Open Access
Vet. Res.
Volume 40, Number 6, November-December 2009
Number of page(s) 12
Published online 24 June 2009
How to cite this article Vet. Res. (2009) 40:52
How to cite this article: Vet. Res. (2009) 40:52
DOI: 10.1051/vetres/2009036

Modulation of the immunogenicity of the Trypanosoma congolense cysteine protease, congopain, through complexation with $\alpha_2$-macroglobulin

Laura Elizabeth Joan Huson1, Edith Authié2, 3, Alain François Boulangé1, 2, James Phillip Dean Goldring1 and Theresa Helen Taillefer Coetzer1

1  School of Biochemistry, Genetics and Microbiology, University of KwaZulu-Natal (Pietermaritzburg campus), Private Bag X01, Scottsville, 3209, South Africa
2  Trypanosomoses humaines et animales, UMR-IRD/CIRAD 017, CIRAD-Emvt, 34398 Montpellier, France
3  UR086 Base, INRA, Centre de Tours, 37380 Nouzilly, France

Received 27 February 2009; accepted 19 June 2009; published online 24 June 2009

Abstract - The protozoan parasite Trypanosoma congolense is the main causative agent of livestock trypanosomosis. Congopain, the major lysosomal cysteine proteinase of T. congolense, contributes to disease pathogenesis, and antibody-mediated inhibition of this enzyme may contribute to mechanisms of trypanotolerance. The potential of different adjuvants to facilitate the production of antibodies that would inhibit congopain activity was evaluated in the present study. Rabbits were immunised with the recombinant catalytic domain of congopain (C2), either without adjuvant, with Freund's adjuvant or complexed with bovine or rabbit $\alpha_2$-macroglobulin ($\alpha_2$M). The antibodies were assessed for inhibition of congopain activity. Rabbits immunised with C2 alone produced barely detectable anti-C2 antibody levels and these antibodies had no effect on recombinant C2 or native congopain activity. Rabbits immunised with C2 and Freund's adjuvant produced the highest levels of anti-C2 antibodies. These antibodies either inhibited C2 and native congopain activity to a small degree, or enhanced their activity, depending on time of production after initial immunisation. Rabbits receiving C2-$\alpha_2$M complexes produced moderate levels of anti-C2 antibodies and these antibodies consistently showed the best inhibition of C2 and native congopain activity of all the antibodies, with maximum inhibition of 65%. Results of this study suggest that antibodies inhibiting congopain activity could be raised in livestock with a congopain catalytic domain-$\alpha_2$M complex. This approach improves the effectiveness of the antigen as an anti-disease vaccine candidate for African trypanosomosis.

Key words: trypanosomosis / congopain / $\alpha_2$-macroglobulin / anti-disease vaccine

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© INRA, EDP Sciences 2009