S. Chollet-Martin

Neutropenic Mice Provide Insight into the Role of Skin-Infiltrating Neutrophils in the Host Protective Immunity against Filarial Infective Larvae

Our knowledge and control of the pathogenesis induced by the filariae remain limited due to experimental obstacles presented by parasitic nematode biology and the lack of selective prophylactic or curative drugs. Here we thought to investigate the role of neutrophils in the host innate immune response to the infection caused by the Litomosoides sigmodontis murine model of human filariasis using mice harboring a gain-of-function mutation of the chemokine receptor CXCR4 and characterized by a profound blood neutropenia (Cxcr4+/1013). We provided manifold evidence emphasizing the major role of neutrophils in the control of the early stages of infection occurring in the skin. Firstly, we uncovered that the filarial parasitic success was dramatically decreased in Cxcr4+/1013 mice upon subcutaneous delivery of the infective stages of filariae (infective larvae, L3). This protection was linked to a larger number of neutrophils constitutively present in the skin of the mutant mice herein characterized as compared to wild type (wt) mice. Indeed, the parasitic success in Cxcr4+/1013 mice was normalized either upon depleting neutrophils, including the pool in the skin, or bypassing the skin via the intravenous infection of L3. Second, extending these observations to wt mice we found that subcutaneous delivery of L3 elicited an increase of neutrophils in the skin. Finally, living L3 larvae were able to promote in both wt and mutant mice, an oxidative burst response and the release of neutrophil extracellular traps (NET). This response of neutrophils, which is adapted to the large size of the L3 infective stages, likely directly contributes to the anti-parasitic strategies implemented by the host. Collectively, our results are demonstrating the contribution of neutrophils in early anti-filarial host responses through their capacity to undertake different anti-filarial strategies such as oxidative burst, degranulation and NETosis.

Protein kinase CK2 controls T-cell polarization through dendritic cell activation in response to contact sensitizers

Allergic contact dermatitis (ACD) represents a severe health problem with increasing worldwide prevalence. It is a T‐cell‐mediated inflammatory skin disease caused by chemicals present in the daily or professional environment. NiSO4 and 2,4‐dinitrochlorobenzene (DNCB) are 2 chemicals involved in ACD. These contact sensitizers are known to induce an up‐regulation of phenotypic markers and cytokine secretion in dendritic cells (DCs; professional APCs), leading to the generation of CD8+ Tc1/Tc17 and CD4+ Th1/Th17 effector T cells. In the present study, using a peptide array approach, we identified protein kinase CK2 as a novel kinase involved in the activation of human monocyte‐derived DCs (MoDCs) in response to NiSO4 and DNCB. Inhibition of CK2 activity in MoDCs led to an altered mature phenotype with lower expression of CD54, PDL‐1, CD86, and CD40 in response to NiSO4 or DNCB. CK2 activity also regulated proinflammatory cytokine production, such as TNF‐α, IL‐1β, and IL‐23 in MoDCs. Moreover, in a DC/T cell coculture model in an allogeneic setup, CK2 activity in MoDCs played a major role in Th1 polarization in response to NiSO4 and DNCB. CK2 inhibition in MoDCs led to an enhanced Th2 polarization in the absence of contact sensitizer stimulation.

Low end-tidal CO2 as a real-time severity marker of intra-anaesthetic acute hypersensitivity reactions

Background Prompt diagnosis of intra-anaesthetic acute hypersensitivity reactions (AHR) is challenging because of the possible absence and/or difficulty in detecting the usual clinical signs and because of the higher prevalence of alternative diagnoses. Delayed epinephrine administration during AHR, because of incorrect/delayed diagnosis, can be associated with poor prognosis. Low end-tidal CO2 (etCO2) is known to be linked to low cardiac output. Yet, its clinical utility during suspected intra-anaesthetic AHR is not well documented. Methods Clinical data from the 86 patients of the Neutrophil Activation in Systemic Anaphylaxis (NASA) multicentre study were analysed. Consenting patients with clinical signs consistent with intra-anaesthetic AHR to a neuromuscular blocking agent were included. Severe AHR was defined as a Grade 3-4 of the Ring and Messmer classification. Causes of AHR were explored following recommended guidelines. Results Among the 86 patients, 50% had severe AHR and 69% had a confirmed/suspected IgE-mediated event. Occurrence and minimum values of arterial hypotension, hypocapnia and hypoxaemia increased significantly with the severity of AHR. Low etCO2 was the only factor able to distinguish mild [median 3.5 (3.2;3.9) kPa] from severe AHR [median 2.4 (1.6;3.0) kPa], without overlap in inter-quartile range values, with an area under the receiver operator characteristic curve of 0.92 [95% confidence interval: 0.79-1.00]. Among the 41% of patients who received epinephrine, only half received it as first-line therapy despite international guidelines. Conclusions An etCO2 value below 2.6 kPa (20 mm Hg) could be useful for prompt diagnosis of severe intra-anaesthetic AHR, and could facilitate early treatment with titrated doses of epinephrine. Clinical trial registration NCT01637220.

