IL-13 is required for eosinophil entry into the lung during respiratory syncytial virus vaccine-enhanced disease

Area of Science:

• Immunology
• Virology
• Respiratory Medicine

Background:

• Respiratory syncytial virus (RSV) causes significant lower respiratory tract disease in children.
• Formalin-inactivated RSV vaccines have been linked to enhanced disease severity and mortality in children upon natural infection.
• Pulmonary eosinophilia, indicative of Th2 immune responses, was observed in children with enhanced RSV disease.

Purpose of the Study:

• To investigate the role of Interleukin-13 (IL-13) in eosinophil recruitment to the lungs during RSV infection.
• To elucidate the mechanism by which eosinophils contribute to vaccine-enhanced RSV disease.

Main Methods:

• Utilized IL-13-deficient mice immunized with a recombinant vaccinia virus expressing the RSV G protein (vvG) and subsequently challenged with RSV.
• Performed histological analysis to assess pulmonary infiltrate, specifically eosinophils.
• Measured pulmonary chemokine levels (CCL11, CCL22) and RSV G protein-specific CD4 T cell responses.

Main Results:

• IL-13 is essential for eosinophils to migrate into the lung parenchyma and airways of vvG-immunized mice challenged with RSV.
• Eosinophils were present in the blood and bone marrow but not the lungs of IL-13-deficient mice, indicating impaired lung transit.
• Pulmonary levels of CCL11 and CCL22 were reduced in IL-13-deficient mice, suggesting IL-13 induces chemokines for eosinophil and Th2 cell recruitment.

Conclusions:

• IL-13 plays a critical role in mediating eosinophil recruitment to the lungs during RSV infection, likely through the induction of specific chemokines.
• This mechanism may contribute to the pathogenesis of vaccine-enhanced RSV disease observed in clinical settings.
• Targeting IL-13 or its downstream chemokines could be a therapeutic strategy for managing severe RSV infections.