Persistence of proinflammatory response after severe respiratory syncytial virus disease in children
2007; Elsevier BV; Volume: 119; Issue: 6 Linguagem: Inglês
10.1016/j.jaci.2007.03.014
ISSN1097-6825
AutoresJesús F. Bermejo-Martín, M. Carmen Garcia-Arevalo, Ana Alonso, Raúl Ortíz de Lejarazu, María Pino, Salvador Resino, Alberto Tenorio, David Bernardo, Alberto J. León, José Antonio Garrote, J Ardura, Marta Domínguez‐Gil, José María Eirós Bouza, Alfredo Blanco-Quirós, María Ángeles Muñoz‐Fernández, David J. Kelvin, Eduardo Arranz,
Tópico(s)Respiratory Support and Mechanisms
ResumoTo the Editor:In spite of abundant reports describing cytokine and chemokine expression profiles during respiratory syncytial virus (RSV) infection, their role in the pathogenesis of the disease is not yet well understood.1Becker Y. Respiratory syncytial virus (RSV) evades the human adaptive immune system by skewing the Th1/Th2 cytokine balance toward increased levels of Th2 cytokines and IgE, markers of allergy—a review.Virus Genes. 2006; 33: 235-252PubMed Google Scholar Therefore the objective of our study was to evaluate the patterns of expression of 27 immune mediators during the recovery process from severe RSV infection and after complete resolution of symptoms.We recruited 37 children younger than 2 years of age admitted to the hospital with clinical signs of lower respiratory tract infection of viral origin. Children younger than 2 years of age given diagnoses of asymptomatic heart murmurs were recruited as control subjects. Informed consent was obtained from the parents of all patients before enrollment. Full approval of the study protocol by the hospital ethics committee was obtained.Patients were classified as having a suspected RSV infection by using a rapid immunochromatographic test. Viral presence was subsequently confirmed in infected infants and excluded in control subjects by means of direct immunofluorescent staining of viral cultures from nasopharyngeal aspirates (NPAs; IMAGEN; DakoCytomation, Glostrup, Denmark, for RSV, adenovirus, influenza A and B, and parainfluenza 1, 2, and 3 viruses) on appropriated cells. All subjects included in the study as cases had positive cultures for RSV and negative cultures for all other viruses tested. The modified Wood's Clinical Asthma Score2Martinon-Torres F. Rodriguez-Nunez A. Martinon-Sanchez J.M. Heliox therapy in infants with acute bronchiolitis.Pediatrics. 2002; 109: 68-73Crossref PubMed Scopus (109) Google Scholar was used to evaluate clinical severity. Children presented with severe respiratory compromise at admission (mean O2 saturation mean. 91.8%). All the RSV-infected children received bronchodilator treatment with β2-agonists. Thirty-one received additional treatment with methylprednisolone. No significant differences were found in the modified Wood's Clinical Asthma Score at admission between corticoid-treated and non–corticoid-treated children (Mann-Whitney U test). Serial NPAs were obtained by means of intranasal instillation of 5 mL of an isotonic saline solution (ClNa 0.9%). Samples were taken at admission (n = 37), discharge (n = 37), and 1 month after discharge (n = 23). A single NPA was collected from each control child (n = 27). The NPA supernatants were analyzed with a multiplex assay (Bio-Rad, Hercules, Calif) on a Luminex platform (Austin, Tex). Limits of detection were calculated, considering a detectable signal as greater than 2 SDs above blank (isotonic solution ClNa 0.9%): eotaxin, 4.57 pg/mL; GM-CSF, 18.38 pg/mL; IL-1 receptor antagonist (IL-1RA), 2.17 pg/mL; IL-5, 0.27 pg/mL; IL-9, 5.85 pg/mL; IL-13, 0.26 pg/mL; IL-1β, 1.93 pg/mL; monocyte chemoattractant protein 1 (MCP-1), 9.2 pg/mL; platelet-derived growth factor (PDGF-BB), 2.19 pg/mL; vascular endothelial growth factor (VEGF), 4.4 pg/mL; human fibroblast growth factor–basic (FGF-b), 6.15 pg/mL; IL-2, 1.49 pg/mL; IL-6, 3.81 pg/mL; IL-10, 0.46 pg/mL; IL-15, 6.28 pg/mL; IL-8, 5.52 pg/mL; macrophage inflammatory protein 1α (MIP-1α), 1.12 pg/mL; RANTES, 1.18 pg/mL; granulocyte colony-stimulating factor, 0.42 pg/mL; IFN-γ, 4.14 