Ovalbumin serves as a neo-transplantation antigen in retinal pigment epithelial cells

Our long-term goal is to determine the optimal methods for inducing allograft tolerance to facilitate transplantation of retinal pigment epithelial cells or stem cells for the treatment of retinal degenerative diseases. These goals have been hampered by the extreme complexity of allograft rejection and the heterogeneity of responding T cells. The current studies were undertaken to develop a simplified transplant model for studying rejection and tolerance in the unique environment of the eye.

To provide a defined transplantation antigen, transgenic C57BL/6 (B6) mice were produced, which express the exogenous chicken egg ovalbumin (OVA) gene under the regulation of the mouse tyrosinase related protein-1 (TRP-1) promoter that is transcriptionally active in retinal pigmented epithelial (RPE) cells. To determine whether the transgene was expressed as a neo-transplantation antigen, RPE from TRP-1-OVA mice were injected into the subretinal space of B6 mice or B6 mice expressing the OVA-specific (OT1) TCR transgenes and examined for inflammatory cell infiltration.

The TRP-1-OVA transgenic mice expressed OVA mRNA in the brain and eye but not the heart or kidney. RPE cells from TRP-1-OVA transgenic mice expressed mRNA and protein encoded by the OVA gene and RPE expressing TRP-1-OVA induced an inflammatory response within the subretinal space of OT1 mice but not in B6 mice.

OVA serves as a defined, neo-transplantation antigen in RPE that is recognized by mice whose CD8+ T cells recognize OVA peptide. These observations provide new tools for future studies of the mechanisms of rejection and prolongation of RPE transplants in the eye.