Platelets expressing IgG receptor FcγRIIA/CD32A determine the severity of experimental anaphylaxis

Platelet-derived serotonin contributes to FcγRIIA/CD32A-induced IgG-dependent anaphylaxis. Potent platelets Anaphylaxis results from inappropriate immune responses to allergens. Human platelets express the IgG receptor FcγRIIA/CD32A and release inflammatory mediators in response to their engagement, but their contribution to anaphylaxis is not well understood. Beutier et al. developed mouse models that express either human FcγRIIA/CD32A alone or the full human IgG receptor complexity to understand the role of platelets in anaphylaxis. Anaphylaxis induced a marked decrease in platelet levels, but preventive platelet depletion reduced anaphylaxis severity. A clinical study of patients with drug-induced anaphylaxis revealed that a severe reaction was likewise associated with fewer circulating platelets. Activated platelets released serotonin, which contributed to anaphylaxis severity. These results reveal a critical role for platelets in IgG-mediated anaphylaxis. Platelets are key regulators of vascular integrity; however, their role in anaphylaxis, a life-threatening systemic allergic reaction characterized by the loss of vascular integrity and vascular leakage, remains unknown. Anaphylaxis is a consequence of inappropriate cellular responses triggered by antibodies to generally harmless antigens, resulting in a massive mediator release and rapidly occurring organ dysfunction. Human platelets express receptors for immunoglobulin G (IgG) antibodies and can release potent mediators, yet their contribution to anaphylaxis has not been previously addressed in mouse models, probably because mice do not express IgG receptors on platelets. We investigated the contribution of platelets to IgG-dependent anaphylaxis in human IgG receptor–expressing mouse models and a cohort of patients suffering from drug-induced anaphylaxis. Platelet counts dropped immediately and markedly upon anaphylaxis induction only when they expressed the human IgG receptor FcγRIIA/CD32A. Platelet depletion attenuated anaphylaxis, whereas thrombocythemia substantially worsened its severity. FcγRIIA-expressing platelets were directly activated by IgG immune complexes in vivo and were sufficient to restore susceptibility to anaphylaxis in resistant mice. Serotonin released by activated platelets contributed to anaphylaxis severity. Data from a cohort of patients suffering from drug-induced anaphylaxis indicated that platelet activation was associated with anaphylaxis severity and was accompanied by a reduction in circulating platelet numbers. Our findings identify platelets as critical players in IgG-dependent anaphylaxis and provide a rationale for the design of platelet-targeting strategies to attenuate the severity of anaphylactic reactions.

Aspergillus-induced pneumonia in adult without obvious immunodeficiency: test the burst!

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency caused by a germline defect in one of the genes (CYBB, NCF1, CYBA, NCF2) encoding the NADPH oxidase 2 (NOX2) components responsible for the phagocyte oxidative burst and the production of reactive oxygen species (ROS). An early diagnosis and a prompt treatment are crucial for improving outcomes in affected patients. CGD is usually diagnosed in early childhood, and more than 95% of cases are diagnosed by the age of 5 years [1, 2]. However, CGD can be diagnosed late in adulthood [1–3]. Aside from residual NOX2 activity, factors underlying late diagnosis of CGD remain poorly investigated. Here, we report a case of Aspergillus-induced pneumonia rapidly extending to fatal acute respiratory distress syndrome (ARDS) revealing a late diagnosis of CGD, which was associated with a residual mitochondria-driven neutrophil extracellular trap release (NETosis) counterbalancing the lack of functional NOX2. Written informed consent was obtained from the deceased patients next-of-kin for publication of this case report and accompanying images. Unusual pathogen-driven sepsis should prompt to screen for chronic granulomatous disease, even in adult patients http://ow.ly/2FSi30iXUsa

FRI0461 Do the anti-saccharomyces cerevisiae antibodies (ASCA) modify the ankylosing spondylitis phenotype?

Background The anti-saccharomyces cerevisiae antibodies (ASCA) are serum markers in inflammatory bowel disease (IBD) either Crohn’s disease (CD) or ulcerative colitis (UC), which are present in almost 50% patients with CD. In spondylarthritis (SpA), there is a lack of specific markers to help the clinician for the diagnosis and management of the disease. ASCA, often the IgA form, are found in 30% patients who have SpA even without any digestives symptoms. Objectives We performed in our department a cross-sectional study evaluating the prevalence and the influence of the ASCA status on disease phenotype. Methods 223 SpA patients (all fulfilling the ESSG criteria) were included. Demographic (age, gender, disease duration), clinical (axial and/or peripheral presentation, presence of arthritis, enthesitis, spine pain, psoriasis, uveitis, IBD), biological (HLAB27 status) data, and use of treatments (DMARDs, anti-inflammatory drugs and anti-TNFa) were collected. For each patient, ASCA determination was performed by serum indirect immunofluorescence. Demographic characteristics, clinical features and blood tests of SpA patients ASCA positive and negative were compared. Results 223 SpA patients (mean age: 46.7±14.4 years, 54.3% men, 55% HLAB27+) were included. The mean disease duration was 105.7±116.9 months. 86% of patients had axial involvement, 70.4% had peripheral involvement. 10.6% suffered of IBD. 20.6%, 22.9% and 61.2% of patients received anti-inflammatory drugs, DMARDs or anti-TNFa respectively. Among the 223 SpA patients included, positivity of ASCA was observed in 24.7% (n= 55) (IgG: 9.4%; IgA: 21.1%). The positivity of ASCA was associated with lower frequency of HLAB27 positivity (60.4% vs 38.3%, P = 0.011) and axial involvement (91.1% vs 69.9%, P < 0.0001). Moreover, ASCA positivity was more frequently observed in patients with isolated peripheral involvement (10.7% vs 30.9%, P = 0.001), arthritis (27.3% vs 59.3%, P < 0.0001) and dactylitis (9.8% vs 26.9%, P = 0.004). There was no difference between ASCA+ and ASCA- SpA patients regarding the presence of uveitis, IBD, enthesitis and psoriasis. Conclusions These findings suggest that ASCA could influence the phenotype of SpA, the ASCA positive status being associated with peripheral involvement, including dactylitis, and a decrease of frequency of HLA B27 antigen. Disclosure of Interest None Declared