pg/mL; IL-4, 1.68 pg/mL; IL-7, 0.65 pg/mL; IL-12p70, 2.41 pg/mL; IL-17, 1.9 pg/mL; IFN-inducible protein 10, 2.51 pg/mL; MIP-1β, 6.41 pg/mL; and TNF-α, 37.87 pg/mL. Those values less than the level of detection were reported as being equal to the level of detection.The Mann-Whitney U test was used to assess the significance of differences in the levels of mediators between the control group and each of the 3 time points evaluated. Differences in the levels of mediators between admission (n = 37) and discharge (n = 37) were assessed by using the Wilcoxon signed-ranks test. Differences in the levels of mediators between admission (n = 23), discharge (n = 23), and 1 month after discharge (n = 23) were assessed by using the Friedman test. If the Friedman test indicated a significant difference in the level of a particular mediator, statistical significance was further assessed by using the Wilcoxon test (P < .05 considered statistically significant, Table I). Results were represented also in the form of a heat map (see Fig E1 in the Online Repository at www.jacionline.org) by using the JColorGrid software (University of California San Francisco and University of California Berkeley).3Joachimiak M.P. Weissman J.L. May B.C.H. JColorGrid: software for the visualization of biological measurements.BMC Bioinformatics. 2006; 7: 225Crossref PubMed Scopus (89) Google ScholarTable IComparison of immune mediators levels over timeAdmission (A), n = 37Discharge (D), n = 37One month (M), n = 23Control (C), n = 27A/D P valueA/D/M P valueA/M P valueD/M P valueIL-1RA6886 (13,230)∗Significant difference versus control.4819 (5558)∗Significant difference versus control.4501 (13,842)2825 (4189).483.840——IL-50.7 (0.5)∗Significant difference versus control.0.4 (0.2)∗Significant difference versus control.0.6 (0.8)∗Significant difference versus control.0.3 (0.3).018†Significant difference between admission and discharge..160——IL-133.7 (3.9)∗Significant difference versus control.2.1 (1.7)1.6 (1.2)1.3 (2.0).000†Significant difference between admission and discharge..070——IL-1β422.0 (1030)∗Significant difference versus control.226.9 (597.1)∗Significant difference versus control.231.7 (1337.3)∗Significant difference versus control.32.6 (176.1).267.840——FGF-b8.3 (14.6)∗Significant difference versus control.6.2 (0.0)6.2 (0.0)6.2 (0.0).000†Significant difference between admission and discharge..004‡Significant difference between admission, discharge, and 1 month after discharge..022§Significant difference between admission and 1 month after discharge..917IFN-γ103.4 (45.1)∗Significant difference versus control.63.1 (55.2)∗Significant difference versus control.54.3 (41.4)∗Significant difference versus control.22.4 (59.3).005†Significant difference between admission and discharge..066——MCP-19.2 (18.3)∗Significant difference versus control.9.2 (3.2)9.2 (15.5)9.2 (0.0).362.545——PDGF-BB17.4 (19.9)∗Significant difference versus control.13.6 (12.7)∗Significant difference versus control.10.8 (13.8)4.1 (6.6).394.119——IL-24.0 (4.1)∗Significant difference versus control.2.4 (2.5)∗Significant difference versus control.1.8 (3.2)∗Significant difference versus control.1.5 (0.0).004†Significant difference between admission and discharge..124——IL-6198.5 (424.8)∗Significant difference versus control.108.8 (301.7)∗Significant difference versus control.30.0 (38.0)∗Significant difference versus control.8.0 (37.6).118.004‡Significant difference between admission, discharge, and 1 month after discharge..006§Significant difference between admission and 1 month after discharge..009‖Significant difference between discharge and 1 month after discharge.IL-1011.8 (18.0)∗Significant difference versus control.4.6 (6.3)∗Significant difference versus control.3.8 (12.1)∗Significant difference versus control.1.2 (2.8).000†Significant difference between admission and discharge..003‡Significant difference between admission, discharge, and 1 month after discharge..089.101IP-1012,201 (18,148)∗Significant difference versus control.3507 (7227)∗Significant difference versus control.5316 (7535)∗Significant difference