Incidence, characterization, and impact of newly detected donor-specific anti-HLA antibody in the first year after pediatric heart transplantation: A report from the CTOTC-04 study

Data on the clinical importance of newly detected donor-specific anti-HLA antibodies (ndDSAs) after pediatric heart transplantation are lacking despite mounting evidence of the detrimental effect of de novo DSAs in solid organ transplantation. We prospectively tested 237 pediatric heart transplant recipients for ndDSAs in the first year posttransplantation to determine their incidence, pattern, and clinical impact. One-third of patients developed ndDSAs; when present, these were mostly detected within the first 6 weeks after transplantation, suggesting that memory responses may predominate over true de novo DSA production in this population. In the absence of preexisting DSAs, patients with ndDSAs had significantly more acute cellular rejection but not antibody-mediated rejection, and there was no impact on graft and patient survival in the first year posttransplantation. Risk factors for ndDSAs included common sensitizing events. Given the early detection of the antibody response, memory responses may be more important in the first year after pediatric heart transplantation and patients with a history of a sensitizing event may be at risk even with a negative pretransplantation antibody screen. The impact on late graft and patient outcomes of first-year ndDSAs is being assessed in an extended cohort of patients.

Pediatric heart transplantation across a positive crossmatch: First year results from the CTOTC-04 multi-institutional study

Sensitization is common in pediatric heart transplant candidates and waitlist mortality is high. Transplantation across a positive crossmatch may reduce wait time, but is considered high risk. We prospectively recruited consecutive candidates at eight North American centers. At transplantation, subjects were categorized as nonsensitized or sensitized (presence of ≥1 HLA antibody with MFI ≥1000 using single antigen beads). Sensitized subjects were further classified as complement-dependent cytotoxicity crossmatch (CDC-crossmatch) positive or negative and as donor-specific antibodies (DSA) positive or negative. Immunosuppression was standardized. CDC-crossmatch-positive subjects also received perioperative antibody removal, maintenance corticosteroids, and intravenous immunoglobulin. The primary endpoint was the 1 year incidence rate of a composite of death, retransplantation, or rejection with hemodynamic compromise. 317 subjects were screened, 290 enrolled and 240 transplanted (51 with pretransplant DSA, 11 with positive CDC-crossmatch). The incidence rates of the primary endpoint did not differ statistically between groups; nonsensitized 6.7% (CI: 2.7%, 13.3%), sensitized crossmatch positive 18.2% (CI: 2.3%, 51.8%), sensitized crossmatch negative 10.7% (CI: 5.7%, 18.0%), P = .2354. The primary endpoint also did not differ by DSA status. Freedom from antibody-mediated and cellular rejection was lower in the crossmatch positive group and/or in the presence of DSA. Follow-up will determine if acceptable outcomes can be achieved long-term.

A randomized double-blind, placebo controlled trial of steroid withdrawal after pediatric renal transplantation

In an effort to reduce rejection, extend allograft survival and minimize complications, we hypothesized that robust immunosuppression during the first 6 months after transplantation would allow for the safe withdrawal of steroids. A total of 274 pediatric subjects were enrolled and received an anti-CD25 antibody, sirolimus, calcineurin inhibitor and steroids. At 6 months after transplantation, subjects were randomized to steroid withdrawal (n=73) versus continued low-dose steroids (n=59). This study was stopped prior to target enrollment because of the incidence of post-transplant lymphoproliferative disorder. At the time of study termination, 132 subjects had been randomized and were available for analysis. At 18 months after transplantation, there was no difference in the standardized height z score; however, the standardized height velocity was greater in the steroid withdrawal group compared to the control group (p=0.033). There were no differences in acute rejection episodes between treatment groups. The 3-year allograft survival rate was 84.5% in the control group and 98.6% in the steroid withdrawal group (p=0.002). The immunosuppressive protocol utilized in this study allowed for the withdrawal of steroids without an increased risk of rejection or allograft loss. However, the complications associated with the use of this immunosuppressive protocol were too high to recommend its routine use in pediatric patients.