Rapid full engraftment and successful immune reconstitution after allogeneic hematopoietic stem cell transplantation with reduced intensity conditioning in Omenn syndrome

Effect of Early Bacillus Calmette-Guerin Vaccination of Pediatric Severe Combined Immunodeficiency Patients on the Outcome of Hematopoietic Stem Cell Transplantation Using a Reduced-Intensity Conditioning Regimen

The eminence of Bacillus Calmette-Guerin (BCG) vaccine in newborn vaccination programs has been conspicuous throughout the years, especially in low-income developing countries where tuberculosis is prevalent; however, application of the BCG vaccine is not without constraints, especially in patients afflicted with immunodeficiency diseases, such as severe combined immunodeficiency (SCID). The present study aimed to evaluate whether the administration of BCG vaccine at birth could improve the outcomes of hematopoietic stem cell transplantation (HSCT) in pediatric patients with SCID. In this study, 30 SCID patients who underwent HSCT using a reduced-intensity conditioning regimen (RIC) were followed-up for 2 years post-HSCT. The outcomes of HSCT were evaluated in both non-BCG-vaccinated patients (n = 12) and BCG-vaccinated patients (n = 18). Our results show a higher incidence of acute graft-versus-host disease (aGVHD), but not of chronic GVHD, in the BCG-vaccinated patients, and a similar overall survival (OS) rate in the 2 groups. We speculate that the similar OS rate in the 2 groups, despite the risk of BGC vaccination, was because this group received an RIC conditioning regimen. There was no other difference between the 2 groups. Considering the effect of the BCG vaccine on HSCT outcome, we suggest that the administration of BCG vaccine be deferred until age 3 months so that APT testing without the interference of maternal antibodies can be performed. However, this study could benefit from a larger cohort to further validate our findings, as the possible reason for some factors not being statistically significant was our small sample size.

Successful Hematopoietic Stem Cell Transplant in a Patient with Omenn Syndrome: A Case Report

Omenn syndrome is a rare subtype of severe combined immunodeficiency. Affected patients present recurrent infections, lymphadenopathy, skin eruptions, eosinophilia, hepatosplenomegaly, failure to thrive, and gastrointestinal complications with variable severity. A 3-month-old female infant, born to consanguineous healthy parents, presented with splenomegaly, erythroderma, failure to thrive, and history of recurrent otitis media, hypothyroidism, and Bacille Calmette-Guérin lymphadenitis following Bacille Calmette-Guérin vaccination.The immunologic workup showed lymphopenia; low levels of CD3+ T cells, CD4+ T cells, and CD8+ T cells; normal levels of CD19+ B cells and CD16+/CD56+ natural killer cells; hypogammaglobulinemia; and a high level of serum immunoglobulin E. She was clinically diagnosed with T-B+NK+ severe combined immunodeficiency. Genetic study revealed a missense homozygous alteration (c.617G>A, p.Arg206Gln) in exon 5 of the IL7R gene in the patient, as well as carrier states for the same variant in both parents. The patient received a peripheral blood stem cell transplant from a matched unrelated donor. A reduced intensity conditioning regimen was applied, including fludarabine, melphalan, rabbit antithymocyte globulin, and graft- versus-host disease prophylaxis by cyclosporine and mycophenolate mofetil. She clinically improved, and after engraftment the donor chimerism was 100% at 1 year after transplant. Hematopoietic stem cell transplantis a curative therapeutic option for patients with Omenn syndrome and, when combined with an early diagnosis, can prevent complications and improve patient survival.

Analysis of Peripheral Blood Mononuclear Cells Gene Expression Highlights the Role of Extracellular Vesicles in the Immune Response following Hematopoietic Stem Cell Transplantation in Children

Hematopoietic stem cell transplantation (HSCT) is an effective treatment method used in many neoplastic and non-neoplastic diseases that affect the bone marrow, blood cells, and immune system. The procedure is associated with a risk of adverse events, mostly related to the immune response after transplantation. The aim of our research was to identify genes, processes and cellular entities involved in the variety of changes occurring after allogeneic HSCT in children by performing a whole genome expression assessment together with pathway enrichment analysis. We conducted a prospective study of 27 patients (aged 1.5–18 years) qualified for allogenic HSCT. Blood samples were obtained before HSCT and 6 months after the procedure. Microarrays were used to analyze gene expressions in peripheral blood mononuclear cells. This was followed by Gene Ontology (GO) functional enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and protein–protein interaction (PPI) analysis using bioinformatic tools. We found 139 differentially expressed genes (DEGs) of which 91 were upregulated and 48 were downregulated. “Blood microparticle”, “extracellular exosome”, “B-cell receptor signaling pathway”, “complement activation” and “antigen binding” were among GO terms found to be significantly enriched. The PPI analysis identified 16 hub genes. Our results provide insight into a broad spectrum of epigenetic changes that occur after HSCT. In particular, they further highlight the importance of extracellular vesicles (exosomes and microparticles) in the post-HSCT immune response.

Anti-CD3ε mAb improves thymic architecture and prevents autoimmune manifestations in a mouse model of Omenn syndrome: therapeutic implications

Omenn syndrome (OS) is an atypical primary immunodeficiency characterized by severe autoimmunity because of activated T cells infiltrating target organs. The impaired recombinase activity in OS severely affects expression of the pre-T-cell receptor complex in immature thymocytes, which is crucial for an efficient development of the thymic epithelial component. Anti-CD3ε monoclonal antibody (mAb) treatment in RAG2(-/-) mice was previously shown to mimic pre-TCR signaling promoting thymic expansion. Here we show the effect of anti-CD3ε mAb administration in the RAG2(R229Q) mouse model, which closely recapitulates human OS. These animals, in spite of the inability to induce the autoimmune regulator, displayed a significant amelioration in thymic epithelial compartment and an important reduction of peripheral T-cell activation and tissue infiltration. Furthermore, by injecting a high number of RAG2(R229Q) progenitors into RAG2(-/-) animals previously conditioned with anti-CD3ε mAb, we detected autoimmune regulator expression together with the absence of peripheral immunopathology. These observations indicate that improving epithelial thymic function might ameliorate the detrimental behavior of the cell-autonomous RAG defect. Our data provide important therapeutic proof of concept for future clinical applications of anti-CD3ε mAb treatment in severe combined immunodeficiency forms characterized by poor thymus function and autoimmunity.

Successful second bone marrow transplantation in Omenn's syndrome after bone marrow aplasia: a case report

Omenn's syndrome is a rare inherited variant of SCID. It is inevitably fatal, unless treated by bone marrow or stem cell transplantation. However, treatment-related complications and graft rejection are major obstacles to the success of transplantation. In this report, we describe an eight-month-old baby with Omenn's syndrome and disseminated BCGosis, who underwent allogenic BMT from his HLA-matched sister using anti-GVHD prophylaxis but without a conditioning regimen. Ten days after BMT, he developed acute GVHD involving the skin only (grade 1) with a flare of local BCGosis. Engraftment of 55% was demonstrated by FISH as early as the 11th day post-BMT. On day +48 post-BMT, he developed GVHD that was complicated by refractory pancytopenia, resistant to three doses of rituximab. Patient was re-transplanted (from the same donor) after receiving fludarabine and ATG, with successful engraftment and complete recovery from pancytopenia.