versus control.2510 (3961.5).004†Significant difference between admission and discharge..070——IL-87898 (6246)∗Significant difference versus control.3999 (6177)∗Significant difference versus control.5007 (7293)∗Significant difference versus control.573.0 (3221.4).088.599——G-CSF1317 (1979)∗Significant difference versus control.1354 (1994)∗Significant difference versus control.608.9 (1532.2)∗Significant difference versus control.155.6 (338.0).922.154——MIP-1α48.6 (109.7)∗Significant difference versus control.42.2 (81.0)∗Significant difference versus control.17.6 (53.8)∗Significant difference versus control.2.0 (17.1).126.019‡Significant difference between admission, discharge, and 1 month after discharge..144.136RANTES71.5 (100.8)47.9 (87.5)49.1 (59.4)47.3 (118.5).202.104——IL-42.3 (1.6)∗Significant difference versus control.1.7 (0.4)1.7 (0.6)∗Significant difference versus control.1.7 (0.0).008†Significant difference between admission and discharge..116——IL-79.3 (7.1)9.0 (7.3)10.7 (14.2)4.0 (13.6).780.401——IL-12p703.8 (3.0)∗Significant difference versus control.2.8 (1.3)∗Significant difference versus control.2.6 (1.8)∗Significant difference versus control.2.4 (0.1).006†Significant difference between admission and discharge..034‡Significant difference between admission, discharge, and 1 month after discharge..012§Significant difference between admission and 1 month after discharge..983TNF-α103.1 (1140)∗Significant difference versus control.37.9 (130)∗Significant difference versus control.37.9 (45)∗Significant difference versus control.37.9 (0.0).018†Significant difference between admission and discharge..219——Eotaxin34.6 (35.8)42.9 (47.9)∗Significant difference versus control.55.2 (68.8)∗Significant difference versus control.25.6 (38.2).167.018‡Significant difference between admission, discharge, and 1 month after discharge..006§Significant difference between admission and 1 month after discharge..191IL-178.5 (8.1)∗Significant difference versus control.4.3 (5.2)∗Significant difference versus control.3.5 (6.1)∗Significant difference versus control.1.9 (2.3).001†Significant difference between admission and discharge..103——MIP-1β676.3 (1448)∗Significant difference versus control.597.8 (904)∗Significant difference versus control.155.3 (407.8)∗Significant difference versus control.30.1 (109.7).129.005‡Significant difference between admission, discharge, and 1 month after discharge..045§Significant difference between admission and 1 month after discharge..036‖Significant difference between discharge and 1 month after discharge.VEGF1370 (1666)∗Significant difference versus control.1016 (1193)∗Significant difference versus control.1169 (2875)∗Significant difference versus control.377.5 (921.1).126.738——Results are expressed as median + interquartile range.IP-10, IFN-inducible protein 10; G-CSF, granulocyte colony-stimulating factor.∗ Significant difference versus control.† Significant difference between admission and discharge.‡ Significant difference between admission, discharge, and 1 month after discharge.§ Significant difference between admission and 1 month after discharge.‖ Significant difference between discharge and 1 month after discharge. Open table in a new tab Levels of IL-9, IL-15, and GM-CSF were consistently less than the limits of detection and therefore were not included in our analyses. At the time of admission, the levels of all mediators considered in this analysis were significantly higher in the patients with RSV than in the control patients, with the exception of RANTES, IL-7, and eotaxin (Table I). Four different patterns of expression were identified for the immune mediators studied.Pattern I. The first pattern was found for a group of 11 mediators (IL-4, IL-13, IL-5, IL-10, IL-17 [TH2 cytokines], TNF-α, IFN-γ, IL-2, IL-12p70 [TH1 cytokines], IP10, and FGF-b) and is characterized by a significant decrease from the time of admission to discharge. IL-4 and IL-5 mediate the development of airway hyperresponsiveness.4Schwarze J. Cieslewicz G. Joetham A. Ikemura T. Makela M.J. Dakhama A. et al.Critical roles for interleukin-4 and interleukin-5 during respiratory syncytial virus infection in the development of airway hyperresponsiveness after airway sensitization.Am J Respir Crit Care Med. 2000; 162: 380-386Crossref PubMed Scopus (62) Google Scholar IL-4 and IL-5 are, along with IL-13, major effectors of TH2 inflammation. IL-17 plays a role in the production of mucus in the bronchi.5Hashimoto K. Durbin J.E. Zhou W. Collins R.D. Ho S.B. Kolls J.K. et al.Respiratory syncytial virus infection in the absence of STAT 1 results in airway dysfunction, airway mucus, and augmented IL-17 levels.J Allergy Clin Immunol. 