Infection, eosinophilia and childhood asthma

Abstract

There is a growing list of viruses and bacteria associated with wheezing illness and asthma. It is well known that a few of these pathogens are strongly associated with wheezing illness and asthma exacerbations. What is not known is if early childhood infections with these pathogens cause asthma, and, if so, exactly what are the pathophysiologic mechanisms behind its development. The current consensus is respiratory infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between respiratory infection and asthma may be the eosinophil, a cell that plays prominently in asthma and allergy, but can also be found in the body in response to infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can also be used for diagnosis, treatment and monitoring. The optimal care of a patient must take into consideration not only symptoms, but also the underlying disease mechanisms.

Keywords: Asthma; Eosinophil-derived neurotoxin; Eosinophilia; Infection; Respiratory virus; Wheezing.

Fig. 1

Infection of bronchial epithelial cells leads to release of mediators, including cytokines, chemokines, and growth factors. Recruited immune cells (eosinophils, neutrophils, and mast cells) release a number of mediators, as well. CCL, CC chemokine ligand; CXCL, CXC chemokine ligand; ECP, eosinophil cationic protein; EDN, eosinophilderived neurotoxin; EPO, eosinophil peroxidase; FGF-2, fibroblast growth factor-2; GM-CSF, granulocyte macrophage-colony stimulating factor; IL, interleukin; LT, leukotriene; MBP, major basic protein; PAF, platelet activating factor; PG, prostaglandin; TNF, tumour necrosis factor; VEGF, vascular endothelial growth factor.