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.

Sialic acid-containing glycolipids mediate binding and viral entry of SARS-CoV-2.

Emerging evidence suggests that host glycans influence severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Here, we reveal that the receptor-binding domain (RBD) of the spike (S) protein on SARS-CoV-2 recognizes oligosaccharides containing sialic acid (Sia), with preference for monosialylated gangliosides. Gangliosides embedded within an artificial membrane also bind to the RBD. The monomeric affinities (Kd = 100-200 µM) of gangliosides for the RBD are similar to another negatively charged glycan ligand of the RBD proposed as a viral co-receptor, heparan sulfate (HS) dp2-dp6 oligosaccharides. RBD binding and infection of SARS-CoV-2 pseudotyped lentivirus to angiotensin-converting enzyme 2 (ACE2)-expressing cells is decreased following depletion of cell surface Sia levels using three approaches: sialyltransferase (ST) inhibition, genetic knockout of Sia biosynthesis, or neuraminidase treatment. These effects on RBD binding and both pseudotyped and authentic SARS-CoV-2 viral entry are recapitulated with pharmacological or genetic disruption of glycolipid biosynthesis. Together, these results suggest that sialylated glycans, specifically glycolipids, facilitate viral entry of SARS-CoV-2.

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.

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.

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.

The experiences of children with a cardiac transplant, their families and health care providers in the COVID-19 pandemic.

BACKGROUND: The COVID-19 pandemic has had deleterious impacts on pediatric patients and families, as well as the healthcare providers who have attended to their care needs. METHODS: In this qualitative study, children with a cardiac transplant, as well as their families and healthcare providers were interviewed to explore the impact of the COVID-19 pandemic on pediatric care, as well as on patients' and their families' daily lives. Participants were recruited from a children's hospital in western Canada. Fifteen caregiving parents of transplanted children, 2 young patients, and 8 healthcare providers participated in interviews. RESULTS: Findings highlighted how families and their healthcare providers experienced pandemic-related shifts. Themes highlighted experiences, which entailed (1) initially hearing about the COVID-19 pandemic; (2) learning about their new reality; (3) adjusting to the pandemic; (4) adjusting to shifts in pediatric services; (5) evolving a view on the future, and (6) offering recommendations for cardiac care in a pandemic. CONCLUSIONS: Study implications emphasize the need to critically reflect on, and advance, methods of helping young patients and their families in pandemic circumstances, and supporting healthcare providers.

Alterations in the immune phenotype of thymectomized children and the development of atopic disorders after heart transplantation.

BACKGROUND: Atopic disorders are more common in children after heart transplant (HTx). We hypothesized that HTx at an early age and thymus excision (TE) affect development of T and B cells, especially regulatory T cells (Tregs), which help maintain tolerance. METHODS: In this single-center study including 24 patients transplanted between 2013 and 2018, we investigated lymphocyte patterns in relation to these factors using flow cytometry. Clinical data were collected from standardized questionnaires and medical charts. Patients were stratified into TE and non-TE groups as well as patients with and without post-transplant atopy development/worsening. RESULTS: 64% of TE patients experienced new or worsening asthma/eczema post-transplant compared to 20% of non-TE patients. TE patients had higher total Treg proportions (CD4+CD25+CD127lo) than non-TE patients (p = .043), but borderline significantly lower naïve Tregs (CD45RA+CD27-) (p = .057). Memory CD4+ T cells were higher in TE patients in trend (p = .084). Total Tregs did not differ between atopic/nonatopic groups, although naïve Tregs were significantly lower in atopic patients (p = .028). Memory CD4+ T cells were higher in atopic patients in trend (p = .082). IgM+IgD+ B cells were higher in nonatopic patients in trend (p = .064). CONCLUSIONS: New/worsening atopy is more common in thymectomized HTx children and is associated with alterations in T-cell profiles. Avoiding TE may prevent these alterations and reduce incidence of atopy post-HTx.

Mental health impacts of the COVID-19 pandemic on children with underlying health and disability issues, and their families and health care providers.

