Is the composition of exhaled breath condensate a key to explain the
course of COVID-19 in children?
Abstract
Background: The relative resistance of children to severe course of
novel coronavirus infection remains unclear. We hypothesized that there
might be a link between this phenomenon and observation from our
previous studies, concerning an inhibitory or cytotoxic effect of
children exhaled breath condensate (EBC) on endothelial cell cultures.
Since we could not find any data on similar effect caused by EBC from
adults, the aim of our study was to evaluate and compare the biological
activity of EBC from adults and children in an experimental in vitro
model. Furthermore, in order to identify a putative agent responsible
for these properties of children EBC, we attempted to analyse the
composition of selected EBC samples. Methods: The influence of EBC
samples on metabolic activity of endothelial cell line C-166 was
assessed using colorimetric tetrazolium salt reduction assay (MTT
assay). Selected EBC samples were fractionated using size exclusion
chromatography and subjected to mass spectrometry analysis. Results:
Exhaled breath condensates from healthy children, but not from adults,
revealed a cytotoxic effect on in vitro cell cultures. This effect was
most significant in condensate fraction, which contained a prominent 4.8
kDa peak in the mass spectra. Conclusion: Breath condensates from
healthy children contain the factor, which reveals inhibitory/cytotoxic
effect on endothelial cell cultures. Although physiological role of this
agent remains unclear, its identification may potentially be useful in
ongoing research on SARS-CoV-2/COVID-19.