Childhood bullying involvement predicts low-grade systemic inflammation into adulthood.

Bullying is a common childhood experience that involves repeated mistreatment to improve or maintain one's status. Victims display long-term social, psychological, and health consequences, whereas bullies display minimal ill effects. The aim of this study is to test how this adverse social experience is biologically embedded to affect short- or long-term levels of C-reactive protein (CRP), a marker of low-grade systemic inflammation. The prospective population-based Great Smoky Mountains Study (n = 1,420), with up to nine waves of data per subject, was used, covering childhood/adolescence (ages 9-16) and young adulthood (ages 19 and 21). Structured interviews were used to assess bullying involvement and relevant covariates at all childhood/adolescent observations. Blood spots were collected at each observation and assayed for CRP levels. During childhood and adolescence, the number of waves at which the child was bullied predicted increasing levels of CRP. Although CRP levels rose for all participants from childhood into adulthood, being bullied predicted greater increases in CRP levels, whereas bullying others predicted lower increases in CRP compared with those uninvolved in bullying. This pattern was robust, controlling for body mass index, substance use, physical and mental health status, and exposures to other childhood psychosocial adversities. A child's role in bullying may serve as either a risk or a protective factor for adult low-grade inflammation, independent of other factors. Inflammation is a physiological response that mediates the effects of both social adversity and dominance on decreases in health.

Biochemical and Structural Studies on PrfA, the Transcriptional Regulator of Virulence in Listeria monocytogenes

Abstract

Listeria monocytogenes is a gram-positive soil saprophytic bacterium that is capable of causing fatal infection in humans. The main virulence regulator PrfA, a member of the Crp/FNR family of transcriptional regulators, activates the expression of essential proteins required for host cell invasion and cell-to-cell spread. The mechanism of PrfA activation and the identity of its small molecule coactivator have remained a mystery for more than 20 years, but it is hypothesized that PrfA shares mechanistic similarity to the E. coli cAMP binding protein, Crp. Crp activates gene expression by binding cAMP, increasing the DNA binding affinity of the protein and causing a significant DNA bend that facilitates RNA polymerase binding and downstream gene activation. Our data suggests PrfA activates virulence protein expression through a mechanism distinct from the canonical Crp activation mechanism that involves a combination of cysteine residue reduction and glutathione (GSH) binding.

Listeria lacking glutathione synthase (ΔgshF) is avirulent in mice; however virulence is rescued when the bacterium expresses the constitutively active PrfA mutant G145S. Interestingly, Listeria expressing a PrfA mutant in which its four cysteines are mutated to alanine (Quad PrfA), demonstrate a 30-fold decrease in virulence. The Quad and ΔgshF double mutant strains are avirulent. DNA-binding affinity, measured through fluorescence polarization assays, indicate reduction of the cysteine side chains is sufficient to allow PrfA to binds its physiological promoters Phly and PactA with low nanomolar affinity. Oxidized PrfA binds the promoters poorly.

Unexpectedly, Quad also binds promoter DNA with nanomolar affinity, suggesting that the cysteines play a role in transcription efficiency in addition to DNA binding. Both PrfA and Quad bind GSH at physiologically relevant and comparable affinities, however GSH did not affect DNA binding in either case. Thermal denaturation assays suggest that Quad and wild-type PrfA differ structurally upon binding GSH, which supports the in vivo difference in infection between the regulator and its mutant.

Structures of PrfA in complex with cognate DNA, determined through X-ray crystallography, further support the disparity between PrfA and Crp activation mechanisms as two structures of reduced PrfA bound to Phly (PrfA-Phly30 and PrfA-Phly24) suggest the DNA adopts a less bent DNA conformation when compared to Crp-cAMP- DNA. The structure of Quad-Phly30 confirms the DNA-binding data as the protein-DNA complex adopts the same overall conformation as PrfA-Phly.

From these results, we hypothesize a two-step activation mechanism wherein PrfA, oxidized upon cell entry and unable to bind DNA, is reduced upon its intracellular release and binds DNA, causing a slight bend in the promoter and small increase in transcription of PrfA-regulated genes. The structures of PrfA-Phly30 and PrfA-Phly24 likely visualize this intermediate complex. Increasing concentrations of GSH shift the protein to a (PrfA-GSH)-DNA complex which is fully active transcriptionally and is hypothesized to resemble closely the transcriptionally active structure of the cAMP-(Crp)-DNA complex. Thermal denaturation results suggest Quad PrfA is deficient in this second step, which explains the decrease in virulence and implicates the cysteine residues as critical for transcription efficiency. Further structural and biochemical studies are on-going to clarify this mechanism of activation.

Vitamin D, d-dimer, Interferon γ, and sCD14 Levels are Independently Associated with Immune Reconstitution Inflammatory Syndrome: A Prospective, International Study

© 2015.To determine the immunological profile most important for IRIS prediction, we evaluated 20 baseline plasma biomarkers in Acquired Immunodeficiency Syndrome (AIDS) patients initiating antiretroviral therapy (ART). Patients were enrolled in a randomized, placebo-controlled ART initiation trial in South Africa and Mexico to test whether maraviroc could prevent IRIS. Participants were classified prospectively as having IRIS within 6. months of ART initiation. Twenty plasma biomarkers were measured at study enrollment for 267 participants. Biomarkers were tested for predicting IRIS with adjustment for covariates chosen through forward stepwise selection. Sixty-two participants developed IRIS and of these 21 were tuberculosis (TB)-IRIS. Baseline levels of vitamin D and higher d-dimer, interferon gamma (IFNγ), and sCD14 were independently associated with risk of IRIS in multivariate analyses. TB-IRIS cases exhibited a distinct biosignature from IRIS related to other pathogens, with increased levels of C-reactive protein (CRP), sCD14, IFNγ, and lower levels of Hb that could be captured by a composite risk score. Elevated markers of Type 1 T helper (Th1) response, monocyte activation, coagulation and low vitamin D were independently associated with IRIS risk. Interventions that decrease immune activation and increase vitamin D levels warrant further study.