Let's get physical: Aerobic capacity, muscle strength, and muscle endurance after pediatric heart transplantation.

BACKGROUND: Pediatric heart (HTx) and kidney transplant (KTx) recipients may have lower physical fitness than healthy children. This study sought to quantify fitness levels in transplant recipients, investigate associations to clinical factors and quality of life, and identify whether a quick, simple wall-sit test is feasible as a surrogate for overall fitness for longitudinal assessment. METHODS: Aerobic capacity (6-min walk test, 6MWT), normalized muscle strength, muscle endurance, physical activity questionnaire (PAQ), and quality of life (PedsQL™) were prospectively assessed in transplanted children and matched healthy controls. RESULTS: Twenty-two HTx were compared to 20 controls and 6 KTx. 6MWT %predicted was shorter in HTx (87.2 [69.9-118.6] %) than controls (99.9 [80.4-120] %), but similar to KTx (90.3 [78.6-115] %). Muscle strength was lower in HTx deltoids (6.15 [4.35-11.3] kg/m2) and KTx quadriceps (9.27 [8.65-19.1] kg/m2) versus controls. Similarly, muscle endurance was lower in HTx push-ups (28.6 [0-250] %predicted), KTx push-ups (8.35 [0-150] %predicted), HTx curl-ups (115 [0-450] %predicted), and KTx wall-sit time (18.5 [10.0-54.0] s) than controls. In contrast to HTx with only 9%, all KTx were receiving steroid therapy. The wall-sit test significantly correlated with other fitness parameters (normalized quadriceps strength R = .31, #push-ups R = .39, and #curl-ups R = .43) and PedsQL™ (R = .36). CONCLUSIONS: Compared to controls, pediatric HTx and KTx have similarly lower aerobic capacity, but different deficits in muscle strength, likely related to steroid therapy in KTx. The convenient wall-sit test correlates with fitness and reported quality of life, and thus could be a useful easy routine for longitudinal assessment.

ABO-incompatible heart transplantation-evolution of a revolution.

In the 1990s, neonates born with severe congenital heart disease faced more than 50% mortality awaiting an ABO-compatible (ABOc) transplant donor. This desperate situation, together with knowledge of gaps in the adaptive immune system in early childhood, led to the clinical exploration of intentional ABO-incompatible (ABOi) heart transplantation. In 2001, West et al. reported the first series of 10 infants in Canada. Since then, consideration of ABOi heart donors has become the standard of care for children awaiting transplantation in the first few years of life, resulting in reduced wait times and better organ utilization with noninferior post-transplant outcomes compared to ABOc recipients. This state-of-the-art review discusses the clinical development and evolution, underlying and resulting immunological aspects, current challenges, and future directions of ABOi heart transplantation.

Advancing mouse models for transplantation research.

Mouse models have been instrumental in understanding mechanisms of transplant rejection and tolerance, but cross-study reproducibility and translation of experimental findings into effective clinical therapies are issues of concern. The Mouse Models in Transplantation symposium gathered scientists and physician-scientists involved in basic and clinical research in transplantation to discuss the strengths and limitations of mouse transplant models and strategies to enhance their utility. Participants recognized that increased procedure standardization, including the use of prespecified, defined endpoints, and statistical power analyses, would benefit the field. They also discussed the generation of new models that incorporate environmental and genetic variables affecting clinical outcomes as potentially important. If implemented, these strategies are expected to improve the reproducibility of mouse studies and increase their translation to clinical trials and, ideally, new Food and Drug Administration-approved drugs.

Evaluating a Telemedicine Video Game-Linked High-Intensity Interval Training Exercise Programme in Paediatric Heart Transplant Recipients.

