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.
Berna Biotech Ltd., Department of Live Bacterial Vaccines, Rehhagstrasse 79, 3018 Bern, Switzerland. didier.favre@bernabiotech.com
Didier
D
Favre
Stefan
S
Lüdi
Michael
M
Stoffel
Joachim
J
Frey
Michael P
MP
Horn
Guido
G
Dietrich
Simone
S
Spreng
Jean-François
JF
Viret
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