E. Scott Halstead

In vivo stimulation of CD137 broadens primary antiviral CD8+ T cell responses.

Given the key role CD8+ T cells play in controlling viral infection, strategies to enhance these responses may have important clinical applications. We found that in vivo CD137 stimulation with an agonistic monoclonal antibody enhanced the primary CD8+ T cell response to influenza type A viral infection in mice. Stimulation of CD137 increased the absolute number of CD8+ T cells to influenza epitopes in the lungs of infected animals, preferentially expanded CD8+ T cells that recognized nondominant epitopes and greatly enhanced direct ex vivo cytotoxicity. CD137 stimulation also restored the CD8+ T cell response to the immunodominant influenza epitope in CD28−/− mice. Thus, in vivo CD137 stimulation enhances and broadens the CD8+ T cell response to influenza virus and can restore the CD8+ T cell response when CD28 costimulation is absent. This suggests that CD137 stimulation may be useful as a strategy to enhance the CD8+ T cell response to viruses.

Reduced frequency of CD56 dim CD16 pos natural killer cells in pediatric systemic inflammatory response syndrome/sepsis patients

Background:Sepsis continues to be a leading cause of death in infants and children. Natural killer (NK) cells serve as a bridge between innate and adaptive immunity, yet their role in pediatric sepsis has not been well characterized.Methods:We tested the hypothesis that decreased NK cell cytotoxicity is a common feature of pediatric systemic inflammatory response syndrome (SIRS)/sepsis patients by measuring, using flow cytometry, NK cell cytotoxicity and cell surface phenotype in the peripheral blood of 38 pediatric intensive care patients who demonstrated signs and symptoms of SIRS and/or sepsis.Results:NK cell cytotoxicity was significantly reduced in peripheral blood mononuclear cells (PBMCs) of pediatric SIRS/sepsis patients as compared with healthy controls, and the percentage of CD56dim CD16+ cytotoxic NK cells in PBMCs was lower in patients with SIRS/sepsis than in normal donors. However, on a per cell basis, CD56dim CD16+ NK cells in patients mediated cytotoxicity as well as those in normal donors.Conclusion:The NK cell dysfunction in pediatric SIRS/sepsis patients reflects a quantitative rather than a qualitative difference from healthy controls.

Three Hypothetical Inflammation Pathobiology Phenotypes and Pediatric Sepsis-Induced Multiple Organ Failure Outcome.

Objectives: We hypothesize that three inflammation pathobiology phenotypes are associated with increased inflammation, proclivity to develop features of macrophage activation syndrome, and multiple organ failure-related death in pediatric severe sepsis. Design: Prospective cohort study comparing children with severe sepsis and any of three phenotypes: 1) immunoparalysis-associated multiple organ failure (whole blood ex vivo tumor necrosis factor response to endotoxin < 200 pg/mL), 2) thrombocytopenia-associated multiple organ failure (new onset thrombocytopenia with acute kidney injury and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 activity < 57%), and/or 3) sequential multiple organ failure with hepatobiliary dysfunction (respiratory distress followed by liver dysfunction with soluble Fas ligand > 200 pg/mL), to those without any of these phenotypes. Setting: Tertiary children’s hospital PICU. Patients: One hundred consecutive severe sepsis admissions. Interventions: Clinical data were recorded daily, and blood was collected twice weekly. Measurements and Main Results: Multiple organ failure developed in 75 cases and eight died. Multiple organ failure cases with any of the three inflammation phenotypes (n = 37) had higher inflammation (C-reactive protein, p = 0.009 and ferritin, p < 0.001) than multiple organ failure cases without any of these phenotypes (n = 38) or cases with only single organ failure (n = 25). Development of features of macrophage activation syndrome and death were more common among multiple organ failure cases with any of the phenotypes (macrophage activation syndrome: 10/37, 27%; death: 8/37, 22%) compared to multiple organ failure cases without any phenotype (macrophage activation syndrome: 1/38, 3%; p = 0.003 and death: 0/38, 0%; p = 0.002). Conclusions: Our approach to phenotype categorization remains hypothetical, and the phenotypes identified need to be confirmed in multicenter studies of pediatric multiple organ dysfunction syndrome.

