Koon-Wing Chan

Susceptibility to mycobacterial infections in children with x-linked chronic granulomatous disease: A review of 17 patients living in a region endemic for tuberculosis

Background: Chronic granulomatous disease (CGD) is a rare disorder of phagocytic oxidative bursts leading to recurrent pyogenic infections. Affected individuals are most prone to infections caused by staphylococci, Salmonella, Candida, and Aspergillus, but previously we observed a high incidence of Mycobacterium tuberculosis infection in Chinese children with CGD. Objective: To determine the spectrum of infections in patients with X-linked CGD, with an emphasis on mycobacterial infections, and to review all CYBB gene mutations identified in our center. Results: From 1988 to 2005, 17 Chinese male children were diagnosed to have X-linked CGD. Fifteen mutations were identified, including 3 splice site defects (IVS1-1G>C, 266G>A, IVS3-1G>A), 5 missense mutations (591T>C, 627T>A, 949T>A, 1039T>A, 1512G>C), 3 nonsense mutations (882C>T, 1451C>A, 1569G>T), 1 insertion (756_757insA), and 3 deletions (660_662delTTC, 727delT, 1341delT). Eight of these were novel mutations. Recurrent pneumonia, lymphadenitis, and bacterial skin abscess were the commonest types of infection. Seven patients had tuberculosis (TB). Seven patients had prolonged scarring or abscess formation at the Calmette-Guérin bacillus (BCG) injection site, and 1 had disseminated BCG infection. Three patients had pulmonary aspergillosis. Four patients underwent hemopoietic stem cell transplantation, but 2 died of complications. Conclusions: Patients with CGD are susceptible to TB and BCG complications. Our observation suggests that oxidative burst is probably important in host defense against mycobacterial infections. Because interferon-γ is the key cytokine involved in mycobacterial immunity, there may be a stronger indication for its use in CGD patients living in areas endemic for TB.

Identification and Characterization of a Receptor from Goldfish Specific for a Teleost Growth Hormone-Releasing Hormone-Like Peptide

In mammals, growth hormone-releasing hormone (GHRH), acting via the GHRH receptor, plays an important role in the regulation of growth hormone (GH) synthesis and secretion as well as the proliferation and differentiation of somatotropes in the pituitary. In fishes, information concerning the functional role of the characterized GHRHs is limited. For that reason, a putative goldfish GHRH receptor cDNA was characterized in this study. The receptor cDNA is 2,243 bp in length, encoding a 438-amino-acid-long polypeptide with 7 putative transmembrane-spanning regions, which is a characteristic of G-protein-coupled receptors. The receptor, when expressed in COS-7 cells, showed minimal responses (2-fold cAMP responses) when stimulated with 100 nM of human GHRH, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP). However, this receptor was found to be specific for a carp GHRH-like peptide isolated from the brain of common carp (Cyprinus carpio); there was a significant and dose-dependent increase in intracellular cAMP (a maximum response of 22-fold increase with an EC50 of 0.1 nM) when the transfected cells were stimulated with this peptide. As a preliminary study to investigate the functional role of this receptor, the tissue distribution of the mRNA was analyzed by reverse-transcription-polymerase chain reaction. The receptor mRNA was found to be present in the brain, pituitary, gut, gill, heart, liver, skeletal muscle, spleen, ovary and testis. Together with a goldfish PACAP type 1 receptor and a VIP1 receptor recently isolated in our laboratory, characterization of this putative GHRH receptor provides the molecular basis for the future understanding of the neuroendocrine control of growth and reproduction by these neuropeptides in goldfish as well as other teleosts.

Clinical Characteristics and Genotype-phenotype Correlation in 62 Patients with X-linked Agammaglobulinemia

IntroductionX-linked agammagobulinemia (XLA) is a primary immunodeficiency disorder caused by Brutons tyrosine kinase (Btk) gene mutation. Recent studies suggested genotype-phenotype correlation in XLA, but a definitive association remains controversial.Patients and MethodsWe examined the relationship between specific Btk gene mutations and severity of clinical presentation in 62 patients with XLA. Disease severity was assessed by the age of disease onset and the presence of severe infections, while mutations were classified into severe and mild based on structural and functional consequence by bioinformatics analysis.ResultsFifty-six Btk mutations were identified in 62 patients from 57 kindreds. Variation in phenotypes was observed, and there was a tendency of association between genotype and age of disease onset as well as occurrence of severe infections.ConclusionA critical analysis of the circumstances upon presentation also revealed that under-recognition of recurrent infections and relevant family history are important hurdles to timely diagnosis of XLA.

