Combined agonism of immune checkpoint receptors, PD-1 and TIGIT, suppresses development of experimental autoimmune uveitis

Abstract

Purpose : The immune checkpoint receptors, PD-1 and TIGIT, are regulators of lymphocyte activation and effector function. We have previously identified PD-1 and TIGIT expression on infiltrating T cells and natural killer cells during experimental autoimmune uveitis. Whether agonists targeting these receptors can suppress ocular inflammation is unknown.

Methods : Experimental autoimmune uveitis was induced by subcutaneous immunisation with IRBP_1-20 emulsified with Complete Freund’s Adjuvant and intraperitoneal pertussis toxin in hPD1/hTIGIT transgenic mice, which express humanised extracellular domains of both PD-1 and TIGIT receptors. Mice were treated with monoclonal antibodies by intraperitoneal injection on study days 0 and 7: receiving either a 1:1 mixture of 5 mg/kg anti-human PD-1 agonist and 5 mg/kg anti-human TIGIT agonist (n=12), or 10 mg/kg isotype control antibody (n=12). Confocal scanning laser ophthalmoscopy (cSLO) and optical coherence tomography (OCT) were performed on day 13 to assess the severity of uveitis in each eye. Retinas from mice were mechanically dissociated for flow cytometry to examine infiltrating leukocytes and checkpoint receptor target engagement.

Results : At post-immunisation day 13, the agonist-treated group displayed significantly lower uveitis severity scores (median score = 0) compared to isotype control (median score = 0.375; Mann-Whitney U = 32, two-tailed p=0.016). Flow cytometry of retinal infiltrating leukocytes revealed a rich inflammatory infiltrate comprising of diverse activated T cell and myeloid subsets in treated eyes. Target receptor engagement was inferred by a reduction in receptor staining on infiltrating leukocytes in agonist-treated mice compared to controls.

Conclusions : Agonistic monoclonal antibodies targeting human PD-1 and TIGIT suppressed the development of autoimmune uveitis in humanised mice. Flow cytometry successfully captured the diverse inflammatory infiltrate present in experimental autoimmune uveitis and provides an additional readout for target receptor engagement. Future work will further examine the mechanisms of experimental autoimmune uveitis suppression by PD-1/TIGIT agonism and determine whether this represents a potentially translatable strategy to treat non-infectious posterior uveitis in human patients.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.