Chemokine decoy receptor D6 mimicking trap (D6MT) prevents allosensitization and immune rejection in murine corneal allograft model

Abstract

Although corneal allotransplantation is performed in the immune-privileged cornea, many grafts are still rejected after transplantation. This study examined the role of chemokine receptor D6 expression in a corneal allograft rejection, investigated the modulation of D6 expression in cells, and determined the effect of D6 on graft survival. Interestingly, D6 was highly expressed in CD45 -: cells and the corneal epithelium of accepted corneal allografts. From the mouse corneal allograft model, TGF-β was found to play a key role in D6 up-regulation, leading to reduced CCL2, CCL5, and CCL3. To modulate D6 chemokine binding, a D6MT was developed and showed effective chemokine trapping through SPR and FACS assays. By treating corneal allografts with D6MT, the allograft survival rate was improved, and (lymph) angiogenesis was reduced. Direct allosensitization and DC LN homing was drastically reduced in the mouse corneal allograft model. These findings suggest that TGF-β is a positive regulator of D6 expression, and it is a potential therapeutic target to enhance the survival of corneal allografts.

Overview and potential unifying themes of the atypical chemokine receptor family

“…All ACKRs are expressed on epithelial tissues of barrier organs (ACKR1 [60,82,83]; ACKR2 [84,85]; ACKR3 [20,86]; ACKR4 [48,55,56,[87][88][89][90][91][92]; ackr5 [93]) and on trophoblast cells, the epithelial cells of fetal origin that form the physical placental barrier between the mother and the developing conceptus (ACKR1 [94]; ACKR2 [94][95][96][97]; ACKR3 [97][98][99][100]; ACKR4 [25,94]). No data are available on the expression of ackr5 in placenta, although elevated levels of its ligand chemerin have been reported recently [101].…”

The atypical chemokine receptor-2 does not alter corneal graft survival but regulates early stage of corneal graft-induced lymphangiogenesis

“…The role of ACKR2 in various inflammatory models is considered to be a general one of limiting excessive inflammation and promoting inflammatory resolution by “scavenging” inflammatory chemokines [ 5 , 8 – 10 ]. Few studies have addressed the role of ACKR2 in allo-immunity [ 11 , 26 , 27 ]. Deletion of ACKR2 had a protective effect in graft-versus-host disease attributed to increased numbers and enhanced immunosuppressive activity of Ly6C high monocytes [ 26 ] while a pro-inflammatory effect was observed in syngeneic but not allogeneic corneal grafts [ 11 ].…”

Gr-1intCD11b+ myeloid-derived suppressor cells accumulate in corneal allograft and improve corneal allograft survival

“…Grafts were considered rejected when they became opaque and the iris details could not be recognized clearly by using a standardized opacity grading scheme. Protocol for evaluating corneal opacities is described in our previous work [23,24]. This model allows easy, direct evaluation of graft progression over time, including end points, without sacrificing the animals.…”

“…Peripheral blood, BM, and grafted corneas were harvested, and single-cell suspensions were prepared according to a previous protocol [24]. In brief, singlecell suspensions of corneal samples were prepared by collagenase digestion.…”

“…1A). According to graft opacities, allografts were separated as Ac and Rj allografts as described previously [24] and the frequency of Gr-1 + CD11b + cells was determined. According to expression levels of Gr-1, Gr-1 + CD11b + cells were separated into Gr-1 hi CD11b + , which displayed as a clear cluster, and Gr-1 int CD11b + , which represented the rest of the population of Gr-1 + CD11b + cells ( Fig.…”