Immunogenicity of a Yersinia pestis vaccine antigen monomerized by circular permutation

Infect Immun. 2006 Dec;74(12):6624-31. doi: 10.1128/IAI.00437-06. Epub 2006 Sep 18.


Caf1, a chaperone-usher protein from Yersinia pestis, is a major protective antigen in the development of subunit vaccines against plague. However, recombinant Caf1 forms polymers of indeterminate size. We report the conversion of Caf1 from a polymer to a monomer by circular permutation of the gene. Biophysical evaluation confirmed that the engineered Caf1 was a folded monomer. We compared the immunogenicity of the engineered monomer with polymeric Caf1 in antigen presentation assays to CD4 T-cell hybridomas in vitro, as well as in the induction of antibody responses and protection against subcutaneous challenge with Y. pestis in vivo. In C57BL/6 mice, for which the major H-2(b)-restricted immunodominant CD4 T-cell epitopes were intact in the engineered monomer, immunogenicity and protective efficacy were preserved, although antibody titers were decreased 10-fold. Disruption of an H-2(d)-restricted immunodominant CD4 T-cell epitope during circular permutation resulted in a compromised T-cell response, a low postvaccination antibody titer, and a lack of protection of BALB/c mice. The use of circular permutation in vaccine design has not been reported previously.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antigens, Bacterial / chemistry
  • Antigens, Bacterial / genetics
  • Antigens, Bacterial / immunology
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / immunology*
  • Biological Assay
  • CD4-Positive T-Lymphocytes / immunology
  • Hybridomas / immunology
  • Immunodominant Epitopes / chemistry
  • Immunodominant Epitopes / genetics
  • Immunodominant Epitopes / immunology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred Strains
  • Mutation
  • Plague / prevention & control*
  • Plague Vaccine / genetics
  • Plague Vaccine / immunology*
  • Protein Conformation
  • Protein Engineering*
  • Protein Folding
  • Solutions / chemistry
  • Yersinia pestis / immunology*


  • Antigens, Bacterial
  • Bacterial Proteins
  • Immunodominant Epitopes
  • Plague Vaccine
  • Solutions
  • caf1 protein, Yersinia pestis