Impact and predictors of positive response to desensitization in pediatric heart transplant candidates.

BACKGROUND: Desensitization, the process of reducing anti-human leukocyte antigen (HLA) antibodies in sensitized patients awaiting heart transplantation (HT), has unclear efficacy in pediatric HT candidates. METHODS: Pediatric HT candidates listed at our institution between January 1, 2013 and June 30, 2018 were retrospectively evaluated. Sensitization was defined as the calculated panel reactive antibody (cPRA) ≥ 10% with ≥ 1 a strong positive antibody. The desensitization response was defined as a ≥ 25% reduction in the mean fluorescence intensity (MFI) for ≥ 90% of the strong positive antibodies on follow-up panel reactive antibody (PRA) testing before waitlist removal, HT, or death (data available for 13 patients). RESULTS: The HT candidates were categorized as sensitized receiving desensitization therapy (ST, n = 14), sensitized not receiving therapy (SNT, n = 18), or non-sensitized (n = 55). A desensitization response was observed in 8 (62%) of the ST upon repeat PRA testing, with the ST responders receiving more doses of intravenous immunoglobulin (IVIG) (8 vs 2, p < 0.05). The anti-HLA class I antibodies were particularly resistant for non-responders (p = 1.9 × 10-4). The combination of homograft and ventricular assist device was more sensitizing than either alone (p = 3.1 × 10-4). However, these sensitization risk factors did not impact the desensitization response. The ST was associated with a higher likelihood of remaining listed and a longer waitlist time without substantially impacting the HT rate, waitlist mortality, or early post-HT outcomes. CONCLUSIONS: Most ST patients had a favorable response to desensitization, with a dose-dependent response observed for IVIG. The anti-HLA class likely impacts the ST response, whereas traditional sensitization risk factors had no impact on the response.

Assessing the utilization of high-resolution 2-field HLA typing in solid organ transplantation.

HLA typing in solid organ transplantation (SOT) is necessary for determining HLA-matching status between donor-recipient pairs and assessing patients' anti-HLA antibody profiles. Histocompatibility has traditionally been evaluated based on serologically defined HLA antigens. The evolution of HLA typing and antibody identification technologies, however, has revealed many limitations with using serologic equivalents for assessing compatibility in SOT. The significant improvements to HLA typing introduced by next-generation sequencing (NGS) require an assessment of the impact of this technology on SOT. We have assessed the role of high-resolution 2-field HLA typing (HR-2F) in SOT by retrospectively evaluating NGS-typed pre- and post-SOT cases. HR-2F typing was highly instructive or necessary in 41% (156/385) of the cases. Several pre- and posttransplant scenarios were identified as being better served by HR-2F typing. Five different categories are presented with specific case examples. The experience of another center (Temple University Hospital) is also included, whereby 21% of the cases required HR-2F typing by Sanger sequencing, as supported by other legacy methods, to properly address posttransplant anti-HLA antibody issues.