Objectives: The COVID-19 pandemic has impacted mental health at a population level. Families of children with health vulnerabilities have been disproportionately affected by pandemic-related policies and service disruptions as they substantially rely on the health and social care system. We elicited the impact of the COVID-19 pandemic on children with health and disability-related vulnerabilities, their families, and their health care providers (HCPs). Methods: Children with diverse health vulnerabilities (cardiac transplantation, respiratory conditions, sickle cell disease, autism spectrum disorder, mental health issues, and nearing the end of life due to a range of underlying causes), as well as their parents and HCPs, participated in semi-structured interviews. Data were analyzed using qualitative content analysis in determining themes related to impact and recommendations for practice improvement. Results: A total of 262 participants (30 children, 76 parents, 156 HCPs) were interviewed. Children described loneliness and isolation; parents described feeling burnt out; and HCPs described strain and a sense of moral distress. Themes reflected mental health impacts on children, families, and HCPs, with insufficient resources to support mental health; organizational and policy influences that shaped service delivery; and recommendations to enhance service delivery. Conclusion: Children with health vulnerabilities, their families and HCPs incurred profound mental health impacts due to pandemic-imposed public health restrictions and care shifts. Recommendations include the development and application of targeted pandemic information and mental health supports. These findings amplify the need for capacity building, including proactive strategies and mitigative planning in the event of a future pandemic.

Characterization of ABH-subtype donor-specific antibodies in ABO-A-incompatible kidney transplantation.

ABO-incompatible (ABOi) transplantation requires preemptive antibody reduction; however, the relationship between antibody-mediated rejection (AMR) and ABO-antibodies, quantified by hemagglutination (HA), is inconsistent, possibly reflecting variable graft resistance to AMR or HA assay limitations. Using an ABH-glycan microarray, we quantified ABO-A antigen-subtype (A-subtype)-specific IgM and IgG in 53 ABO-O recipients of ABO-A kidneys, before and after antibody removal (therapeutic plasma exchange [TPE] or ABO-A-trisaccharide immunoadsorption [IA]) and 1-year posttransplant. IgM binding to all A-subtypes correlated highly (R2  ≥ .90) and A-subtype antibody specificities was reduced equally by IA versus TPE. IgG binding to the A-subtypes (II-IV) expressed in kidney correlated poorly (.27 ≤ R2  ≤ .69). Reduction of IgG specific to A-subtype-II was equivalent for IA and TPE, whereas IgG specific to A-subtypes-III/IV was not as greatly reduced by IA (p < .005). One-year posttransplant, IgG specific to A-II remained the most reduced antibody. Immunostaining revealed only A-II on vascular endothelium but A-subtypes II-III/IV on tubular epithelium. These results show that ABO-A-trisaccharide is sufficient for IgM binding to all A-subtypes; this is true for IgG binding to A-II, but not subtypes-III/IV, which exhibits varying degrees of specificity. We identify A-II as the major, but importantly not the sole, antigen relevant to treatment and immune modulation in adult ABO-A-incompatible kidney transplantation.

Benefits and challenges with diagnosing chronic and late acute GVHD in children using the NIH consensus criteria.

Chronic graft-versus-host disease (cGVHD) and late acute graft-versus-host disease (L-aGVHD) are understudied complications of allogeneic hematopoietic stem cell transplantation in children. The National Institutes of Health Consensus Criteria (NIH-CC) were designed to improve the diagnostic accuracy of cGVHD and to better classify graft-versus-host disease (GVHD) syndromes but have not been validated in patients <18 years of age. The objectives of this prospective multi-institution study were to determine: (1) whether the NIH-CC could be used to diagnose pediatric cGVHD and whether the criteria operationalize well in a multi-institution study; (2) the frequency of cGVHD and L-aGVHD in children using the NIH-CC; and (3) the clinical features and risk factors for cGVHD and L-aGVHD using the NIH-CC. Twenty-seven transplant centers enrolled 302 patients <18 years of age before conditioning and prospectively followed them for 1 year posttransplant for development of cGVHD. Centers justified their cGVHD diagnosis according to the NIH-CC using central review and a study adjudication committee. A total of 28.2% of reported cGVHD cases was reclassified, usually as L-aGVHD, following study committee review. Similar incidence of cGVHD and L-aGVHD was found (21% and 24.7%, respectively). The most common organs involved with diagnostic or distinctive manifestations of cGVHD in children include the mouth, skin, eyes, and lungs. Importantly, the 2014 NIH-CC for bronchiolitis obliterans syndrome perform poorly in children. Past acute GVHD and peripheral blood grafts are major risk factors for cGVHD and L-aGVHD, with recipients ≥12 years of age being at risk for cGVHD. Applying the NIH-CC in pediatrics is feasible and reliable; however, further refinement of the criteria specifically for children is needed.

The Impact of Sex on Alloimmunity.