Paediatric heart transplant recipients (HTRs) have reduced exercise capacity, physical activity (PA), health-related quality of life (HRQoL), and self-efficacy towards PA. Exercise interventions have demonstrated improvements in exercise capacity and functional status in adult HTRs, with a specific emerging interest in the role of high-intensity interval training (HIIT). Studies of exercise interventions in paediatric HTRs have been limited and nonrandomized to date. HIIT has not yet been evaluated in paediatric HTRs. We thus seek to evaluate the safety and feasibility of a randomized crossover trial of a 12-week, home-based, video game-linked HIIT intervention using a cycle ergometer with telemedicine and remote physiological monitoring capabilities (MedBIKE) in paediatric HTRs. The secondary objective is to evaluate the impact of the intervention on (1) exercise capacity, (2) PA, (3) HRQoL and self-efficacy towards PA, and (4) sustained changes in secondary outcomes at 6 and 12 months after intervention. After a baseline assessment of the secondary outcomes, participants will be randomized to receive the MedBIKE intervention (12 weeks, 36 sessions) or usual care. After the intervention and a repeated assessment, all participants will cross over. Follow-up assessments will be administered at 6 and 12 months after the MedBIKE intervention. We anticipate that the MedBIKE intervention will be feasible and safely yield sustained improvements in exercise capacity, PA, HRQoL, and self-efficacy towards PA in paediatric HTRs. This study will serve as the foundation for a larger, multicentre randomized crossover trial and will help inform exercise rehabilitation programmes for paediatric HTRs.

La tolérance à l'effort, le niveau d'activité physique (AP), le score de la qualité de vie liée à la santé (QVLS) ainsi que l'auto-efficacité à la pratique d'une AP se trouvent diminués chez les patients pédiatriques ayant reçu une transplantation cardiaque. Il a été montré que les exercices physiques permettent d'améliorer la tolérance à l'effort ainsi que le statut fonctionnel chez les patients adultes ayant reçu une transplantation cardiaque. D'ailleurs, le rôle de l'entraînement par intervalles de haute intensité (EIHI) suscite depuis peu un nouvel intérêt à cet égard. Les études réalisées à ce jour sur les programmes d'activité physique chez les patients pédiatriques ayant reçu une transplantation cardiaque sont toutefois peu nombreuses et ne reposent pas sur une répartition aléatoire. De plus, l'EIHI n'a pas encore été évalué chez ce groupe de patients. La présente étude a donc pour objectif d'évaluer la faisabilité et l'innocuité d'un essai clinique croisé à répartition aléatoire d'une durée de 12 semaines chez des patients pédiatriques ayant reçu une transplantation cardiaque. Le programme d'activité physique prendra la forme d'un EIHI à la maison au moyen d'un jeu vidéo et d'une bicyclette ergométrique permettant une assistance et une surveillance des données physiologiques à distance (MedBIKE). Les objectifs secondaires de l'étude consistent à évaluer les effets du programme sur : 1) la tolérance à l'effort; 2) le niveau d'AP; 3) la QVLS ainsi que l'auto-efficacité à la pratique d'une AP; et 4) le maintien des améliorations relatives aux critères d'évaluation se-condaires à 6 et 12 mois. Après une évaluation initiale des critères d'évaluation secondaires, les participants seront répartis aléatoirement dans le groupe suivant le programme à l'aide du vélo MedBIKE (36 séances réparties sur 12 semaines) ou dans le groupe recevant le traitement usuel. Tous les participants changeront ensuite de groupe, et une nouvelle évaluation des critères d'évaluation se-condaires sera effectuée. Les évaluations de suivi auront lieu 6 et 12 mois après la fin du programme. On s'attend à ce que ce dernier soit sûr, facile à suivre et accompagné d'améliorations soutenues de la tolérance à l'effort, du niveau d'AP, de la QVLS et de l'auto-efficacité à la pratique d'une AP chez les patients pédiatriques ayant reçu une transplantation cardiaque. Cette étude servira de modèle à un essai clinique croisé, multicentrique, à répartition aléatoire de plus grande envergure. Elle permettra aussi de générer des renseignements utiles pour les programmes de réadaptation destinés aux patients pédiatriques ayant reçu une transplantation cardiaque.

First-in-human therapy with Treg produced from thymic tissue (thyTreg) in a heart transplant infant.

Due to their suppressive capacity, regulatory T cells (Tregs) have attracted growing interest as an adoptive cellular therapy for the prevention of allograft rejection, but limited Treg recovery and lower quality of adult-derived Tregs could represent an obstacle to success. To address this challenge, we developed a new approach that provides large quantities of Tregs with high purity and excellent features, sourced from thymic tissue routinely removed during pediatric cardiac surgeries (thyTregs). We report on a 2-year follow-up of the first patient treated worldwide with thyTregs, included in a phase I/II clinical trial evaluating the administration of autologous thyTreg in infants undergoing heart transplantation. In addition to observing no adverse effects that could be attributed to thyTreg administration, we report that the Treg frequency in the periphery was preserved during the 2-year follow-up period. These initial results are consistent with the trial objective, which is to confirm safety of the autologous thyTreg administration and its capacity to restore the Treg pool.