2005; 116: 550-557Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar IL-10 is an anti-inflammatory cytokine, and it has been suggested that RSV might inhibit an effective antiviral immune response by inducing increased production of this cytokine.6Panuska J.R. Merolla R. Rebert N.A. Hoffmann S.P. Tsivitse P. Cirino N.M. et al.Respiratory syncytial virus induces interleukin-10 by human alveolar macrophages. Suppression of early cytokine production and implications for incomplete immunity.J Clin Invest. 1995; 96: 2445-2453Crossref PubMed Scopus (119) Google Scholar IFN-inducible protein 10 is a lymphocyte-targeting CXC chemokine produced at high concentrations by activated bronchial epithelial cells in response to infection. Production of the proinflammatory TH1 cytokine TNF-α during the inductive immune response to RSV seems to serve an important protective role, whereas exaggerated production of TNF-α during the adaptive phase of the immune response seems to induce significant lung immunopathology.7Rutigliano J.A. Graham B.S. Prolonged production of TNF-alpha exacerbates illness during respiratory syncytial virus infection.J Immunol. 2004; 173: 3408-3417PubMed Google Scholar FGF-b synergistically enhances inflammatory mediator–induced leukocyte recruitment, at least in part, by enhancing upregulation of endothelial adhesion molecules. IFN-γ, IL-2, and IL-12p70 are key contributors to adaptive immunity, promoting a TH1 proinflammatory/cellular response around days 4 to 7 after infection.8Openshaw P.J.M. Tregoning J.S. Immune responses and disease enhancement during respiratory syncytial virus infection.Clin Microbiol Rev. 2005; 18: 541-555Crossref PubMed Scopus (247) Google Scholar In consequence, the decrease in this group of mediators included in pattern I could lead theoretically to attenuation of the hyperresponsive proinflammatory responses and mucus production, thereby diminishing bronchial obstruction. Therapeutic interventions aimed at modulating levels of these immune mediators could potentially ameliorate respiratory function during the acute phase of the disease. In addition, ratios comparing levels of TH1-like versus TH2-like cytokines at admission versus discharge among IL-1β, IL-2, IL-12, and IFN-γ and IL-4, IL-5, IL-6, IL-10, and IL-13 were calculated. Clinical improvement in patients with RSV paralleled an increase in the relative strength of the TH1 response, as shown by the significant increase from admission to discharge in the following ratios: IFN-γ/IL-10, IL-2/IL-10, IL-12/IL-13, and IL-12/IL-10 (P < .05, Wilcoxon test with the Bonferroni correction). The tendency toward relatively greater TH1-like cytokine expression during disease resolution attests to the physiologic role of the TH1 response, which is to promote the appropriate host response to intracellular pathogens, such as viruses.Pattern II. The second pattern of cytokine/chemokine expression was exemplified by IL-6 and MIP-1β, the levels of which did not decrease significantly compared with levels at admission until 1 month after discharge.Pattern III. The third expression pattern identified was that of IL-1RA, IL-8, IL-1β, granulocyte colony-stimulating factor, PDGF-BB, MCP-1, and VEGF, which did not show any significant variation compared with levels at admission over the course of the study (neither from admission to discharge nor from admission to 1 month after discharge). Patterns II and III reveal that certain proinflammatory responses induced by RSV persist well beyond the