Clinical,immunological and genetic characterization of patients with X-linked agammaglobulinemia in Costa Rica

X-linked agammaglobulinemia is caused by mutations in the gene encoding Bruton tyrosine kinase. It produces an arrest in the maturation and differentiation of B cells with very low levels of all immunoglobulins isotypes. The aim of the study was to characterize the clinical, immunological and genetic defects in patients with XLA in Costa Rica. Sixteen cases were identified over a period of 30 years, a case every 2 years, approximately. Three patients were asymptomatic and diagnosis was made on family history. The average age of onset of symptoms was 1.46 years-old (0.08–6.1). Six patients (44%) had onset of symptoms before 1 year of age and 12 (81%) patients before 5 years of age. The average age of diagnosis was 3.63 years-old (0.17–13, SD 3.51 years-old the average time between the onset of symptoms and the diagnosis was 2.5 years (2.5 months to 12 years, SD 3 years). The initial reason to study the patients was a recurrent infection, family history of XLA, arthritis and neutropenia. Four patients had pneumonia and two had suppurative lung disease. Nine patients had recurrent infections: acute otitis media, sinusitis, mastoiditis and recurrent diarrhoea. Three patients presented with arthritis. Neutropenia as an isolated event was not identified in any case. All patients receive monthly IVIG and no deaths were reported. Three new likely pathogenic/pathogenic variants in BTK gene have been described in our population. This is the first report of XLA Costa Rican patients and their BTK mutations.     

A mutation in X‐linked inhibitor of apoptosis (G466X) leads to memory inflation of Epstein–Barr virus‐specific T cells

Mutations in the X‐linked inhibitor of apoptosis (XIAP) gene have been associated with XLP‐like disease, including recurrent Epstein–Barr virus (EBV)‐related haemophagocytic lymphohystiocytosis (HLH), but the immunopathogenic bases of EBV‐related disease in XIAP deficiency is unknown. We present the first analysis of EBV‐specific T cell responses in functional XIAP deficiency. In a family of patients with a novel mutation in XIAP (G466X) leading to a late‐truncated protein and varying clinical features, we identified gradual hypogammaglobulinaemia and large expansions of T cell subsets, including a prominent CD4⁺CD8⁺ population. Extensive ex‐vivo analyses showed that the expanded T cell subsets were dominated by EBV‐specific cells with conserved cytotoxic, proliferative and interferon (IFN)‐γ secretion capacity. The EBV load in blood fluctuated and was occasionally very high, indicating that the XIAP^G466X mutation could impact upon EBV latency. XIAP deficiency may unravel a new immunopathogenic mechanism in EBV‐associated disease.     

Clinical and genetic analysis of patients with X‐linked hyper‐IgM syndrome

Congenital adrenal hyperplasia (CAH) due to 21‐hydroxylase deficiency (21‐OHD) is a common autosomal recessive disorder caused by mutations in the CYP21A2 gene. The carrier frequency of CYP21A2 mutations has been estimated to be 1:25 to 1:10 on the basis of newborn screening. The main objective of this study was to determine the carrier frequency in the Cypriot population of mutations in the CYP21A2 gene. Three hundred unrelated subjects (150 males and 150 females) from the general population of Cyprus were screened for mutations in the CYP21A2 gene and its promoter. The CYP21A2 genotype analysis identified six different mutants and revealed a carrier frequency of 9.83% with the mild p.Val281Leu being the most frequent (4.3%), followed by p.Qln318stop (2.5%), p.Pro453Ser (1.33%), p.Val304Met (0.83%), p.Pro482Ser (0.67%) and p.Met283Val (0.17%). The notable high CYP21A2 carrier frequency of the Cypriot population is one of the highest reported so far by genotype analysis. Knowledge of the mutational spectrum of CYP21A2 will enable to optimize mutation detection strategy for genetic diagnosis of 21‐OHD not only in Cyprus, but also the greater Mediterranean region.     

