Expression of enterotoxigenic Escherichia coli colonization factors in Vibrio cholerae.
As a first step towards a vaccine against diarrhoeal disease caused by enterotoxigenic Escherichia coli (ETEC), we have studied the expression of several ETEC antigens in the live attenuated Vibrio cholerae vaccine strain CVD 103-HgR. Colonization factors (CF) CFA/I, CS3, and CS6 were expressed at the surface of V. cholerae CVD 103-HgR. Both CFA/I and CS3 required the co-expression of a positive regulator for expression, while CS6 was expressed without regulation. Up-regulation of CF expression in V. cholerae was very efficient, so that high amounts of CFA/I and CS3 similar to those in wild-type ETEC were synthesized from chromosomally integrated CF and positive regulator loci. Increasing either the operon and/or the positive regulator gene dosage resulted in only a small increase in CFA/I and CS3 expression. In contrast, the level of expression of the non-regulated CS6 fimbriae appeared to be more dependent on gene dosage. While CF expression in wild-type ETEC is known to be tightly thermoregulated and medium dependent, it seems to be less stringent in V. cholerae. Finally, co-expression of two or three CFs in the same strain was efficient even under the control of one single regulator gene.
Favre
Didier
D
Berna Biotech Ltd., Department of Live Bacterial Vaccines, Rehhagstrasse 79, 3018 Bern, Switzerland. didier.favre@bernabiotech.com
Lüdi
Stefan
S
Stoffel
Michael
M
Frey
Joachim
J
Horn
Michael P
MP
Dietrich
Guido
G
Spreng
Simone
S
Viret
Jean-François
JF
D000942:Antigens, Bacterial / Q000235:genetics*; D002876:Chromosomes, Bacterial; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000378:metabolism*; D018628:Gene Dosage; D008854:Microscopy, Electron; D009876:Operon; D010957:Plasmids; D014734:Vibrio cholerae / Q000235:genetics*
D000942:Antigens, Bacterial