Transplantation outcomes are known to be affected by multiple factors, including donor and recipient sex. Aside from the physiological characteristics of male and female donor allografts, accumulating evidence suggests that additional features underlie sex-specific immune responses that affect graft survival. We discuss here aspects of innate and adaptive alloimmunity that are specific to males and females in the context of underlying genetic and hormonal factors. These differences likely contribute to the observed disparities in graft survival. Understanding these features in more detail may lead to improved strategies for optimizing the results of organ transplantation.

Patient-reported outcome measures in pediatric solid organ transplantation: Exploring stakeholder perspectives on clinical implementation through qualitative description.

PURPOSE: Patient-reported outcome measures (PROMs) are standardized instruments used to collect data about the subjective assessment of medical care from the patient perspective. Implementing PROMs within pediatric clinical settings has gained increasing importance as health services prioritize patient-centred pediatric care. This study explores the perspectives of pediatric solid organ transplant patients, caregivers, and healthcare practitioners (HCPs) on implementing PROMs into clinical practice. METHODS: Qualitative description methods were used to elicit stakeholder perspectives. Semi-structured interviews were conducted across five Canadian transplant centres. Purposive sampling was used to obtain maximum variation across age, gender, and transplant program for all participants, as well as discipline for HCPs. RESULTS: The study included a total of 63 participants [patients (n = 20), caregivers (n = 22) and HCPs (n = 21)]. Nearly all participants endorsed the implementation of PROMs to enhance pediatric transplant clinical care. Three primary roles for PROMs emerged: (1) to bring a transplant patient's overall well-being into the clinical care conversation; (2) to improve patient communication and engagement; and, (3) to inform the practice of clinical pediatric transplant care. Insights for effective implementation included completing electronic PROMs remotely and prior to clinical appointments by patients who are eight to 10 years of age or older. CONCLUSIONS: This study contributes to current research that supports the use of PROMs in clinical pediatric care and guides their effective implementation into practice. Future directions include the development, usability testing, and evaluation of a proposed electronic PROM platform that will inform future research initiatives.

Cryopreservation timing is a critical process parameter in a thymic regulatory T-cell therapy manufacturing protocol.

Regulatory T cells (Tregs) are a promising therapy for several immune-mediated conditions but manufacturing a homogeneous and consistent product, especially one that includes cryopreservation, has been challenging. Discarded pediatric thymuses are an excellent source of therapeutic Tregs with advantages including cell quantity, homogeneity and stability. Here we report systematic testing of activation reagents, cell culture media, restimulation timing and cryopreservation to develop a Good Manufacturing Practice (GMP)-compatible method to expand and cryopreserve Tregs. By comparing activation reagents, including soluble antibody tetramers, antibody-conjugated beads and artificial antigen-presenting cells (aAPCs) and different media, we found that the combination of Dynabeads Treg Xpander and ImmunoCult-XF medium preserved FOXP3 expression and suppressive function and resulted in expansion that was comparable with a single stimulation with aAPCs. Cryopreservation tests revealed a critical timing effect: only cells cryopreserved 1-3 days, but not >3 days, after restimulation maintained high viability and FOXP3 expression upon thawing. Restimulation timing was a less critical process parameter than the time between restimulation and cryopreservation. This systematic testing of key variables provides increased certainty regarding methods for in vitro expansion and cryopreservation of Tregs. The ability to cryopreserve expanded Tregs will have broad-ranging applications including enabling centralized manufacturing and long-term storage of cell products.

Patient-reported outcome measures within pediatric solid organ transplantation: A systematic review.

Subjective evaluation of medical care and disease outcomes from patients' perspectives has become increasingly important. Patient-reported outcome measures (PROMs) play a prominent role in engaging patients, capturing their experiences and improving patient care. This systematic review sought to identify PROMs that are used in the field of pediatric solid organ transplantation, with the aim to inform the implementation of PROMs into clinical practice for this population. A systematic review of English language, peer-reviewed articles was performed on key health science databases to identify publications using PROMs in pediatric solid organ transplantation. The search yielded 3670 articles, with a final data set of 62 articles that included 47 different PROMs. The three most frequently used PROMs included the following: (a) PedsQL™ Generic Core Scales (n = 25); (b) Children's Depression Inventory (n = 6); and (c) Child Health Questionnaire (n = 6). Of the 47 PROMs, 42 were generic and five were disease-specific; only six PROMS had a documented psychometric evaluation within a pediatric solid organ transplant population. This review outlines the attributes of the instruments (eg, domains captured), as well as the psychometric properties of those evaluated. PROMs are increasingly used in the field of pediatric transplantation; however, there are limited details in the current literature about their conceptual underpinnings and psychometric properties. This review highlights the need for additional psychometric evaluation of identified measures to establish the necessary foundation to inform the implementation of PROMs into clinical care for pediatric solid organ transplant patients.

