Abdulaziz Al-Ghonaium

Pyogenic bacterial infections in humans with IRAK-4 deficiency.

MyD88 is a key downstream adapter for most Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs). MyD88 deficiency in mice leads to susceptibility to a broad range of pathogens in experimental settings of infection. We describe a distinct situation in a natural setting of human infection. Nine children with autosomal recessive MyD88 deficiency suffered from life-threatening, often recurrent pyogenic bacterial infections, including invasive pneumococcal disease. However, these patients were otherwise healthy, with normal resistance to other microbes. Their clinical status improved with age, but not due to any cellular leakiness in MyD88 deficiency. The MyD88-dependent TLRs and IL-1Rs are therefore essential for protective immunity to a small number of pyogenic bacteria, but redundant for host defense to most natural infections.

Mutations of CD40 gene cause an autosomal recessive form of immunodeficiency with hyper IgM

CD40 is a member of the tumor necrosis factor receptor superfamily, expressed on a wide range of cell types including B cells, macrophages, and dendritic cells. CD40 is the receptor for CD40 ligand (CD40L), a molecule predominantly expressed by activated CD4+ T cells. CD40/CD40L interaction induces the formation of memory B lymphocytes and promotes Ig isotype switching, as demonstrated in mice knocked-out for either CD40L or CD40 gene, and in patients with X-linked hyper IgM syndrome, a disease caused by CD40L/TNFSF5 gene mutations. In the present study, we have identified three patients with an autosomal recessive form of hyper IgM who fail to express CD40 on the cell surface. Sequence analysis of CD40 genomic DNA showed that one patient carried a homozygous silent mutation at the fifth base pair position of exon 5, involving an exonic splicing enhancer and leading to exon skipping and premature termination; the other two patients showed a homozygous point mutation in exon 3, resulting in a cysteine to arginine substitution. These findings show that mutations of the CD40 gene cause an autosomal recessive form of hyper IgM, which is immunologically and clinically undistinguishable from the X-linked form.

Clinical features and outcome of patients with IRAK-4 and MyD88 deficiency

Autosomal recessive interleukin-1 receptor-associated kinase (IRAK)-4 and myeloid differentiation factor (MyD)88 deficiencies impair Toll-like receptor (TLR)- and interleukin-1 receptor-mediated immunity. We documented the clinical features and outcome of 48 patients with IRAK-4 deficiency and 12 patients with MyD88 deficiency, from 37 kindreds in 15 countries. The clinical features of IRAK-4 and MyD88 deficiency were indistinguishable. There were no severe viral, parasitic, and fungal diseases, and the range of bacterial infections was narrow. Noninvasive bacterial infections occurred in 52 patients, with a high incidence of infections of the upper respiratory tract and the skin, mostly caused by Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The leading threat was invasive pneumococcal disease, documented in 41 patients (68%) and causing 72 documented invasive infections (52.2%). P. aeruginosa and Staph. aureus documented invasive infections also occurred (16.7% and 16%, respectively, in 13 and 13 patients, respectively). Systemic signs of inflammation were usually weak or delayed. The first invasive infection occurred before the age of 2 years in 53 (88.3%) and in the neonatal period in 19 (32.7%) patients. Multiple or recurrent invasive infections were observed in most survivors (n = 36/50, 72%). Clinical outcome was poor, with 24 deaths, in 10 cases during the first invasive episode and in 16 cases of invasive pneumococcal disease. However, no death and invasive infectious disease were reported in patients after the age of 8 years and 14 years, respectively. Antibiotic prophylaxis (n = 34), antipneumococcal vaccination (n = 31), and/or IgG infusion (n = 19), when instituted, had a beneficial impact on patients until the teenage years, with no seemingly detectable impact thereafter. IRAK-4 and MyD88 deficiencies predispose patients to recurrent life-threatening bacterial diseases, such as invasive pneumococcal disease in particular, in infancy and early childhood, with weak signs of inflammation. Patients and families should be informed of the risk of developing life-threatening infections; empiric antibacterial treatment and immediate medical consultation are strongly recommended in cases of suspected infection or moderate fever. Prophylactic measures in childhood are beneficial, until spontaneous improvement occurs in adolescence. Abbreviations: CRP = C-reactive protein, ELISA = enzyme-linked immunosorbent assay, IFN = interferon, IKBA = I&kgr;B&agr;, IL = interleukin, IL-1R = interleukin-1 receptor, InvBD = invasive bacterial disease, IRAK = interleukin-1 receptor-associated kinase, MyD = myeloid differentiation factor, NEMO = nuclear factor-kappaB essential modulator, NInvBD = noninvasive bacterial disease, TIR = Toll/IL-1R, TLR = Toll-like receptor, TNF = tumor necrosis factor.

