Current Practices on Diagnosis, Prevention and Treatment of Post-Transplant Lymphoproliferative Disorder in Pediatric Patients after Solid Organ Transplantation: Results of ERN TransplantChild Healthcare Working Group Survey.

(1) Background: Post-transplant lymphoproliferative disease (PTLD) is a significant complication of solid organ transplantation (SOT). However, there is lack of consensus in PTLD management. Our aim was to establish a present benchmark for comparison between international centers and between various organ transplant systems and modalities; (2) Methods: A cross-sectional questionnaire of relevant PTLD practices in pediatric transplantation was sent to multidisciplinary teams from 17 European center members of ERN TransplantChild to evaluate the centers' approach strategies for diagnosis and treatment and how current practices impact a cross-sectional series of PTLD cases; (3) Results: A total of 34 SOT programs from 13 European centers participated. The decision to start preemptive treatment and its guidance was based on both EBV viremia monitoring plus additional laboratory methods and clinical assessment (61%). Among treatment modalities the most common initial practice at diagnosis was to reduce the immunosuppression (61%). A total of 126 PTLD cases were reported during the period 2012-2016. According to their histopathological classification, monomorphic lesions were the most frequent (46%). Graft rejection after PTLD remission was 33%. Of the total cases diagnosed with PTLD, 88% survived; (4) Conclusions: There is still no consensus on prevention and treatment of PTLD, which implies the need to generate evidence. This might successively allow the development of clinical guidelines.

Haploidentical transplantation in pediatric non-malignant diseases: A retrospective analysis on behalf of the Spanish Group for Hematopoietic Transplantation (GETH).

OBJECTIVE: Describe the GETH haploidentical stem cell transplantation (haplo-HSCT) activity in non-malignant disease (NMDs). METHODS: We retrospectively analyzed data from children with NMDs who underwent haplo-HSCT. RESULTS: From January 2001 to December 2016, 26 pediatric patients underwent 31 haplo-HSCT through ex vivo T cell-depleted (TCD) graft platforms or post-transplantation cyclophosphamide (PT-Cy) at 7 Spanish centers. Five cases employed unmanipulated PT-Cy haplo-HSCT, 16 employed highly purified CD34+ cells, and 10 employed ex vivo TCD grafts manipulated either with CD3+ CD19+ depletion, TCRαß+ CD19+ selection or naive CD45RA+ T-cell depletion. Peripheral blood stem cells were the sole source for patients following TCD haplo-HSCT, and bone marrow was the source for one PT-Cy haplo-HSCT. The most common indications for transplantation were primary immunodeficiency disorders (PIDs), severe aplastic anemia, osteopetrosis, and thalassemia. The 1-year cumulative incidence of graft failure was 27.4%. The 1-year III-IV acute graft-versus-host disease (GvHD) and 1-year chronic GvHD rates were 34.6% and 16.7%, respectively. The 2-year overall survival was 44.9% for PIDs, and the 2-year graft-versus-host disease-free and relapse-free survival rate was 37.6% for the other NMDs. The transplantation-related mortality at day 100 was 30.8%. CONCLUSION: Although these results are discouraging, improvements will come if procedures are centralized in centers of expertise.

Evaluation of B-cell intracellular signaling by monitoring the PI3K-Akt axis in patients with common variable immunodeficiency and activated phosphoinositide 3-kinase delta syndrome.

BACKGROUND: Primary antibody deficiencies (PADs) are characterized by hypogammaglobulinemia and impaired B-cell differentiation. Patients with common variable immunodeficiency (CVID) present severe reductions in at least 2 serum immunoglobulins and impaired terminal differentiation of B cells. Most patients with CVID do not appear to present monogenic defects. Activated phosphoinositide 3-kinase delta syndrome (APDS), caused by gain-of-function mutations in the PIK3CD gene (p110δ), can present in patients with a CVID-like phenotype. Memory B-cell differentiation requires the orchestrated activation of numerous intracellular signaling pathways, which promote transcriptional programs required for long-term B-cell survival. The aim of this study was to develop a flow cytometry assay to trace the PI3K-Akt-mTOR pathway, a critical component of B-cell homeostasis, and analyze its status in PADs. METHODS: We analyzed the intracellular expression of Akt and S6 by flow cytometry and their phosphorylation status in both baseline conditions and upon B-cell receptor activation with anti-IgM in various primary B-cell subsets of patients with CVID and APDS. RESULTS: B cells from CVID patients showed reduced phosphorylation in Akt and S6 proteins after anti-IgM stimulation. Constitutive high baseline B-cell levels of Akt and S6 phosphorylation in a patient with APDS were reduced once m-TOR inhibition therapy was initiated. CONCLUSIONS: Intracellular flow cytometry can be routinely employed to explore alterations in the PI3K-Akt-mTOR pathway in B cells from patients with PADs. AKT and S6 phosphorylation levels are informative biomarkers that could be employed as mTOR inhibitors for monitoring therapies targeting this pathway.