resolution of symptoms because all of the mediators included in these patterns except IL-1RA mediate or facilitate migration of inflammatory cells to the focus of infection. This finding is also supported by the expression pattern of MIP-1α. The levels of this proinflammatory chemokine were consistently higher than control levels at admission and also at discharge and 1 month later. The Friedman test revealed significant differences among these time points, but the Wilcoxon test failed to evidence differences in the paired comparisons.Pattern IV. The fourth pattern of expression identified is exemplified by eotaxin and is characterized by significantly higher levels in patients with RSV at discharge, as well as at 1 month after discharge, than those in control patients. Furthermore, when levels at admission were compared against those found 1 month after discharge, a significant increase in eotaxin expression was observed.Some of the mediators included in patterns II, III, and IV have been implicated either directly or indirectly in asthma pathogenesis. Enhanced epithelial cell gene expression of IL-6 and IL-8 is present in bronchial biopsy specimens of asthmatic subjects.9Oh J.W. Lee H.B. Park I.K. Kang J.O. Interleukin-6, interleukin-8, interleukin-11, and interferon-gamma levels in nasopharyngeal aspirates from wheezing children with respiratory syncytial virus or influenza A virus infection.Pediatr Allergy Immunol. 2002; 13: 350-356Crossref PubMed Scopus (35) Google Scholar PDGF-BB mediates airway smooth muscle proliferation. VEGF signaling plays a critical role in the initiation and maintenance of asthma through regulation of matrix metalloproteinase 9 expression. Eotaxin plays a significant role in inducing chemotaxis and activating eosinophils (one of the most important cells in allergic inflammation). Infants with a severe RSV disease seem to be predisposed to asthma in childhood. In consequence, the persistence of high levels of these mediators after hospital discharge could represent a substratum for the development of the pathogenic events leading to asthma. On the basis of these results, we propose that downmodulation of specific mediators after disease resolution should be considered and further investigated as a potential strategy for the prevention of asthma in children with severe RSV disease.In conclusion, our results indicate that RSV infection induces distinct and specific expression profiles of a number of cytokines, chemokines, and growth factors and that these expression profiles parallel clinical recovery. In addition, we have documented the persistence of proinflammatory responses in the long term in fully recovered patients with RSV. These findings might have important implications in the therapeutic management of RSV disease and have identified a number of avenues to consider in the development of new approaches toward asthma prophylaxis in patients with RSV. To the Editor: In spite of abundant reports describing cytokine and chemokine expression profiles during respiratory syncytial virus (RSV) infection, their role in the pathogenesis of the disease is not yet well understood.1Becker Y. Respiratory syncytial virus (RSV) evades the human adaptive immune system by skewing the Th1/Th2 cytokine balance toward increased levels of Th2 cytokines and IgE, markers of allergy—a review.Virus Genes. 2006; 33: 235-252PubMed Google Scholar Therefore the objective of our study was to evaluate the patterns of expression of 27 immune mediators during the recovery process from severe RSV infection and after complete resolution of symptoms. We recruited 37 children younger than 2 years of age admitted to the hospital with clinical signs of lower respiratory tract infection of viral origin. Children younger than 2 years of age given diagnoses of asymptomatic heart murmurs were recruited as control subjects. Informed consent was obtained from the parents of all patients before enrollment. Full approval of the study protocol by the hospital ethics committee was obtained. Patients were classified as having a suspected RSV infection