Inherited interleukin-12 deficiency: IL12B genotype and clinical phenotype of 13 patients from six kindreds.

Interleukin-12 (IL12) is a cytokine that is secreted by activated phagocytes and dendritic cells and that induces interferon-gamma production by natural-killer and T lymphocytes. It consists of two subunits, p35 and p40, which are encoded by IL12A and IL12B, respectively. The first reported patient with a genetic cytokine disorder was a Pakistani child, who was homozygous for a large loss-of-function deletion (g.482+82_856-854del) in IL12B. This IL12-deficient child suffered from infections caused by bacille Calmette-Guérin (BCG) and Salmonella enteritidis. We herein report 12 additional patients from five other kindreds. In one kindred from India, the same large deletion that was described elsewhere (g.482+82_856-854del) was identified. In four kindreds from Saudi Arabia, a recessive loss-of-function frameshift insertion (g.315_316insA) was found. A conserved haplotype encompassing the IL12B gene suggested that a founder effect accounted for the recurrence of each mutation. The two founder mutational events-g.482+82_856-854del and g.315_316insA-were estimated to have occurred approximately 700 and approximately 1,100 years ago, respectively. Among a total of 13 patients with IL12 deficiency, 1 child had salmonellosis only and 12 suffered from clinical disease due to BCG or environmental nontuberculous mycobacteria. One patient also had clinical disease caused by virulent Mycobacterium tuberculosis, five patients had clinical disease caused by Salmonella serotypes, and one patient had clinical disease caused by Nocardia asteroides. The clinical outcome varies from case to case, since five patients (aged 2-11 years) died of overwhelming infection, whereas eight patients (aged 3-12 years) are still in good health and are not currently taking antibiotics. In conclusion, IL12 deficiency is not limited to a single kindred, shows significant variability of outcome, and should be considered in the genetic diagnosis of patients with mycobacteriosis and/or salmonellosis. To date, two founder IL12B mutations have been identified, accounting for the recurrence of a large deletion and a small insertion within populations from the Indian subcontinent and from the Arabian Peninsula, respectively.

Human TLR-7-, -8-, and -9-Mediated Induction of IFN-α/β and -λ Is IRAK-4 Dependent and Redundant for Protective Immunity to Viruses

Summary Five TLRs are thought to play an important role in antiviral immunity, sensing viral products and inducing IFN-α/β and -λ. Surprisingly, patients with a defect of IRAK-4, a critical kinase downstream from TLRs, are resistant to common viruses. We show here that IFN-α/β and -λ induction via TLR-7, TLR-8, and TLR-9 was abolished in IRAK-4-deficient blood cells. In contrast, IFN-α/β and -λ were induced normally by TLR-3 and TLR-4 agonists. Moreover, IFN-β and -λ were normally induced by TLR-3 agonists and viruses in IRAK-4-deficient fibroblasts. We further show that IFN-α/β and -λ production in response to 9 of 11 viruses tested was normal or weakly affected in IRAK-4-deficient blood cells. Thus, IRAK-4-deficient patients may control viral infections by TLR-3- and TLR-4-dependent and/or TLR-independent production of IFNs. The TLR-7-, TLR-8-, and TLR-9-dependent induction of IFN-α/β and -λ is strictly IRAK-4 dependent and paradoxically redundant for protective immunity to most viruses in humans.

Gains of glycosylation comprise an unexpectedly large group of pathogenic mutations

Mutations involving gains of glycosylation have been considered rare, and the pathogenic role of the new carbohydrate chains has never been formally established. We identified three children with mendelian susceptibility to mycobacterial disease who were homozygous with respect to a missense mutation in IFNGR2 creating a new N-glycosylation site in the IFNγR2 chain. The resulting additional carbohydrate moiety was both necessary and sufficient to abolish the cellular response to IFNγ. We then searched the Human Gene Mutation Database for potential gain-of-N-glycosylation missense mutations; of 10,047 mutations in 577 genes encoding proteins trafficked through the secretory pathway, we identified 142 candidate mutations (∼1.4%) in 77 genes (∼13.3%). Six mutant proteins bore new N-linked carbohydrate moieties. Thus, an unexpectedly high proportion of mutations that cause human genetic disease might lead to the creation of new N-glycosylation sites. Their pathogenic effects may be a direct consequence of the addition of N-linked carbohydrate.