Construction of Multivalent Homo- and Heterofunctional ABO Blood Group Glycoconjugates Using a Trifunctional Linker Strategy.

The design and synthesis of multivalent ligands displaying complex oligosaccharides is necessary for the development of therapeutics, diagnostics, and research tools. Here, we report an efficient conjugation strategy to prepare complex glycoconjugates with 4 copies of 1 or 2 separate glycan epitopes, providing 4-8 carbohydrate residues on a tetravalent poly(ethylene glycol) scaffold. This strategy provides complex glycoconjugates that approach the size of glycoproteins (15-18 kDa) while remaining well-defined. The synthetic strategy makes use of three orthogonal functional groups, including a reactive N-hydroxysuccinimide (NHS)-ester moiety on the linker to install the first carbohydrate epitope via reaction with an amine. A masked amine functionality on the linker is revealed after the removal of a fluorenylmethyloxycarbonyl (Fmoc)-protecting group, allowing the attachment to the NHS-activated poly(ethylene glycol) (PEG) scaffold. An azide group in the linker was then used to incorporate the second carbohydrate epitope via catalyzed alkyne-azide cycloaddition. Using a known tetravalent PEG scaffold (PDI, 1.025), we prepared homofunctional glycoconjugates that display four copies of lactose and the A-type II or the B-type II human blood group antigens. Using our trifunctional linker, we expanded this strategy to produce heterofunctional conjugates with four copies of two separate glycan epitopes. These heterofunctional conjugates included Neu5Ac, 3'-sialyllactose, or 6'-sialyllactose as a second antigen. Using an alternative strategy, we generated heterofunctional conjugates with three copies of the glycan epitope and one fluorescent group (on average) using a sequential dual-amine coupling strategy. These conjugation strategies should be easily generalized for conjugation of other complex glycans. We demonstrate that the glycan epitopes of heterofunctional conjugates engage and cluster target B-cell receptors and CD22 receptors on B cells, supporting the application of these reagents for investigating cellular response to carbohydrate antigens of the ABO blood group system.

Current state of transfusion practices for ABO-incompatible pediatric heart transplant patients in the United States and Canada.

BACKGROUND: ABO compatibility restriction on solid organ transplantation limits organ availability. In an effort to increase organ availability, pediatric ABO-incompatible heart transplants (ABOiHT) are now performed with similar outcomes to ABO-compatible transplants. Transfusion support can be challenging and currently there are no standard guidelines for blood product support, ABO isohemagglutinin (IH) titer cutoffs for transplant eligibility, or therapeutic intervention for these patients. The study aim was to survey current blood bank and antibody reduction practices for pediatric ABOiHT in the United States and Canada. STUDY DESIGN AND METHODS: A Web-based survey was sent to 50 US and Canadian pediatric blood bank directors. Participants were queried regarding pre-, intra-, and postoperative blood product support; ABO IH titer testing; and antibody reduction practices in ABOiHT recipients. RESULTS: We analyzed 21 responses from US and Canadian centers that perform pediatric ABOiHT. There is wide variation in the type of blood products transfused and the modification of these products among respondents in the pre-, intra-, and postoperative settings. The frequency of testing ABO IH titers, implementing therapeutic intervention, and the type of therapeutic intervention also vary greatly among the institutions. CONCLUSION: Transfusion support of children with ABOiHT varies widely among blood banks in the United States and Canada. The choice of blood products and modifications utilized, titer thresholds for organ selection and medical decision points, and antibody reduction strategies are not standardized from center to center. As pediatric ABOiHTs become more common, a better understanding of optimal transfusion support and therapeutic intervention is needed.

Toward a solution for cardiac failure in the newborn.

The newborn infant with severe cardiac failure owed to congenital structural heart disease or cardiomyopathy poses a daunting therapeutic challenge. The ideal solution for both might be cardiac transplantation if availability of hearts was not limiting and if tolerance could be induced, obviating toxicity of immunosuppressive therapy. If one could safely and effectively exploit neonatal tolerance for successful xenotransplantation of the heart, the challenge of severe cardiac failure in the newborn infant might be met. We discuss the need, the potential for applying neonatal tolerance in the setting of xenotransplantation and the possibility that other approaches to this problem might emerge.