DOCK8 and MyD88 have been implicated in serologic memory. Here we report antibody responses were impaired and CD27+ memory B cells were severely reduced in DOCK8-deficient patients. Toll-like receptor 9 (TLR9)- but not CD40-driven B cell proliferation and immunoglobulin production were severely reduced in DOCK8-deficient B cells. In contrast, TLR9-driven expression of AICDA, CD23 and CD86, and activation of NF-κB, p38 and Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. Following TLR9 ligation, DOCK8 became tyrosine phosphorylated by Pyk2, bound the Src family kinase Lyn and linked TLR9 to a Src-Syk-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.

Background Phenotypic presentations in young children with asthma are varied and may contribute to differential responses to asthma controller medications. Methods The Individualized Therapy for Asthma in Toddlers (INFANT) study was a multicenter, randomized, double-blind, double-dummy, clinical trial in children age 12-59 months (n=300) with asthma necessitating treatment with daily controller (Step 2) therapy. Participants completed a 2-8 week run-in period followed by three crossover periods with daily inhaled corticosteroid (ICS), daily leukotriene receptor antagonist (LTRA), and as-needed ICS treatment co-administered with albuterol. The primary outcome was differential response to asthma medication based on a composite measure of asthma control. The primary analysis involved two stages: determination of differential response, and assessment of whether three pre-specified features (aeroallergen sensitization, previous exacerbations, sex) predicted differential response. Results 74% (170 of 230) of children with analyzable data had a differential response to the three treatment strategies. Within differential responders, the probability of best response was highest for daily ICS and was predicted by aeroallergen sensitization, but not exacerbation history or sex. The probability of best response to daily ICS was further increased in children with both aeroallergen sensitization and blood eosinophils ≥300/μL. In these children, daily ICS was associated with more asthma control days and fewer exacerbations compared to the other treatments. Conclusions In young children with asthma necessitating Step 2 treatment, phenotyping with aeroallergen sensitization and blood eosinophils is useful for guiding treatment selection and identifies children with a high exacerbation probability for whom treatment with daily ICS is beneficial despite possible risks of growth suppression.

IMPORTANCE Many preschool children develop recurrent, severe episodes of lower respiratory tract illness (LRTI). Although viral infections are often present, bacteria may also contribute to illness pathogenesis. Strategies that effectively attenuate such episodes are needed. OBJECTIVE To evaluate if early administration of azithromycin, started prior to the onset of severe LRTI symptoms, in preschool children with recurrent severe LRTIs can prevent the progression of these episodes. DESIGN, SETTING, AND PARTICIPANTS A randomized, double-blind, placebo-controlled, parallel-group trial conducted across 9 academic US medical centers in the National Heart, Lung, and Blood Institute’s AsthmaNet network, with enrollment starting in April 2011 and follow-up complete by December 2014. Participants were 607 children aged 12 through 71 months with histories of recurrent, severe LRTIs and minimal day-to-day impairment. INTERVENTION Participants were randomly assigned to receive azithromycin (12 mg/kg/d for 5 days; n = 307) or matching placebo (n = 300), started early during each predefined RTI (child’s signs or symptoms prior to development of LRTI), based on individualized action plans, over a 12-through 18-month period. MAIN OUTCOMES AND MEASURES The primary outcome measure was the number of RTIs not progressing to a severe LRTI, measured at the level of the RTI, that would in clinical practice trigger the prescription of oral corticosteroids. Presence of azithromycin-resistant organisms in oropharyngeal samples, along with adverse events, were among the secondary outcome measures. RESULTS A total of 937 treated RTIs (azithromycin group, 473; placebo group, 464) were experienced by 443 children (azithromycin group, 223; placebo group, 220), including 92 severe LRTIs (azithromycin group, 35; placebo group, 57). Azithromycin significantly reduced the risk of progressing to severe LRTI relative to placebo (hazard ratio, 0.64 [95% CI, 0.41-0.98], P = .04; absolute risk for first RTI: 0.05 for azithromycin, 0.08 for placebo; risk difference, 0.03 [95% CI, 0.00-0.06]). Induction of azithromycin-resistant organisms and adverse events were infrequently observed. CONCLUSIONS AND RELEVANCE Among young children with histories of recurrent severe LRTIs, the use of azithromycin early during an apparent RTI compared with placebo reduced the likelihood of severe LRTI. More information is needed on the development of antibiotic-resistant pathogens with this strategy.