Susan T. Stephenson

Blocking of α4β7 Gut-Homing Integrin during Acute Infection Leads to Decreased Plasma and Gastrointestinal Tissue Viral Loads in Simian Immunodeficiency Virus-Infected Rhesus Macaques

Intravenous administration of a novel recombinant rhesus mAb against the α4β7 gut-homing integrin (mAb) into rhesus macaques just prior to and during acute SIV infection resulted in significant decrease in plasma and gastrointestinal (GI) tissue viral load and a marked reduction in GI tissue proviral DNA load as compared with control SIV-infected rhesus macaques. This mAb administration was associated with increases in peripheral blood naive and central memory CD4+ T cells and maintenance of a high frequency of CCR5+CD4+ T cells. Additionally, such mAb administration inhibited the mobilization of NK cells and plasmacytoid dendritic cells characteristically seen in the control animals during acute infection accompanied by the inhibition of the synthesis of MIP-3α by the gut tissues. These data in concert suggest that blocking of GI trafficking CD4+ T cells and inhibiting the mobilization of cell lineages of the innate immune system may be a powerful new tool to protect GI tissues and modulate acute lentiviral infection.

Decreased NK cell frequency and function is associated with increased risk of KIR3DL allele polymorphism in simian immunodeficiency virus-infected rhesus macaques with high viral loads.

NK cells have been established as an important effector of innate immunity in a variety of viral infections. In HIV-1 infection in humans, alterations of NK cell function, frequency, and expression of various NK receptors have been reported to be associated with differential dynamics of disease progression. Expression of certain alleles of KIR3DL and KIR3DS receptors on NK cells was shown to correlate with levels of virus replication. In the SIV-infected rhesus macaque (RM) model of AIDS, several families of killer inhibitory Ig-related receptors (KIR receptors) corresponding to their human counterparts have been characterized, but only at the level of individual sequence variants. Here we define 14 different alleles of KIR3DL expressed among 38 SIV-infected RM, characterized by either high or low levels of SIV replication, by analyzing multiple sequences from individual animals and show an unequal distribution of certain alleles in these cohorts. High levels of SIV replication were associated with significant increases in KIR3DL mRNA levels in addition to decreases in both the frequency and function of NK cells in these animals. The higher frequency of inheritance of two KIR3DL alleles characterized by a single nucleotide polymorphism 159 H/Q was associated with RM that exhibited high plasma viral load. This data for the first time defines multiple alleles of KIR3DL in RM and shows an association between virus control, NK cell function and genetic polymorphisms of KIR receptors.

Characterization of a high TNF-α phenotype in children with moderate-to-severe asthma

Systemic TNF-α expression is increased in a subset of children with moderate-to-severe asthma despite aggressive corticosteroid treatment and is associated with poor asthma control. Phenotypic-directed TNF-α inhibition may be of benefit in some asthmatic children.

Letter to the editorCharacterization of a high TNF-α phenotype in children with moderate-to-severe asthma

Systemic TNF-α expression is increased in a subset of children with moderate-to-severe asthma despite aggressive corticosteroid treatment and is associated with poor asthma control. Phenotypic-directed TNF-α inhibition may be of benefit in some asthmatic children.

Multiple KIR gene polymorphisms are associated with plasma viral loads in SIV-infected rhesus macaques

Innate immune mechanisms play a deterministic role in the rate of disease progression during acute infection in HIV infected humans and SIV infection of non-human primates. The role NK cells play in mediating such an effect has thus gained importance. One of the major sets of molecules that regulate NK cell function are the killer cell immunoglobulin-like molecules (KIRs). Our laboratory has previously shown an association of KIR3DL alleles 13 and 14 with high plasma viral loads in a cohort of SIV-infected rhesus macaques. To gain a more detailed understanding of the role of KIR polymorphisms, our laboratory herein conducted studies of three additional KIR loci and show that select KIR3DH alleles appear to be more strongly associated with high plasma viral loads than KIR3DL alleles 13 and 14. In addition, we herein document the existence of additional new alleles for the KIR1D, KIR2DL4, and the KIR3DH loci.