Clinical, immunological and genetic features in Taiwanese patients with the phenotype of hyper-immunoglobulin E recurrent infection syndromes (HIES)

Hyper-immunoglobulin E recurrent infection syndromes (HIES) have distinct features, with identified associated mutations of STAT3, TYK2, and DOCK8. Among 197 Taiwanese patients with primary immunodeficiency on a referral-base of over 23 million inhabitants, STAT3 (R382W and Q469R) and DOCK8 mutations (exon 1-9 deletion) were identified in two patients each from six AD-HIES and five AR-HIES patients, respectively. Aside from decreased Th17 and memory B cells, characteristic facies and pneumatocele were not mutually exclusive regardless of STAT3 and DOCK8 mutations. One with novel DOCK8 deletion had notable cytomegalovirus retinitis, cerebral vasculitis, lead deposition, and amenorrhea. In adolescence, three AD-HIES patients without STAT3 mutation died of myocardial infarction, staphylococcus sepsis, and proteus sepsis while receiving chemotherapy for lymphoma. Close follow-up of the HIES phenotype rather than identifying genetic mutations should be the cornerstone of intervention at this juncture because of relatively lower percentage of identifying mutations in Taiwanese HIES (4/11; 36.5%).     

Retrospective analysis of patients with severe combined immunodeficiency and alternative diagnostic criteria: A 20-year single centre experience

Severe combined immunodeficiency (SCID) is an inborn errors of immunity (IEI) disorder characterized by impairment in the development and function of lymphocytes and could be fatal if not treated with hematopoietic stem cell transplant in the first 2 years of life. There are various diagnostic criteria for SCID among different primary immunodeficiency societies. We retrospectively evaluated clinical and laboratory findings of 59 patients followed up with the diagnosis of SCID at our clinic over the past 20 years in order to develop an algorithm that would help diagnosis of SCID for the countries where a high ratio of consanguineous marriage is present because these countries have not launched TREC assay in their newborn screening programs. The mean age at diagnosis was 5.80 ± 4.90 months, and the delay was 3.29 ± 3.99 months. The most common complaint and physical examination findings were cough (29.05%), eczematous rash (63%) and organomegaly (61%). ADA (17%), Artemis (14%), RAG1/2 (15%), MHC Class II (12%) and IL-2R (12%) deficiencies were the most common genetic defects. Lymphopenia (87.5%) was the most frequent abnormal laboratory finding and below 3000/mm³ in 95% of the patients. The CD3⁺ T cell count was 300/mm³ and below in 83% of the patients. As a result, a combination of low lymphocyte count and CD3 lymphopenia for SCID diagnosis would be more reliable for countries with high rate of consanguineous marriage. Physicians should consider diagnosis of SCID in a patient presenting with severe infections and lymphocyte counts below 3000/mm³ under 2 years of age.     

Bruton tyrosine kinase gene mutations in Turkish patients with presumed X‐linked agammaglobulinemia

X‐linked agammglobulinemia (XLA) is a ptototypical humoral immunodeficiency caused by mutations in the gene coding for Bruton tyrosine kinase (BTK). The genetic defect in XLA impairs early B cell development resulting in marked reduction of mature B cells in the blood. Studies from different countries have demonstrated that approximately 90% of males with presumed XLA bear mutations in BTK. In this study, we report for the first time the occurrence of BTK mutations in Turkey. We performed mutational analysis of the BTK gene in 16 Turkish male patients from 13 separate families with presumed XLA based on abnormally low peripheral blood B‐cell numbers (lt; 1%), hypogammaglobulinemia, and recurrent bacterial infections. We found that in nine of the 13 families (69%) a Btk mutation caused XLA. Two of the mutations were previously described, but seven novel mutations were identified: two missense (Y39C, G584R), one nonsense (Q343X), and 4 deletions (1800‐1821del, 1843‐1847del, 1288‐1292del, 291del) resulting in frameshift and premature stop codon. By contrast, no mutations in the BTK gene were identified in the other 4 families. A consanguinity in three of these families raises the possibility that mutations in other autosomal genes which affect early B cell development may contribute to their phenotype resembling XLA. Hum Mutat 18:356, 2001. © 2001 Wiley‐Liss, Inc.     