by using a rapid immunochromatographic test. Viral presence was subsequently confirmed in infected infants and excluded in control subjects by means of direct immunofluorescent staining of viral cultures from nasopharyngeal aspirates (NPAs; IMAGEN; DakoCytomation, Glostrup, Denmark, for RSV, adenovirus, influenza A and B, and parainfluenza 1, 2, and 3 viruses) on appropriated cells. All subjects included in the study as cases had positive cultures for RSV and negative cultures for all other viruses tested. The modified Wood's Clinical Asthma Score2Martinon-Torres F. Rodriguez-Nunez A. Martinon-Sanchez J.M. Heliox therapy in infants with acute bronchiolitis.Pediatrics. 2002; 109: 68-73Crossref PubMed Scopus (109) Google Scholar was used to evaluate clinical severity. Children presented with severe respiratory compromise at admission (mean O2 saturation mean. 91.8%). All the RSV-infected children received bronchodilator treatment with β2-agonists. Thirty-one received additional treatment with methylprednisolone. No significant differences were found in the modified Wood's Clinical Asthma Score at admission between corticoid-treated and non–corticoid-treated children (Mann-Whitney U test). Serial NPAs were obtained by means of intranasal instillation of 5 mL of an isotonic saline solution (ClNa 0.9%). Samples were taken at admission (n = 37), discharge (n = 37), and 1 month after discharge (n = 23). A single NPA was collected from each control child (n = 27). The NPA supernatants were analyzed with a multiplex assay (Bio-Rad, Hercules, Calif) on a Luminex platform (Austin, Tex). Limits of detection were calculated, considering a detectable signal as greater than 2 SDs above blank (isotonic solution ClNa 0.9%): eotaxin, 4.57 pg/mL; GM-CSF, 18.38 pg/mL; IL-1 receptor antagonist (IL-1RA), 2.17 pg/mL; IL-5, 0.27 pg/mL; IL-9, 5.85 pg/mL; IL-13, 0.26 pg/mL; IL-1β, 1.93 pg/mL; monocyte chemoattractant protein 1 (MCP-1), 9.2 pg/mL; platelet-derived growth factor (PDGF-BB), 2.19 pg/mL; vascular endothelial growth factor (VEGF), 4.4 pg/mL; human fibroblast growth factor–basic (FGF-b), 6.15 pg/mL; IL-2, 1.49 pg/mL; IL-6, 3.81 pg/mL; IL-10, 0.46 pg/mL; IL-15, 6.28 pg/mL; IL-8, 5.52 pg/mL; macrophage inflammatory protein 1α (MIP-1α), 1.12 pg/mL; RANTES, 1.18 pg/mL; granulocyte colony-stimulating factor, 0.42 pg/mL; IFN-γ, 4.14 pg/mL; IL-4, 1.68 pg/mL; IL-7, 0.65 pg/mL; IL-12p70, 2.41 pg/mL; IL-17, 1.9 pg/mL; IFN-inducible protein 10, 2.51 pg/mL; MIP-1β, 6.41 pg/mL; and TNF-α, 37.87 pg/mL. Those values less than the level of detection were reported as being equal to the level of detection. The Mann-Whitney U test was used to assess the significance of differences in the levels of mediators between the control group and each of the 3 time points evaluated. Differences in the levels of mediators between admission (n = 37) and discharge (n = 37) were assessed by using the Wilcoxon signed-ranks test. Differences in the levels of mediators between admission (n = 23), discharge (n = 23), and 1 month after discharge (n = 23) were assessed by using the Friedman test. If the Friedman test indicated a significant difference in the level of a particular mediator, statistical significance was further assessed by using the Wilcoxon test (P < .05 considered statistically significant, Table I). Results were represented also in the form of a heat map (see Fig E1 in the Online Repository at www.jacionline.org) by using the JColorGrid software (University of California San Francisco and University of California Berkeley).3Joachimiak M.P. Weissman J.L. May B.C.H. JColorGrid: software for the visualization of biological measurements.BMC Bioinformatics. 