Deep intronic mis-splicing mutation in JAK3 gene underlies T−B+NK− severe combined immunodeficiency phenotype

Janus Kinase 3 (JAK3): A Critical Conserved Node in Immunity Disrupted in Immune Cell Cancer and Immunodeficiency

The Janus kinase (JAK) family is a small group of protein tyrosine kinases that represent a central component of intracellular signaling downstream from a myriad of cytokine receptors. The JAK3 family member performs a particularly important role in facilitating signal transduction for a key set of cytokine receptors that are essential for immune cell development and function. Mutations that impact JAK3 activity have been identified in a number of human diseases, including somatic gain-of-function (GOF) mutations associated with immune cell malignancies and germline loss-of-function (LOF) mutations associated with immunodeficiency. The structure, function and impacts of both GOF and LOF mutations of JAK3 are highly conserved, making animal models highly informative. This review details the biology of JAK3 and the impact of its perturbation in immune cell-related diseases, including relevant animal studies.

Clinical, immunological and molecular findings of 8 patients with typical and atypical severe combined immunodeficiency: identification of 7 novel mutations by whole exome sequencing

Severe combined immunodeficiency (SCID) is one of the severe inborn errors of the immune system associated with life-threatening infections. Variations in SCID phenotypes, especially atypical SCID, may cause a significant delay in diagnosis. Therefore, SCID patients need to receive an early diagnosis. Here, we describe the clinical manifestations and genetic results of four SCID and atypical SCID patients. All patients (4 males and 4 females) in early infancy presented with SCID phenotypes within 6 months of birth. The mutations include RAG2 (p.I273T,p.G44X), IL7R (p.F361WfsTer17), ADA (c.780+1G>A), JAK3 (p.Q228Ter), LIG4 (p.G428R), and LAT (p.Y207fsTer33), as well as a previously reported missense mutation in RAG1 (p.A444V). The second report of LAT deficiency in SCID patients is presented in this study. Moreover, all variants were confirmed in patients and their parents as a heterozygous state by Sanger sequencing. The results of our study expand the clinical and molecular spectrum associated with SCID and leaky SCID phenotypes and provide valuable information for the clinical management of the patients.

Screening patients with autoimmune endocrine disorders for cytokine autoantibodies reveals monogenic immune deficiencies

BACKGROUND

Autoantibodies against type I interferons (IFN) alpha (α) and omega (ω), and interleukins (IL) 17 and 22 are a hallmark of autoimmune polyendocrine syndrome type 1 (APS-1), caused by mutations in the autoimmune regulator (AIRE) gene. Such antibodies are also seen in a number of monogenic immunodeficiencies.

OBJECTIVES

To determine whether screening for cytokine autoantibodies (anti-IFN-ω and anti-IL22) can be used to identify patients with monogenic immune disorders.

METHODS

A novel ELISA assay was employed to measure IL22 autoantibodies in 675 patients with autoimmune primary adrenal insufficiency (PAI) and a radio immune assay (RIA) was used to measure autoantibodies against IFN-ω in 1778 patients with a variety of endocrine diseases, mostly of autoimmune aetiology. Positive cases were sequenced for all coding exons of the AIRE gene. If no AIRE mutations were found, we applied next generation sequencing (NGS) to search for mutations in immune related genes.

RESULTS

We identified 29 patients with autoantibodies against IFN-ω and/or IL22. Of these, four new APS-1 cases with disease-causing variants in AIRE were found. In addition, we identified two patients with pathogenic heterozygous variants in CTLA4 and NFKB2, respectively. Nine rare variants in other immune genes were identified in six patients, although further studies are needed to determine their disease-causing potential.

CONCLUSION

Screening of cytokine autoantibodies can efficiently identify patients with previously unknown monogenic and possible oligogenic causes of autoimmune and immune deficiency diseases. This information is crucial for providing personalised treatment and follow-up of patients and their relatives.

Targeting Janus Kinase (JAK) for Fighting Diseases: The Research of JAK Inhibitor Drugs

Janus Kinase (JAK), a nonreceptor protein tyrosine kinase, has emerged as an excellent target through research and development since its discovery in the 1990s. As novel small-molecule targeted drugs, JAK inhibitor drugs have been successfully used in the treatment of rheumatoid arthritis (RA), myofibrosis (MF) and ulcerative colitis (UC). With the gradual development of JAK targets in the market, JAK inhibitors have also received very considerable feedback in the treatment of autoimmune diseases such as atopic dermatitis (AD), Crohn's disease (CD) and graft-versus host disease (GVHD). This article reviews the research progress of JAK inhibitor drugs: introducing the existing JAK inhibitors on the market and some JAK inhibitors in clinical trials currently. In addition, the synthesis of various types of JAK inhibitors were summarized, and the effects of different drug structures on drug inhibition and selectivity.