Circulating phenotypic B‐1 cells are decreased in common variable immunodeficiency and correlate with immunoglobulin M levels

B‐1 cells are innate‐like lymphocytes characterized by spontaneous production of ‘natural’ polyspecific antibodies, often of self‐specificity, and thought to be responsible for tissue homeostasis, mucosal protection, maintaining resting serum immunoglobulin (Ig)M levels and for early immunoglobulin production following infection. Although defined most clearly in mice, a human B‐1 cell counterpart, defined by the phenotype CD19 or 20⁺CD27⁺CD43⁺CD69 or 70^–, has been proposed recently, facilitating a study of their role in human humoral immunodeficiencies, such as common variable immunodeficiency (CVID). This study examined circulating B‐1 cells in 27 CVID patients in comparison to age‐matched controls (n = 28). Phenotypic putative B‐1 cell proportions varied widely, but there was an overall 60–70% decrease in CVID (0·039 ± 0·033% of lymphocytes, mean ± standard deviation) compared with controls (0·110 ± 0·159% of lymphocytes, P = 0·0012). This decrease was, however, explained largely by concomitant loss of total CD27⁺ memory B cells characteristic of CVID, although those with higher memory B cell proportions appeared to show a true decrease. No age‐related effects were apparent in B‐1 cell proportions. However, among CVID patients, there was a strong positive correlation between the B‐1 cell proportion and serum IgM levels, a relationship that was not evident for IgA, nor was there a relationship between memory B cell proportions and serum IgM. Patients with CVID have fewer circulating putative phenotypic B‐1 cells, which largely reflected the overall decrease in memory B cells. However, B‐1 cell proportions correlated with resting serum IgM levels, suggesting a possible role in IgM deficiency in CVID.     

Human antiviral B cell responses: Emerging lessons from hepatitis B and COVID‐19

Humoral immunity is a critical component of the coordinated response required to resolve viral infections and mediate protection following pathogen clearance or vaccination. A better understanding of factors shaping the memory B cell response will allow tailored development of efficient preventative vaccines against emerging acute viral infections, therapeutic vaccines, and immunotherapies for chronic viral infections. Here, we use recent data obtained by profiling antigen‐specific B cell responses in hepatitis B as a framework to explore lessons that can be learnt from different viral infections about the diverse influences on humoral immunity. Hepatitis B provides a paradigm where successful B cell responses in resolved or vaccinated individuals can be contrasted to the failed response in chronic infection, while also exemplifying the degree to which B cell responses within infected individuals can differ to two antigens from the same virus. Drawing on studies in other human and murine infections, including emerging data from COVID‐19, we consider the influence of antigen quantity and structure on the quality of the B cell response, the role of differential CD4 help, the importance of germinal center vs extrafollicular responses and the emerging concept that responses residing in non‐lymphoid organs can participate in B cell memory.     

Invariant natural killer (iNK) T cell deficiency in patients with common variable immunodeficiency

Common variable immunodeficiency (CVID) is a B cell immunodeficiency disorder characterized frequently by failure of memory B cell development and antibody secretion. A unifying cellular pathogenesis for CVID has not been forthcoming, but given the immunoregulatory role of invariant NK (iNK) T cells and their absence in several other immunodeficiencies, we quantified these cells in the blood of 58 CVID patients. There was a marked decrease in the proportion of iNK T cells in CVID patients compared with controls. This was particularly notable in those with low isotype‐switched memory B cells, but subset analysis demonstrated no difference when stratified by specific clinical features. We propose that the decreased proportion of iNK T cells in CVID might be linked to the failure of memory B cell generation, which may contribute to reduced antibody production in these patients.     

