Reduced Serum Brain-Derived Neurotrophic Factor in Infants Affected by Severe Bronchiolitis

Background: Bronchiolitis is an acute viral infection of the lower respiratory tract, typical of infants in their first year of life and causing hypoxia in the most serious cases. Bronchiolitis recognizes various demographic risk factors that are associated with greater clinical severity; however, no laboratory factors are yet able to correlate with the clinical severity. Neurotrophins as Brain-Derived Neurotrophic Factor (BDNF) are mediators of neuronal plasticity. BDNF is constitutively expressed in smooth muscle cells and epithelium of the lower respiratory tract, and as it is released during inflammatory conditions, serum levels may have a relevant role in the prognosis of infants with bronchiolitis. Objective: In the present pilot study, we aimed to disclose the presence of serum BDNF in infants hospitalized with bronchiolitis at discharge as a disease severity indicator. Methods and Results: Serum BDNF, measured at hospital discharge, was significantly lower in severe bronchiolitis (expressed as O2-supplemented infants). Furthermore, no changes were disclosed for the Tropomyosin receptor kinase B, the main BDNF receptor and neurofilament light chain, a biomarker of neuronal degeneration. Conclusion: Low serum BDNF in infants with severe bronchiolitis could be associated with a higher utilization by lung cells or with an altered production by lung cells. Therefore, further research is required to study if a decreased production or increased consumption of this biomarker is at the base of the above-mentioned findings.