Immune profiles provide insights into respiratory syncytial virus disease severity in young children

Area of Science:

• Immunology
• Virology
• Pediatrics

Background:

• Respiratory syncytial virus (RSV) causes significant infant morbidity, but factors determining disease severity remain unclear.
• Understanding RSV pathogenesis is crucial for developing effective vaccines and antiviral therapies.
• Identifying protective immune profiles from natural infection can guide vaccine development and clinical trials.

Purpose of the Study:

• To identify factors associated with mild respiratory syncytial virus (RSV) disease phenotypes in young children.
• To characterize the immune response profiles correlating with disease severity in infants infected with RSV.

Main Methods:

• Integrated analysis of blood transcriptional data, immune cell profiling, RSV viral loads, and clinical data from 190 children under two years old.
• Comparison of immune markers and gene expression between mild (outpatient) and severe (inpatient) RSV cases.
• Multivariable analyses to determine the association of specific immune factors with hospitalization risk.

Main Results:

• Mild RSV cases exhibited higher RSV loads, increased interferon (IFN) and plasma cell gene expression, and reduced inflammation and neutrophil gene expression compared to severe cases.
• Severe RSV cases were characterized by increased HLA-DR^low monocytes, which were absent in mild cases.
• IFN overexpression correlated with decreased hospitalization odds, while increased HLA-DR^low monocytes were linked to higher hospitalization risk.

Conclusions:

• Robust innate immune responses, particularly interferon signaling, are associated with milder respiratory syncytial virus (RSV) infections in infants.
• Specific monocyte populations (HLA-DR^low) may serve as biomarkers for severe RSV disease in infants.
• These findings provide insights into protective immune mechanisms against severe RSV and inform future therapeutic and vaccine strategies.