Host-pathogen interaction

Field of interest

The host defence against microbial agents involves the activity of several specialized cells such as monocytes/macrophages, neutrophils and lymphocytes. The success of their intervention depends on the ability of the cells to coordinate their function via the release of messengers called cytokines: a particular pattern of cyokines produced by the recruited cells during an infection, will contribute to determine the outcome of the infection. Several bacteria have developed mechanisms that make them able to escape the defence system; other bacteria produce molecules that interfere with the dialogue among the cells, which, in turn, are forced to produce particular cytokines that alter the cell cooperation. In many cases, as result, the host is unable to prevent or to eradicate the infection that can cause a strong tissue damage or become chronic.
The main interest of our lab is to identify and characterize bacterial products endowed with immune modulatory properties with the aim of contributing to the development of new therapeutic strategies. Furthermore, considering that several disease, such as allergy, are the results of an inappropriate immune response we plan to test some of these bacterial products in animal model in order to verify their ability to counteract or prevent the pathologic status. In the recent past, we have been focused on three main projects.

Summary of research activity

Role of the protein NapA produced by Borrelia burgdorferi in the pathogenesis of Lyme arthritis

Borrelia burgdorferi is a spirochetal bacterium responsible for the human Lyme disease, a multisistemic illness transmitted by ticks, which can ultimate in the development of the so-called Lyme arthritis, a condition characterized by marked swelling and pain of affected joints, most commonly the knee. Previously, we have characterized a protein produced by Helicobacter pylori, a bacterium that gives chronic infections in humans as B. burgdorferi does, termed HP-NAP (H. pylori Neutrophil Activating Protein). This protein is a strong immunogen and is endowed with immunomodulatory properties (reviewed in de Bernard & D'Elios, Toxicon 2008, doi:10.1016/j.toxicon.2009.09.020). The chromosomal gene bb0690 of B. burgdorferi encodes a protein termed NapA (Neutrophil Activating Protein A), homologous to HP-NAP, that was shown to be essential for the persistence of spirochetae within ticks. Based on these premises, the aim of our study was to evaluate the role of the innate and acquired immune responses elicited by the NapA of B. burgdorferi in Lyme arthritis. We have demonstrated that in patients with Lyme arthritis NapA induces a strong humoral response and drives Th17 inflammation. Furthermore, we found that NapA is a Toll-like receptor (TLR)-2 agonist able to stimulate monocyte expression of IL-23, IL-6, IL-1β and TGF-β, key cytokines for Th17 differentiation. Importantly, we also demonstrated that Th cells from synovial fluid of patients with Lyme arthritis produce IL-17 in response to NapA. Altogether, these results suggest that NapA is a major B. burgdorferi virulence factor involved in the pathogenesis of Th17 inflammation in human Lyme arthritis. Moreover our data represent the clear cut demonstration of the importance of interleukin-17 in human Lyme arthritis, a disease in which IFN-γ secreting Th1 cells, were proposed for several years, to play a central role (Codolo et al., Arthritis Rheum. 58,:3609-3617, 2008).

Use of HP-NAP as adjuvant for the development of T helper type 1 (Th1) immune response

In H. pylori infection the bacterium induces an inflammatory response in the gastric mucosa, characterized by polymorphonuclear and mononuclear cell infiltration. A key factor in orchestrating the recruitment and activation of these cells is HP-NAP. Notably, HP-NAP stimulates neutrophils and monocytes to release IL-12 and IL-23, the two pivotal cytokines responsible for driving the Th response towards the Th1 phenotype. Recently, we have demonstrated that the bacterial protein is capable of redirecting Th2 responses towards the Th1 phenotype (Codolo et al., Cell. Microbiol. 10, 2355-2363, 2008; Del Prete et al., J. Allergy Clin. Immunol. 122, 908-913, 2008). In both studies, HP-NAP was applied in vivo to a Th2-dominated animal model, such as mice affected by allergic asthma in the former study and mice infected with Trichinella spiralis (Ts) in the latter.
The capacity of HP-NAP in inhibiting Th2 responses in vitro and in vivo in humans and mice, makes this bacterial protein an important candidate for novel strategies of prevention and treatment of asthma and allergic diseases. Furthermore, considering that HP-NAP is a very powerful inducer of IL-12 and that IL-12 represents the most effective cytokine in terms of tumor eradication, anti-metastatic activity and long-term anti-tumor immunity, it is tempting to speculate that HP-NAP might be beneficial not only against allergic disease but also to fight cancer, e.g. as adjuvant for local immunotherapy of some neoplasias.