Sex, T Cells, and the Microbiome in Natural ABO Antibody Production in Mice.

BACKGROUND: "Natural" ABO antibodies (Abs) are produced without known exposure to A/B carbohydrate antigens, posing significant risks for hyperacute rejection during ABO-incompatible transplantation. We investigated anti-A "natural" ABO antibodies versus intentionally induced Abs with regard to the need for T-cell help, the impact of sex, and stimulation by the microbiome. METHODS: Anti-A was measured by hemagglutination assay of sera from untreated C57BL/6 wild-type (WT) or T cell-deficient mice of both sexes. Human ABO-A reagent blood cell membranes were injected intraperitoneally to induce anti-A Abs. The gut microbiome was eliminated by maintenance of mice in germ-free housing. RESULTS: Compared with WT mice, CD4 + T-cell knockout (KO), major histocompability complex-II KO, and αß/γδ T-cell receptor KO mice produced much higher levels of anti-A nAbs; females produced dramatically more anti-A nAbs than males, rising substantially with puberty. Sensitization with human ABO-A reagent blood cell membranes did not induce additional anti-A in KO mice, unlike WT. Sex-matched CD4 + T-cell transfer significantly suppressed anti-A nAbs in KO mice and rendered mice responsive to A-sensitization. Even under germ-free conditions, WT mice of several strains produced anti-A nAbs, with significantly higher anti-A nAbs levels in females than males. CONCLUSIONS: Anti-A nAbs were produced without T-cell help, without microbiome stimulation, in a sex- and age-dependent manner, suggestive of a role for sex hormones in regulating anti-A nAbs. Although CD4 + T cells were not required for anti-A nAbs, our findings indicate that T cells regulate anti-A nAb production. In contrast to anti-A nAbs, induced anti-A production was T-cell dependent without a sex bias.

Perceived Needs Among Healthcare Providers Caring for Seriously Ill Adults Regarding Electronic Health Record Triggers for Palliative Care Referral.

Many healthcare facilities in the United States currently utilize electronic health record triggers to promote and facilitate palliative care referral. The purpose of this study was to explore perceived needs regarding electronic health record trigger criteria for palliative care referral among healthcare providers caring for seriously ill adult hospitalized patients in a teaching hospital in New York State. A qualitative descriptive approach was utilized with use of individual semistructured interviews. Braun and Clarke's Reflexive Thematic Analysis method was used to analyze data. Data analysis generated one overarching theme, I'm in Favor of an Electronic Health Record Automatic Trigger for Palliative Care , and three key themes, Build a Checklist Screening Tool Into Epic With Predefined Conditions and a Palliative Consult in the Admission Order Set , If Providers Call a Palliative Care Consult Sooner, We Give Patients a Better Quality of Life , and Providers Need to Be Aware of the Different Facets of What Palliative Care Actually Does. Findings revealed that all participants supported incorporating electronic health record palliative care triggers. Future research is needed exploring provider palliative care education approaches to promote understanding of palliative care services and to address personal and/or professional bias.

Prospective examination of HLA sensitization after VAD implantation in children and adults.

