Douglas R. McDonald

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.

DOCK8 functions as an adaptor that links TLR-MyD88 signaling to B cell activation

The adaptors DOCK8 and MyD88 have been linked to serological memory. Here we report that DOCK8-deficient patients had impaired antibody responses and considerably fewer CD27+ memory B cells. B cell proliferation and immunoglobulin production driven by Toll-like receptor 9 (TLR9) were considerably lower in DOCK8-deficient B cells, but those driven by the costimulatory molecule CD40 were not. In contrast, TLR9-driven expression of AICDA (which encodes the cytidine deaminase AID), the immunoglobulin receptor CD23 and the costimulatory molecule CD86 and activation of the transcription factor NF-κB, the kinase p38 and the GTPase Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. After ligation of TLR9, DOCK8 became tyrosine-phosphorylated by Pyk2, bound the Src-family kinase Lyn and linked TLR9 to a Src–kinase Syk–transcription factor STAT3 cascade essential for TLR9-driven B cell proliferation and differentiation. Thus, DOCK8 functions as an adaptor in a TLR9-MyD88 signaling pathway in B cells.

Small-molecule screen identifies reactive oxygen species as key regulators of neutrophil chemotaxis

Neutrophil chemotaxis plays an essential role in innate immunity, but the underlying cellular mechanism is still not fully characterized. Here, using a small-molecule functional screening, we identified NADPH oxidase–dependent reactive oxygen species as key regulators of neutrophil chemotactic migration. Neutrophils with pharmacologically inhibited oxidase, or isolated from chronic granulomatous disease (CGD) patients and mice, formed more frequent multiple pseudopodia and lost their directionality as they migrated up a chemoattractant concentration gradient. Knocking down NADPH oxidase in differentiated neutrophil-like HL60 cells also led to defective chemotaxis. Consistent with the in vitro results, adoptively transferred CGD murine neutrophils showed impaired in vivo recruitment to sites of inflammation. Together, these results present a physiological role for reactive oxygen species in regulating neutrophil functions and shed light on the pathogenesis of CGD.

RIP Links TLR4 to Akt and Is Essential for Cell Survival in Response to LPS Stimulation

Receptor-interacting protein (RIP) has been reported to associate with tumor necrosis–associated factor (TRAF)2 and TRAF6. Since TRAF2 and TRAF6 play important roles in CD40 signaling and TRAF6 plays an important role in TLR4 signaling, we examined the role of RIP in signaling via CD40 and TLR4. Splenocytes from RIP−/− mice proliferated and underwent isotype switching normally in response to anti-CD40–IL-4 but completely failed to do so in response to LPS–IL-4. However, they normally up-regulated TNF-α and IL-6 gene expression and CD54 and CD86 surface expression after LPS stimulation. RIP−/− splenocytes exhibited increased apoptosis and impaired Akt phosphorylation after LPS stimulation. These results suggest that RIP is essential for cell survival after TLR4 signaling and links TLR4 to the phosphatidylinositol 3 kinase–Akt pathway.

Successful engraftment of donor marrow after allogeneic hematopoietic cell transplantation in autosomal-recessive hyper-IgE syndrome caused by dedicator of cytokinesis 8 deficiency

A child with homozygous partial deletion of the DOCK8 gene showed characteristic clinical findings of autosomal recessive hyper-IgE syndrome and full donor chimerism early after matched sibling bone marrow transplantation.

TH17 deficiency in human disease

The differentiation of naive T cells into distinct subsets of effector T cells is critical for effective immunity against a wide variety of infectious agents in the environment. Activation of innate immune responses by Candida species through pattern-recognition receptors directs the subsequent development of naive T cells into T(H)17 cells, which are essential for effective mucosal immunity against fungi. Thorough analyses of cohorts of patients with unusual susceptibility to chronic mucocutaneous candidiasis resulting from T(H)17 deficiency have confirmed the role of T(H)17 cells and T(H)17 cytokines in human host defense against Candida species and have provided valuable insights into the complex process of T(H)17 cell development.

Flow cytometry diagnosis of dedicator of cytokinesis 8 (DOCK8) deficiency

To the Editor: Biallelic mutations in the dedicator of cytokinesis 8 (DOCK8) gene cause autosomal-recessive hyper-IgE syndrome, a combined immunodeficiency characterized by sinopulmonary infections, skin and systemic viral infections, eczema, and food allergy. DOCK8 deficiency can lead to early death from infection and malignancy. The disease is curable by hematopoietic cell transplantation (HCT). Thus, it is important to ascertain the diagnosis of DOCK8 deficiency to institute early treatment. The vast majority of DOCK8-deficient patients lack DOCK8 expression and many have deletions in the DOCK8 gene. Confirmation of the diagnosis has relied on immunoblotting of blood cell lysates and/or gene sequencing, techniques that are not routinely available. We present here a flow cytometry assay that could facilitate the diagnosis of DOCK8 deficiency, detection of carrier status, and investigation of lineage-specific DOCK8 expression following HCT.

