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Infection and Immunity, November 2005, p. 7274-7280, Vol. 73, No. 11
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.11.7274-7280.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Partially Assembled K99 Fimbriae Are Required for Protection

Miguel A. Ascón,² Javier Ochoa-Repáraz,¹ Nancy Walters,¹ and David W. Pascual^1*

Veterinary Molecular Biology, Montana State University, Bozeman, Montana 59717-3610,¹ Division of Infectious Diseases, Department of Medicine, Johns Hopkins University, Baltimore, Maryland 21205²

Received 7 June 2005/ Returned for modification 11 July 2005/ Accepted 28 July 2005

Antibodies to K99 fimbriae afford protection to F5⁺ bovine enterotoxigenic Escherichia coli (ETEC). Previous studies show that murine dams immunized with Salmonella vaccine vectors stably expressing K99 fimbriae confer protection to ETEC-challenged neonatal pups. To begin to address adaptation of the K99 scaffold to display heterologous B- and T-cell epitopes, studies were conducted to determine how much of the assembled K99 fimbria is required to maintain protective immunity. Sequential deletions in the K99 gene clusters were made, resulting in diminished localization of the K99 fimbrial subunit in the outer membrane. As placement of the K99 fimbrial subunit became progressively contained within the vaccine vector, diminished immunoglobulin A (IgA) and IgG1 antibody titers, as well as diminished Th2-type cytokine responses, were observed in orally immunized mice. Deletion of fanGH, which greatly reduced the export of the fimbrial subunit to the outer membrane, showed only partial reduction in protective immunity. By contrast, deletion of fanDEFGH, which also reduced the export of the fimbrial subunit to the outer membrane but retained more subunit in the cytoplasm, resulted in protective immunity being dramatically reduced. Thus, these studies showed that retention of K99 fimbrial subunit as native fimbriae or with the deletion of fanGH is sufficient to confer protection.

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* Corresponding author. Mailing address: Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717-3610. Phone: (406) 994-6244. Fax: (406) 994-4303. E-mail: dpascual{at}montana.edu.

Editor: J. T. Barbieri

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Infection and Immunity, November 2005, p. 7274-7280, Vol. 73, No. 11
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.11.7274-7280.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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