SP-R210 (Myo18A) Isoforms as Intrinsic Modulators of Macrophage Priming and Activation

The surfactant protein (SP-A) receptor SP-R210 has been shown to increase phagocytosis of SP-A-bound pathogens and to modulate cytokine secretion by immune cells. SP-A plays an important role in pulmonary immunity by enhancing opsonization and clearance of pathogens and by modulating macrophage inflammatory responses. Alternative splicing of the Myo18A gene results in two isoforms: SP-R210S and SP-R210L, with the latter predominantly expressed in alveolar macrophages. In this study we show that SP-A is required for optimal expression of SP-R210L on alveolar macrophages. Interestingly, pre-treatment with SP-A prepared by different methods either enhances or suppresses responsiveness to LPS, possibly due to differential co-isolation of SP-B or other proteins. We also report that dominant negative disruption of SP-R210L augments expression of receptors including SR-A, CD14, and CD36, and enhances macrophages’ inflammatory response to TLR stimulation. Finally, because SP-A is known to modulate CD14, we used a variety of techniques to investigate how SP-R210 mediates the effect of SP-A on CD14. These studies revealed a novel physical association between SP-R210S, CD14, and SR-A leading to an enhanced response to LPS, and found that SP-R210L and SP-R210S regulate internalization of CD14 via distinct macropinocytosis-like mechanisms. Together, our findings support a model in which SP-R210 isoforms differentially regulate trafficking, expression, and activation of innate immune receptors on macrophages.

Lethal influenza infection: Is a macrophage to blame?

Alveolar macrophages (AMs) are critical for immunity against influenza A virus (IAV) infection. Depletion, hyporeactivity, and disruption of AM development and differentiation are all associated with lethal IAV infection. AMs drive the innate immune response that limits IAV infection. AMs are crucial for steady-state homeostasis of pulmonary surfactant, and in turn surfactant proteins regulate AMs and participate in host defense against IAV. Known factors that are necessary for AM function and differentiation in vivo include surfactant proteins, the growth factor GM-CSF, the hormone receptor PPARγ, and the transcription factors PU.1 and Bach2. Although PU.1 and PPARγ are downstream effectors of GM-CSF, Bach2 works independently. GM-CSF and Bach2-deficient AMs have phenotypes with immature or alternatively activated states of differentiation, respectively, and both extremes are unsuitable for surfactant homeostasis. The activation state of AMs and the local microenvironment may determine the development of symptomatic versus asymptomatic IAV infection in different individuals.

Rapid Onset of Hippocampal Atrophy in Febrile-Infection Related Epilepsy Syndrome (FIRES)

Febrile infection-related epilepsy syndrome (FIRES) is a catastrophic and usually refractory epilepsy syndrome that occurs after a febrile illness in previously normal children. The pathogenesis of the syndrome is unknown, and the diagnosis is typically made by exclusion after an exhaustive negative workup for central nervous system infections and autoimmune or metabolic disorders. Magnetic resonance imaging of patients with this condition has previously shown hippocampal abnormalities, typically found several months or longer after initial seizures. We report a previously healthy 5-year-old child who developed hippocampal atrophy by day 37 of his illness. The development of early hippocampal atrophy in this epileptic encephalopathy may provide insight into pathogenesis and highlights the need for aggressive and effective interventions early in the disease process.

A Systemic Inflammation Mortality Risk Assessment Contingency Table for Severe Sepsis.

Objectives: We tested the hypothesis that a C-reactive protein and ferritin-based systemic inflammation contingency table can track mortality risk in pediatric severe sepsis. Design: Prospective cohort study. Setting: Tertiary PICU. Patients: Children with 100 separate admission episodes of severe sepsis were enrolled. Interventions: Blood samples were attained on day 2 of sepsis and bi-weekly for biomarker batch analysis. A 2 × 2 contingency table using C-reactive protein and ferritin thresholds was developed. Measurements and Main Results: A C-reactive protein of 4.08 mg/dL and a ferritin of 1,980 ng/mL were found to be optimal cutoffs for outcome prediction at first sampling (n = 100) using the Youden index. PICU mortality was increased in the “high-risk” C-reactive protein greater than or equal to 4.08 mg/dL and ferritin greater than or equal to 1,980 ng/mL category (6/13 [46.15%]) compared with the “intermediate-risk” C-reactive protein greater than or equal to 4.08 mg/dL and ferritin less than 1,980 ng/mL or C-reactive protein less than 4.08 mg/dL and ferritin greater than or equal to 1,980 ng/mL categories (2/43 [4.65%]), and the “low-risk” C-reactive protein less than 4.08 mg/dL and ferritin less than 1,980 ng/mL category (0/44 [0%]) (odds ratio, 36.43 [95% CI, 6.16–215.21]). The high-risk category was also associated with the development of immunoparalysis (odds ratio, 4.47 [95% CI, 1.34–14.96]) and macrophage activation syndrome (odds ratio, 24.20 [95% CI, 5.50–106.54]). Sixty-three children underwent sequential blood sampling; those who were initially in the low-risk category (n = 24) and those who subsequently migrated (n = 19) to the low-risk category all survived, whereas those who remained in the “at-risk” categories had increased mortality (7/20 [35%]; p < 0.05). Conclusions: A C-reactive protein- and ferritin-based contingency table effectively assessed mortality risk. Reduction in systemic inflammation below a combined threshold C-reactive protein of 4.08 mg/dL and ferritin of 1,980 ng/mL appeared to be a desired response in children with severe sepsis.

