Evasion of human innate immunity without antagonizing TLR4 by mutant Salmonella enterica serovar Typhimurium having penta-acylated lipid A.

Modification of a lipid A moiety in Gram-negative bacterial LPS to a less acylated form is thought to facilitate bacterial evasion of host innate immunity, thereby enhancing pathogenicity. The contribution of less-acylated lipid A to interactions of whole bacterial cells with host cells (especially in humans) remains unclear. Mutant strains of Salmonella enterica serovar Typhimurium with fewer acylated groups were generated. The major lipid A form in wild-type (WT) and the mutant KCS237 strain is hexa-acylated; in mutant strains KCS311 and KCS324 it is penta-acylated; and in KCS369 it is tetra-acylated. WT and KCS237 formalin-killed and live bacteria, as well as their LPS, strongly stimulated production of pro-inflammatory cytokines in human U937 cells; this stimulation was suppressed by TLR4 suppressors. LPS of other mutants produced no agonistic activity, but strong antagonistic activity, while their formalin-killed and live bacteria preparations had weak agonistic and no antagonistic activity. Moreover, these less-acylated mutants had increased resistance to phagocytosis by U937 cells. Our results indicate that a decrease of one acyl group (from six to five) is enough to allow Salmonella to evade human innate immunity and that the antagonistic activity of less-acylated lipid A is not utilized for this evasion

Autoimmune Gastro-Pancreatitis with Anti-Protein Disulfide Isomerase-Associated 2 Autoantibody in Aire-Deficient BALB/cAnN Mice

<div><p>Although the autoimmune regulator (Aire) knockout (KO) mouse model has been reported to present various organ-specific autoimmune diseases depending on genetic background, autoimmune pancreatitis in mice of BALB/c background has not yet been reported. Here, we report that Aire KO mice with BALB/cAnN background showed significant lymphoid cell infiltration in the pancreas and stomach. To examine whether the phenotype in the pancreas and stomach is due to autoimmune reaction associated with autoantibody production, indirect immunofluorescence staining followed by Western blot analysis was performed. Consequently, the autoantibody against pancreas and stomach was detected in the sera of Aire KO mice, and the target antigen of the autoantibody was identified as protein disulfide isomerase-associated 2 (Pdia2), which was reported to be expressed preferentially in the pancreas and stomach. Thus, Aire KO mice of BALB/cAnN background can serve as a useful animal model for autoimmune gastro-pancreatitis with anti-Pdia2 autoantibody production.</p></div

Phosphorylation of the adaptor ASC acts as a molecular switch that controls the formation of speck-like aggregates and inflammasome activity.

炎症応答を制御する新たな仕組みを解明 -慢性炎症や自己炎症性疾患の病態理解に貢献-. 京都大学プレスリリース. 2013-11-04.The inflammasome adaptor ASC contributes to innate immunity through the activation of caspase-1. Here we found that signaling pathways dependent on the kinases Syk and Jnk were required for the activation of caspase-1 via the ASC-dependent inflammasomes NLRP3 and AIM2. Inhibition of Syk or Jnk abolished the formation of ASC specks without affecting the interaction of ASC with NLRP3. ASC was phosphorylated during inflammasome activation in a Syk- and Jnk-dependent manner, which suggested that Syk and Jnk are upstream of ASC phosphorylation. Moreover, phosphorylation of Tyr144 in mouse ASC was critical for speck formation and caspase-1 activation. Our results suggest that phosphorylation of ASC controls inflammasome activity through the formation of ASC specks

Listeriolysin O-Induced Membrane Permeation Mediates Persistent Interleukin-6 Production in Caco-2 Cells during Listeria monocytogenes Infection In Vitro

Listeriolysin O (LLO), a major virulence factor of Listeria monocytogenes, is a member of the cholesterol-dependent cytolysin family and plays important roles not only in survival of this bacterium in phagocytes but also in induction of various cellular responses, including cytokine production. In this work, we examined the involvement of LLO in induction of the cytokine response in intestinal epithelial cells, the front line of host defense against food-borne listeriosis. Infection of Caco-2 cells with wild-type L. monocytogenes induced persistent expression of interleukin-6 (IL-6) mRNA. In contrast, IL-6 expression was observed only transiently during infection with non-LLO-producing strains. A sublytic dose of recombinant LLO (rLLO) induced the expression of IL-6 via formation of membrane pores. Under conditions of LLO-induced pore formation without extensive cell lysis, Ca(2+) influx was observed, and the IL-6 expression induced by rLLO was inhibited by pretreatment with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA-AM), an intracellular Ca(2+) chelator. LLO secreted by cytoplasmic L. monocytogenes appeared to induce pore formation in the membrane and to enable the trafficking of intracellular and extracellular molecules. Pretreatment with BAPTA-AM inhibited persistent IL-6 expression in Caco-2 cells infected with wild-type L. monocytogenes. These results suggest that LLO is involved in IL-6 production in the late phase of infection through the formation of Ca(2+)-permeable pores and subsequent Ca(2+)-dependent modulation of signaling and gene expression

Identification of the target antigen by MALDI-TOF/TOF Mass analysis.

<p>A. CBB-staining and Western blotting analysis with pancreas tissue sample. Band corresponding to Western blotting was cut from CBB-stained gel and analyzed by MALDI-TOF/TOF Mass. M: marker. B. Number of hits of candidate protein by MALDI-TOF/TOF Mass analysis and its significance score. Because the left part was lower than the threshold of protein score, that part had a lower confidence in candidate protein. Only Pdia2 had the high score, to be a sufficient candidate molecule as a target antigen. C. Sequence of Pdia2 identified by MALDI-TOF/TOF analysis and other four peptide sequences suggested from the analysis data. Sequence coverage was 12%. D. Pdia2 protein expression in BL21. M: marker, S: supernatant, P: pellet. E. Absorption test for WT mouse pancreas and stomach in 12-wk-old Aire KO or WT mice pooled sera. M: marker. F. The difference of the absorbance in WT or KO mouse CD4+ T cells stimulated with pdia2-pulsed BMDC. Each graph represents the mean ± SD of 3 replicates.</p