Comparison of 2 delivery vehicles for viscous budesonide to treat eosinophilic esophagitis in children.

Objectives: Oral viscous budesonide (OVB) using Splenda as a delivery vehicle has become an attractive therapeutic option for children with eosinophilic esophagitis (EoE). Many families are wary of giving the artificial sweetener in high doses to their children. The aim of the present study was to determine whether OVB mixed with Neocate Nutra, a hypoallergenic nutritional supplement, is at least as efficacious as OVB mixed with Splenda at healing EoE. Methods: Our institutional review board approved a retrospective chart review of patients with well-documented EoE treated with OVB at the Boston Childrens Hospital Eosinophilic Gastrointestinal Disorder program between June 2008 and June 2013. Primary outcome measured was histologic response defined as change in peak eosinophil count to <15 eosinophils per high-power field (eos/HPF) after at least 10 weeks of OVB therapy. Results: A total of 46 children were treated with OVB mixed with Splenda, and 14 were treated with OVB mixed with Neocate Nutra. The 2 groups were not significantly different in their demographic (race, age, sex) or clinical (initial eosinophil count, proton pump inhibitor use, or concomitant dietary elimination) characteristics. On follow-up endoscopy, 30 of 46 patients on Splenda and 13 of 14 patients on Neocate Nutra achieved histologic response. Mean pretreatment and posttreatment peak eosinophil counts for the children taking Neocate Nutra were 62 eos/HPF ([high-power field] range 20–120 eos/HPF) and 9 eos/HPF (range 0–100 eos/HPF), respectively. Mean pretreatment and posttreatment peak eosinophil counts for the Splenda group were 59.5 eos/HPF (range 20–180 eos/HPF) and 25.5 eos/HPF (range 0–200 eos/HPF), respectively. The odds ratio (OR) of success with Neocate Nutra as compared with Splenda was 6.93 (95% CI 0.83–57.91, P = 0.0728), demonstrating the noninferiority of Neocate Nutra. Conclusions: We demonstrate that OVB mixed with Neocate Nutra is at least as effective as OVB mixed with Splenda at treating children with EoE. Neocate Nutra is an innovative, effective, and palatable mixing agent to create a viscous budesonide slurry for families who prefer not to use the standard recipe with Splenda.

Impaired T-cell receptor activation in IL-1 receptor–associated kinase-4–deficient patients

BACKGROUND IL-1 receptor-associated kinase 4 (IRAK-4) is an effector of the Toll-like receptor and IL-1 receptor pathways that plays a critical role in innate immune responses. The role of IRAK-4 in adaptive immune functions in human subjects is incompletely understood. OBJECTIVE We sought to evaluate T-cell function in IRAK-4 deficient patients. METHODS We compared upregulation of CD25 and CD69 on T cells and production of IL-2, IL-6, and IFN-gamma after stimulation of PBMCs from 4 IRAK-4-deficient patients and healthy control subjects with anti-CD3 and anti-CD28. RESULTS Upregulation of CD25 and CD69 on T cells and production of IL-6 and IFN-gamma, but not IL-2, was significantly reduced in IRAK-4-deficient patients. CONCLUSIONS IRAK-4-deficient patients have defects in T-cell activation.

Impact of Gastroesophageal Reflux Disease on Mucosal Immunity and Atopic Disorders

Atopic disorders and gastroesophageal reflux disease (GERD) are some of the most common medical conditions treated by primary care physicians and specialists alike. The observation that atopic disorders, like asthma, allergic rhinitis and sinusitis, food allergies, atopic dermatitis, contact dermatitis, and eosinophilic esophagitis are common comorbidities in patients with GERD raises the question of the nature of the relationship that may exist between GERD and atopic disorders. In this article, we review the pathophysiology of GERD, its effect on the immune system, the effect of acid-blocking medications on allergic responses, as well as several common atopic conditions that have been associated with GERD including asthma, chronic rhinosinusitis (CRS), allergic rhinitis (AR), atopic dermatitis (AD), contact dermatitis (CD), food allergies, proton pump inhibitor (PPI)-responsive esophageal eosinophilia (PPI-REE), and eosinophilic esophagitis (EoE). In each condition, the evidence of a causal link is not definitive. Although the relationship between asthma and GERD remains controversial, evidence suggests that a subset of asthma patients with documented GERD may experience improved asthma control following appropriate treatment of GERD. The relationship of GERD to allergic rhinitis and chronic sinusitis is weak; however, studies support the concept that treatment of frequent episodes of GERD can have a positive effect on rhinitis and sinusitis overall. The relationship between allergic sensitization and GERD is likely bidirectional. GERD may induce changes in the mucosal immune system that may favor the development of food allergy and allergic sensitization to aeroallergens; however, the underlying mechanisms have not been established.