Diamino Allose Phosphates: Novel, Potent, and Highly Stable Toll-like Receptor 4 Agonists.

Most known synthetic toll-like receptor 4 (TLR4) agonists are carbohydrate-based lipid-A mimetics containing several fatty acyl chains, including a labile 3-O-acyl chain linked to the C-3 position of the non-reducing sugar known to undergo cleavage impacting stability and resulting in loss of activity. To overcome this inherent instability, we rationally designed a new class of chemically more stable synthetic TLR4 ligands that elicit robust innate and adaptive immune responses. This new class utilized a diamino allose phosphate (DAP) scaffold containing a nonhydrolyzable 3-amide bond instead of the classical 3-ester. Accordingly, the DAPs have significantly improved thermostability in aqueous formulations and potency relative to other known natural and synthetic TLR4 ligands. Furthermore, the DAP analogues function as potent vaccine adjuvants to enhance influenza-specific antibodies in mice and provide protection against lethal influenza virus challenges. This novel set of TLR4 ligands show promise as next-generation vaccine adjuvants and stand-alone immunomodulators.

Dysregulation of Alveolar Macrophage PPARγ, NADPH Oxidases, and TGFß1 in Otherwise Healthy HIV-Infected Individuals.

Despite antiretroviral therapy (ART), respiratory infections increase mortality in individuals living with chronic human immunodeficiency virus (HIV) infection. In experimental and clinical studies of chronic HIV infection, alveolar macrophages (AMs) exhibit impaired phagocytosis and bacterial clearance. Peroxisome proliferator-activated receptor (PPAR)γ, NADPH oxidase (Nox) isoforms Nox1, Nox2, Nox4, and transforming growth factor-beta 1 (TGFß1) are critical mediators of AM oxidative stress and phagocytic dysfunction. Therefore, we hypothesized that HIV alters AM expression of these targets, resulting in chronic lung oxidative stress and subsequent immune dysfunction. A cross-sectional study of HIV-infected (n = 22) and HIV-uninfected (n = 6) subjects was conducted. Bronchoalveolar lavage (BAL) was performed, and AMs were isolated. Lung H2O2 generation was determined by measuring H2O2 in the BAL fluid. In AMs, PPARγ, Nox1, Nox2, Nox4, and TGFß1 mRNA (quantitative real-time polymerase chain reaction) and protein (fluorescent immunomicroscopy) levels were assessed. Compared with HIV-uninfected (control) subjects, HIV-infected subjects were relatively older and the majority were African American; ∼86% were on ART, and their median CD4 count was 445, with a median viral load of 0 log copies/ml. HIV infection was associated with increased H2O2 in the BAL, decreased AM mRNA and protein levels of PPARγ, and increased AM mRNA and protein levels of Nox1, Nox2, Nox4, and TGFß1. PPARγ attenuation and increases in Nox1, Nox2, Nox4, and TGFß1 contribute to AM oxidative stress and immune dysfunction in the AMs of otherwise healthy HIV-infected subjects. These findings provide novel insights into the molecular mechanisms by which HIV increases susceptibility to pulmonary infections.

Comparison of Glutathione, Cysteine, and Their Redox Potentials in the Plasma of Critically Ill and Healthy Children.

BACKGROUND: Oxidative stress is known to play a role in critical illness due to an imbalance in reactive oxygen species and reactive nitrogen species, and the body's ability to detoxify pro-oxidants using small molecule anti-oxidants and anti-oxidant enzymes. OBJECTIVE: To compare the concentrations of plasma redox metabolites and redox potentials for the Cys/CySS and GSH/GSSG thiol/disulfide pairs in critically ill children with healthy control children. METHODS: We performed a prospective clinical observational study of children ages ≤18 years and weight ≥6 kg, who were hospitalized between January 2010 and April 2012 in a 30-bed multidisciplinary medical-surgical pediatric intensive care unit (PICU). We measured the plasma concentrations of Cys, CySS, GSH, and GSSG within the first 24 h of PICU arrival, and we calculated the redox potential for the Cys/CySS (Eh Cys/CySS) and GSH/GSSG (Eh GSH/GSSG) thiol/disulfide pairs in the plasma of 61 critically ill children and 16 healthy control children. RESULTS: Critically ill children have less Cys (p = 0.009), less CySS (p = 0.011), less Total Cys ([Cys] + 2[CySS], p = 0.01), more GSSG (p < 0.001), and more oxidized Eh GSH/GSSG (p < 0.001) compared to healthy children. CONCLUSION: Our results demonstrate that in the presence of pediatric critical illness, the Total Cys/CySS thiol pool decreases while GSH is likely one component of the cellular redox system that reduces CySS back to Cys, thus maintaining Eh Cys/CySS. The Total Cys pool is more abundant than the Total GSH pool in the plasma of children. Further investigation is needed to elucidate the differences in redox potentials in subgroups of critically ill children, and to determine whether differences in redox metabolite concentrations and redox potentials correlate with severity of critical illness and clinical outcomes.

Exhaled breath condensate in intubated neonates--a window into the lung's glutathione status.

BACKGROUND: Analysis of exhaled breath condensates (EBC) is a non-invasive technique to evaluate biomarkers such as antioxidants in the pediatric population, but limited data exists of its use in intubated patients, particularly newborns. Currently, tracheal aspirate (TA) serves as the gold standard collection modality in critically ill newborns, but this method remains invasive. We tested the hypothesis that glutathione status would positively correlate between EBC and TA collections in intubated newborns in the Newborn Intensive Care Unit (NICU). We also hypothesized that these measurements would be associated with alveolar macrophage (AM) glutathione status in the newborn lung. METHODS: Reduced glutathione (rGSH), glutathione disulfide (GSSG), and total GSH (rGSH + (2 X GSSG)) were measured in sequential EBC and TA samples from 26 intubated newborns via high performance liquid chromatography (HPLC). Additionally, AM glutathione was evaluated via immunofluorescence. Pearson's correlation coefficient and associated 95% confidence intervals were used to quantify the associations between raw and urea-corrected concentrations in EBC and TA samples and AM staining. Statistical significance was defined as p ≤ 0.05 using two-tailed tests. The sample size was projected to allow for a correlation coefficient of 0.5, with 0.8 power and alpha of 0.05. RESULTS: EBC was obtainable from intubated newborns without adverse clinical events. EBC samples demonstrated moderate to strong positive correlations with TA samples in terms of rGSH, GSSG and total GSH. Positive correlations between the two sampling sites were observed in both raw and urea-corrected concentrations of rGSH, GSSG and total GSH. AM glutathione staining moderately correlated with GSSG and total GSH status in both the TA and EBC. CONCLUSIONS: GSH status in EBC samples of intubated newborns significantly correlated with the GSH status of the TA sample and was reflective of cellular GSH status in this cohort of neonatal patients. Non-invasive EBC sampling of intubated newborns holds promise for monitoring antioxidant status such as GSH in the premature lung. Further studies are necessary to evaluate the potential relationships between EBC biomarkers in the intubated premature newborn and respiratory morbidities.