W231 - Single Cell Analysis Reveals Distinct CD8 T Cell Phenotypes and Functions in CMV Primary Infection and Reactivation in Kidney Transplant Recipients

Harry Pickering; Rajesh Parmar; Subha Sun; Elaine Reed

Abstract Text: Cytomegalovirus (CMV) infection is a risk factor for graft loss and patient mortality in solid-organ transplantation. Single-cell transcriptomics of peripheral blood CD8 T cells from kidney transplant (Tx) recipients (KTRs) pre and 1wk post-CMV viremia and 1yr post-Tx identified terminal effector populations (CD28-, TCF7-, IL7R-, KLRG1+, GZMB+) enriched in KTRs with reactivation of latent CMV infection (n=2) compared to KTRs (n=2) after primary CMV infection. Highly cytotoxic FCGRIIIA+ (CD16) clusters (GZMB+, PRF1+, GNLY+) and “NK cell-mediated cytotoxicity” and “FcγR-mediated phagocytosis” pathways (KEGG database) were enriched in KTRs at 1wk and 1yr post-reactivation. We evaluated peripheral blood CD8 T cell response of KTRs with CMV primary infection (n=4) and reactivation (n=4), with paired CMV- KTRs, pre- and ~2yrs post-Tx against CMV peptides and anti-CD16 antibody. KTRs with CMV reactivation and KTRs with poorly-controlled primary infection (peak CMV viral load >10,000 IU/mL; multiple episodes of viremia) had high CD8 T cell activation (CD69, CD137), effector cytokine secretion (IFN-γ and TNF-α) and degranulation (CD107a) to anti-CD16 stimulation, post-viremia, but primary infection resulted in poor CMV recall response 2yrs post-viremia compared to KTRs with reactivation both pre- and post-viremia. CMV-responsive CD8 T cells also lack CD16 expression. Our results suggest that CMV memory response can be difficult to establish and maintain after primary infection under immunosuppression. While latent CMV infection can be better controlled under immunosuppression, the presence of CMV-induced CD16+ CD8 T cells suggests an NK-like potential in mediating allograft injury, such as via ADCC in KTRs producing donor-specific anti-HLA antibodies.