Analysis of the local and systemic inflammatory response in hospitalized infants with respiratory syncitial virus bronchiolitis

Background: Respiratory syncytial virus acute bronchiolitis (RSV-AB) is a major cause of hospital admission among our infants. The immune and inflammatory mechanisms involved in the RSV-AB and factors influencing severity have not been clearly established, although an imbalanced Th1 and Th2 response seems to be crucial. Objectives: To assess the local and systemic inflammatory response in RSV-AB. To find a possible marker of clinical severity and/or oxygen requirements. Patients and methods: Levels of nine cytokines were measured in nasopharyngeal aspirate (NPA) and peripheral blood (PB) of 45 infants with RSV-AB and 27 peer controls, including IFN-gamma, TNF alpha, VEGF, interleukins 4, 6 and 10, and chemokines (IL-8 and macrophage inflammatory proteins 1-alpha and 1-beta). Results: The levels of the analyzed cytokines and chemokines were significantly higher in the NPA of RSV-AB group, with a decrease in IL-4/IFN-gamma ratio. IL-6 and MIP-1 beta levels in NPA were directly correlated to oxygen therapy. PB showed an increase in IL-8 and a decrease in MIP-1 alpha and MIP-1 beta in the RSV-AB group (only MIP-1 beta associated to the need for oxygen therapy). No correlation was found between cytokines and chemokines levels in NPA and PB. Conclusions: This study shows that RSV triggers an inflammatory response fundamentally at the respiratory level, with scant systemic repercussion. This local response is characterized by an increase in Th1 and Th2 cytokines, although with a relative predominance of Th1. The determination upon patient admission of IL-6 and MIP-1 beta levels in NPA, and of MIP-1 beta in PB could help predict severe forms and the need for oxygenotherapy. (C) 2013 SEICAP Published by Elsevier Espana, S.L.U. All rights reserved.