The Bordetella adenylate cyclase repeat-in-toxin (RTX) domain is immunodominant and elicits neutralizing antibodies

J Biol Chem. 2015 Feb 6;290(6):3576-91. doi: 10.1074/jbc.M114.585281. Epub 2014 Dec 10.


The adenylate cyclase toxin (ACT) is a multifunctional virulence factor secreted by Bordetella species. Upon interaction of its C-terminal hemolysin moiety with the cell surface receptor αMβ2 integrin, the N-terminal cyclase domain translocates into the host cell cytosol where it rapidly generates supraphysiological cAMP concentrations, which inhibit host cell anti-bacterial activities. Although ACT has been shown to induce protective immunity in mice, it is not included in any current acellular pertussis vaccines due to protein stability issues and a poor understanding of its role as a protective antigen. Here, we aimed to determine whether any single domain could recapitulate the antibody responses induced by the holo-toxin and to characterize the dominant neutralizing antibody response. We first immunized mice with ACT and screened antibody phage display libraries for binding to purified ACT. The vast majority of unique antibodies identified bound the C-terminal repeat-in-toxin (RTX) domain. Representative antibodies binding two nonoverlapping, neutralizing epitopes in the RTX domain prevented ACT association with J774A.1 macrophages and soluble αMβ2 integrin, suggesting that these antibodies inhibit the ACT-receptor interaction. Sera from mice immunized with the RTX domain showed similar neutralizing activity as ACT-immunized mice, indicating that this domain induced an antibody response similar to that induced by ACT. These data demonstrate that RTX can elicit neutralizing antibodies and suggest it may present an alternative to ACT.

Keywords: Adenylate Cyclase; Antibody Engineering; Antigen; Bacterial Toxin; Bordetella pertussis; CyaA; Immunogen Engineering; Immunogenicity; Protein Engineering; Structural Vaccinology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenylate Cyclase Toxin / chemistry
  • Adenylate Cyclase Toxin / immunology*
  • Animals
  • Antibodies, Bacterial / immunology*
  • Antibodies, Neutralizing / immunology*
  • Bacterial Toxins / chemistry
  • Bacterial Toxins / immunology*
  • Bordetella pertussis / enzymology
  • Bordetella pertussis / immunology*
  • Cell Line
  • Humans
  • Immunodominant Epitopes*
  • Mice
  • Mice, Inbred BALB C


  • Adenylate Cyclase Toxin
  • Antibodies, Bacterial
  • Antibodies, Neutralizing
  • Bacterial Toxins
  • Immunodominant Epitopes