The role of eosinophils in viral infections

Respiratory viruses are a leading cause of severe respiratory infections normally seen in infants and children. As there is currently no known vaccine against major respiratory viruses, the pressure is on the innate immune cells to clear these infections more efficiently. For a long time, the role of eosinophils in the pathogenesis and pathophysiology of respiratory virus infections has been examined and opinions seem very diverse. Eosinophils became the main research focus in 1960 following unsuccessful respiratory syncytial virus (RSV) vaccination trial. Vaccine contained formalininactivated RSV triggering the recruitment of eosinophils to the lung tissue, which resulted in several deaths and severe tissue damage. Ever since, eosinophil role in viral infections has been investigated and numerous studies have shown that these cells have the potential to play beneficial role in the clearance on the viral infections. In this review, we have summarised the findings of studies that examined the role of eosinophils in respiratory virus infections involving viruses such as Respiratory Syncytial virus (RSV), Rhinovirus, Pneumonia virus of mice (PVM) as well as their role as antigen presenting cells (APCs) in viral infections. This review will show that the challenge is to ensure that the benefits of the eosinophilic leukocytes are harnessed to effect successful therapeutic intervention and this remains the main challenge in achieving successful vaccine against respiratory virus infections.