Differentiating transfusion‐transmitted infection from reactivation of viruses

Clinicians tend to attribute acute viral infections in transfused patients to transfusion despite unprecedented viral safety. An increasing proportion of blood product recipients are immunodeficient or immunosuppressed and susceptible to viral reactivation of previous infections. This presentation will examine how to discriminate between transfusion‐transmitted and reactivated viral infections.     

Signaling pathways involved in the T‐cell‐mediated immunity against Epstein‐Barr virus: Lessons from genetic diseases

Primary immunodeficiencies (PIDs) provide researchers with unique models to understand in vivo immune responses in general and immunity to infections in particular. In humans, impaired immune control of Epstein‐Barr virus (EBV) infection is associated with the occurrence of several different immunopathologic conditions; these include non‐malignant and malignant B‐cell lymphoproliferative disorders, hemophagocytic lymphohistiocytosis (HLH), a severe inflammatory condition, and a chronic acute EBV infection of T cells. Studies of PIDs associated with a predisposition to develop severe, chronic EBV infections have led to the identification of key components of immunity to EBV – notably the central role of T‐cell expansion and its regulation in the pathophysiology of EBV‐associated diseases. On one hand, the defective expansion of EBV‐specific CD8 T cells results from mutations in genes involved in T‐cell activation (such as RASGRP1, MAGT1, and ITK), DNA metabolism (CTPS1) or co‐stimulatory pathways (CD70, CD27, and TNFSFR9 (also known as CD137/4‐1BB)) leads to impaired elimination of proliferating EBV‐infected B cells and the occurrence of lymphoma. On the other hand, protracted T‐cell expansion and activation after the defective killing of EBV‐infected B cells is caused by genetic defects in the components of the lytic granule exocytosis pathway or in the small adapter protein SH2D1A (also known as SAP), a key activator of T‐ and NK cell‐cytotoxicity. In this setting, the persistence of EBV‐infected cells results in HLH, a condition characterized by unleashed T‐cell and macrophage activation. Moreover, genetic defects causing selective vulnerability to EBV infection have highlighted the role of co‐receptor molecules (CD27, CD137, and SLAM‐R) selectively involved in immune responses against infected B cells via specific T‐B cell interactions.     

Prevalence of persistent and latent viruses in untreated patients infected with HIV‐1 from Ghana,West Africa

Only limited epidemiological data, pertaining to the prevalence of common persistent viruses has been reported in Ghana. This study was conducted to determine the prevalence of persistent viruses in individuals with untreated HIV‐1 infection and uninfected blood donors. Paired plasma and cellular samples from HIV‐negative blood donors, asymptomatic HIV and symptomatic/AIDS cohorts were screened by multiplex PCR then qPCR for parvovirus B19 (B19V), hepatitis B virus (HBV), GB virus‐C (GBV‐C), cytomegalovirus (CMV), Epstein–Barr virus (EBV), human herpesvirus‐8 (HHV‐8) and varicella‐zoster virus (VZV). IgG antibodies specific to each target virus were tested to determine exposure rates. No evidence of viraemia was found for B19V and VZV in any group. Prevalence of GBV‐C plasma viraemia was significantly higher in asymptomatic and symptomatic HIV infection (16.7%) and (16.2%) than in blood donors (4%) P < 0.005. Occult HBV infection was significantly more frequent in symptomatic HIV infection (10.9%) compared to asymptomatic HIV (3.6%) and blood donors (1.6%) P < 0.005. Although there was a high background of EBV viraemia in cellular fractions of blood donors (8.3%), it was significantly higher in asymptomatic (44.6%) and symptomatic HIV (14.6%) P < 0.0001. For CMV, the significantly increased prevalence of viraemia was only observed in the plasma fraction of the symptomatic HIV‐1/AIDS patients (7.6%) compared to asymptomatic individuals (1.8%) and blood donors (0.8%) P ≤ 0.001. The background seroprevalence in blood donors was high for B19V (≥64%), HBV (≥70%), CMV and EBV (≥90%) and was significantly increased in HIV infections for HBV, CMV, VZV (symptomatic HIV), and HHV‐8 (asymptomatic and symptomatic HIV). J. Med. Virol. 81:1860–1868, 2009. © 2009 Wiley‐Liss, Inc.     

