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Updated: Aug 30, 2026
Expression of Exogenous Antigens in the Mycobacterium bovis BCG Vaccine via Non-genetic Surface Decoration with the Avidin-biotin System
Published on: January 31, 2018
Vaccine and skin testing properties of two avirulent Mycobacterium bovis mutants with and without an additional
D M Collins1, R P Kawakami, B J Wards
1AgResearch, Wallaceville Animal Research Centre, P.O. Box 40063, Upper Hutt, New Zealand. desmond.collins@agresearch.co.nz
Setting:
Molecular techniques are now available to develop new live tuberculosis vaccines by producing avirulent strains of the Mycobacterium tuberculosis complex with known genes deleted.
Objectives:
Determine if removal of esat-6 from new live tuberculosis vaccines with known attenuating mutations affects their vaccine efficacy and if it could enable the development of discriminating diagnostic tests.
Design:
Remove the esat-6 gene by allelic exchange from two illegitimate mutants of Mycobacterium bovis that had previously been shown to have similar vaccine efficacy to BCG in a guinea pig vaccination model. Determine the effect this removal has on virulence, vaccine efficacy and skin test reactivity in guinea pigs.
Results:
Two double knockout strains of M. bovis were produced and their virulence and vaccine efficacy were compared to their parent strains. Removal of the esat-6 gene had no significant effect on vaccine efficacy. In skin tests, animals inoculated with the double knockout strains reacted to PPD but not ESAT-6, whereas those inoculated with the parent strains had similar skin test reactivity to both PPD and esat-6.
Conclusion:
Removal of esat-6 from new live tuberculosis vaccine candidates has no significant effect on vaccine properties but does enable the use of skin tests to distinguish between vaccination and infection.
