Anthrax toxins suppress T lymphocyte activation by disrupting antigen receptor signaling

Anthrax is an infection caused by pathogenic strains of Bacillus anthracis, which secretes a three-component toxic complex consisting of protective antigen (PA), edema factor (EF), and lethal factor (LF). PA forms binary complexes with either LF or EF and mediates their entry into host cells. Although the initial phases of bacterial growth occur in the lymph node, the host fails to mount an effective immune response. Here, we show that LT and ET are potent suppressors of human T cell activation and proliferation triggered through the antigen receptor. Both LT and ET inhibit the mitogen-activated protein and stress kinase pathways, and both toxins inhibit activation of NFAT and AP-1, two transcription factors essential for cytokine gene expression. These data identify a novel strategy of immune evasion by B. anthracis, based on both effector subunits of the toxic complex, and targeted to a key cellular component of adaptive immunity

Models of classroom assessment for course-based research experiences

Course-based research pedagogy involves positioning students as contributors to authentic research projects as part of an engaging educational experience that promotes their learning and persistence in science. To develop a model for assessing and grading students engaged in this type of learning experience, the assessment aims and practices of a community of experienced course-based research instructors were collected and analyzed. This approach defines four aims of course-based research assessment—(1) Assessing Laboratory Work and Scientific Thinking; (2) Evaluating Mastery of Concepts, Quantitative Thinking and Skills; (3) Appraising Forms of Scientific Communication; and (4) Metacognition of Learning—along with a set of practices for each aim. These aims and practices of assessment were then integrated with previously developed models of course-based research instruction to reveal an assessment program in which instructors provide extensive feedback to support productive student engagement in research while grading those aspects of research that are necessary for the student to succeed. Assessment conducted in this way delicately balances the need to facilitate students’ ongoing research with the requirement of a final grade without undercutting the important aims of a CRE education

IL-13 R130Q, a common variant associated with allergy and asthma, enhances effector mechanisms essential for human allergic inflammation

Genetic factors are known to strongly influence susceptibility to allergic inflammation. The Th2 cytokine IL-13 is a central mediator of allergy and asthma, and common single-nucleotide polymorphisms in IL13 are associated with allergic phenotypes in several ethnically diverse populations. In particular, IL13+2044G→A is expected to result in the nonconservative replacement of arginine 130 (R130) with glutamine (Q). We examined the impact of IL13+2044G→A on the functional properties of IL-13 by directly comparing the activity of WT IL-13 and IL-13 R130Q on primary human cells involved in the effector mechanisms of allergic inflammation. Our results show that IL-13 R130Q was significantly more active than WT IL-13 in inducing STAT6 phosphorylation and CD23 expression in monocytes and hydrocortisone-dependent IgE switching in B cells. Notably, IL-13 R130Q was neutralized less effectively than WT IL-13 by an IL-13Rα2 decoy. Decreased neutralization of the minor variant could contribute to its enhanced in vivo activity. Neither IL-13 variant was able to engage T cells, which suggests that increased allergic inflammation in carriers of IL13+2044A depends on enhanced IL-13–mediated Th2 effector functions rather than increased Th2 differentiation. Collectively, our data indicate that natural variation in the coding region of IL13 may be an important genetic determinant of susceptibility to allergy

Generation of transgenic mice expressing EGFP protein fused to NP68 MHC class I epitope using lentivirus vectors

International audienceImmune tolerance to self-antigens is a complex process that utilizes multiple mechanisms working in concert to maintain homeostasis and prevent autoimmunity. Considerable progress in deciphering the mechanisms controlling the activation or deletion of T cells has been made by using T cell receptor (TCR) transgenic mice. One such model is the F5 model in which CD8 T cells express a TCR specific for an epitope derived from the influenza NP68 protein. Our aim was to create transgenic mouse models expressing constitutively the NP68 epitope fused to enhanced green fluorescent protein (EGFP) in order to assess unambiguously the relative levels of NP68 epitope expressed by single cells. We used a lentiviral-based approach to generate two independent transgenic mouse strains expressing the fusion protein EGFP-NP68 under the control of CAG (CMV immediate early enhancer and the chicken β-actin promoter) or spleen focus-forming virus (SFFV) promoters. Analysis of the pattern of EGFP expression in the hematopoietic compartment showed that CAG and SFFV promoters are differentially regulated during T cell development. However, both promoters drove high EGFP-NP68 expression in dendritic cells (pDCs, CD8α+ cDCs, and CD8α− cDCs) from spleen or generated in vitro following differentiation from bone-marrow progenitors. NP68 epitope was properly processed and successfully presented by dendritic cells (DCs) by direct presentation and cross-presentation to F5 CD8 T cells. The models presented here arevaluable tools to investigate the priming of F5 CD8 T cells by different subsets of DCs