Recombinant human PRG4 alleviates signs of allergic conjunctivitis in vivo

Abstract

Purpose : Allergic conjunctivitis (AC) is a multifactorial disease associated with redness and swelling of the conjunctiva, increased lacrimation, and severe itching. Management includes lubricants, topical corticosteroids, NSAIDs, and antihistamines. Limited efficacy and drug-induced adverse reactions call for novel safer and more efficacious treatments. Recombinant human proteoglycan 4 (rhPRG4; lubricin) is an endogenous proteoglycan that has emerged as a key natural molecule in the lubrication of the ocular surface. Compound 48/80 (C48/80) promotes mast cell degranulation and topical instillation of C48/80 is a well-established model for AC in rabbits. The purpose of this study was to investigate the efficacy of rhPRG4 in models for C48/80-induced AC.

Methods : In vitro, human corneal epithelial (HCE-T) cells were pre-treated with rhPRG4 (300 μg/ml) for 24 hours and subsequently exposed to C48/80 (5 μg/ml) for 5 h. Cytokine release was quantified by 48-plex bead-based immunoassay. In vivo, AC was induced by single topical instillation of 2% C48/80 (50 µl) in New Zealand White (NZW) rabbits. Anterior segment ophthalmic exams were performed prior to C48/80 instillation, and 4 h, 6 h and 24 h post-challenge and scored using the SPOTS system. rhPRG4 (150 μg/ml) was administered topically for 72 h prior to C48/80 challenge. Ketotifen was used as positive control.

Results : C48/80 did not cause a significant increase in secretion of inflammatory cytokines, neither did rhPRG4 have any significant effects cytokine release from HCE-T cells. In vivo, C48/80 induced AC peaking at 6 h with phenotypes of severe hyperemia and chemosis, moderate discharge and mild blepharitis, all of which resolved by 24 h. The positive control, Ketitofen, reduced hyperemia at 4 h and 6 h (p<0.001) and chemosis at 4 h (p<0.001). rhPRG4 was well-tolerated and reduced hyperemia (p<0.05) and chemosis (p<0.01) at 6 h post C48/80 instillation. Neither test article reduced blepharitis or discharge.

Conclusions : HCE-T cells did not respond to C48/80 with increased pro-inflammatory cytokine release, consistent with C48/80 resulting in mast cell degranulation and histamine release. rhPRG4 reduced signs of C48/80-induced AC, however, to a lesser extent than ketotifen. Our data suggest that rhPRG4 may exert direct or indirect effects resulting in inhibition of mast cell degranulation.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.