Pediatric transplantation in Europe during the COVID-19 pandemic: Early impact on activity and healthcare.

The current pandemic SARS-CoV-2 has required an unusual allocation of resources that can negatively impact chronically ill patients and high-complexity procedures. Across the European Reference Network on Pediatric Transplantation (ERN TransplantChild), we conducted a survey to investigate the impact of the COVID-19 outbreak on pediatric transplant activity and healthcare practices in both solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT). The replies of 30 professionals from 18 centers in Europe were collected. Twelve of 18 centers (67%) showed a reduction in their usual transplant activity. Additionally, outpatient visits have been modified and restricted to selected ones, and the use of telemedicine tools has increased. Additionally, a total of 14 COVID-19 pediatric transplanted patients were identified at the time of the survey, including eight transplant recipients and six candidates for transplantation. Only two moderate-severe cases were reported, both in HSCT setting. These survey results demonstrate the limitations in healthcare resources for pediatric transplantation patients during early stages of this pandemic. COVID-19 disease is a major worldwide challenge for the field of pediatric transplantation, where there will be a need for systematic data collection, encouraging regular discussions to address the long-term consequences for pediatric transplantation candidates, recipients, and their families.

Age-associated distribution of normal B-cell and plasma cell subsets in peripheral blood.

BACKGROUND: Humoral immunocompetence develops stepwise throughout life and contributes to individual susceptibility to infection, immunodeficiency, autoimmunity, and neoplasia. Immunoglobulin heavy chain (IgH) isotype serum levels can partly explain such age-related differences, but their relationship with the IgH isotype distribution within memory B-cell (MBC) and plasma cell (PCs) compartments remains to be investigated. OBJECTIVE: We studied the age-related distribution of MBCs and PCs expressing different IgH isotypes in addition to the immature/transitional and naive B-cell compartments. METHODS: B-cell and PC subsets and plasma IgH isotype levels were studied in cord blood (n = 19) and peripheral blood (n = 215) from healthy donors aged 0 to 90 years by using flow cytometry and nephelometry, respectively. RESULTS: IgH-switched MBCs expressing IgG1, IgG2, IgG3, IgA1, and IgA2 were already detected in cord blood and newborns at very low counts, whereas CD27+IgM++IgD+ MBCs only became detectable at 1 to 5 months and remained stable until 2 to 4 years, and IgD MBCs peaked at 2 to 4 years, with both populations decreasing thereafter. MBCs expressing IgH isotypes of the second immunoglobulin heavy chain constant region (IGHC) gene block (IgG1, IgG3, and IgA1) peaked later during childhood (2-4 years), whereas MBCs expressing third IGHC gene block immunoglobulin isotypes (IgG2, IgG4, and IgA2) reached maximum values during adulthood. PCs were already detected in newborns, increasing in number until 6 to 11 months for IgM, IgG1, IgG2, IgG3, IgA1, and IgA2; until 2 to 4 years for IgD; and until 5 to 9 years for IgG4 and decreasing thereafter. For most IgH isotypes (except IgD and IgG4), maximum plasma levels were reached after PC and MBC counts peaked. CONCLUSIONS: PC counts reach maximum values early in life, followed by MBC counts and plasma IgH isotypes. Importantly, IgH isotypes from different IGHC gene blocks show different patterns, probably reflecting consecutive cycles of IgH isotype switch recombination through life.