Virus-triggered exacerbation in allergic asthmatic children: neutrophilic airway inflammation and alteration of virus sensors characterize a subgroup of patients

Abstract

Background: Viruses are important triggers of asthma exacerbations. They are also detected outside of exacerbation. Alteration of anti-viral response in asthmatic patients has been shown although the mechanisms responsible for this defect remain unclear. The objective of this study was to compare in virus-infected and not-infected allergic asthmatic children, aged 6 to 16 years, admitted to hospital for a severe exacerbation, the innate immune response and especially the expression of pattern recognition receptor (PRR) and their function.

Methods: Virus identification was performed both during the exacerbation and at steady state (eight weeks later). Data assessed at both periods included clinical features, anti-viral response and inflammation (in sputum and plasma), and PRR expression/function in blood mononuclear cells.

Results: Viruses were identified in 46 out of 72 children (median age 8.9 years) during exacerbation, and among them, in 17 at steady state. IFN-β, IFN-γ and IL-29 levels in sputum and plasma were similar between infected and not infected patients at both times, as well as the expression of TLR3, RIG-I and MDA5 in blood monocytes and dendritic cells. Airway inflammation in infected patients was characterized by significantly higher IL-5 concentration and eosinophil count. Compared to patients only infected at exacerbation, the re-infected children significantly exhibited lower levels of IFN-γ in plasma and sputum at exacerbation associated with modifications in PRR expression and function in blood mononuclear cells. These re-infected patients also presented an airway neutrophilic inflammation at steady state.

Conclusion: Our results reports in asthmatic children that impaired anti-viral response during virus-induced exacerbation is more pronounced in a subgroup of patients prone to re-infection by virus. This subgroup is characterized by altered PRR function and a different pattern of airway inflammation.

Trial registration: This multicenter prospective study was approved by the regional investigational review board (ref: 08/07).

Keywords: Allergic asthma; Exacerbation; Interferon; Pattern recognition receptor; Viral infection.

Conflict of interest statement

Ethics approval and consent to participate

This multicenter prospective study, approved by the regional investigational review board (Comité de protection des personnes Nord Ouest, ref.: 08/07) involved the Pediatrics Departments of Lille University Hospital (Lille, France) and Roubaix Hospital (Roubaix, France). Parental written informed consents were obtained for all children.

Consent for publication

Not applicable

Competing interests

A Des reports grants from Région Nord-Pas de Calais, grants from Société Française d’Allergologie, grants from Comité de Maladies Respiratoires, during the conduct of the study; personal fees from Novartis, personal fees from ALK, personal fees from TEVA, personal fees and other from GSK, personal fees from Stallergenes, personal fees from MSD, personal fees from MEDA, outside the submitted work. CM reports personal fees from NOVARTIS, outside the submitted work. MP and PG have received funding from GSK for an unrelated work.

All other authors (IE, CL, ED, GP, DR, SB, IB, ADew, CT, VN, DH) declare that they have no conflicts of interest.

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Figures

Fig. 1

The viral status of the population during the exacerbation and at steady state. hRV: human rhinovirus, RSV: respiratory syncytial virus; V+: viral infection; V-: no detected virus. In this study, we first compared infected and not-infected groups (V+ versus V- patients, shaded boxes) and then among V + V- and V + V+ patients

Fig. 2

Impact of the viral status on cytokine concentrations and polymorphonuclear cells in sputum from asthmatic children collected during exacerbation and at steady state. Concentrations of IFN-β, IFN-γ and IL-29 (a) and of IL-5 and IL-6 (b) were measured in the sputum fluids collected from infected patients (V+) and non-infected patients (V-) during asthma exacerbation and at steady state. c) The percentages of eosinophils and neutrophils in the sputum are also reported. The median of our results was reported by the horizontal line, the 25 and 75 interquartile range by the box and the minimum and the maximum by the whiskers. *: p < 0.05 versus V- patients

Fig. 3

Impact of viral status on blood mononuclear cell phenotype during asthma exacerbation and at steady state. a-b) CD86 expression was measured on circulating cDCs, pDCs and monocytes from asthmatic children during the exacerbation (a) and steady state (b), using flow cytometry. During the exacerbation, patients were classified as being infected (V+) or not infected (V-). c) The levels of IL-6, IL-5 and IL-22 were measured in supernatants of PBMCs incubated in medium alone (baseline) and then stimulated with the TLR7-8 ligand gardiquimod. The median of our results was reported by the horizontal line, the 25 and 75 interquartile range by the box and the minimum and the maximum by the whiskers. *: p < 0.05 versus V- patients

Fig. 4

Viral re-infection in asthmatic patients modulates cytokine secretion. a) IFN-β, IFNγ and IL-29 concentrations were measured in the sputum fluids and the plasma (B) collected during the exacerbation and at steady state in V+ patients separated in re-infected ones (V + V+) and not-infected ones at steady state (V + V-). b) Concentrations of IFN-β, IFNγ and IL-29 were analyzed in the plasma collected at exacerbation in both groups. c) Levels of IL-1β, IL-5 and IL-6 were evaluated in the sputum fluids collected during the exacerbation from the same groups. d) Concentrations of IL-1β, IL-5 and IL-22 were also reported in the sputum fluids collected at steady state. The median of our results was reported by the horizontal line, the 25 and 75 interquartile range by the box and the minimum and the maximum by the whiskers. *: p < 0.05 versus V+V- patients

Fig. 5

Viral re-infection in asthmatic patients modulate blood mononuclear cell phenotype and cytokine secretion. a) TLR3 expression was measured by flow cytometry on cDC, pDC and monocytes studied during the exacerbation and at steady state. Blood cells were collected from V+ patients separated in re-infected ones (V + V+) and not-infected ones at steady state (V + V-). b) The fluorescence intensity for RIGI was also evaluated in these cells studied during the exacerbation and at steady state. c) Concentrations of IFN-γ and IL-29 were measured in supernatants of PBMC collected in V + V+ and V + V- patients during the exacerbation and at steady state. PBMC were incubated in medium alone and stimulated with Poly(I:C) or lipopoly(I:C). The median of our results was reported by the horizontal line, the 25 and 75 interquartile range by the box and the minimum and the maximum by the whiskers. *: p < 0.05 versus the other group