Bronchiolitis is an acute lower respiratory tract infection mainly affecting children under 24 months, primarily caused by Respiratory Syncytial Virus (RSV). Interferons (IFNs), cytokines central to innate and adaptive immunity, are secreted in response to viral infections. In RSV bronchiolitis, Type I and III IFN Signatures modulate antiviral responses and impact disease severity. This study aimed to evaluate the correlation between Type I and III IFNs transcriptional signatures in blood and nasal swabs with clinical presentation.

We analyzed transcription levels of Type I and III IFN Signatures using a PCR real-time TaqMan assay in blood and nasal swabs from children hospitalized for RSV bronchiolitis and from healthy controls (HC).

Interferon score I was significantly higher in bronchiolitis patients at admission than at discharge and compared to HC, in both blood and nasal swabs (p < 0.0001). A strong positive correlation for IFN score I between the two sample types was found (p < 0.0001). Patients with severe disease (requiring intensive care) had lower IFN score I than those with milder disease, in both blood (p = 0.0005) and nasal swabs (p = 0.0078). IFN score III was down-regulated in bronchiolitis patients compared to HC in blood samples (p < 0.0001), while in nasal swabs, this down-regulation was evident only at discharge (p < 0.0001 vs admission; p = 0.0546 vs HC).

This study enhances understanding of IFN signature dynamics in RSV bronchiolitis, emphasizing the importance of sample type and signature specificity, and suggests their potential use as prognostic tools to improve patient management.