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Published on: October 15, 2013
Characterization of the Burkholderia pseudomallei K96243 capsular polysaccharide I coding region
Jon Cuccui1, Timothy S Milne, Nicholas Harmer
1Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Abstract:
Burkholderia pseudomallei is the causative agent of melioidosis, a disease endemic to regions of Southeast Asia and Northern Australia. Both humans and a range of other animal species are susceptible to melioidosis, and the production of a group 3 polysaccharide capsule in B. pseudomallei is essential for virulence. B. pseudomallei capsular polysaccharide (CPS) I comprises unbranched manno-heptopyranose residues and is encoded by a 34.5-kb locus on chromosome 1. Despite the importance of this locus, the role of all of the genes within this region is unclear. We inactivated 18 of these genes and analyzed their phenotype using Western blotting and immunofluorescence staining. Furthermore, by combining this approach with bioinformatic analysis, we were able to develop a model for CPS I biosynthesis and export. We report that inactivating gmhA, wcbJ, and wcbN in B. pseudomallei K96243 retains the immunogenic integrity of the polysaccharide despite causing attenuation in the BALB/c murine infection model. Mice immunized with the B. pseudomallei K96243 mutants lacking a functional copy of either gmhA or wcbJ were afforded significant levels of protection against a wild-type B. pseudomallei K96243 challenge.
Insights
Investigating Burkholderia pseudomallei capsular polysaccharide I revealed that specific gene mutations (gmhA, wcbJ) create less virulent but immunogenic bacterial strains. These mutants offer protection against melioidosis in mice.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Melioidosis, caused by Burkholderia pseudomallei, is prevalent in Southeast Asia and Northern Australia.
- The group 3 polysaccharide capsule (CPS I) of B. pseudomallei is crucial for virulence.
- The genetic locus encoding CPS I is well-defined, but the function of all its genes remains largely unknown.
Purpose of the Study:
- To elucidate the function of genes within the B. pseudomallei CPS I biosynthesis locus.
- To develop a model for CPS I biosynthesis and export.
- To assess the potential of attenuated B. pseudomallei mutants as vaccine candidates.
Main Methods:
- Inactivation of 18 genes within the CPS I locus in B. pseudomallei K96243.
- Phenotypic analysis using Western blotting and immunofluorescence staining.
- Bioinformatic analysis to model CPS I biosynthesis and export pathways.
- Murine infection models (BALB/c) to evaluate bacterial virulence and vaccine efficacy.
Main Results:
- Inactivation of gmhA, wcbJ, and wcbN genes resulted in attenuated B. pseudomallei strains.
- These mutants maintained the immunogenic integrity of the CPS I.
- Mice immunized with gmhA or wcbJ mutants showed significant protection against wild-type B. pseudomallei challenge.
Conclusions:
- The study identified key genes (gmhA, wcbJ) involved in B. pseudomallei CPS I biosynthesis and export.
- Attenuated B. pseudomallei mutants lacking functional gmhA or wcbJ are promising vaccine candidates for melioidosis.
- Understanding CPS I biosynthesis provides insights into bacterial virulence and potential therapeutic targets.
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