BACKGROUND: Ventricular assist devices (VADs) have improved survival to heart transplantation (HTx). However, VADs have been associated with development of antibodies against human leukocyte antigen (HLA-Ab) which may limit the donor pool and decrease survival post-HTx. Since HLA-Ab development after VAD insertion is poorly understood, the purpose of this prospective single-center study was to quantify the incidence of and evaluate risk factors for HLA-Ab development across the age spectrum following VAD implantation. METHODS: Adult and pediatric patients undergoing VAD placement as bridge to transplant or transplant candidacy between 5/2016 and 7/2020 were enrolled. HLA-Ab were assessed pre-VAD and at 1-, 3-, and 12-months post-implant. Factors associated with HLA-Ab development post-VAD implant were explored using univariate and multivariate logistic regression. RESULTS: 15/41 (37%) adults and 7/17 (41%) children developed new HLA-Ab post-VAD. The majority of patients (19/22) developed HLA-Ab within two months of implant. New class I HLA-Ab were more common (87% adult, 86% pediatric). Prior pregnancy was strongly associated with HLA-Ab development in adults post-VAD (HR 16.7, 95% CI 1.8-158, p = 0.01). Of the patients who developed new HLA-Ab post-VAD, in 45% (10/22) the HLA-Ab resolved while in 55% (12/22) the HLA-Ab persisted. CONCLUSION: More than one-third of adult and pediatric VAD patients developed new HLA-Ab early after VAD implant with the majority having class I antibodies. Prior pregnancy was strongly associated with post-VAD HLA-Ab development. Further studies are needed to predict regression or persistence of HLA-Ab developed post-VAD, to understand modulation of individuals' immune responses to sensitizing events, and to determine whether transiently detected HLA-Ab post-VAD recur and have long-term clinical impact post-heart transplantation.

Regulatory T Cell Biomarkers Identify Patients at Risk of Developing Acute Cellular Rejection in the First Year Following Heart Transplantation.

BACKGROUND: Acute cellular rejection (ACR), an alloimmune response involving CD4+ and CD8+ T cells, occurs in up to 20% of patients within the first year following heart transplantation. The balance between a conventional versus regulatory CD4+ T cell alloimmune response is believed to contribute to developing ACR. Therefore, tracking these cells may elucidate whether changes in these cell populations could signal ACR risk. METHODS: We used a CD4+ T cell gene signature (TGS) panel that tracks CD4+ conventional T cells (Tconv) and regulatory T cells (Treg) on longitudinal samples from 94 adult heart transplant recipients. We evaluated combined diagnostic performance of the TGS panel with a previously developed biomarker panel for ACR diagnosis, HEARTBiT, while also investigating TGS' prognostic utility. RESULTS: Compared with nonrejection samples, rejection samples showed decreased Treg- and increased Tconv-gene expression. The TGS panel was able to discriminate between ACR and nonrejection samples and, when combined with HEARTBiT, showed improved specificity compared with either model alone. Furthermore, the increased risk of ACR in the TGS model was associated with lower expression of Treg genes in patients who later developed ACR. Reduced Treg gene expression was positively associated with younger recipient age and higher intrapatient tacrolimus variability. CONCLUSIONS: We demonstrated that expression of genes associated with CD4+ Tconv and Treg could identify patients at risk of ACR. In our post hoc analysis, complementing HEARTBiT with TGS resulted in an improved classification of ACR. Our study suggests that HEARTBiT and TGS may serve as useful tools for further research and test development.

Immunogenicity, Safety, and Breakthrough Severe Acute Respiratory Syndrome Coronavirus 2 Infections After Coronavirus Disease 2019 Vaccination in Organ Transplant Recipients: A Prospective Multicenter Canadian Study.

Background: Solid organ transplant (SOT) recipients are at risk for severe coronavirus disease 2019 (COVID-19), despite vaccination. Our study aimed to elucidate COVID-19 vaccine immunogenicity and evaluate adverse events such as hospitalization, rejection, and breakthrough infection in a SOT cohort. Methods: We performed a prospective, observational study on 539 adult SOT recipients (age ≥18 years old) recruited from 7 Canadian transplant centers. Demographics including transplant characteristics, vaccine types, and immunosuppression and events such as hospitalization, infection, and rejection were recorded. Follow ups occurred every 4-6 weeks postvaccination and at 6 and 12 months from first dose. Serum was processed from whole blood to measure anti-receptor binding domain (RBD) antibodies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein to assess immunogenicity. Results: The COVID-19 vaccines were found to be safe in SOT recipients with low rates of rejection requiring therapy (0.7%). Immunogenicity improved after the third vaccine dose, yet 21% developed no anti-RBD response. Factors such as older age, lung transplantation, chronic kidney disease, and shorter duration from transplant were associated with decreased immunogenicity. Patients with at least 3 doses were protected from hospitalization when experiencing breakthrough infections. Significantly increased anti-RBD levels were observed in patients who received 3 doses and had breakthrough infection. Conclusions: Three or four doses of COVID-19 vaccines were safe, increased immunogenicity, and protected against severe disease requiring hospitalization. Infection paired with multiple vaccinations significantly increased anti-RBD response. However, SOT populations should continue to practice infection prevention measures, and they should be prioritized for SARS-CoV-2 pre-exposure prophylactics and early therapeutics.

