Introduction: Previous studies had made efforts to find the optimal regimens to reduce xenogeneic rejection in corneal xenotransplantation. Immunosuppressants currently applied to allotransplantation including various biological agents had been tested in corneal xenotransplantation. However, it had not been fully determined which immunosuppressive choice could lead to long-term graft survival. We aimed to compare clinical results in wild type pig-to rhesus corneal xenotransplantation depending on various immunosuppressant agents.

Methods: Medical records of 25 Chinese rhesus macaques who had conducted full thickness corneal transplantation with genetically unmodified SNU miniature pigs were retrospectively analyzed. They were injected various immunosuppressants including steroid, steroid/tacrolimus combination, anti-CD20 antibody or co-stimulation blockade as programmed schedules. According to the immunosuppressive regimens, they were grouped. Graft survival, intraocular pressure, central corneal thickness, changes in blood effector T and B cell subsets, plasma anti-αGal and donor-specific antibodies, and the changes of aqueous complement levels were compared between the groups with different immunosuppressants. Graft survival was compared with log-rank test, and other parameters were compared at postoperative 2-4 weeks with Kruskal-Wallis test.

Results: Graft survival time of steroid (S) or steroid/tacrolimus (S/T) group was significantly shorter than that of anti-CD20 antibody (aCD20) or co-stimulation blockade (CoB) group. Intraocular pressure and central corneal thickness in surviving grafts did not show significant differences between groups. For blood effector T and B cell comparison, CD8+IFNγ+ cell concentration showed increase in S group while revealing decrease in S/T, aCD20 and CoB groups although without statistical significance. Activated B cell concentration was significantly lower in aCD20 group than in S, S/T, or CoB group. Plasma anti-αGal IgG level was significantly higher in S group than in CoB group, and donor-specific IgG level was shown significantly higher in S group than in aCD20 or CoB group. Lastly, for aqueous C3a level, it was significantly higher in S/T group than S or aCD20 group.

Conclusion: It suggests that the co-stimulation blockade or anti-CD20 antibody based immunosuppressive regimens has superior effects on clinical and immunological outcome in wild type pig-to-rhesus corneal xenotransplantation than steroid or steroid/tacrolimus combination.