Treatment of cynolmolgus monkey (NHP) renal transplant recipients with a combination of 2 rhesus-mouse chimeric α-CD45RB (r6G3R1; 6G3) and α-CD40 (r2C10R4; 2C10) mAbs increased circulating donor-specific CD25⁺FoxP3⁺ Tregs and induced long-term GS/operational tolerance in 1/3 of recipients (n=3/9). α-CD40 (2C10) alone could not induce long-term GS or this regulatory signature. Transplanted kidney can participate in immunoregulation and promote Tregs, although the mechanisms are poorly understood. Kidney tubular epithelial cells (TEC) express CD40, a TNF-family receptor linked to receptor-interacting protein 1 (RIP1), a death domain–containing kinase with diverse and context-specific roles in inflammation, cell survival and death. Therefore, we tested effects of a-CD40 on NHP and human TEC function.

CD40 ligation on human KTECs by CD154 was shown to promote inflammation by enhancing IL-6, IL-8, RANTES, MCP-1 and CD40 expression. Here, we exposed NHP KTEC (Vero cells) to inflammatory conditions (IL-2 and IFN-γ) with or without 2C10 for 3d. Targeting CD40 with 2C10 markedly reduced TEC secretion of IL-6 by ELISA, compared to controls without 2C10 (181 vs. 295 pg/ml; p<0.05). In contrast there was no significant change in TGF-β expression. The inhibition of IL-6 expression by 2C10 increased with time and concentration. Importantly, 2C10 similarly inhibited IL-6 expression by human TEC (PT-2 cells). Of note, another α-CD40 (3A8), which was minimally effective in prolonging cyno renal GS, enhanced rather than reduced IL-6 expression by TEC. Finally, addition of 2C10 to 3d co-cultures of Vero TEC and allogeneic NHP PBMCs consistently induced a 2X increase in CD4⁺CD25⁺FoxP3⁺ Tregs, and concomitantly decreased TEC CD40 expression (MFU 43 vs. 113), compared to untreated control cultures. α-CD45RB mAb had no effect on KTECs.

Thus, targeting CD40 expressed by KTEC may directly enhance kidney immunoregulatory capacity by attenuating inflammation and promoting Treg expansion. These results provide new insight into prolongation of renal allograft survival by α-CD40 and may provide strategies to further enhance the efficacy of α-CD45RB/α-CD40 in vivo.

CITATION INFORMATION: Arp J, Ma Y, Yang H, El Warrak A, Haig A, Liu W, Reimann K, Luke P, Zhang Z, Rothstein D, Jevnikar A. Anti-CD40 mAb Promotes Kidney Immunoregulatory Capacity in NHP Transplants by Altering Kidney Tubular Cell (TEC) Expression of CD40 and IL-6. Am J Transplant. 2017;17 (suppl 3).

« Back to 2017 American Transplant Congress