Severe Cardiomyopathy in an Infant After Iatrogenic Fosphenytoin Overdose

Seizures are common occurrences in both community and pediatric emergency care units. The first line of anticonvulsant treatment for patients with status epilepticus is benzodiazepine administration, whereas the second line of treatment for refractory status epilepticus, and/or seizure prophylaxis, is phenytoin or its prodrug, fosphenytoin. We report the case of severe, but reversible, cardiomyopathy in an infant who received an iatrogenic fosphenytoin overdose. The patient’s initial corrected serum phenytoin level was 109 μg/mL. Myocardial function was greatly depressed with a fractional shortening (FS) nadir of 6% to 8% at presentation, but with spontaneous recovery to a normal FS within 2 weeks of the fosphenytoin overdose.

Racial and Ethnic Disparities and Bias in the Evaluation and Reporting of Abusive Head Trauma

Objective To characterize racial and ethnic disparities in the evaluation and reporting of suspected abusive head trauma (AHT) across the 18 participating sites of the Pediatric Brain Injury Research Network (PediBIRN). We hypothesized that such disparities would be confirmed at multiple sites and occur more frequently in patients with a lower risk for AHT. Study design Aggregate and site‐specific analysis of the cross‐sectional PediBIRN dataset, comparing AHT evaluation and reporting frequencies in subpopulations of white/non‐Hispanic and minority race/ethnicity patients with lower vs higher risk for AHT. Results In the PediBIRN study sample of 500 young, acutely head‐injured patients hospitalized for intensive care, minority race/ethnicity patients (n = 229) were more frequently evaluated (P < .001; aOR, 2.2) and reported (P = .001; aOR, 1.9) for suspected AHT than white/non‐Hispanic patients (n = 271). These disparities occurred almost exclusively in lower risk patients, including those ultimately categorized as non‐AHT (P = .001 [aOR, 2.4] and P = .003 [aOR, 2.1]) or with an estimated AHT probability of ≤25% (P < .001 [aOR, 4.1] and P < .001 [aOR, 2.8]). Similar site‐specific analyses revealed that these results reflected more extreme disparities at only 2 of 18 sites, and were not explained by local confounders. Conclusion Significant race/ethnicity‐based disparities in AHT evaluation and reporting were observed at only 2 of 18 sites and occurred almost exclusively in lower risk patients. In the absence of local confounders, these disparities likely represent the impact of local physicians’ implicit bias.

SH3GLB2/endophilin B2 regulates lung homeostasis and recovery from severe influenza A virus infection

New influenza A viruses that emerge frequently elicit composite inflammatory responses to both infection and structural damage of alveolar-capillary barrier cells that hinders regeneration of respiratory function. The host factors that relinquish restoration of lung health to enduring lung injury are insufficiently understood. Here, we investigated the role of endophilin B2 (B2) in susceptibility to severe influenza infection. WT and B2-deficient mice were infected with H1N1 PR8 by intranasal administration and course of influenza pneumonia, inflammatory, and tissue responses were monitored over time. Disruption of B2 enhanced recovery from severe influenza infection as indicated by swift body weight recovery and significantly better survival of endophilin B2-deficient mice compared to WT mice. Compared to WT mice, the B2-deficient lungs exhibited induction of genes that express surfactant proteins, ABCA3, GM-CSF, podoplanin, and caveolin mRNA after 7 days, temporal induction of CCAAT/enhancer binding protein CEBPα, β, and δ mRNAs 3–14 days after infection, and differences in alveolar extracellular matrix integrity and respiratory mechanics. Flow cytometry and gene expression studies demonstrated robust recovery of alveolar macrophages and recruitment of CD4+ lymphocytes in B2-deficient lungs. Targeting of endophilin B2 alleviates adverse effects of IAV infection on respiratory and immune cells enabling restoration of alveolar homeostasis.