Allogeneic Stem Cell Transplantation Using Myeloablative and Reduced-Intensity Conditioning in Patients with Major Histocompatibility Complex Class II Deficiency

Major histocompatibility complex class II (MHC II) deficiency is a rare combined immunodeficiency disease. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment. Between June 1994 and February 2007, 30 children with MHC II deficiency underwent a total of 33 HSCT procedures. Median age at HSCT was 27 months. The stem cell source was unmanipulated bone marrow from HLA-identical related donors in 26 patients, one HLA antigen-mismatched bone marrow in 3 patients, and unrelated umbilical cord blood in 1 patient. Conditioning was with one of 3 myeloablative regimens--regimen A (18 patients): busulfan (Bu), cyclophosphamide (Cy), and etoposide; regimen B (2 patients): Bu, Cy, and antithymocyte globulin (ATG); or regimen C (1 patient): CY and total body irradiation (TBI)--or with a reduced-intensity regimen (12 patients): fludarabine, melphalan, and ATG. The median CD34 cell dose was 8.3 x 10(6)/kg. Twenty patients experienced immune reconstitution and had sustained engraftment ranging from 9% to 100% for lymphoid lines and from 5% to 100% for myeloid lines that were significant to cure the disease. The overall disease-free survival rate was 66% and 76% after HLA-identical HSCT, with a median follow-up of 6.3 years, which is higher than previously reported. In HLA-identical transplant recipients, reliable donor stem cell engraftment and immune reconstitution were achieved through myeloablative or reduced-intensity conditioning. Further studies and long-term follow-up are needed to determine the appropriate conditioning regimen.

Ocular manifestations in chronic granulomatous disease in Saudi Arabia

INTRODUCTION Chronic granulomatous disease (CGD) is a primary immunodeficiency disease caused by a genetic defect in the NADPH oxidase complex of phagocytic cells. Recent reports indicate that chorioretinal lesions are more common than previously suspected. In this study, ocular findings of CGD patients are described with particular emphasis on chorioretinal lesions as a potentially serious ocular complication of CGD. METHODS Medical records of CGD patients attending an immunodeficiency clinic at a tertiary care center from January 2004 to December 2006 were reviewed. Patients underwent full ophthalmologic examination. Patients with chorioretinal lesions were investigated for various causes of chorioretinitis. Molecular studies for common CGD-causing genes were performed in patients with chorioretinal lesions. RESULTS This cohort included 32 CGD patients: 14 (44%) had abnormal eye findings, 11 (34%) had anterior segment disease, and 4 (12.5%) had chorioretinal lesions. Posterior segment findings consisted of uniformly similar hypopigmented atrophic punched-out chorioretinal scars around the arcades and mid-equator sparing of the macula. One patient had exudative hemorrhagic total retinal detachment in the right eye. Two siblings with chorioretinal lesions had mutation in CYBB, an X-linked gene. Another patient carried a missense mutation in NCF2, causing autosomal-recessive disease. CONCLUSIONS While ocular manifestation is common in CGD, chorioretinal lesions seem less frequent. However, they present potential risk of visual loss; it is recommended that patients undergo regular ophthalmologic examinations. This report provides further evidence that chorioretinal lesions occur not only in X-linked, but they can also occur in the autosomal-recessive form of CGD.

A novel mutation in purine nucleoside phosphorylase in a child with normal uric acid levels.

BACKGROUND Purine nucleoside phosphorylase (PNP) deficiency is an autosomal recessive disease in which affected children present with recurrent infection and may present with failure to thrive, neurological impairment, autoimmunity, or malignancy. The diagnosis of PNP is usually suggested by a reduced level of serum uric acid. We report here a novel mutation in the nucleoside phosphorylase gene (NP gene) in a patient with primary immunodeficiency and neurological impairment but with normal uric acid levels. The diagnosis was confirmed biochemically and showed a reduced PNP activity, and also by molecular gene analysis. METHODS A case report and a complete NP gene DNA analysis. RESULT The sequencing analysis showed a novel homozygous missense mutation, c.487T>C in the NP gene, resulting in a substitution of serine by proline at residue 163 (S163P) in the mature NP protein. CONCLUSION This NP missense mutation reported here is associated with recurrent infection, developmental delay, and primary immunodeficiency combined with normal uric acid levels in the affected child most likely due to a residual PNP enzyme activity. PNP deficiency causing primary immunodeficiency is still possible, even with normal uric acid levels.

Purine nucleoside phosphorylase deficiency in two unrelated Saudi patients.

Purine nucleoside phosphorylase (PNP) deficiency is a rare autosomal recessive metabolic disorder that results in combined immunodeficiency, neurologic dysfunction and autoimmunity. PNP deficiency has never been reported from Saudi Arabia or in patients with an Arabic ethnic background. We report on two Saudi girls with PNP deficiency. Both showed severe lymphopenia and neurological involvement. Sequencing of the PNP gene of one girl revealed a novel missense mutation Pro146>Leu in exon 4 due to a change in the codon from CCT>CTT. Expression of PNP (146L) cDNA in E coli indicated that the mutation greatly reduced, but did not completely eliminate PNP activity.