Rapid desensitization through immunoadsorption during cardiopulmonary bypass. A novel method to facilitate human leukocyte antigen incompatible heart transplantation.

BACKGROUND: Anti-human leukocyte antigen (HLA)-antibody production represents a major barrier to heart transplantation, limiting recipient compatibility with potential donors and increasing the risk of complications with poor waiting-list outcomes. Currently there is no consensus to when desensitization should take place, and through what mechanism, meaning that sensitized patients must wait for a compatible donor for many months, if not years. We aimed to determine if intraoperative immunoadsorption could provide a potential desensitization methodology. METHODS: Anti-HLA antibody-containing whole blood was added to a Cardiopulmonary bypass (CPB) circuit set up to mimic a 20 kg patient undergoing heart transplantation. Plasma was separated and diverted to a standalone, secondary immunoadsorption system, with antibody-depleted plasma returned to the CPB circuit. Samples for anti-HLA antibody definition were taken at baseline, when combined with the CPB prime (on bypass), and then every 20 min for the duration of treatment (total 180 min). RESULTS: A reduction in individual allele median fluorescence intensity (MFI) to below clinically relevant levels (<1000 MFI), and in the majority of cases below the lower positive detection limit (<500 MFI), even in alleles with a baseline MFI >4000 was demonstrated. Reduction occurred in all cases within 120 min, demonstrating efficacy in a time period usual for heart transplantation. Flowcytometric crossmatching of suitable pseudo-donor lymphocytes demonstrated a change from T cell and B cell positive channel shifts to negative, demonstrating a reduction in binding capacity. CONCLUSIONS: Intraoperative immunoadsorption in an ex vivo setting demonstrates clinically relevant reductions in anti-HLA antibodies within the normal timeframe for heart transplantation. This method represents a potential desensitization technique that could enable sensitized children to accept a donor organ earlier, even in the presence of donor-specific anti-HLA antibodies.

Lung transplantation in an 18-month-old with donor specific antibodies - The use of intraoperative, targeted plasma exchange.

BACKGROUND: Sensitised patients undergoing Human Leukocyte Antigen-incompatible transplantation are at increased risk of hyperacute rejection and may be predisposed to antibody-mediated rejection, chronic lung allograft dysfunction and higher mortality. CASE: We present a case of primary lung transplantation in the setting of late identification of donor specific antibodies treated with intraoperative target plasma exchange. The patient was treated with fresh human plasma to a final volume of 1.5 times the patient's systemic circulation. From a pre-transplant mean fluorescence intensity of 5002, donor-specific antibodies were undetectable following plasma exchange on single antigen bead assay. CONCLUSIONS: This method represents a potential desensitisation technique for use in the intraoperative period.

Pediatric heart transplantation following donation after circulatory death, distant procurement, and ex-situ perfusion.

BACKGROUND: Limited availability of suitable donor hearts remains a challenge to pediatric heart transplantation, contributing to waitlist mortality. Controlled donation after circulatory death (DCD) has demonstrated success in adults. Early series of pediatric DCD heart transplantation using cold storage alone reported significant early mortality. We report a collaboration between 2 centers in the United Kingdom, combining expertise in adult DCD organ retrieval and pediatric transplantation. METHODS: This retrospective series comprises 6 children (4 male, all >20 kg) undergoing DCD heart transplantation at Great Ormond Street Hospital between 1 February and 30 September 2020, following retrieval with direct procurement and perfusion using portable normothermic machine perfusion by the Royal Papworth Hospital service. Baseline characteristics and 1-year follow-up were compared to 9 children who underwent donation after brain death (DBD) transplants contemporaneously. RESULTS: Mean DCD donor age was 24.67 years and mean DCD recipient age was 13.83 years. Mean functional warm ischemic time was 28.5 minutes and ex-situ heart perfusion time was 280 minutes. Median ICU and hospital stay were 9 and 17 days, respectively. All children survived to 1-year post-transplant. Survival and ICU and hospital stay were similar between the DCD and DBD cohorts. Performing DCD transplants resulted in a 66.7% increase in transplants for children >20 kg at GOSH during the study. CONCLUSIONS: This series demonstrates that DCD heart transplant can be performed safely with excellent short-term survival in children. Although the cohort is small, there was no significant difference in major outcomes compared to a DBD cohort.