Siglec-6 mediates the uptake of extracellular vesicles through a noncanonical glycolipid binding pocket.

Immunomodulatory Siglecs are controlled by their glycoprotein and glycolipid ligands. Siglec-glycolipid interactions are often studied outside the context of a lipid bilayer, missing the complex behaviors of glycolipids in a membrane. Through optimizing a liposomal formulation to dissect Siglec-glycolipid interactions, it is shown that Siglec-6 can recognize glycolipids independent of its canonical binding pocket, suggesting that Siglec-6 possesses a secondary binding pocket tailored for recognizing glycolipids in a bilayer. A panel of synthetic neoglycolipids is used to probe the specificity of this glycolipid binding pocket on Siglec-6, leading to the development of a neoglycolipid with higher avidity for Siglec-6 compared to natural glycolipids. This neoglycolipid facilitates the delivery of liposomes to Siglec-6 on human mast cells, memory B-cells and placental syncytiotrophoblasts. A physiological relevance for glycolipid recognition by Siglec-6 is revealed for the binding and internalization of extracellular vesicles. These results demonstrate a unique and physiologically relevant ability of Siglec-6 to recognize glycolipids in a membrane.

Endothelial phosphoinositide 3-kinase-ß inactivation confers protection from immune-mediated vascular injury.

Heart transplant and recipient survival are limited by immune cell-mediated injury of the graft vasculature. We examined the role of the phosphoinositide 3-kinase-ß (PI3Kß) isoform in endothelial cells (EC) during coronary vascular immune injury and repair in mice. In minor histocompatibility-antigen mismatched allogeneic heart grafts, a robust immune response was mounted to each wild-type, PI3Kß inhibitor-treated, or endothelial-selective PI3Kß knockout (ECßKO) graft transplanted to wild-type recipients. However, microvascular EC loss and progressive occlusive vasculopathy only developed in control, but not PI3Kß-inactivated hearts. We observed a delay in inflammatory cell infiltration of the ECßKO grafts, particularly in the coronary arteries. Surprisingly, this was accompanied by an impaired display of proinflammatory chemokine and adhesion molecules by the ECßKO ECs. In vitro, tumor necrosis factor α-stimulated endothelial ICAM1 and VCAM1 expression was blocked by PI3Kß inhibition or RNA interference. Selective PI3Kß inhibition also blocked tumor necrosis factor α-stimulated degradation of inhibitor of nuclear factor kappa Bα and nuclear translocation of nuclear factor kappa B p65 in EC. These data identify PI3Kß as a therapeutic target to reduce vascular inflammation and injury.

Successful ABO incompatible heart transplantation after desensitization therapy in an older child.

BACKGROUND: ABO-incompatible heart transplantation (HTx) has become a standard procedure for children below 2 years of age due to an immunologically immature immune system and associated low isohemagglutinin titers. METHODS: We report a case of an ABO-incompatible HTx (recipient blood group O, donor blood group A) at the age of 5 years and 11 months with a fully matured immune system and previously high isohemagglutinin titers that diminished as a result of human leucocyte antigen (HLA) desensitization therapy with rituximab and immunoglobulins. RESULTS: The anti-A titer at the time of HTx was 1:16 with post-transplant isoagglutinin titers never exceeding 1:4 without any signs of rejection with now 3 years of post-HTx follow-up. CONCLUSIONS: ABO isohemagglutinin titers should be routinely assessed in children undergoing desensitization therapy since ABOi transplantation can be considered in selected cases to expand the donor pool with the option of crossing the ABO barrier to find a better-matched allograft.

'My Transplanted Self': Adolescent recipients' experience of post-traumatic growth following thoracic transplantation.

