Vet. Res. 36 (2005) 827-838
DOI: 10.1051/vetres:2005033

Immunogenicity in dogs of three recombinant antigens (TSA, LeIF and LmSTI1) potential vaccine candidates for canine visceral leishmaniasis

Ricardo Toshio Fujiwara^{a, b}, André Macedo Vale^a, João Carlos França da Silva^a, Roberto Teodoro da Costa^a, Josiane da Silva Quetz^a, Olindo Assis Martins Filho^c, Alexandre Barbosa Reis^{d, e}, Rodrigo Corrêa Oliveira^d, George Lins Machado-Coelho^e, Lilian Lacerda Bueno^b, Jeffrey Michael Bethony^{d, b}, Glen Frank^f, Evaldo Nascimento^a, Odair Genaro^a, Wilson Mayrink^a, Steven Reed^g and Antonio Campos-Neto<sup>h

a</sup>  Laboratório de Leishmanioses e Vacinas, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), CEP 31270-901, Belo Horizonte, MG, Brazil
^b  The George Washington University, Washington, DC 20037, USA
^c  Laboratório de Doença de Chagas, Centro de Pesquisas René Rachou - FIOCRUZ/MG, CEP 30190-002, Belo Horizonte, MG, Brazil
^d  Laboratório de Imunologia Celular e Molecular, Centro de Pesquisas René Rachou - FIOCRUZ/MG, CEP 30190-002, Belo Horizonte, MG, Brazil
^e  Escola de Farmácia, Universidade Federal de Ouro Preto (UFOP), CEP 35400-000, Ouro Preto, MG, Brazil
^f  Heska Corporation, Fort Collins, CO, USA
^g  The Infectious Disease Research Institute, Seattle, WA 98104, USA
^h  The Forsyth Institute, Boston, MA 02115, USA

(Received 9 September 2004; accepted 12 April 2005)

Abstract - Control of canine visceral leishmaniasis (VL) remains a difficult and serious problem mostly because there is no reliable and effective vaccine available to prevent this disease. A mixture of three recombinant leishmanial antigens (TSA, LeIF and LmSTI1) encoded by three genes highly conserved in the Leishmania genus have been shown to induce excellent protection against infection in both murine and simian models of cutaneous leishmaniasis. A human clinical trial with these antigens is currently underway. Because of the high degree of conservation, these antigens might be useful vaccine candidates for VL as well. In the present study, using the dog model of the visceral disease, we evaluated the immunogenicity of these three antigens formulated with two different adjuvants, MPL-SE^® and AdjuPrime^®. The results were compared with a whole parasite vaccine formulated with BCG as the adjuvant. In order to investigate if sensitization with the recombinant antigens would result in recognition of the corresponding native parasite antigens upon infection, the animals were exposed for four weeks after the termination of the immunization protocol with the recombinant antigens to a low number of L. chagasi promastigotes, an etiological agent of VL. Immune response was evaluated by quantitative ELISA in the animal sera before and after exposure to the viable parasites. Both antigen specific IgG1 and IgG2 antibody levels were measured. Immunization of dogs with the recombinant antigens formulated in either MPL-SE^® or AdjuPrime^® resulted in high antibody levels particularly to LmSTI1. In addition, this immunization although to low levels, resulted in the development of antibody response to the whole parasite lysate. Importantly, experimental exposure with low numbers of culture forms of L. chagasi promastigotes caused a clear boost in the immune response to both the recombinant antigens and the corresponding native molecules. The boost response was predominantly of the IgG2 isotype in animals primed with the recombinant antigens plus MPL-SE^®. In contrast, animals primed with the recombinant antigens formulated in AdjuPrime^® as well as animals vaccinated with crude antigen preparation responded with mixed IgG1/IgG2 isotypes. These results point to the possible use of this antigen cocktail formulated with the adjuvant MPL-SE^® in efficacy field trials against canine VL.

Key words: visceral leishmaniasis / dogs / vaccine / Leishmania chagasi

Corresponding author: Ricardo Toshio Fujiwara mtmrtf@gwumc.edu

© INRA, EDP Sciences 2005