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Infection and Immunity, January 2006, p. 202-212, Vol. 74, No. 1
0019-9567/06/$08.00+0 doi:10.1128/IAI.74.1.202-212.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Karl Walravens,2 and
Kris Huygen1*
Laboratory of Mycobacterial Immunology, WIV-Pasteur Institute, 642 Engelandstraat, B1180 Brussels, Belgium,1 Veterinary and Agrochemical Research Center, Groeselenberg 99, B1180 Brussels, Belgium2
Received 25 May 2005/ Returned for modification 5 July 2005/ Accepted 1 October 2005
The characterization of protective antigens is essential for the development of an effective, subunit-based vaccine against paratuberculosis. Surface-exposed and secreted antigens, present abundantly in mycobacterial culture filtrate (CF), are among the well-known protective antigens of Mycobacterium tuberculosis and Mycobacterium bovis. Culture filtrate, prepared from Mycobacterium avium subsp. paratuberculosis ATCC 19698 grown as a surface pellicle on synthetic Sauton medium, was strongly and early recognized in experimentally infected B6 bg/bg beige mice and cattle, as indicated by elevated spleen cell gamma interferon (IFN-
) secretion and lymphoproliferative responses of peripheral blood mononuclear cells, respectively. Strong proliferative and ex vivo IFN-
responses against antigen 85 (Ag85) complex (a major protein component from M. bovis BCG culture filtrate) could be detected in cattle as early as 10 weeks after oral M. avium subsp. paratuberculosis infection. Synthetic peptides from the Ag85A and Ag85B components of this complex were strongly recognized, whereas T-cell responses were weaker against peptides from the Ag85C protein. A promiscuous T-cell epitope spanning amino acids 145 to 162 of Ag85B (identical sequence in M. bovis and M. avium subsp. paratuberculosis) was identified in experimentally infected cattle. Finally, young calves, born from cows with confirmed paratuberculosis, demonstrated proliferative responses to purified, recombinant Ag85A and Ag85B from M. avium subsp. paratuberculosis. These results indicate that the M. avium subsp. paratuberculosis Ag85 homologues are immunodominant T-cell antigens that are recognized early in experimental and natural infection of cattle.
Present address: University of Pretoria, Faculty of Veterinary Science, Private Bag XO4, Onderstepoort 0110, South Africa.
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