Phenotypic Shift of an Inflammatory Eosinophil Subset into a Steady-State Resident Phenotype after 2 Years of Vaccination against IL-5 in Equine Insect Bite Hypersensitivity.

The research explores the changes in a subtype of eosinophils in the blood of horses suffering from insect bite hypersensitivity (IBH), resulting from their vaccination against IL-5 for two years. This then reduces the severity of their allergy symptoms.

Overview and Introduction

• This study focuses on eosinophils, these are white blood cells that play a critical role in allergic diseases like Insect Bite Hypersensitivity (IBH).
• The research develops on previous findings which identified two distinct types of eosinophils: steady-state resident eosinophils (rEos) and inflammatory eosinophils (iEos).
• These types of eosinophils could be distinguished by their expression of integrin CD49f, a kind of protein that aids the movement and activation of eosinophils.

Methods and Vaccine Treatment

• The investigation used a virus-like particle (VLP)-based vaccine targeting equine interleukin-5 (the signaling molecule involved in the differentiation and activation of eosinophils, referred to as eIL-5 in the study) in an attempt to interfere with the role of IL-5 in IBH.
• The vaccine, named eIL-5-CuMV-TT, stimulated the production of antibodies against IL-5 and was expected to alleviate the clinical symptoms in IBH-affected horses.
• The scientists tracked the behavior and quantities of eosinophils in vaccinated horses for two years to understand the vaccine’s long-term effects.

Findings and Conclusion

• The results from the first year of vaccination showed a significant reduction in total eosinophils and specifically, iEos. However, the remaining eosinophils still possessed the inflammatory phenotype similar to iEos, as indicated by their larger size and higher granularity.
• In the second year, the researchers noticed relatively low levels of iEos and a significant increase of rEos in vaccinated horses, suggesting a shift in the eosinophils subtype.
• The alteration in the size, granularity, and expression of integrin CD49f in eosinophils during the second year suggests a benefit of extended treatment with the eIL-5-CuMV-TT vaccine, showing its impact on shifting the eosinophils towards a phenotype resembling that found in healthy horses.