Research-based flow cytometry assays for pathogenic assessment in the human B-cell biology of gene variants revealed in the diagnosis of inborn errors of immunity: a Bruton's tyrosine kinase case-study.

Introduction: Inborn errors of immunity (IEI) are an expanding group of rare diseases whose field has been boosted by next-generation sequencing (NGS), revealing several new entities, accelerating routine diagnoses, expanding the number of atypical presentations and generating uncertainties regarding the pathogenic relevance of several novel variants. Methods: Research laboratories that diagnose and provide support for IEI require accurate, reproducible and sustainable phenotypic, cellular and molecular functional assays to explore the pathogenic consequences of human leukocyte gene variants and contribute to their assessment. We have implemented a set of advanced flow cytometry-based assays to better dissect human B-cell biology in a translational research laboratory. We illustrate the utility of these techniques for the in-depth characterization of a novel (c.1685G>A, p.R562Q) de novo gene variant predicted as probably pathogenic but with no previous insights into the protein and cellular effects, located in the tyrosine kinase domain of the Bruton's tyrosine kinase (BTK) gene, in an apparently healthy 14-year-old male patient referred to our clinic for an incidental finding of low immunoglobulin (Ig) M levels with no history of recurrent infections. Results and discussion: A phenotypic analysis of bone marrow (BM) revealed a slightly high percentage of pre-B-I subset in BM, with no blockage at this stage, as typically observed in classical X-linked agammaglobulinemia (XLA) patients. The phenotypic analysis in peripheral blood also revealed reduced absolute numbers of B cells, all pre-germinal center maturation stages, together with reduced but detectable numbers of different memory and plasma cell isotypes. The R562Q variant allows Btk expression and normal activation of anti-IgM-induced phosphorylation of Y551 but diminished autophosphorylation at Y223 after anti IgM and CXCL12 stimulation. Lastly, we explored the potential impact of the variant protein for downstream Btk signaling in B cells. Within the canonical nuclear factor kappa B (NF-κB) activation pathway, normal IκBα degradation occurs after CD40L stimulation in patient and control cells. In contrast, disturbed IκBα degradation and reduced calcium ion (Ca2+) influx occurs on anti-IgM stimulation in the patient's B cells, suggesting an enzymatic impairment of the mutated tyrosine kinase domain.

Actualización del tratamiento con L-asparraginasa en Pediatría / Update on L-asparaginase treatment in paediatrics

La L-asparraginasa (L-ASP) es una de las piedras angulares del tratamiento de la leucemia linfoblástica aguda y del linfoma no Hodgkin. Es una enzima de origen bacteriano con capacidad de transformar la L-Asparragina en ácido aspártico; la depleción extracelular de este aminoácido inhibe la síntesis proteica en los linfoblastos induciendo su apoptosis. Numerosos estudios han demostrado que los tratamientos con L-ASP mejoran la supervivencia de estos pacientes, pero existen diferencias en las características de las 3 formulaciones disponibles en la actualidad. Este artículo revisa la dosificación, actividad y efectos secundarios de las 2 L-ASP derivadas de Escherichia coli (la nativa y la pegilada) y de la única derivada de Erwinia chrysanthemi (Erwinia ASP). A pesar de su indiscutible indicación en los últimos 50 años, siguen existiendo numerosos puntos de controversia, y su uso todavía sigue marcado por los efectos secundarios derivados de la inhibición de la síntesis proteica. La vida media corta de las formas nativas y la vía de administración intramuscular, la más utilizada hasta el momento, afecta la calidad de vida de estos pacientes por la frecuencia con la que han de acudir al centro hospitalario y las múltiples punciones que conlleva. Por ello, los estudios más recientes pretenden valorar otras alternativas como la formulación de vida media más larga (L-ASP pegilada) y la vía intravenosa, con resultados alentadores. Aun así, son necesarios más estudios para establecer cuál es la formulación y la vía de administración indicada en primera línea, la dosificación óptima y el manejo de los efectos adversos (AU)

L-asparaginase (L-ASP) is one of the cornerstones of the treatment of acute lymphoblastic leukemia and non-Hodgkin lymphoma. It is an enzyme of bacterial origin capable of transforming L-asparagine to aspartic acid. The extracellular depletion of L-asparagine inhibits protein synthesis in lymphoblasts, inducing their apoptosis. Numerous studies have demonstrated that treatment with L-ASP improves survival of patients, but there are clear differences in the characteristics of the three currently available formulations. This article reviews the dosage, activity and side effects of the two L-ASP derived from Escherichia coli (native and pegylated), and the one derived from Erwinia chrysanthemi (Erwinia ASP). Despite its indisputable indication over the past50 years, there are still many points of contention, and its use is still marked by the side effects of the inhibition of protein synthesis. The short half-life of native forms, and the most frequently used parenteral administration by intramuscular injections, affects the quality of life of the patients. Therefore, recent studies claim to evaluate alternatives, such as the formulation of longer half-life pegylated L-ASP, and the use of intravenous formulations. There are encouraging results to date with both preparations. Still, further studies are needed to establish which should be the formulation and frontline indicated route of administration, optimal dosing, and management of adverse effects (AU)

[Update on L-asparaginase treatment in paediatrics]. / Actualización del tratamiento con L-asparraginasa en Pediatría.