The effect of mutatio-type on proteo-phenotype and clinico-phenotype in selected primary immunodeficiencies

In the diagnosis of primary immunodeficiencies which are heterogeneous groups of genetic disorders, next-generation sequencing strategies take an important place. Protein expression analyses and some functional studies which are fundamental to determine the pathogenicity of the mutation are also performed to accelerate the diagnosis of PIDs before sequencing. However, protein expressions and functions do not always reflect the genetic and clinical background of the disease even the existence of a pathogenic variant or vice versa. In this study, it was aimed to understand genotype-proteophenotype-clinicophenotype correlation by investigating the effect of mutation types on protein expression, function, and clinical severity in X-linked, autosomal dominant, and autosomal recessive forms of PIDs. It was searched in PubMed and Web of Science without any restrictions on study design and publication time. Totally, 1178 patients with PIDs who have 553 different mutations were investigated from 174 eligible full-text articles. For all mutations, the effect of mutation type on protein expressions and protein functions was analyzed. Furthermore, the most frequent missense and nonsense mutations that were identified in patients with PIDs were evaluated to determine the genotype-clinicophenotype correlation. Protein expressions and functions were changed depending on the mutation type and the affected domain. A significant relationship was observed between protein expression level and clinical severity among all investigated patients. There was also a positive correlation between clinical severity and the affected domains. Mutation types and affected domains should be carefully evaluated with respect to protein expression levels and functional changes during the evaluation of clinico-phenotype.

Neonatal Lymphopenia Screening Is Important For Early Diagnosis of Severe Combined Immunodeficiency

OBJECTIVE

 T-cell receptor excision circles are expensive for neonatal severe combined immunodeficiency screening in developing countries. We aimed to detect immunodeficiencies presenting with lymphopenia to enable screening in the general population and to improve awareness regarding lymphopenia among clinicians.

STUDY DESIGN

 This study was conducted prospectively. In all newborns included, complete blood count from umbilical cord blood samples was recorded. Absolute lymphopenia was defined as absolute lymphocyte count <3,000/mm³ in umbilical cord blood sample. Complete blood count was repeated at month 1 in cases found to have lymphopenia.

RESULTS

 Overall, 2,000 newborns were included in the study. Absolute lymphopenia was detected in 42 newborns (2.1%), while lymphocyte count was >3,000/mm³ in 1,958 newborns (97.9%). Two infants with persisted lymphopenia at the end of the first month; therefore, further evaluations such as lymphocyte subsets for severe combined immunodeficiency (SCID) were done. In the first infant, the lymphocyte subgroups were detected as compatible with T (-), B (-), natural killer cells (NK) (+) SCID phenotype RAG defect. Sanger sequencing revealed that NM_000448 c.2209C > T (p.R737C) homozygous mutation of RAG1 gene. In the other infant, the lymphocyte subgroups were found as considered with T (-), B (+) NK (-) SCID phenotype JAK3 defect. Both patients underwent hematopoietic stem cell transplantation from human leukocyte antigen-matched family member.

CONCLUSION

 Absolute lymphopenia by complete blood count is a more simpler, relatively noninvasive and inexpensive screening methodfor detection of SCID in newborns compared with T-cell receptor excision circles technique.

KEY POINTS

· Our study was conducted with a much smaller number of study groups compared with the previous ones.. · However, SCID was found at a higher rate compared with other studies.. · Our study for this disease that is common in our country where consanguineous marriages are common.

Working and safety profiles of JAK/STAT signaling inhibitors. Are these small molecules also smart?

The Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway is an important intracellular route through which many different extracellular soluble molecules, by reaching membrane receptors, can signal the nucleus. The spectrum of soluble molecules that use the JAK/STAT pathway through their corresponding receptors is quite large (almost 50 different molecules), and includes some cytokines involved in the pathogenesis of many immune-mediated diseases. Such diseases, when left untreated, present an evident hyperactivation of JAK/STAT signaling. Therefore, given the pathogenetic role of JAK/STAT, drugs known as JAK inhibitors (JAKi), that target one or more JAKs, have been developed to counteract JAK/STAT signal hyperactivation. As some hematological malignancies present an intrinsic JAK/STAT hyperactivation due to a JAK mutation, some JAKi have also been successfully used in this context. Regulatory agencies for drug administration in different countries have already approved a few JAKi in the setting of either immune-mediated diseases or hematological malignancies. Aim of this review is to describe the physiology of intracellular JAK/STAT pathway signaling and the pathological conditions associated to its dysregulation. Then, the rationale for targeting JAK in rheumatic autoimmune diseases is discussed, along with clinical data from registration studies showing the efficacy of these drugs. Finally, the excellent safety profile of JAKi is discussed in the context of the apparent poor specificity of JAK/STAT pathway signal.

