In-silico immune cell deconvolution of the airway proteomes of infants with pneumonia reveals a link between reduced airway eosinophils and an increased risk of mortality

Charles J Sande; Jacqueline M Waeni; James M Njunge; Martin N Mutunga; Elijah Gicheru; Nelson K Kibinge; Agnes Gwela

Airway-resident eosinophils have not been extensively characterised in previous pneumonia studies, although proteins expressed predominantly by eosinophils including leukotriene C4, eosinophil-derived neurotoxin (RNASE2) and eosinophil cationic protein (ECP) are expressed at high levels during viral pneumonia [17] [18] [19] . Taken together with the results of the current study, there appears to be a clear role for eosinophils in the response to pneumonia infection and that the failure to sufficiently recruit them to the airway may be a significant factor in mortality. A potential limitation of our study is that it was carried out using samples collected from the upper airway and not the lung. While lung samples would have undoubtedly been more informative of responses at the site of disease, the collection of these samples is a highly invasive process and exposes children to substantial additional risk without providing additional diagnostic value above nasopharyngeal or peripheral blood sampling. As a result, these samples are generally only available in settings with paediatric intensive care facilities, and even here, they are generally collected in children with atypically severe disease.