Penicillium marneffei infection and impaired IFN-γ immunity in humans with autosomal-dominant gain-of-phosphorylation STAT1 mutations

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Penicilliosis in Children Without HIV Infection—Are They Immunodeficient?

BACKGROUNDnPenicillium marneffei infection is indigenous to Southeast Asia. Majority of penicilliosis occurs in patients with AIDS, and less commonly with secondary immunodeficiencies. Penicilliosis is rare in otherwise healthy persons, but information on their immunological status is often lacking.nnnMETHODSnFrom 1996 to 2009, we diagnosed penicilliosis in 5 children. Their clinical features, immunological findings, and genetic studies were analyzed. A systematic review of the English and Chinese literature was performed. Case reports/series on patients <18 years with penicilliosis were included, and patients stated to be human immunodeficiency virus (HIV)-positive excluded.nnnRESULTSnAll of our 5 patients were HIV negative. Presentations included fungemia (n = 2), multifocal lymphadenopathy (n = 2), and necrotizing pneumonia (n = 1). Four patients had recurrent mucocutaneous candidiasis. Hyperimmunoglobin E syndrome was diagnosed in 1 patient, while another had functional defect in interleukin-12/interferon-γ axis. Three patients were lymphopenic with low natural killer cell counts, but a specific immune defect was not identified. Systematic review of 509 reports on human penicilliosis identified 32 patients aged 3 months to 16 years with no known HIV infection. Twenty-four patients (75%) had disseminated disease, and 55% died of penicilliosis. Eight patients had primary immunodeficiencies or blood disorders, while 4 others had abnormal immune functions. Immune evaluations of the remaining patients were unstated.nnnCONCLUSIONnPenicilliosis is a severe disease causing high mortality in children. As an AIDS-defining illness, penicilliosis should be regarded as an indicator for underlying immunodeficiency in HIV-negative individuals. Immunological investigations should be performed, especially in those with recurrent infections. Multicentered collaborative studies are needed to collect information on long-term prognosis and define immune defects underlying penicilliosis.

Chronic Granulomatous Disease: Two Decades of Experience From a Tertiary Care Centre in North West India

Chronic granulomatous disease (CGD) results from an inherited defect in the phagocytic cells of the immune system. It is a genetically heterogenous disease caused by defects in one of the five major subunits of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. There is a paucity of data from India on CGD. We herein describe the clinical features in 17 children with CGD from a single tertiary referral center in India. A detailed analysis of the clinical features, laboratory investigations and outcome of 17 children 7 with X-linked (XL) and 10 with autosomal recessive (AR) form was performed. Diagnosis of CGD was based on an abnormal granulocyte oxidative burst evaluated by either Nitroblue Tetrazolium (NBT) test or flow cytometry based Dihyrorhodamine 123 assay or both. The molecular diagnosis was confirmed by genetic mutation analysis in 13 cases. The mean age at diagnosis and the age at onset of symptoms was significantly lower in children diagnosed with XL- CGD compared those with AR disease. Mutations were detected in CYBB gene in 6 patients with XL-CGD and NCF-1 gene mutations were observed in 7 cases of AR- CGD. The course and outcome of the disease was much worse in children diagnosed with X-linked form of disease compared to AR forms of the disease; 4/7 (57xa0%) children with X-CGD were dead at the time of data analysis. This is one of the largest series on chronic granulomatous disease from any developing country.

Clinical and molecular characteristics of 35 Chinese children with Wiskott-Aldrich syndrome.

BackgroundWiskott–Aldrich syndrome (WAS) is a rare primary immunodeficiency disease, with an incidence of 4/1,000,000 live male births. In China, an estimated number of 35 babies with WAS are born each year, but likely many remain undiagnosed.ObjectivesThe objectives of study were to review the clinical and molecular characteristics of a cohort of Chinese children with WAS and to describe the long-term outcome of those who underwent hematopoietic stem cell transplant (HSCT).Materials and MethodRecords of 35 patients diagnosed with WAS during 1991–2008 were reviewed. Genetic diagnosis was established by direct gene sequencing.ResultsAll patients had classical WAS phenotype. WASP mutations were identified in 33 patients from 29 families. Nine patients underwent HSCT at a mean age of 22.1xa0months (match-unrelated donor, nu2009=u20095; mismatched related donor, nu2009=u20092; matched-sibling donor, nu2009=u20092). Post-transplant immune hemolytic anemia and thrombocytopenia occurred in three patients with complete resolution. All patients survived without significant long-term complications and had full platelet, T and B lymphocyte recovery within 2xa0years post-transplant.ConclusionIn the past decade, there has been significant improvement in clinical and genetic diagnosis of WAS in Chinese. We demonstrated excellent long-term survival in patients who underwent HSCT. Early workup for transplant should be advocated for children with classical WAS before they suffer from major disease complications and morbidities.

