Fel d 1-Expressing Plant-Derived Bioparticle: A Novel Treatment for Cat Allergy.

Abstract

Allergen immunotherapy (AIT) is the only disease-modifying therapeutic approach for cat allergy, though it requires at least three years of treatment and can potentially induce severe systemic reactions. Plant-derived bioparticles expressing Fel d 1 allergen (Fel d 1 eBP) have been developed as a novel therapeutic candidate for cat allergy. We aimed to investigate the allergenicity and immunogenicity profile of Fel d 1 eBP. Fel d 1 eBP was synthesised in vivo in Nicotiana benthamiana and confirmed by cryo-electron microscopy and tomography. Immune modulatory properties of purified natural Fel d 1 (nFel d 1) and Fel d 1 eBP were assessed at T and B cells by flow cytometry in 12 cat-allergic subjects (CA) and 12 non-atopic controls (NAC). Single-cell RNA-seq was used to assess molecular mechanisms of Fel d 1 eBP immune skewing. The safety of Fel d 1 eBP was assessed by measuring basophil responsiveness in whole blood and further confirmed in vivo by its administration as a skin prick test (SPT) in 20 cat-allergic individuals. Fel d 1 eBP was shown to be a strong inducer of Th1 cells (p < 0.05) and IL-10⁺ non-Th2 cells (p < 0.05) in CA subjects. Fel d 1 eBP showed a stronger trend for inducing IL-10⁺ Breg cells compared to nFel d 1, peaking at 3 μg/mL. scRNA-seq analyses demonstrated that Fel d 1 eBP targets the induction of protective metallothionein genes, CCL18⁺ monocytes and naïve B cells that are interferon responsive and metabolically activated. Moreover, Fel d 1 eBP demonstrated reduced capacity to elicit basophil activation (p < 0.001) and histamine release (p < 0.01), indicating their hypoallergenic nature. Administration of titrated doses of Fel d 1 eBP through skin prick test revealed that they are well-tolerated with reduced mean wheal compared to native Fel d 1 in an open-label Phase 0 study (all, p < 0.001). We demonstrate that Fel d 1 eBP is hypoallergenic and demonstrates tolerogenic properties, making it a novel candidate for use in AIT for cat allergy.