Gaia Codolo

The neutrophil-activating protein of Helicobacter pylori promotes Th1 immune responses

The Helicobacter pylori neutrophil-activating protein (HP-NAP) is a virulence factor of H. pylori that stimulates in neutrophils high production of oxygen radicals and adhesion to endothelial cells. We report here that HP-NAP is a TLR2 agonist able to induce the expression of IL-12 and IL-23 by neutrophils and monocytes. Addition in culture of HP-NAP, as an immune modulator, to antigen-induced T cell lines resulted in a remarkable increase in the number of IFN-gamma-producing T cells and decrease of IL-4-secreting cells, thus shifting the cytokine profile of antigen-activated human T cells from Th2 to a Th1 cytotoxic phenotype. We also found that in vivo HP-NAP elicited an antigen-specific Th1-polarized T cell response in the gastric mucosa of H. pylori-infected patients. These data indicate HP-NAP as an important factor of H. pylori able to elicit cells of the innate immune system to produce IL-12 and IL-23, and they suggest it as a new tool for promoting Th1 immune responses.

Triggering of inflammasome by aggregated α-synuclein, an inflammatory response in synucleinopathies.

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. It is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta of the brain. Another feature is represented by the formation in these cells of inclusions called Lewy bodies (LB), principally constituted by fibrillar α-synuclein (αSyn). This protein is considered a key element in the aetiology of a group of neurodegenerative disorders termed synucleinopathies, which include PD, but the cellular and molecular mechanisms involved are not completely clear. It is established that the inflammatory process plays a crucial role in the pathogenesis and/or progression of PD; moreover, it is known that aggregated αSyn, released by neurons, activates microglia cells to produce pro-inflammatory mediators, such as IL-1β. IL-1β is one of the strongest pro-inflammatory cytokines; it is produced as an inactive mediator, and its maturation and activation requires inflammasome activation. In particular, the NLRP3 inflammasome is activated by a wide variety of stimuli, among which are crystallized and particulate material. In this work, we investigated the possibility that IL-1β production, induced by fibrillar αSyn, is involved the inflammasome activation. We demonstrated the competence of monomeric and fibrillar αSyn to induce synthesis of IL-1β, through TLR2 interaction; we found that the secretion of the mature cytokine was a peculiarity of the fibrillated protein. Moreover, we observed that the secretion of IL-1β involves NLRP3 inflammasome activation. The latter relies on the phagocytosis of fibrillar αSyn, followed by increased ROS production and cathepsin B release into the cytosol. Taken together, our data support the notion that fibrillar αSyn, likely released by neuronal degeneration, acts as an endogenous trigger inducing a strong inflammatory response in PD.

Borrelia burgdorferi NapA-driven Th17 cell inflammation in lyme arthritis.

OBJECTIVE Human Lyme arthritis caused by Borrelia burgdorferi is characterized by an inflammatory infiltrate that consists mainly of neutrophils and T cells. This study was undertaken to evaluate the role of the innate and acquired immune responses elicited by the neutrophil-activating protein A (NapA) of B burgdorferi in patients with Lyme arthritis. METHODS Serum anti-NapA antibodies were measured in 27 patients with Lyme arthritis and 30 healthy control subjects. The cytokine profile of synovial fluid T cells specific for NapA was investigated in 5 patients with Lyme arthritis. The cytokine profile induced by NapA in neutrophils and monocytes was also investigated. RESULTS Serum anti-NapA antibodies were found in 48% of the patients with Lyme arthritis but were undetectable in the healthy controls. T cells from the synovial fluid of patients with Lyme arthritis produced interleukin-17 (IL-17) in response to NapA. Moreover, NapA was able to induce the expression of IL-23 in neutrophils and monocytes, as well as the expression of IL-6, IL-1beta, and transforming growth factor beta (TGFbeta) in monocytes, via Toll-like receptor 2. CONCLUSION These findings indicate that NapA of B burgdorferi is able to drive the expression of IL-6, IL-1beta, IL-23, and TGFbeta by cells of the innate immune system and to elicit a synovial fluid Th17 cell response that might play a crucial role in the pathogenesis of Lyme arthritis.