Characterization of the molecular mechanism underlying the H. pylori VacA-triggered apoptosis

Many recent reports stress that the biological activity of the H. pylori vacuolating cytotoxin VacA consists in promoting cell death via apoptosis. In collaboration with the unit of Dr. Scorrano at the VIMM, which possess expertise and tools in this field, we have decided to clarify the molecular mechanism involved. This study, although not directly related to inflammation processes, that remains our main scientific interest, is very intriguing because apoptosis has been suggested to be involved in stomach atrophy and, eventually, in gastric cancer development. VacA is an important virulence factor of H. pylori with pleiotropic effects on mammalian cells, including the ability to trigger mitochondria-dependent apoptosis. However, the mechanism by which VacA exerts its apoptotic function is unclear. By using a genetic approach, we show that killing by VacA requires the proapoptotic Bcl-2 family members BAX and BAK at the mitochondrial level, but not adequate endoplasmic reticulum Ca2+ levels, similarly controlled by BAX and BAK. A combination of subcellular fractionation and imaging shows that wild type VacA, but not mutants in its channel forming region, induces the accumulation of BAX on endosomes and endosomes-mitochondria juxtaposition that precedes the retrieval of active BAX on mitochondria. Of note, in Bax, Bak deficient cells VacA is unable to cause endosomes-mitochondria juxtaposition and is not retrieved in mitochondria. Thus, VacA causes BAX/BAK dependent juxtaposition of endosomes and mitochondria early in the process of cell death, revealing a new function for these proapoptotic proteins in the regulation of relative position of organelles.

Synoptic CV

Selected VIMM Publications

• Debellis L, Diana A, Arcidiacono D, Fiorotto R, Portincasa P, Altomare DF, Spirlì C, de Bernard M (2009) The Vibrio cholerae cytolysin promotes chloride secretion from intact human intestinal mucosa. PLoS ONE 4:e5074.
• Codolo G, Amedei A, Steere AC, Papinutto E, Cappon A, Polenghi A, Benagiano M, Paccani SR, Sambri V, Del Prete G, Baldari CT, Zanotti G, Montecucco C, D'Elios MM, de Bernard M (2008) Borrelia burgdorferi NapA-driven Th17 cell inflammation in lyme arthritis. Arthritis Rheum. 58:3609-17.
• Codolo G, Mazzi P, Amedei A, Del Prete G, Berton G, D'Elios MM, de Bernard M (2008) The neutrophil-activating protein of Helicobacter pylori down-modulates Th2 inflammation in ovalbumin-induced allergic asthma. Cell. Microbiol. 10:2355-63.
• Polenghi A, Bossi F, Fischetti F, Durigutto P, Cabrelle A, Tamassia N, Cassatella MA, Montecucco C, Tedesco F, de Bernard M (2007) The neutrophil-activating protein of Helicobacter pylori crosses endothelia to promote neutrophil adhesion in vivo. J. Immunol. 178:1312-20.
• Amedei A, Cappon A, Codolo G, Cabrelle A, Polenghi A, Benagiano M, Tasca E, Azzurri A, D'Elios MM, Del Prete G, de Bernard M (2006) The neutrophil-activating protein of Helicobacter pylori promotes Th1 immune responses. J. Clin. Invest. 116:1092-101.