BACKGROUND: Despite heart and lung transplantation being life-saving therapies for children and adolescents, little research has focused on recipients' lived experience post-transplant. This study captures the subjective experiences of adolescent thoracic transplant recipients, providing insight into the impact of life changes following transplantation in this population. METHODS: A grounded theory approach guided an iterative process of data collection and data analysis. Adolescent heart and lung transplant recipients were recruited from a large Canadian pediatric teaching hospital to participate in one-on-one semi-structured interviews. Analysis using line-by-line coding and constant comparison methods facilitated reflection and agreement on categories and emergent themes. RESULTS: A total of 27 heart and 5 lung transplant recipients (66% female) participated at a median age of 15.9 years and a median time post-transplant of 2.7 years. Participant narratives illuminated three themes describing (1) personal growth - an awareness of personal strengths and coping abilities, (2) relationship growth - a greater appreciation for family and friends, and (3) introspective growth - a developing life philosophy. Findings suggest that adolescents experience an emergent 'transplanted self', positioning thoracic transplantation as a potential catalyst for positive growth and personal change. CONCLUSIONS: The study findings describe pediatric thoracic transplantation as potentially transformative in nature and sheds light on the application of post-traumatic growth theory. Practitioners and researchers are encouraged to acknowledge the possibility of growth, transformation, and positive change that may be possible within the adolescent thoracic transplant experience and leverage such strengths in clinical care.

Evaluating the Potential for ABO-incompatible Islet Transplantation: Expression of ABH Antigens on Human Pancreata, Isolated Islets, and Embryonic Stem Cell-derived Islets.

BACKGROUND: ABO-incompatible transplantation has improved accessibility of kidney, heart, and liver transplantation. Pancreatic islet transplantation continues to be ABO-matched, yet ABH antigen expression within isolated human islets or novel human embryonic stem cell (hESC)-derived islets remain uncharacterized. METHODS: We evaluated ABH glycans within human pancreata, isolated islets, hESC-derived pancreatic progenitors, and the ensuing in vivo mature islets following kidney subcapsular transplantation in rats. Analyses include fluorescence immunohistochemistry and single-cell analysis using flow cytometry. RESULTS: Within the pancreas, endocrine and ductal cells do not express ABH antigens. Conversely, pancreatic acinar tissues strongly express these antigens. Acinar tissues are present in a substantial portion of cells within islet preparations obtained for clinical transplantation. The hESC-derived pancreatic progenitors and their ensuing in vivo-matured islet-like clusters do not express ABH antigens. CONCLUSIONS: Clinical pancreatic islet transplantation should remain ABO-matched because of contaminant acinar tissue within islet preparations that express ABH glycans. Alternatively, hESC-derived pancreatic progenitors and the resulting in vivo-matured hESC-derived islets do not express ABH antigens. These findings introduce the potential for ABO-incompatible cell replacement treatment and offer evidence to support scalability of hESC-derived cell therapies in type 1 diabetes.

Extending the in vivo persistence of synthetic glycoconjugates using a serum-protein binder.

Synthetic glycoconjugates are used in the development of vaccines and the design of inhibitors for glycan-protein interactions. The in vivo persistence of synthetic glycoconjugates is an important factor in their efficacy, especially when prolonged interactions with specific cell types may be required. In this study, we applied a strategy for non-covalent association of an active compound with serum proteins for extension of glycoconjugate half-life in serum. The small molecule, AG10, has previously been used to extend the half-life of small molecules through its high affinity for transthyretin (TTR), a serum protein. Using a tetravalent polyethylene glycol (PEG)-based scaffold we developed a synthetic strategy for glycoconjugates that allowed for controlled addition of multiple tags, such as a TTR affinity tag or fluorophore. We designed a version of AG10 modified at the pyrazole core, named GD10, amenable to our conjugation strategy and introduced to glycoconjugates using a tri-functional linker. This approach allowed for attachment of GD10 and fluorophore tags, as well as carbohydrate antigens. We then tested the influence of the GD10 tag on glycoconjugate half-life in vivo using a mouse model. Our results suggest that the combination of the GD10 tag and the PEG scaffold extended the half-life of glycoconjugates by as much as 10-fold when compared to proteins of similar molecular weight. The GD10 tag was able to extend the half-life of similar glycoconjugates by as much as 2-fold. We observed a role for the terminal saccharide residue of the carbohydrate antigen and confirmed that conjugates were able to penetrate multiple compartments in vivo including bone marrow, lymph nodes, and other organs. The introduction of the GD10 tag did not obstruct the ability of conjugates to interact with lectin receptors. We conclude that serum protein binders can be used to extend the persistence of glycoconjugates in vivo.