The neutrophil-activating protein of Helicobacter pylori down-modulates Th2 inflammation in ovalbumin-induced allergic asthma.

The Helicobacter pylori neutrophil‐activating protein (HP‐NAP) is able in vitro to elicit IL‐12 and IL‐23 production via agonistic interaction with toll‐like receptor 2, and to promote Th1 polarization of allergen‐specific T‐cell responses. This study was aimed to assess whether systemic/intraperitoneal and/or mucosal HP‐NAP administration inhibited the Th2‐mediated bronchial inflammation using a mouse model of allergic asthma induced by inhaled ovalbumin (OVA). Systemic HP‐NAP delivery markedly reduced the lung eosinophilia in response to repeated challenge with aerosolized OVA. Likewise, the production of IL‐4, IL‐5 and GM‐CSF was significantly lower in the bronchoalveolar lavage of animals treated with systemic HP‐NAP plus OVA than that of animals treated with OVA alone. Systemic HP‐NAP also significantly resulted in both reduction of total serum IgE and increase of IL‐12 plasma levels. Mucosal administration of HP‐NAP was equally successful as the systemic delivery in reducing eosinophilia, IgE and Th2 cytokine levels in bronchoalveolar lavage. However, no suppression of lung eosinophilia and bronchial Th2 cytokines was observed in toll‐like receptor 2‐knock‐out mice following HP‐NAP treatment. These results identify HP‐NAP as a candidate for novel strategies of prevention and treatment of allergic diseases.

Endosome–mitochondria juxtaposition during apoptosis induced by H. pylori VacA

The vacuolating cytotoxin (VacA) is an important virulence factor of Helicobacter 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. Using a genetic approach, in this study 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 endosome–mitochondria juxtaposition that precedes the retrieval of active BAX on mitochondria. It is noteworthy that in Bax- and Bak-deficient cells, VacA is unable to cause endosome–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.

Helicobacter pylori, asthma and allergy

Bronchial asthma and allergic diseases are orchestrated by T-cells producing T-helper type 2 (Th2) cytokines, such as interleukin-4 (IL-4) and IL-5, and are inhibited by Th1 responses. Helicobacter pylori has chronically infected the human population for c. 100,000 years and preferentially elicits a Th1 mucosal immune response with the production of interferon-gamma and IL-12. Among several bacterial factors, the neutrophil-activating protein of H. pylori (HP-NAP) not only plays a key role in driving Th1 inflammation but it is also able to inhibit Th2 responses in vitro and in vivo in allergic bronchial asthma, in humans and mice. Both systemic and mucosal administrations of HP-NAP are successful in reducing eosinophilia, immunoglobulin E and systemic Th2 cytokines at the bronchial level. Thus, these results identify HP-NAP as a candidate for novel strategies for the prevention and treatment of allergic diseases.

Immunosuppression of TH2 responses in Trichinella spiralis infection by Helicobacter pylori neutrophil-activating protein

BACKGROUND The Helicobacter pylori neutrophil-activating protein (HP-NAP) is able to induce IL-12 expression by cells of innate immunity and to shift to T(H)1 human allergen-specific T(H)2 cells in vitro. OBJECTIVE We performed an in vivo investigation of the ability of HP-NAP to downmodulate the T(H)2 response induced in mice by Trichinella spiralis infection. METHODS Groups of T spiralis-infected BALB/c mice received intraperitoneal PBS/rat IgG2b (control animals) or 10 microg of HP-NAP with or without anti-Toll-like receptor 2 antibody on days 10 and 28 after infection. Blood eosinophils, total and T spiralis-specific IgE levels, and cytokine levels were measured in the plasma up to day 42, when splenocytes were cultured for cytokine production. RESULTS Although control animals showed significant eosinophilia and increase of total and T spiralis-specific IgE, IL-4, and IL-5 levels from days 10 to 14, HP-NAP-treated animals showed less eosinophilia and total and excretory/secretory antigens of T spiralis-specific IgE in the blood. HP-NAP-treated animals also had higher IL-12 and IFN-gamma plasma levels and lower IL-4 and IL-5 levels. The addition of anti-Toll-like receptor 2 antibody abrogated the anti-T(H)2/pro-T(H)1 activity of HP-NAP. CONCLUSION This study provides evidence that HP-NAP enhances endogenous IL-12 and IFN-gamma response and exerts a powerful anti-T(H)2 activity in vivo, targeting both IL-5-induced eosinophilia and IL-4-mediated hyper-IgE responses induced by parasitic infection.