Bacillus Calmette-Guerin (BCG) Vaccine-associated Complications in Immunodeficient Patients Following Stem Cell Transplantation

PURPOSE

Bacillus Calmette-Guerin (BCG) is a live attenuated vaccine with the potential of causing severe iatrogenic complications in patients with primary immunodeficiency diseases (PID) before and after hematopoietic stem cell transplantation (HSCT). We aim to investigate risk factors of post-HSCT BCG-related complications in PID patients.

METHODS

A retrospective analysis of pediatric PID patients who had received the BCG vaccine and underwent HSCT at Hadassah-Hebrew University Medical Center, between 2007 and 2019.

RESULTS

We found 15/36 (41.67%) patients who developed post-HSCT BCG-related complications. The most significant risk factor for developing BCG-related complications was T cell deficiency (47.6% of the non-complicated vs 83.3% of the BCGitis and 100% of the BCGosis groups had T cell lymphopenia, p = 0.013). None of the chronic granulomatous patients developed BCG-related manifestation post-transplant. Among T cell-deficient patients, lower NK (127 vs 698 cells/μl, p = 0.04) cell counts and NK-SCID were risk factors for ongoing post-HSCT BCGosis, as was pretransplant disseminated BCGosis (33.3% of patients with BCGosis vs none of the non-BCGosis patients, p = 0.04). Immune reconstitution inflammatory syndrome (IRIS) was observed in 3/5 patients with Omenn syndrome. Prophylactic antimycobacterial treatment was not proven effective.

CONCLUSION

BCG vaccination can cause significant morbidity and mortality in the post-transplant T cell-deficient patient, especially in the presence of pre-transplant disease. Taking a detailed medical history prior to administering, the BCG vaccine is crucial for prevention of this complication.

Recent advances in primary immunodeficiency: from molecular diagnosis to treatment

The technological advances in diagnostics and therapy of primary immunodeficiency are progressing at a fast pace. This review examines recent developments in the field of inborn errors of immunity, from their definition to their treatment. We will summarize the challenges posed by the growth of next-generation sequencing in the clinical setting, touch briefly on the expansion of the concept of inborn errors of immunity beyond the classic immune system realm, and finally review current developments in targeted therapies, stem cell transplantation, and gene therapy.

A rare deep intronic mutation of PKHD1 gene, c.8798-459 C > A, causes autosomal recessive polycystic kidney disease by pseudoexon activation

Autosomal recessive polycystic kidney disease (ARPKD), is a rare hepatorenal fibrocystic disorder primarily associated with progressive growth of multiple cysts in the kidneys causing progressive loss of renal function. The disease is linked to mutations in the PKHD1 gene. In this study, we describe the gene diagnosis and prenatal diagnosis for a consanguineous family with two fetuses diagnosed with polycystic kidney disease by fetal sonography during the pregnancy. Sequence analysis of cDNA synthesized from the PKHD1 mRNA of the second induced fetus identified a 111-nucleotide insert at the junction of exon 56 and 57 that originated from intervening sequence (IVS) 56. Further genomic sequencing of IVS 56 of the PKHD1 gene identified a rare homozygous deep intronic mutation (c.8798-459 C > A), which was inherited from the parents and not detectable in 100 unrelated control subjects. Moreover, we explored the pathogenicity of this deep intronic mutation by conducting a minigene splicing assay experiment, which demonstrated that the mutation causes a pseudoexon insertion, which results in a frameshift followed by a premature termination codon in exon 57. Eventually, the parents had a healthy baby by undergoing prenatal genetic diagnosis based on the targeted detection of the intron mutation. The newly identified deep intronic mutation is associated with a rare mechanism of abnormal splicing that expands the spectrum of known PKHD1 gene mutations. It can be used in evidence-based genetic and reproductive counseling for families with ARPKD.

