives

Methods

Results

Conclusion