Cytokine BAFF Released by Helicobacter pylori–Infected Macrophages Triggers the Th17 Response in Human Chronic Gastritis

BAFF is a crucial cytokine that affects the activity of both innate and adaptive immune cells. It promotes the expansion of Th17 cells in autoimmune disorders. With this study, we investigated the BAFF/Th17 responses in Helicobacter pylori–induced gastritis in humans. Our results show that the mucosa from Helicobacter+ patients with chronic gastritis is enriched in IL-17 and BAFF, whereas the two cytokines are weakly expressed in Helicobacter− patients with chronic gastritis; moreover, the expression of both BAFF and IL-17 decreases after bacteria eradication. We demonstrate that BAFF accumulates in macrophages in vivo and that it is produced by monocyte-derived macrophages in vitro, after Helicobacter stimulation. Application of BAFF on monocytes triggers the accumulation of reactive oxygen species that are crucial for the release of pro-Th17 cytokines, such as IL-23, IL-1β, and TGF-β. Moreover, BAFF directly promotes the differentiation of Th17 cells. In conclusion, our results support the notion that an axis BAFF/Th17 exists in chronic gastritis of Helicobacter+ patients and that its presence strictly depends on the bacterium. Moreover, we demonstrated that BAFF is able to drive Th17 responses both indirectly, by creating a pro-Th17 cytokine milieu through the involvement of innate immune cells, and directly, via the differentiation of T cells toward the specific profile. The results obtained in this study are of great interest for Helicobacter-related diseases and the development of novel therapeutic strategies based on the inhibition of the BAFF/IL-17 response.

The effect of Helicobacter pylori on asthma and allergy

Current evidence indicates an inverse association between Helicobacter pylori and asthma and allergy. H. pylori is a Gram-negative bacterium which represents the major cause of peptic ulcer and gastric cancer, and preferentially elicits a T helper (Th)-1 response. Many H. pylori factors, such as the neutrophil-activating factor of H. pylori (HP-NAP), are able to drive Th-1 polarization and to display a powerful inhibition of allergic Th-2 response. This article proposes an overview of the actual knowledge about the effects of H. pylori on asthma and allergy. Special attention has been drawn to HP-NAP as a potential novel strategy for the prevention and treatment of asthma and atopy.

HP-NAP inhibits the growth of bladder cancer in mice by activating a cytotoxic Th1 response

Intravesical Bacillus Calmette–Guérin (BCG) is the gold standard treatment for intermediate and high-risk non-muscle-invasive bladder cancer. BCG therapy is the most successful example of immunotherapy in cancer. Unfortunately, the treatment-related side effects are still relevant. Furthermore, non-responder patients are candidate to radical cystectomy in the absence of valuable alternative options. These aspects have prompted the search for newer biological response modifiers (BRM) with a better benefit/side effects ratio. The toll-like receptor (TLR) 2 ligand, Helicobacter pylori protein HP-NAP, has been shown to deserve a potential role as BRM. HP-NAP is capable of driving the differentiation of T helper (Th) 1 cells, both in vitro and in vivo, because of its ability to create an IL-12-enriched milieu. Herein, we report that local administration of HP-NAP decreases tumour growth by triggering tumour necrosis in a mouse model of bladder cancer implant. The effect is accompanied by a significant accumulation of both CD4+ and CD8+ IFN-γ-secreting cells, within tumour and regional lymph nodes. Noteworthy, HP-NAP-treated tumours show also a reduced vascularization due to the anti-angiogenic activity of IFN-γ induced by HP-NAP. Our findings strongly indicate that HP-NAP might become a novel therapeutic “bullet” for the cure of bladder tumours.