CD4+ T Cells from Simian Immunodeficiency Virus Disease-Resistant Sooty Mangabeys Produce More IL-2 Than Cells from Disease-Susceptible Species: Involvement of p300 and CREB at the Proximal IL-2 Promoter in IL-2 Up-Regulation

IL-2 is an important cytokine required for the physiological function of CD4+ T cells. Immunological unresponsiveness—anergy— of CD4+ T cells is characterized by the inability of these cells to synthesize IL-2. Both progressive HIV infection leading to AIDS in humans and SIV infection in rhesus macaques (RM) are associated with dysregulation of IL-2 synthesis. In certain nonhuman primate species, such as sooty mangabeys (SM), SIV infection does not lead to AIDS. We have shown that this is associated with the resistance of the CD4+ T cells from SM to undergo anergy in vitro. In this study, we show that CD4+ T cells from SM spontaneously synthesize 2- to 3-fold higher levels of IL-2 than corresponding cells from RM. Proximal IL-2 promoter constructs derived from SM show significantly higher activity than the RM-derived constructs in primary CD4+ T cells, which is associated with an element at approximately nt −200. Activity of both constructs was up-regulated by p300 and down-regulated by CREB to a similar degree. Chromatin immunoprecipitation analysis showed significantly higher binding of p300 and lower binding of CREB to the SM promoter in vivo. Two single nucleotide substitutions present in the SM sequence around position −200 and −180 seem to increase the affinity of these sites for the binding of transcription factors, one of which was identified as Oct-1. These unique characteristics of the proximal IL-2 promoter in SM therefore can represent one of the mechanisms contributing to the resistance of these cells to undergo anergy.

Systemic Corticosteroid Responses in Children with Severe Asthma: Phenotypic and Endotypic Features

BACKGROUND Severe asthma in children is a heterogeneous disorder associated with variable responses to corticosteroid treatment. Criterion standards for corticosteroid responsiveness assessment in children are lacking. OBJECTIVE This study sought to characterize systemic corticosteroid responses in children with severe asthma after treatment with intramuscular triamcinolone and to identify phenotypic and molecular predictors of an intramuscular triamcinolone response. METHODS Asthma-related quality of life, exhaled nitric oxide, blood eosinophils, lung function, and inflammatory cytokine and chemokine mRNA gene expression in peripheral blood mononuclear cells were assessed in 56 children with severe asthma at baseline and 14 days after intramuscular triamcinolone injection. The Asthma Control Questionnaire was used to classify children with severe asthma into corticosteroid response groups. RESULTS Three groups of children with severe asthma were identified: controlled severe asthma, children who achieved control after triamcinolone, and children who did not achieve control. At baseline, these groups were phenotypically similar. After triamcinolone, discordance between symptoms, lung function, exhaled nitric oxide, and blood eosinophils was noted. Clinical phenotypic predictors were of limited utility in predicting the triamcinolone response, whereas systemic mRNA expression of inflammatory cytokines and chemokines related to IL-2, IL-10, and TNF signaling pathways, namely, AIMP1, CCR2, IL10RB, and IL5, strongly differentiated children who failed to achieve control with triamcinolone administration. CONCLUSIONS Systemic corticosteroid responsiveness in children with severe asthma is heterogeneous. Alternative prediction models that include molecular endotypic as well as clinical phenotypic features are needed to identify which children derive the most clinical benefit from systemic corticosteroid step-up therapy given the potential side effects.

TGF-β1 Suppresses the Type I IFN Response and Induces Mitochondrial Dysfunction in Alveolar Macrophages

TGF-β1 is a pleiotropic cytokine with an established role in fibrosis; however, the immunosuppressive effects of TGF-β1 are less characterized. Elevated levels of TGF-β1 are found in patients with acute and chronic lung diseases, and the underlying disease processes are exacerbated by respiratory viral infections. The alveolar macrophage is the first line of cellular defense against respiratory viral infections, and its response to infections is dependent on environmental cues. Using the mouse alveolar macrophage line, MH-S, and human CD14+ monocyte-derived macrophages, we examined the effects of TGF-β1 on the type I IFN antiviral response, macrophage polarization, and mitochondrial bioenergetics following a challenge with human respiratory syncytial virus (RSV). Our results showed that TGF-β1 treatment of macrophages decreased the antiviral and proinflammatory response, and suppressed basal, maximal, spare mitochondrial respiration, and mitochondrial ATP production. Challenge with RSV following TGF-β1 treatment further exacerbated mitochondrial dysfunction. The TGF-β1 and TGF-β1+RSV–treated macrophages had a higher frequency of apoptosis and diminished phagocytic capacity, potentially through mitochondrial stress. Disruption of TGF-β1 signaling or rescue of mitochondrial respiration may be novel therapeutically targetable pathways to improve macrophage function and prevent secondary bacterial infections that complicate viral respiratory infections.

Decreased expression of acetaminophen-metabolizing enzymes and glutathione in asthmatic children after acetaminophen exposure

Children with moderate-to-severe asthma have decreased expression of acetaminophen metabolizing genes and glutathione that may account for the previously-reported risk of acetaminophen in this vulnerable population.