title: [Distribution of Salmonella paratyphi A outer membrane protein X gene and immune-protective effect related to its recombinant expressed products].
abstract: OBJECTIVE
  To determine the distribution and sequence conservation of outer membrane protein X(ompX)gene in Salmonella paratyphi A isolates as well as the immunogenicity and immuno-protection of ompX gene products.
  
  
  METHODS
  OmpX gene in Salmonella paratyphi A isolates was detected by PCR and the amplification products were sequenced after the T-A cloning process. OmpX gene product was expressed with E. coli expression system and the expressed rOmpX was extracted by Ni-NTA affinity chromatography. SDS-PAGE and Bio-Rad Gel Image Analyzer were applied to examine the expression and yield of rOmpX. Both antigenicity and immune-reactivity of rOmpX were detected by immune-diffusion test, ELISA and Western blot assay. The immunoprotective effect of rOmpX against infection of Salmonella paratyphi in mice was determined and the agglutinative titers of sera from rOmpX-immunized mice was measured by micro-Widal's test.
  
  
  RESULTS
  All the tested Salmonella paratyphi A isolates had ompX gene with high nucleotide or amino acid sequence identity (99.2%-100.0% or 98.4%-100.0%). When rOmpX was induced to rabbits to produce high level antibody and combined with antiserum against whole cell of Salmonella paratyphi A, the results displayed a positive Western hybridization signal. Results from ELISA demonstrated that 95.6% (65/68) of the serum samples from paratyphoid-A patients were positive on rOmpX antibody. Mice that were immunized with 100 µg or 200 µg rOmpX displayed an immune-protective rate of 93.3% (14/15) or 100.0% (15/15). Sera from those rOmpX-immunized mice provided 1 : 10-1 : 40 agglutination titers in both H antigens of Salmonella paratyphi A and Salmonella typhi.
  
  
  CONCLUSIONS
  The recombinant expression product of ompX gene could be used as a candidate antigen for developing genetic engineering vaccines against Salmonella paratyphi A infection.
authors: Yiwu Central Hospital of Zhejiang Province, Yiwu 322000, China.
authors: Ming-lei
authors: ML
authors: Li
authors: Yiwu Central Hospital of Zhejiang Province, Yiwu 322000, China.
authors: Hai-jun
authors: HJ
authors: Fang
authors: Zhejiang Medical College, School of Laboratory Medical Science and Life Science, Wenzhou Medical University.
authors: Xing-li
authors: XL
authors: Fan
authors: Zhejiang Medical College, School of Laboratory Medical Science and Life Science, Wenzhou Medical University.
authors: Jia
authors: J
authors: Zhang
authors: School of Medicine,Zhejiang University.
authors: Jie
authors: J
authors: Yan
authors: Zhejiang Medical College, School of Laboratory Medical Science and Life Science, Wenzhou Medical University. Email: sunah123@126.com.
authors: Ai-hua
authors: AH
authors: Sun
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification*; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D012482:Salmonella paratyphi A / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification
chemical_list: D001425:Bacterial Outer Membrane Proteins; C078167:OMPA outer membrane proteins