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Articles by Bo Hu
Total Records ( 3 ) for Bo Hu
  Jingyu Liu , Suwen Zhang , Qi Pei , Jinna Di , Hui Zhang , Bo Hu and Hao Ai
  Tuberculosis remains a major infectious disease worldwide due to the low efficacy of available vaccine of the Mycobacterium bovis Bacillus Calmette-Guerin (BCG). There is a need to develop protective vaccines against Tuberculosis (TB) that elicit full immune responses including mucosal immunity. Here, a live attenuated salmonella typhimurium aroA SL7207 vector TB vaccine, namely SL (E6-HspX), harboring the Mycobacterium tuberculosis (Mtb) H37Rv ESAT6-HspX fusion gene was developed. Its immunogenicity and protective efficacy were assessed in a mouse model of tuberculosis. Vaccination with the SL (E6-HspX) significantly increased the frequency of peripheral blood CD4+ and CD8+ T cells and induced significantly higher levels of cell-mediated immune response compared with vaccination with PBS or the pVAX1 vector. Vaccination with the SL (E6-HspX) also induced the strongest TB Ag-specific mucosal, humoral responses and exerted high protective efficacy in mice against virulent Mtb H37Rv challenge compared to the other vaccinated groups (mice immunized with SL (HspX) or BCG only). This strategy may represent a novel promising mucosal vaccine candidate for the prevention of TB and may be used for the prevention and therapeutic intervention of Mtb infection.
  Lu Feng , Bin Liu , Yanqun Liu , Yuli A. Ratiner , Bo Hu , Dan Li , Xiaolin Zong , Wei Xiong and Lei Wang
  The occurrence of unilateral flagellar phase variation was previously demonstrated in Escherichia coli strains carrying the non-fliC flagellin-specifying locus flk. In this study, we investigated the mechanism involved in this process. By using sequencing and sequence analysis, the flk region between the chromosomal genes yhaC and rnpB was characterized in all described flk-positive E. coli strains, including the H35 strain identified in this study (the other strains used are H3, H36, H47, and H53 strains), and this region was found to contain a putative integrase gene and flanking direct repeats in addition to the flk flagellin-specifying gene flkA and a fliC repressor gene, flkB, indicating that there is a typical genomic islet (GI), which was designated the flk GI. The horizontal transfer potential of the flk GI was indicated by detection of the excised extrachromosomal circular form of the flk GI. By generating fliC-expressing variants of H3 and H47 strains, unilateral flagellar phase variation in flk-positive strains was shown to be mediated by excision of the flk GI. The function of the proposed integrase gene was confirmed by deletion and a complementation test. The potential integration sites of the flk GI were identified. A general model for flagellar phase variation in flk-positive E. coli strains can be expressed as fliCoff + flkAonfliCon + flkAnone. This is the first time that a molecular mechanism for flagellar phase variation has been reported for E. coli.
  Inka Brockhausen , Bo Hu , Bin Liu , Kenneth Lau , Walter A. Szarek , Lei Wang and Lu Feng
  The O antigens of outer membrane-bound lipopolysaccharides (LPS) in gram-negative bacteria are oligosaccharides consisting of repeating units with various structures and antigenicities. The O56 and O152 antigens of Escherichia coli both contain a Glc-β1-3-GlcNAc linkage within the repeating unit. We have cloned and identified the genes (wfaP in O56 and wfgD in O152) within the two O-antigen gene clusters that encode glucosyltransferases involved in the synthesis of this linkage. A synthetic substrate analog of the natural acceptor substrate undecaprenol-pyrophosphate-lipid [GlcNAc-α-PO3-PO3-(CH2)11-O-phenyl] was used as an acceptor and UDP-Glc as a donor substrate to demonstrate that both wfgD and wfaP encode glucosyltransferases. Enzyme products from both glucosyltransferases were isolated by high-pressure liquid chromatography and analyzed by nuclear magnetic resonance. The spectra showed the expected Glc-β1-3-GlcNAc linkage in the products, confirming that both WfaP and WfgD are forms of UDP-Glc: GlcNAc-pyrophosphate-lipid β-1,3-glucosyltransferases. Both WfaP and WfgD have a DxD sequence, which is proposed to interact with phosphate groups of the nucleotide donor through the coordination of a metal cation, and a short hydrophobic sequence at the C terminus that may help to associate the enzymes with the inner membrane. We showed that the enzymes have similar properties and substrate recognition. They both require a divalent cation (Mn2+ or Mg2+) for activity, are deactivated by detergents, have a broad pH optimum, and require the pyrophosphate-sugar linkage in the acceptor substrate for full activity. Substrates lacking phosphate or pyrophosphate linked to GlcNAc were inactive. The length of the aliphatic chain of acceptor substrates also contributes to the activity.
 
 
 
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