Assessing the Expression of Enterotoxigenic Escherichia Coli-specific Surface Antigens in Recombinant Strains by Transmission Electron Microscopy and Immunolabeling
Stefan Lüdi 1, Joachim Frey 1, Didier Favre 1 and Michael H. Stoffel 1*
1 Division of Veterinary Anatomy (SL,MHS) and Department of Veterinary Bacteriology (SL,JF), University of Berne Veterinary School, Bern, Switzerland, and Berna Biotech Ltd, Bern, Switzerland (DF)
* To whom correspondence should be addressed. E-mail: michael.stoffel{at}ita.unibe.ch.
Submitted on July 27, 2005
Accepted on 22 November 2005
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Abstract |
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Infections with enterotoxigenic Escherichia coli are a major cause of travelers diarrhea worldwide. Colonization of the small intestine mucosa is dependent on specific Colonization Factor Antigens (CFA) and Coli Surface (CS) Antigens. CFA/1, CS3 and CS6 are the most prevalent fimbrial antigens found in clinical isolates. The goal of our study was to visualize the morphology of CS3 and CS6 fimbriae in wildtype and recombinant E. coli strains by means of transmission electron microscopy in conjunction with negative staining and immunolabeling. Corresponding ETEC genes were cloned into E.coli K12 strain DH10B. Expression of fimbriae was dependent on culture conditions and sample handling. Specific immunolabeling of fimbriae unequivocally demonstrated the presence of all types of surface antigens investigated. Negative staining was effective in revealing CS3 but not CS6. In addition, this technique clearly demonstrated differences in the morphology of genetically and immunologically identical CS3 surface antigens in wildtype strains and recombinant strains. This paper provides a basis for the assessment of recombinant vaccines.
Key Words:
CS3, CS6, fimbriae, immunolabeling, negative staining, vaccine