Tolerance induction in HLA disparate living donor kidney transplantation by donor stem cell infusion: durable chimerism predicts outcome

Abstract

Background: We recently reported that durable chimerism can be safely established in mismatched kidney recipients through nonmyeloablative conditioning followed by infusion of a facilitating cell (FC)-based hematopoietic stem cell transplantation termed FCRx. Here we provide intermediate-term follow-up on this phase II trial.

Methods: Fifteen human leukocyte antigen-mismatched living donor renal transplant recipients underwent low-intensity conditioning (fludarabine, cyclophosphamide, 200 cGy TBI), received a living donor kidney transplant on day 0, then infusion of cryopreserved FCRx on day +1. Maintenance immunosuppression, consisting of tacrolimus and mycophenolate, was weaned over 1 year.

Results: All but one patient demonstrated peripheral blood macrochimerism after transplantation. Engraftment failure occurred in a highly sensitized (panel reactive antibody [PRA] of 52%) recipient. Chimerism was lost in three patients at 2, 3, and 6 months after transplantation. Two of these subjects had received either a reduced cell dose or incomplete conditioning; the other two had PRA greater than 20%. All demonstrated donor-specific hyporesponsiveness and were weaned from full-dose immunosuppression. Complete immunosuppression withdrawal at 1 year after transplantation was successful in all patients with durable chimerism. There has been no graft-versus-host disease or engraftment syndrome. Renal transplantation loss occurred in one patient who developed sepsis following an atypical viral infection. Two subjects with only transient chimerism demonstrated subclinical rejection on protocol biopsy despite donor-specific hyporesponsiveness.

Conclusions: Low-intensity conditioning plus FCRx safely achieved durable chimerism in mismatched allograft recipients. Sensitization represents an obstacle to successful induction of chimerism. Sustained T-cell chimerism is a more robust biomarker of tolerance than donor-specific hyporeactivity.

Figure 1

A. Stability of chimerism over time in subjects who demonstrated high level and/or mixed donor chimerism. B Serum creatinine vs. time for all clinical trial subjects.

Figure 2

A MLR results for subject NW4 at 5 months post-transplant, showing DSH. B MLR results for subject NW4 at 9 months post-transplant showing persistent DSH. C,D NW4 exhibits cytolytic activity to third party but not donor target cells in CML at month 8 and month 18 following transplantation. E First presence of anti-donor proliferative response in MLR.

Figure 2

A MLR results for subject NW4 at 5 months post-transplant, showing DSH. B MLR results for subject NW4 at 9 months post-transplant showing persistent DSH. C,D NW4 exhibits cytolytic activity to third party but not donor target cells in CML at month 8 and month 18 following transplantation. E First presence of anti-donor proliferative response in MLR.

Figure 2

A MLR results for subject NW4 at 5 months post-transplant, showing DSH. B MLR results for subject NW4 at 9 months post-transplant showing persistent DSH. C,D NW4 exhibits cytolytic activity to third party but not donor target cells in CML at month 8 and month 18 following transplantation. E First presence of anti-donor proliferative response in MLR.

Figure 3

Representative hematoxylin and eosin stained sections (10X) of kidney transplant biopsy at 6 months A and one year B post-transplant from subject NW4. Image A shows no acute or chronic rejection, minimal tubular atrophy, and minimal interstitial fibrosis. Image B shows Banff 1A rejection, with interstitial inflammation and lymphocytic infiltration associated with tubulitis. In contrast, all protocol biopsies on subjects with high levels of donor chimerism have been normal at all times tested. C thru E: Periodic acid-Schiff staining (20X magnification) of renal allograft from representative subject (#3) with stable donor chimerism and donor specific tolerance. C Implantation biopsy at time of live donor nephrectomy; D One year post-stem cell/kidney transplant; E Two years post-FcRx/kidney transplant, one year off all immunosuppression.