Newborn screening using TREC/KREC assay for severe T and B cell lymphopenia in Iran

T-cell receptor excision circles (TRECs) and κ-deleting recombination excision circles (KRECs) are recently used for detection of T or B cell lymphopenia in neonates based on region-specific cutoff levels. Here, we report cutoffs for TREC and KREC copies useful for newborn screening and/or diagnosis of primary immunodeficiency diseases (PID) in Iran. DNA was extracted from a single 3.2 mm punch of dried blood spots collected from 2160 anonymized newborns referred to two major referral health centres between 2014 and 2016. For refinement of the cutoffs, 51 patients with a definite diagnosis of severe combined immunodeficiency, X-linked agammaglobulinaemia and combined immunodeficiency, including ataxia telangiectasia, human phosphoglucomutase 3 and Janus kinase-3 deficiency, as well as 47 healthy controls were included. Samples from patients with an X-linked hyper-IgM-syndrome, Wiskott-Aldrich syndrome and DNA ligase 4 deficiency were considered as disease controls. Triplex-quantitative real-time PCR was used. Cutoffs were calculated as TRECs < 11 and KRECs < 6 copies with an ACTB > 700 copies with sensitivity of 100% for TREC and 97% for KREC. Among thirty anonymized newborn samples (1.5%) with abnormal results for TREC and/or KREC, only twenty-one available cases were retested and shown to be in the normal range except for three samples (0.15%). All of the patients with a definitive diagnosis were correctly identified based on our established TREC/KREC copy numbers. Determining cutoffs for TREC/KREC is essential for correctly identifying children with PID in newborn screening. Early diagnosis of PID patients enables appropriate measures and therapies like stem cell transplantation.

JAK3 mutations in Italian patients affected by SCID: New molecular aspects of a long-known gene

Background

Mutations in the Janus Kinase 3 (JAK3) gene cause an autosomal recessive form of severe combined immunodeficiency (SCID) usually characterized by the absence of both T and NK cells, but preserved numbers of B lymphocytes (T‐B+NK‐SCID). The detection of larger (>100 bp) genomic duplications or deletions can be more difficult to be detected by PCR‐based methods or standard NGS protocols, and a broad range of mutation detection techniques are necessary.

Methods

We report four unrelated Italian patients (two females and two males) with SCID phenotype. Protein expression, functional studies, molecular analysis by standard methods and NGS, and transcripts studies were performed to obtain a definitive diagnosis.

Results

Here, we describe four JAK3‐deficient patients from four unrelated families. The first patient is homozygous for the known c.1951 C>T mutation causing the amino acidic change p.R651W. The other two patients, originating from the same small Italian town, resulted compound heterozygotes for the same g.15410_16542del deletion and two different novel mutations, g.13319_13321delTTC and c.933T>G (p.F292V), respectively. The fourth patient was compound heterozygous for the novel mutations p.V599G and p.W709R. Defective STAT5 phosphorylation after IL2 or IL15 stimulation corroborated the mutation pathogenicity. Concerning g.15410_16542del mutation, probably due to an unequal homologous recombination between Alu elements of JAK3 gene, microsatellites analysis revealed that both unrelated Pt2 and Pt3 and their carrier family members shared the same haplotype. These data support the hypothesis of a founder effect for the g.15410_16542del mutation that might have inherited in both unrelated families from the same ancient progenitor.

Conclusion

Different molecular techniques are still required to obtain a definitive diagnosis of AR‐SCID particularly in all cases in which a monoallelic mutation is found by standard mutation scanning methods.

Chronic active Epstein-Barr virus infection as the initial symptom in a Janus kinase 3 deficiency child: Case report and literature review

RATIONALE

With the progress of sequencing technology, an increasing number of atypical primary immunodeficiency (PID) patients have been discovered, including Janus kinase 3 (JAK3) gene deficiency.

PATIENT CONCERNS

We report a patient who presented with chronic active Epstein-Barr virus (CAEBV) infection but responded poorly to treatment with ganciclovir.

DIAGNOSES

Next-generation sequencing (NGS) was performed, including all known PID genes, after which Sanger sequencing was performed to verify the results. Genetic analysis revealed that our patient had 2 novel compound heterozygous mutations of JAK3, a gene previously reported to cause a rare form of autosomal recessive severe combined immunodeficiency with recurrent infections. The p.H27Q mutation came from his father, while p. R222H from his mother. Thus, his diagnosis was corrected for JAK3-deficiency PID and CAEBV.

INTERVENTIONS

Maintenance treatment of subcutaneous injection of recombinant human interferon α-2a was given to our patient with 2 MU, 3 times a week.

OUTCOMES

Interferon alpha was applied and the EBV infection was gradually controlled and his symptoms ameliorated remarkably. Our patient is in good health now and did not have relapses.

LESSONS

The diagnoses of PID should be taken into consideration when CAEBV patients respond poorly to conventional treatments. Good results of our patient indicate that interferon α-2a may be an alternative treatment for those who are unwilling to accept hematopoietic stem cell transplantation (HSCT) like our patient. Literature review identified 59 additional cases of JAK3 deficiency with various infections.