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Published on: September 19, 2016
Immunogenicity and anti-Burkholderia pseudomallei activity in Balb/c mice immunized with plasmid DNA encoding
Yao-Shen Chen1, Yu-Shan Hsiao, His-Hsun Lin
1Section of Infectious Disease, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.
Abstract:
Plasmid DNA encoding the flagella protein (flagellin) was used as a vaccination candidate for the evaluation of its immunogenicity and for protection against infection with Burkholderia pseudomallei. Firstly, flagellin encoding plasmid DNA was injected into Balb/c mice intramuscularly and this elicited both a humoral and a cellular immune response. Total IgG production and the clonal expansion of the spleen cells increased in response to flagellin. The IgG subclass response exhibited a dominance of IgG2a over IgG1 in the sera. In addition, IFN-gamma-secreting cells in the spleen were substantially increased. Furthermore, the anti-B. pseudomallei activity of the peritoneal exudate cells was evaluated by a Transwell tissue-culture plate system where the macrophage-activating related cytokines in upper chamber were allowed to cross the plate's membrane and stimulate the activation of peritoneal exudate cells in lower chamber. Our results indicated that the activated peritoneal exudate cells were able to restrict the growth of B. pseudomallei in vitro. Indeed, subsequent intravenous challenge of the vaccinated Balb/c mice with 10(5)CFU of B. pseudomallei resulted in the number of bacterial cells detected in liver and/or spleen being significantly reduced in the flagellin plasmid DNA vaccinated mice. At 7 days subsequent to infection of B. pseudomallei, 5/6 (83%) of flagellin plasmid DNA vaccinated mice had survived. We suggest that plasmid DNA-encoding flagellin might be useful as a potential immunization route for the future development of a vaccine against melioidosis in related animals.
Insights
Plasmid DNA encoding flagellin induced strong immune responses in mice, significantly reducing Burkholderia pseudomallei bacterial load and improving survival rates. This suggests potential for a flagellin DNA vaccine against melioidosis.
Area of Science:
- Immunology
- Microbiology
- Vaccinology
Background:
- Melioidosis, caused by Burkholderia pseudomallei, is a serious infectious disease.
- Effective vaccines against melioidosis are currently lacking.
- Flagellin, a protein component of bacterial flagella, is a known immunogen.
Purpose of the Study:
- To evaluate the immunogenicity of plasmid DNA encoding flagellin.
- To assess the protective efficacy of this DNA vaccine against B. pseudomallei infection.
- To investigate the type of immune response elicited by flagellin DNA vaccination.
Main Methods:
- Intramuscular injection of flagellin-encoding plasmid DNA into Balb/c mice.
- Assessment of humoral immune response (total IgG, IgG subclasses).
- Evaluation of cellular immune response (spleen cell proliferation, IFN-gamma secretion, peritoneal exudate cell activity).
- In vivo challenge with B. pseudomallei and assessment of bacterial load and survival.
Main Results:
- Flagellin DNA vaccination elicited significant humoral (IgG2a dominant) and cellular immune responses.
- Activated peritoneal exudate cells demonstrated in vitro anti-B. pseudomallei activity.
- Vaccinated mice showed significantly reduced bacterial loads in liver and spleen post-infection.
- Survival rate was 83% in vaccinated mice 7 days after B. pseudomallei challenge.
Conclusions:
- Plasmid DNA encoding flagellin is immunogenic and confers protection against B. pseudomallei infection in mice.
- Flagellin DNA vaccination induces a Th1-biased immune response.
- This approach shows promise for developing a vaccine against melioidosis.
