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  • The American Society for Microbiology (ASM)  (3)
  • The American Association of Immunologists (AAI)  (1)
  • 2015-2019  (4)
  • 2015-2019  (4)
  • 1
    Publication Date: 2018-07-24
    Description: Transmission-blocking vaccines (TBVs) interrupting malaria transmission are an integrated tool for malaria eradication. We characterized a sexual-stage-specific gene (PBANKA_060330) from Plasmodium berghei and studied its potential for use as a TBV. This gene, referred to as pbg37 , encodes a protein of 37 kDa with a signal peptide and multiple transmembrane domains and is preferentially expressed in gametocytes. A recombinant Pbg37 (rPbg37) protein targeting the N-terminal 63 amino acids (amino acids 26 to 88) expressed in bacteria elicited strong antibody responses in mice. Western blotting demonstrated Pbg37 expression in gametocytes, zygotes, and, to a lesser extent, ookinetes and its predominant association with the membranes of gametocytes. Indirect immunofluorescence assay showed an abundant surface localization of Pbg37 on gametes and zygotes but reduced amounts on retorts and ookinetes. Knockout of pbg37 ( pbg37 ) led to a considerable reduction in gametocytemia, which translated into a ~92.1% decrease in the oocyst number in mosquitoes. Deletion of pbg37 had a more substantial influence on the development and maturation of microgametocytes. As a result, the pbg37 lines exhibited a higher female/male gametocyte ratio, fewer mature male gametocytes, and defects in the exflagellation of mature microgametocytes. To test the transmission-blocking potential of Pbg37, an in vitro ookinete assay showed that the major inhibitory effects of anti-Pbg37 antiserum were on the exflagellation and fertilization processes. Direct feeding of mosquitoes on mice immunized with rPbg37 or a control protein showed that rPbg37-immunized and P. berghei -infected mice had a significant reduction (49.1%) in oocyst density compared to the controls. The conservation of this gene in Plasmodium warrants further investigations in human malaria parasites.
    Print ISSN: 0019-9567
    Electronic ISSN: 1098-5522
    Topics: Medicine
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  • 2
    Publication Date: 2018-10-10
    Description: Aberrant activation of the NLRP3 inflammasome contributes to the onset and progression of various inflammatory diseases, making it a highly desirable drug target. In this study, we screened a series of small compounds with anti-inflammatory activities and identified a novel NLRP3 inflammasome inhibitor, AI-44, a curcumin analogue that selectively inhibited signal 2 but not signal 1 of NLRP3 inflammasome activation. We demonstrated that AI-44 bound to peroxiredoxin 1 (PRDX1) and promoted the interaction of PRDX1 with pro–Caspase-1 (CASP1), which led to the suppression of association of pro-CASP1 and ASC. Consequently, the assembly of the NLRP3 inflammasome was interrupted, and the activation of CASP1 was inhibited. Knockdown of PRDX1 significantly abrogated the inhibitory effect of AI-44 on the NLRP3 inflammasome. Importantly, AI-44 alleviated LPS-induced endotoxemia in mice via suppressing NLRP3 inflammasome activation. Taken together, our work highlighted PRDX1 as a negative regulator of NLRP3 inflammasome activation and suggested AI-44 as a promising candidate compound for the treatment of sepsis or other NLRP3 inflammasome-driven diseases.
    Print ISSN: 0022-1767
    Electronic ISSN: 1550-6606
    Topics: Medicine
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  • 3
    Publication Date: 2018-07-31
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
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  • 4
    Publication Date: 2018-05-15
    Description: The spike glycoprotein (S) of murine coronavirus mouse hepatitis virus (MHV) strain A59 uses murine carcinoembryonic antigen-related cell adhesion molecule 1a as its receptor for cell entry, but S protein can also be triggered in the absence of receptor by pH 8.0 alone at 37°C. The mechanism by which conformational changes of this S glycoprotein can be triggered by pH 8.0 has not yet been determined. Here, we show that MHV-A59 S protein is triggered by pH 8.0 at 37°C to induce receptor-independent syncytium (RIS) formation on 293T cells, and that the conformational changes in S proteins triggered by pH 8.0 are very similar to those triggered by receptor binding. We systemically mutated each of 15 histidine residues in S protein and found that H209 is essential for pH 8.0-triggered RIS formation, while H179, H441, H643, and H759 also play important roles in this process. Replacement of H209 with Ala had no effect on receptor binding, but in murine 17Cl.1 cells mutant H209A MHV-A59 showed delayed growth kinetics and was readily outcompeted by wild-type virus when mixed together, indicating that the H209A mutation caused a defect in virus fitness. Finally, the H209A mutation significantly increased the thermostability of S protein in its prefusion conformation, which may raise the energy barrier for conformational change of S protein required for membrane fusion and lead to a decrease in virus fitness in cell culture. Thus, MHV-A59 may have evolved to lower the stability of its S protein in order to increase virus fitness. IMPORTANCE Enveloped viruses enter cells through fusion of viral and cellular membranes, and the process is mediated by interactions between viral envelope proteins and their host receptors. In the prefusion conformation, viral envelope proteins are metastable, and activation to the fusion conformation is tightly regulated, since premature activation would lead to loss of viral infectivity. The stability of viral envelope proteins greatly influences their activation and virus fitness. Here, we report that, similar to the A82V mutation in Ebola glycoprotein, in the S glycoprotein of murine coronavirus MHV-A59, the histidine residue at position of 209 significantly affects the thermal stability of the S protein, determines whether S protein can be activated at 37°C by either pH 8.0 alone or by receptor binding, and affects viral fitness in cell culture. Thus, the spike glycoprotein of MHV-A59 has evolved to retain histidine at position 209 to optimize virus fitness.
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
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