L-asparaginase (L-ASP) is one of the cornerstones of the treatment of acute lymphoblastic leukemia and non-Hodgkin lymphoma. It is an enzyme of bacterial origin capable of transforming L-asparagine to aspartic acid. The extracellular depletion of L-asparagine inhibits protein synthesis in lymphoblasts, inducing their apoptosis. Numerous studies have demonstrated that treatment with L-ASP improves survival of patients, but there are clear differences in the characteristics of the three currently available formulations. This article reviews the dosage, activity and side effects of the two L-ASP derived from Escherichia coli (native and pegylated), and the one derived from Erwinia chrysanthemi (Erwinia ASP). Despite its indisputable indication over the past50 years, there are still many points of contention, and its use is still marked by the side effects of the inhibition of protein synthesis. The short half-life of native forms, and the most frequently used parenteral administration by intramuscular injections, affects the quality of life of the patients. Therefore, recent studies claim to evaluate alternatives, such as the formulation of longer half-life pegylated L-ASP, and the use of intravenous formulations. There are encouraging results to date with both preparations. Still, further studies are needed to establish which should be the formulation and frontline indicated route of administration, optimal dosing, and management of adverse effects.

[Pulmonary symptoms of primary immunodeficiency diseases]. / Manifestaciones pulmonares de las immunodeficiencias primarias.

OBJECTIVE: Patients who lack major components of the immune system carry an increased risk for severe and recurrent pulmonary infections at those respiratory sites were the deficient component would, in the normal state, have its greatest concentration. We report different pulmonary manifestations in pediatric patients with primary immunodeficiency disease (PID). PATIENTS AND METHODS: We studied 44 children younger than 14 years old, who were diagnosed of PID in our pediatric department between January 1990 and May 1996. RESULTS: Antibody deficiencies were the most frequent disorders (27/44; 61.3%) followed by PID associated with or secondary to other disorders (10/44; 22.7%) and defects of phagocyte function (5/44; 11.3%). Twenty-seven patients (61.3%) showed relevant pulmonary manifestations that required assistance in the division of pediatric pulmonology. Bronchial responsiveness was seen in 17/27, 11/27 had recurrent pneumonias with development of bronchiectasis in 7/27. Opportunistic or severe pneumonias leading to acute respiratory failure were diagnosed in 9/27. Necrotizing pneumonias leading to development of pneumatoceles, cavities or abscesses was seen in 3/27 with the same rate for lymphoid interstitial pneumonia. Respiratory symptoms were the first manifestations of PID in 19/27 (70.3%). CONCLUSIONS: The findings of the study emphasize the responsibility of the pediatric pulmonologists in avoiding the delayed diagnosis of PID since the prognosis depends on the precocity of diagnosis.

[Endoscopic evaluation of endobronchial tuberculosis in children]. / Valoración endoscópica de la tuberculosis endobronquial infantil.

The aim of this study was to determine the role of fiberoptic bronchoscopy (FB) in pulmonary tuberculosis in children. We assessed bronchoscopic findings of 36 procedures performed in 30 children who presented the following abnormalities on chest films: lobular or segmentary atelectasis (17), paratracheal or parahilar adenopathies (14), parenchymatous consolidation (9) and localized hyperinflation (5). Premedication for FB included intravenous atropine and diazepam plus ketamine for sedation, as well as lidocaine 2 and 5% in aerosol form for topical anesthesia. FB results showed that involvement was endobronchial in 29 patients. In the 18 patients with X-rays suggestive of endobronchial tuberculosis (EBT), the diagnosis was confirmed by FB. Significantly, EBT was found by FB in 11 (36.6%) patients with no clinical or radiological signs of such involvement. EBT was in the early stages in 3 (10%) patients and was advanced in 8 (26.6%). M. tuberculosis was isolated in 9 (30%) of the 30 patients. Culture was of bronchoalveolar lavage in three, of gastric lavage in four and of endobronchial biopsy in two. We conclude that FB is a safe, important tool for the confirmation of EBT in the management of pulmonary tuberculosis in children. It serves as a guide for the start of steroid treatment, especially in children with no radiological suggestion of EBT.

Carcinoma arising in a calcified bronchogenic cyst.

A round calcified mass located in the anterior mediastinal compartment was removed in a 42-year-old man. The histopathological diagnosis was bronchogenic cyst with foci of anaplastic carcinoma and areas of osseous metaplasia. The rarity of these findings and the possibility of malignancy in bronchogenic cysts is discussed.