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Heterologous antigen expression in Vibrio cholerae vector strains
J R Butterton1, D T Beattie, C L Gardel
1Infectious Disease Unit, Massachusetts General Hospital, Boston 02114, USA.
Infection and Immunity
|July 1, 1995
Summary
Live attenuated Vibrio cholerae vaccine vectors expressing Shiga-like toxin I B subunit (slt-IB) were developed. These novel vectors colonized the gut and induced immune responses, with dual slt-IB gene copies enhancing antibody production.
Area of Science:
- Microbiology and Immunology
- Vaccine Development
- Bacterial Genetics
Background:
- Development of live attenuated Vibrio cholerae strains for oral vaccines.
- Engineering of vaccine vectors to express foreign antigens for enhanced immunogenicity.
Purpose of the Study:
- To construct and evaluate live attenuated Vibrio cholerae vector strains expressing the Shiga-like toxin I B subunit (slt-IB).
- To assess the in vitro expression and in vivo immunogenicity of slt-IB from different promoter systems and gene copy numbers.
- To investigate the potential of these vectors for oral immunization.
Main Methods:
- Construction of Vibrio cholerae Peru-2 derivatives with promoterless slt-IB gene inserted under transcriptional control of iron-regulated irgA or heat shock htpG promoters.
- Allelic exchange techniques, including a novel method for lacZ locus manipulation, to generate vector strains (JRB10, JRB11, JRB12).
- In vitro expression analysis of Slt-IB, colonization studies in rabbit gastrointestinal mucosa, and serologic response evaluation (serum IgG, biliary IgA) following oral immunization.
Main Results:
- In vitro expression of Slt-IB was synergistic from irgA and htpGp promoters, with two gene copies increasing expression.
- Vibrio cholerae vectors successfully colonized rabbit gastrointestinal mucosa, inducing high serum antibody responses to V. cholerae antigens.
- Oral immunization with vector strains elicited serum IgG and biliary IgA responses to Slt-IB; dual gene copies enhanced serum IgG responses.
- Cholera toxin B subunit (CtxB) was found to be a more effective oral immunogen than Slt-IB when expressed from the same promoter.
Conclusions:
- Live attenuated Vibrio cholerae vectors can be engineered to express foreign antigens like Slt-IB and induce protective immune responses.
- The irgA and htpG promoters are effective for antigen expression in vivo, and increased gene copy number can enhance immunogenicity.
- While effective, Slt-IB may be less immunogenic as an oral vaccine candidate compared to CtxB when delivered via these vector systems.