Suppression of alkali burn-induced corneal neovascularization by dendritic cell vaccination targeting VEGF receptor 2

Purpose. To investigate whether the induction of cytotoxic T lymphocytes (CTLs) targeting VEGF receptor 2 inhibits corneal neovascularization caused by alkali injury. Methods. H-2Db-restricted peptide corresponding to amino acids 400 to 408 of VEGF receptor 2 (VEGFR2_400-408) was used as an epitope peptide. Dendritic cells (DCs) were harvested from bone marrow progenitors of C57BL/6 mice. Six- week-old C57BL/6 mice received subcutaneous injections of VEGFR2_400-408- or gp70-pulsed mature DCs three times at 6-day intervals. After the third immunization, corneal neovas- cularization was induced by alkali injury. Two weeks after the injury, the corneal vascularized area was evaluated by lectin angiography. To confirm the peptide-specific CTL activities in C57BL/6 mice, CD8⁺ T cells from immunized mice were subjected to ELISA for interferon (IFN)-γ and tumor necrosis factor (TNF)-α production and ⁵¹Cr-release cytotoxicity assay. To determine the in vivo effector T cells, the immunized mice were intraperitoneally injected with an anti-CD4 or -CD8 depletion antibody. Results. Corneal neovascularization was significantly attenuated in mice immunized with VEGFR2_400-408 compared with those not immunized or immunized with gp70. VEGFR2_400-408 or gp70, but not β-gal_96-103 application led to dose-dependent induction of IFN-γ and TNF-α in the CD8⁺ T cells cocultured with stimulator cells. Cytotoxicity assays showed the specific lysis of major histocompatibility complex-matched cells expressing VEGFR2, but not β-gal_96-103. In vivo depletion of CD8⁺, but not CD4⁺, T cells significantly reversed the suppressive effect of VEGFR2_400-408 immunization on corneal neovascularization to the level observed in nonimmunized or gp70-immunized animals. Conclusions. These results indicate the possibility of DC vaccination targeting VEGFR2 as a novel therapeutic strategy for corneal chemical injury.