Targeting HSP: Tr1 Cell-Mediated Immune Tolerance to HSP60 Attenuates Neurodegeneration in Glaucoma

Abstract

Purpose : Our preliminary findings suggest glaucoma pathogenesis involves a bacteria-primed T cell-mediated autoimmune mechanism, with heat shock proteins (HSPs) as potential autoantigens. We hypothesize that inducing immune tolerance to HSP60 could mitigate the pathogenic immune response, reducing neuron loss in glaucoma.

Methods : Adult C57BL/6J mice received daily nasal administration of low-dose recombinant bacterial HSP60, Ovalbumin (OVA) or saline (controls) for 7 days. Intraocular pressure (IOP) elevation was induced by injecting polystyrene microbeads (MB) into the anterior chamber. T cell responses to HSP60 were evaluated through delayed-type hypersensitivity responses (DTH) and fluorescence-activated cell sorting (FACS) analysis. Visual and retinal functions were assessed using the optomotor response (OMR) and electroretinogram positive scotopic threshold response (pSTR). Glaucomatous neural damage was quantified by counting retinal ganglion cells (RGC). CD4⁺ T cells from HSP60-induced glaucoma mice were adoptively transferred intravenously to untreated glaucoma mice.

Results : Nasal administration of low-dose HSP60 induced immune tolerance in glaucoma mice, evidenced by reduced DTH responses and increased IL-10-producing Type 1 regulatory T (Tr1) cells. We observed HSP60 and OVA did not alter the basal levels of visual acurity (VA), contrast sensitivity (CS) and pSTR prior to MB-injection, as compared to naive and/or saline-treated mice. However, HSP60-treated mice exibited significantly improved VA and CS compared to saline or OVA-treated mice at all time-points after MB-injection. The treatment with HSP60 attenuated RGC loss by 30.03±5.67% as compared to that with OVA (49.23±3.26% ) or saline (50.12±2.27%) at 8 week post MB injection. Adoptive transfer of HSP60-induced tolerogenic CD4+ T cells into glaucoma mice resulted in enhanced visual function and reduced RGC loss by 33.76±4.19%. RGC function as assessed by pSTR was improved in both HSP60-treated mice and HSP60-induced tolerogenic CD4⁺ T cell recipient mice compared to control mice after MB-injection.

Conclusions : Administering low doses of bacterial HSP60 intranasally induced immune tolerance, mitigating neurodegeneration in glaucoma mice. These findings offer compelling evidence supporting the T cell-mediated autoimmune mechanism in glaucoma and advocating for an antigen-specific therapeutic approach to prevent vision loss.

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