Predictive biomarkers for graft rejection in pig-to-non-human primate corneal xenotransplantation

Abstract

Purpose : We investigated predictive biomarkers for graft rejection in pig-to-non-human primates (NHP) full thickness corneal xenotransplantation.

Methods : Thirty-eight rhesus macaques that underwent full thickness pig corneal xenotransplantations were included. Graft score (0-12) was calculated with opacity, edema, and vascularization. Score ≥ 6 was defined as rejection. Recipients were divided into two groups: graft rejection within 6 months (rejection group) and graft survival until 6 months (survival group). The predictability or correlation of biomarkers such as the number of T/B cell subsets, levels of anti-αGal IgG/M, donor-specific IgG/M from blood, and C3a from plasma or aqueous humor (AH) were analyzed in xenogeneic rejection. Receiver operating characteristic (ROC) curve analysis with areas under curve (AUC) was used to determine predictability of biomarkers in the rejection. AUCs of ROC curves were compared using a nonparametric approach by DeLong's test. The value with the maximum Youden index (J = sensitivity + specificity − 1) was regarded as the optimal cutoff.

Results : At week four, AH C3a, anti-αGal IgG, and activated B cells were significantly elevated in rejection group. AUC of ROC for predicting rejection among those biomarkers of week four were the highest in AH C3a (0.884) followed by anti-αGal IgG (0.804) and activated B cells (0.706), which were not significantly different among the biomarkers (DeLong's test). AH C3a of 12.345 ng/mL (sensitivity of 66.7% and specificity of 100%), anti-αGal IgG of 55.0 AU/mL (sensitivity of 81.8% and specificity of 84.2%), and activated B cells of 1.755/mm³ (sensitivity of 68.8% and specificity of 73.7%) were the best cut-off values (Figure 1).

Conclusions : Our results suggest that AH C3a, anti-αGal IgG, and activated B cells seems to be predictive biomarkers in xenogeneic rejection within 6 months in pig-to-NHP corneal xenotransplantation.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. Receiver operator characteristic (ROC) curve analysis for the prediction of graft rejection in biomarkers of week four. The AUC of aqueous humor C3a (0.884) was higher than that of anti-Gal IgG (0.812) or activated B cells (0.721), although the difference was not significant. Each round dot shows the optimal cut off value. W, week.