Role of Lentivirus-Mediated Overexpression of Programmed Death-Ligand 1 on Corneal Allograft Survival

Abstract

To investigate the role of lentivirus-mediated overexpression of programmed death-ligand 1 (PD-L1) on rat corneal allograft survival. A fully allogeneic rat cornea transplant model was used for in vivo studies. Lentiviral (LV) vectors are efficient tools for ex vivo genetic modification of cultured corneas. LV vector encoding for PD-L1 (LV.PD-L1) and LV vector encoding for eGFP (LV.eGFP, as control) were constructed and tested. PD-L1 or eGFP expression was increased on corneal cells upon LV.PD-L1 and LV.eGFP transduction, respectively. Both allogeneic controls and allogeneic LV.eGFP transduced corneas were uniformly rejected (MST: 13.8 ± 1.7 days and 12.3 ± 1.9 days, respectively). In contrast, allogeneic LV.PD-L1 transduced corneas showed a high percentage (83%) of graft survival (MST > 30 days, n = 5, 15 days, n = 1). Graft opacity of PD-L1 transduced corneas was present but was significantly reduced compared to control or eGFP expressing corneas. Flow cytometric analysis revealed that percentages of CD3 + CD8 + CD161 + and CD3 + CD8 + CD161 -lymphocytes were decreased in animals receiving LV.PD-L1 transduced corneas compared to animals grafted with LV.eGFP transduced corneas. Moreover, reduced expression of proinflammatory cytokines (IFN-c and IL-6) in PD-L1 transduced corneas compared to allogeneic controls was also observed. Local PD-L1 gene transfer in cultured corneas is a promising approach for the prolongation of corneal allograft survival and attenuation of graft rejection.

Immune-checkpoint protein VISTA critically regulates the IL-23/IL-17 inflammatory axis

“…For example, a fusion protein CTLA4-Ig (Abatacept) has been used in the clinic for treating autoimmune diseases such as rheumatoid arthritis 48 . Similarly, local overexpression of PD-L1-Ig or administration of purified PD-L1-Ig has been shown to promote allograft survival in murine models 49–52 . Our study indicates that enhancing the anti-inflammatory function of VISTA may benefit the treatment of a variety of inflammatory and autoimmune disorders.…”

Mesenchymal Stem Cell Therapy Promotes Corneal Allograft Survival in Rats by Local and Systemic Immunomodulation

“…Previous results from our group have shown that both lentivirus-mediated overexpression of programmed deathligand 1 on corneal cells (23) and intravenous administration of donor-derived BM-derived dendritic cells (42) can significantly inhibit NKT cell infiltration into the corneal allograft. Although in this study we used a different approach (systemic infusion of MSCs), this finding was replicated in the case of both allo-and third-party MSC treated recipients, perhaps confirming the importance of this cell type in determining the fate of the allograft.…”

“…Orthotopic corneal transplantations were performed and evaluated as reported previously (23). Briefly, graft transparency, as the primary indicator of rejection, was evaluated every second day and graded as follows: 0-completely transparent cornea; 0.5-slight corneal opacity, iris structure easily visible; 1.0-low opacity with visible iris details; 1.5-modest corneal opacity, iris vessels still visible; 2.0-moderate opacity, only some iris details visible; 2.5-high corneal opacity, only pupil margin visible; 3.0-complete corneal opacity, anterior chamber not visible.…”

Gene Therapy Approaches to Prevent Corneal Graft Rejection: Where Do We Stand?

“…Furthermore, systemic application of a soluble PD-L1-Ig fusion protein was able to prolong allogeneic graft survival in a mouse corneal transplant model [39] highlighting the importance of this pathway. We showed that LV-mediated overexpression of PD-L1 in cultured corneas significantly prevents corneal graft rejection by modulating graft-infiltrating cells [40]. This striking result was associated with a reduction of natural killer T cells and cytotoxic CD8+ T cell infiltration, and was also accompanied by attenuation of pro-inflammatory cytokine expression [40].…”

“…We showed that LV-mediated overexpression of PD-L1 in cultured corneas significantly prevents corneal graft rejection by modulating graft-infiltrating cells [40]. This striking result was associated with a reduction of natural killer T cells and cytotoxic CD8+ T cell infiltration, and was also accompanied by attenuation of pro-inflammatory cytokine expression [40]. Interestingly, the neovascularisation of transplanted corneas seemed to be unaffected by this therapy.…”