RASGRP1 mutation in autoimmune lymphoproliferative syndrome-like disease

Background: Autoimmune lymphoproliferative syndrome (ALPS) is a genetic disorder of lymphocyte homeostasis due to impaired apoptosis. It was initially regarded as a very rare disease, but recent studies show that it may be more common than previously thought. Defects in a couple of genes have been identified in a proportion of patients with ALPS, but around one‐third of such patients remain undefined genetically. Objective: We describe 2 siblings presenting with ALPS‐like disease. This study aimed to identify the genetic cause responsible for this phenotype. Methods: Whole‐exome sequencing and molecular and functional analyses were used to identify and characterize the genetic defect. Clinical and immunological analysis was also performed and reported. Results: The 2 patients presented with chronic lymphadenopathy, hepatosplenomegaly, autoimmune hemolytic anemia, immune thrombocytopenia, and the presence of antinuclear autoantibody and other autoantibodies, but normal double‐negative T cells. They also suffered from recurrent infections. Novel compound heterozygous mutations of RASGRP1 encoding Ras guanyl nucleotide releasing protein 1 were identified in the 2 siblings. The mutations impaired T‐cell receptor signaling, leading to defective T‐cell activation and proliferation, as well as impaired activation‐induced cell death of T cells. Conclusions: This study shows for the first time that RASGRP1 mutation should be considered in patients with ALPS‐like disease. We also propose to investigate the intracellular proteins involved in the T‐cell receptor signaling pathway in similar patients but with unknown genetic cause.

Modulating effects of matrix metalloproteinase-3 and -9 polymorphisms on aortic stiffness and aortic root dilation in patients after tetralogy of Fallot repair

Matrix metalloproteinases (MMPs) are capable of degrading extracellular matrix proteins, which are important determinants of arterial stiffness. This study aimed to test the hypothesis that MMP-3 and MMP-9 polymorphisms may modulate aortic stiffness and magnitude of aortic root dilation in patients after surgical repair of tetralogy of Fallot (TOF). We analyzed the MMP-3 promoter and MMP-9 -1562 C>T polymorphism in 79 TOF patients aged 19.9 ± 9.5 years and determined their associations with aortic stiffness and sinotubular dimension. Genotypic and allelic frequencies of MMP-3 for the 6A6A genotype and MMP-9 for the T allele did not differ between patients and published control data (all p>0.05). For the MMP-3 locus, patients with a 6A6A genotype and those with a 6A6A/5A6A genotype had similar aortic stiffness (p=0.60), heart-femoral pulse wave velocity (p=0.63), and z score of sinotubular junction (p=0.81). For the MMP-9 locus, the -1562T allele carriers had significantly lower aortic stiffness (p=0.005), slower heart-femoral pulse wave velocity (p=0.03), and smaller z score of sinotubular junction (p=0.047). Multivariate linear regression identified MMP-9 polymorphism (β=-0.31, p=0.005) as a significant correlate of aortic stiffness after adjustments for age at study, age at operation, sex, body mass index, systolic and diastolic blood pressures, and MMP-3 polymorphism. In conclusion, MMP-9 but not MMP-3 polymorphism exerts a modulating influence on aortic stiffness and aortic root dilation in patients after TOF repair.

Severe hyperbilirubinaemia in a Chinese girl with type I Crigler-Najjar syndrome: First case ever reported in Mainland China

Abstract:u2002 Jaundice is common in ethnic Chinese infants, but to our knowledge Crigler–Najjar syndrome (CN syndrome) type I has never been reported in China. A Chinese girl with severe jaundice was recently diagnosed to have CN syndrome type I by analyzing the bilirubin‐uridinediphospho (UDP)‐glucuronosyltransferase gene (UGT1A1). The patient was homozygous for a nonsense mutation that replaced glutamine (CAG, amino acid 239) with stop codon (TAG) at nucleotide number 715 (715C→T) in exon 1. No mutation was found in exons 2–5. Her parents were heterozygous for the same mutant. The patient had an average bilirubin level of 300–500u2003μmol/L and a peak of 701u2003μmol/L. Daily phototherapy for 15u2003h was required to keep the bilirubin levels within 280–320u2003μmol/L. The unconjugated hyperbilirubinaemia apparently resulted from homozygous nonsense mutation of UGT1A1, which could completely abolish the UGT activity towards bilirubin (hepatic glucuronidation) and result in CN syndrome type I. Identification of the genetic defect is very useful for gene therapy, especially for DNA/RNA chimera therapy, and can be used as an antenatal screening test to identify the affected offsprings.