Long-term safety outcome of systemic immunosuppression in pig-to-nonhuman primate corneal xenotransplantation

Abstract

Background: Safety concerns exist for corneal recipients under immunosuppression. We report long-term safety results of porcine corneal xenotransplantation under immunosuppression in nonhuman primates.

Methods: Systemic monitoring data from 49 Chinese rhesus macaques that received pig corneal transplant between 2009 and 2018 were retrospectively reviewed. The recipients were divided into 4 groups depending on the systemic immunosuppressants used: (a) conventional steroid group; costimulation blockade groups ([b] anti-CD154 antibody, [c] anti-CD40 antibody); and (d) commercially available immunosuppressants (anti-CD20 antibody, tacrolimus, basiliximab) group. We compared results of general condition monitoring; hematologic, biochemical, and electrolyte tests; and Rhesus Cytomegalovirus infection monitoring.

Results: All recipients recovered from early weight loss. White blood cell counts significantly decreased at 6 months in the steroid and anti-CD154 groups. Abnormal liver and kidney function and electrolyte imbalance were not observed in all groups. The mean value of Rhesus Cytomegalovirus DNA copies was consistently lower than 200 copies/mL, and antibody titers did not change over time in all groups. Tacrolimus-associated thrombotic microangiopathy was developed in one case, which resolved after discontinuation of tacrolimus. In 2017, a simian varicella virus outbreak led to clinical signs in 5 that received immunosuppressive therapies, of which 3 died.

Conclusion: Costimulatory blockade-based and anti-CD20 antibody/tacrolimus-based immunosuppressive therapies seem to be comparably safe with steroid therapy in nonhuman primates receiving corneal xenotransplantation, as they did not reactivate Rhesus Cytomegalovirus and maintained manageable systemic status. Although reactivation is rare, antiviral prophylaxis for simian varicella virus should be considered in immunocompromised hosts.

Keywords: cornea; immunosuppression; infection; nonhuman primates; rhesus cytomegalovirus; safety; simian varicella virus; xenotransplantation.

Figure 1. Body weight and body temperature change monitoring

(A) The postoperative/preoperative body weight ratios of the conventional steroid group (CS), anti-CD154 Ab group (CD154), anti-CD40 Ab group (CD40), and commercially available immunosuppressants combination regimen group (CA) were calculated at 1 month, 3 months, and 6 months postoperatively. (B) Body temperature of the CD40 and CA group preoperatively and 1 month, 3 months, and 6 months postoperatively.

Figure 2. Hematological tests

(A) Changes in WBC counts of the conventional steroid group (CS), anti-CD154 Ab group (CD154), anti-CD40 Ab group (CD40), and commercially available immunosuppressants combination regimen group (CA) before transplantation and at 1, 3, and 6 months after transplantation. (B) The changes in Hb levels observed before surgery and at 1, 3, and 6 months after transplantation.

Figure 3. Biochemical tests

(A, B) AST and ALT measured preoperatively and at 1, 3, and 6 months postoperatively in conventional steroid group (CS), anti-CD154 Ab group (CD154), anti-CD40 Ab group (CD40), and commercially available immunosuppressants combination regimen group (CA). (C) BUN values before the transplantation and 1, 3, and 6 months after transplantation collected in CS, CD154, CD40, CA groups. (D) Mean values for creatinine in CS, CD154, CD40 and CA groups evaluated preoperatively and 1, 3, and 6 months postoperatively. (E) Serum glucose level measured preoperatively and at 1, 3, and 6 months postoperatively in CS, CD154, CD40, and CA groups.

Figure 4. Electrolyte tests

(A) The values for Na were monitored before surgery and at 1, 3, and 6 months after the surgery in the conventional steroid group (CS), anti-CD154 Ab group (CD154), anti-CD40 Ab group (CD40), and commercially available immunosuppressants combination regimen group (CA). (B) The K values of the CS, CD154, CD40, and CA groups were measured preoperatively and at 1, 3, and 6 months postoperatively.

Figure 5. RhCMV monitoring

(A) The copy number of RhCMV DNA was measured in the conventional steroid group (CS), anti-CD154 Ab group (CD154), anti-CD40 Ab group (CD40), and commercially available immunosuppressants combination regimen group (CA) before transplantation and at 1, 3, and 6 months after the transplantation. (B) The RhCMV Ab titer was also measured preoperatively and at 1, 3, and 6 months postoperatively in the CS, CD154, CD40, and CA groups.