L-selectin in patients with common variable immunodeficiency (CVID): a comparative study with normal individuals

L-selectin is one of the key members of the selectin family of adhesion molecules and initiates leucocyte attachment to specialized high endothelial venules. The shed form, which retains functional activity, can be detected in biological fluids and is increased in diseases of many kinds. In the present study, we investigated L-selectin expression on leucocytes and measured the soluble form in the plasma of healthy individuals and patients with CVID. A significant loss of L-selectin expression is found on CVID B cells, which is marked by the presence of a substantial population of L-selectin-negative B cells in the peripheral blood of some CVID patients. On CD4⁺ T cells, the loss in L-selectin expression affects mostly the CD45RO⁺ population. Peripheral blood leucocytes other than lymphocytes express L-selectin molecule normally. Moreover, soluble L-selectin was detected in significantly increased levels in CVID plasma compared with healthy controls. Our data suggest that the loss of L-selectin expressed by lymphocytes may be due to increased or aberrant lymphocyte activation in CVID patients who remain immunodeficient, and down-regulation of L-selectin from these lymphocytes may significantly contribute to the elevated levels of soluble L-selectin in the plasma, which may in turn affect further lymphocyte trafficking.     

B‐cell receptor repertoire sequencing in patients with primary immunodeficiency: a review

The advent of next‐generation sequencing (NGS) now allows a detailed assessment of the adaptive immune system in health and disease. In particular, high‐throughput B‐cell receptor (BCR) repertoire sequencing provides detailed information about the functionality and abnormalities of the B‐cell system. However, it is mostly unknown how the BCR repertoire is altered in the context of primary immunodeficiencies (PID) and whether findings are consistent throughout phenotypes and genotypes. We have performed an extensive literature search of the published work on BCR repertoire sequencing in PID patients, including several forms of predominantly antibody disorders and combined immunodeficiencies. It is somewhat surprising that BCR repertoires, even from severe clinical phenotypes, often show only mild abnormalities and that diversity or immunoglobulin gene segment usage is generally preserved to some extent. Despite the great variety of wet laboratory and analytical methods that were used in the different studies, several findings are common to most investigated PIDs, such as the increased usage of gene segments that are associated with self‐reactivity. These findings suggest that BCR repertoire characteristics may be used to assess the functionality of the B‐cell compartment irrespective of the underlying defect. With the use of NGS approaches, there is now the opportunity to apply BCR repertoire sequencing to multiple patients and explore the PID BCR repertoire in more detail. Ultimately, using BCR repertoire sequencing in translational research could aid the management of PID patients by improving diagnosis, estimating functionality of the immune system and improving assessment of prognosis.     

Clinical Characteristics and Outcomes of Primary Immunodeficiencies in Thai Children: An 18-year Experience from a Tertiary Care Center

Introduction  Early diagnosis and treatment are keys to improve survival of patients with primary immunodeficiency diseases (PID). The clinical characteristics of these patients in Thailand were not well defined. Objective  This study aimed to determine the clinical characteristics and outcomes of patients with PID in Thailand. Methods  Medical records of PID patients in the past 18 years were reviewed. Results  Sixty-seven children were registered. Antibody deficiencies were the most common PID (52.2%), followed by combined T cell and B cell immunodeficiencies (25.4%), other well-defined immunodeficiency syndromes (11.9%), and phagocytic defects (10.4%). The most common presentations of antibody deficiencies, combined T cell and B cell immunodeficiencies, and phagocytic defects were infection in the upper respiratory tract (74.3%), gastrointestinal tract (82.4%), and skin (85.7%), respectively. The highest mortality rate (52.9%) was found in severe combined immunodeficiency. Conclusion  These results provide clinical features of PID in Thailand. Knowing these features will lead to prompt diagnosis and appropriate management.