2006; 7: 225Crossref PubMed Scopus (89) Google Scholar Results are expressed as median + interquartile range. IP-10, IFN-inducible protein 10; G-CSF, granulocyte colony-stimulating factor. Levels of IL-9, IL-15, and GM-CSF were consistently less than the limits of detection and therefore were not included in our analyses. At the time of admission, the levels of all mediators considered in this analysis were significantly higher in the patients with RSV than in the control patients, with the exception of RANTES, IL-7, and eotaxin (Table I). Four different patterns of expression were identified for the immune mediators studied. Pattern I. The first pattern was found for a group of 11 mediators (IL-4, IL-13, IL-5, IL-10, IL-17 [TH2 cytokines], TNF-α, IFN-γ, IL-2, IL-12p70 [TH1 cytokines], IP10, and FGF-b) and is characterized by a significant decrease from the time of admission to discharge. IL-4 and IL-5 mediate the development of airway hyperresponsiveness.4Schwarze J. Cieslewicz G. Joetham A. Ikemura T. Makela M.J. Dakhama A. et al.Critical roles for interleukin-4 and interleukin-5 during respiratory syncytial virus infection in the development of airway hyperresponsiveness after airway sensitization.Am J Respir Crit Care Med. 2000; 162: 380-386Crossref PubMed Scopus (62) Google Scholar IL-4 and IL-5 are, along with IL-13, major effectors of TH2 inflammation. IL-17 plays a role in the production of mucus in the bronchi.5Hashimoto K. Durbin J.E. Zhou W. Collins R.D. Ho S.B. Kolls J.K. et al.Respiratory syncytial virus infection in the absence of STAT 1 results in airway dysfunction, airway mucus, and augmented IL-17 levels.J Allergy Clin Immunol. 2005; 116: 550-557Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar IL-10 is an anti-inflammatory cytokine, and it has been suggested that RSV might inhibit an effective antiviral immune response by inducing increased production of this cytokine.6Panuska J.R. Merolla R. Rebert N.A. Hoffmann S.P. Tsivitse P. Cirino N.M. et al.Respiratory syncytial virus induces interleukin-10 by human alveolar macrophages. Suppression of early cytokine production and implications for incomplete immunity.J Clin Invest. 1995; 96: 2445-2453Crossref PubMed Scopus (119) Google Scholar IFN-inducible protein 10 is a lymphocyte-targeting CXC chemokine produced at high concentrations by activated bronchial epithelial cells in response to infection. Production of the proinflammatory TH1 cytokine TNF-α during the inductive immune response to RSV seems to serve an important protective role, whereas exaggerated production of TNF-α during the adaptive phase of the immune response seems to induce significant lung immunopathology.7Rutigliano J.A. Graham B.S. Prolonged production of TNF-alpha exacerbates illness during respiratory syncytial virus infection.J Immunol. 2004; 173: 3408-3417PubMed Google Scholar FGF-b synergistically enhances inflammatory mediator–induced leukocyte recruitment, at least in part, by enhancing upregulation of endothelial adhesion molecules. IFN-γ, IL-2, and IL-12p70 are key contributors to adaptive immunity, promoting a TH1 proinflammatory/cellular response around days 4 to 7 after infection.8Openshaw P.J.M. Tregoning J.S. Immune responses and disease enhancement during respiratory syncytial virus infection.Clin Microbiol Rev. 2005; 18: 541-555Crossref PubMed Scopus (247) Google Scholar In consequence, the decrease in this group of mediators included in pattern I could lead theoretically to attenuation of the hyperresponsive proinflammatory responses and mucus production, thereby diminishing bronchial obstruction. Therapeutic interventions aimed at modulating levels of these immune mediators could potentially ameliorate respiratory function during the acute phase of the disease. In addition, ratios comparing levels of TH1-like versus TH2-like cytokines at admission versus discharge among IL-1β, IL-2, IL-12, and IFN-γ and IL-4, IL-5, IL-6, IL-10, and IL-13 were calculated. Clinical improvement in patients with RSV paralleled an increase in the relative strength of the TH1 response, as shown by the significant increase from admission to discharge in the following ratios: IFN-γ/IL-10, IL-2/IL-10, IL-12/IL-13, and IL-12/IL-10 (P < .05, Wilcoxon test with the Bonferroni correction). The tendency toward relatively greater TH1-like cytokine expression during disease resolution attests to the physiologic role of the TH1 response, which is to promote the appropriate host response to intracellular pathogens, such as viruses. Pattern