VIMM Publications

• [Pubmed ID: 20070310 * PubMed in process or DB hiatus]
• [Pubmed ID: 19818802 * PubMed in process or DB hiatus]
• [Pubmed ID: 19565494 * PubMed in process or DB hiatus]
• Salata C, Curtarello M, Calistri A, Sartori E, Sette P, de Bernard M, Parolin C, Palù G (2009) vOX2 glycoprotein of human herpesvirus 8 modulates human primary macrophages activity. J. Cell. Physiol. 219:698-706.
• [Pubmed ID: 19220467 * PubMed in process or DB hiatus]
• Del Prete G, Chiumiento L, Amedei A, Piazza M, D'Elios MM, Codolo G, de Bernard M, Masetti M, Bruschi F (2008) Immunosuppression of TH2 responses in Trichinella spiralis infection by Helicobacter pylori neutrophil-activating protein. J. Allergy Clin. Immunol. 122:908-913.e5.
• Farinati F, Cardin R, Bortolami M, Nitti D, Basso D, de Bernard M, Cassaro M, Sergio A, Rugge M (2008) Oxidative DNA damage in gastric cancer: CagA status and OGG1 gene polymorphism. Int. J. Cancer 123:51-5.
• Arcidiacono D, Odom S, Frossi B, Rivera J, Paccani SR, Baldari CT, Pucillo C, Montecucco C, de Bernard M (2008) The Vibrio cholerae cytolysin promotes activation of mast cell (T helper 2) cytokine production. Cell. Microbiol. 10:899-907.
• Mazzon C, Baldani-Guerra B, Cecchini P, Kasic T, Viola A, de Bernard M, Aricò B, Gerosa F, Papini E (2007) IFN-gamma and R-848 dependent activation of human monocyte-derived dendritic cells by Neisseria meningitidis adhesin A. J. Immunol. 179:3904-16.
• D'Elios MM, Amedei A, Cappon A, Del Prete G, de Bernard M (2007) The neutrophil-activating protein of Helicobacter pylori (HP-NAP) as an immune modulating agent. FEMS Immunol. Med. Microbiol. 50:157-64.
• D'Elios MM, Montecucco C, de Bernard M (2007) VacA and HP-NAP, Ying and Yang of Helicobacter pylori-associated gastric inflammation. Clin. Chim. Acta 381:32-8.
• Genisset C, Puhar A, Calore F, de Bernard M, Dell'Antone P, Montecucco C (2007) The concerted action of the Helicobacter pylori cytotoxin VacA and of the v-ATPase proton pump induces swelling of isolated endosomes. Cell. Microbiol. 9:1481-90.
• Genisset C, Galeotti CL, Lupetti P, Mercati D, Skibinski DA, Barone S, Battistutta R, de Bernard M, Telford JL (2006) A Helicobacter pylori vacuolating toxin mutant that fails to oligomerize has a dominant negative phenotype. Infect. Immun. 74:1786-94.
• Spirlì C, Fiorotto R, Song L, Santos-Sacchi J, Okolicsanyi L, Masier S, Rocchi L, Vairetti MP, De Bernard M, Melero S, Pozzan T, Strazzabosco M (2005) Glibenclamide stimulates fluid secretion in rodent cholangiocytes through a cystic fibrosis transmembrane conductance regulator-independent mechanism. Gastroenterology 129:220-33.
• de Bernard M, Cappon A, Pancotto L, Ruggiero P, Rivera J, Del Giudice G, Montecucco C (2005) The Helicobacter pylori VacA cytotoxin activates RBL-2H3 cells by inducing cytosolic calcium oscillations. Cell. Microbiol. 7:191-8.
• de Bernard M, Cappon A, Del Giudice G, Rappuoli R, Montecucco C (2004) The multiple cellular activities of the VacA cytotoxin of Helicobacter pylori. Int. J. Med. Microbiol. 293:589-97.
• Montecucco C, de Bernard M (2003) Immunosuppressive and proinflammatory activities of the VacA toxin of Helicobacter pylori. J. Exp. Med. 198:1767-71.

Selected Seminars

Contact

Marina de Bernard Venetian Institute of Molecular Medicine Via Orus 2 35129 Padua — Italy

Tel.:  (+39) 049 7923 223 Tel. lab.:  (+39) 049 7923 225 Fax:  (+39) 049 7923 250

Last updated: 28/03/2010, MDB ·