II. The second pattern of cytokine/chemokine expression was exemplified by IL-6 and MIP-1β, the levels of which did not decrease significantly compared with levels at admission until 1 month after discharge. Pattern III. The third expression pattern identified was that of IL-1RA, IL-8, IL-1β, granulocyte colony-stimulating factor, PDGF-BB, MCP-1, and VEGF, which did not show any significant variation compared with levels at admission over the course of the study (neither from admission to discharge nor from admission to 1 month after discharge). Patterns II and III reveal that certain proinflammatory responses induced by RSV persist well beyond the resolution of symptoms because all of the mediators included in these patterns except IL-1RA mediate or facilitate migration of inflammatory cells to the focus of infection. This finding is also supported by the expression pattern of MIP-1α. The levels of this proinflammatory chemokine were consistently higher than control levels at admission and also at discharge and 1 month later. The Friedman test revealed significant differences among these time points, but the Wilcoxon test failed to evidence differences in the paired comparisons. Pattern IV. The fourth pattern of expression identified is exemplified by eotaxin and is characterized by significantly higher levels in patients with RSV at discharge, as well as at 1 month after discharge, than those in control patients. Furthermore, when levels at admission were compared against those found 1 month after discharge, a significant increase in eotaxin expression was observed. Some of the mediators included in patterns II, III, and IV have been implicated either directly or indirectly in asthma pathogenesis. Enhanced epithelial cell gene expression of IL-6 and IL-8 is present in bronchial biopsy specimens of asthmatic subjects.9Oh J.W. Lee H.B. Park I.K. Kang J.O. Interleukin-6, interleukin-8, interleukin-11, and interferon-gamma levels in nasopharyngeal aspirates from wheezing children with respiratory syncytial virus or influenza A virus infection.Pediatr Allergy Immunol. 2002; 13: 350-356Crossref PubMed Scopus (35) Google Scholar PDGF-BB mediates airway smooth muscle proliferation. VEGF signaling plays a critical role in the initiation and maintenance of asthma through regulation of matrix metalloproteinase 9 expression. Eotaxin plays a significant role in inducing chemotaxis and activating eosinophils (one of the most important cells in allergic inflammation). Infants with a severe RSV disease seem to be predisposed to asthma in childhood. In consequence, the persistence of high levels of these mediators after hospital discharge could represent a substratum for the development of the pathogenic events leading to asthma. On the basis of these results, we propose that downmodulation of specific mediators after disease resolution should be considered and further investigated as a potential strategy for the prevention of asthma in children with severe RSV disease. In conclusion, our results indicate that RSV infection induces distinct and specific expression profiles of a number of cytokines, chemokines, and growth factors and that these expression profiles parallel clinical recovery. In addition, we have documented the persistence of proinflammatory responses in the long term in fully recovered patients with RSV. These findings might have important implications in the therapeutic management of RSV disease and have identified a number of avenues to consider in the development of new approaches toward asthma prophylaxis in patients with RSV. We thank the nursing team of the infants section of our hospital, who kindly performed the nasal washes. We also thank Ana Sanz for her diligence in the sample processing, Steve Bossinger for his assistance in immunoprofiling methods, and Dr Cheryl Cameron for her assistance in translating this manuscript. Appendix. Supplementary data Download .pdf (.15 MB) Help with pdf files Online Repository Download .pdf (.15 MB) Help with pdf files Online Repository
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