title: Protection against experimental visceral leishmaniasis infection in dogs immunized with purified excreted secreted antigens of Leishmania infantum promastigotes.
abstract: The capacity of naturally excreted secreted antigens easily purified from culture supernatant of Leishmania infantum promastigotes (LiESAp), successfully cultivated in completely defined medium called CDM/LP [Lemesre JL. Methods for the culture in vitro of different stages of tissue parasites. International publication WO 94/26899, 1994; Merlen T, Sereno D, Brajon N, Rostand F, Lemesre JL. Leishmania spp: completely defined medium without serum and macromolecules (CDM/LP) for the continuous in vitro cultivation of infective promastigote forms. Am J Trop Med Hyg 1999;60(1):41-50] to protect dogs against experimental L. infantum infections is described. Eighteen healthy Beagle dogs were allocated into four groups that received at a 3-week interval either two subcutaneous injections of 50 microg (group 2, n = 3), 100 microg (group3, n = 6) and 200 microg (group 4, n = 3) LiESAp in formulation with muramyl dipeptide (MDP) or similar injections of placebo (group 1, n = 6). Dogs were intravenously infected with 10(8) metacyclic L. infantum promastigotes. Promastigotes of the MHOM/MA/67/ITMAP-263 and MHOM/FR/78/LEM75 strains were, respectively, administered 2 months (at day 84, homologous challenge 1) and 8 months post-immunization (at day 273, heterologous challenge 2). The data indicated that vaccine candidate confers total protection (100%) against challenges 1 and 2 in dogs from groups 3 and 4 and intermediate protection (66.7%) against challenge 1 in dogs from group 2 as determined by parasite detection in bone marrow aspirates during 14 months post-challenge follow-up. All placebo dogs of group 1 were found infected and failed to respond to LiESAp in cell-mediated assays before and after both challenges. Increased levels of total anti-leishmanial antibodies were exclusively detected in infected dogs from group 1. Vaccine-induced protection correlates with an early establishment of a long lasting predominantly Th1-type cellular immune response specifically directed against LiESAp before and after experimental infections, as demonstrated by: (i) anti-LiESAp IgG2 reactivity, and (ii) LiESAp-specific lymphocyte proliferation assays and enhanced NO-mediated anti-leishmanial activity of canine monocyte-derived macrophages (CM-DM) in response to higher IFNgamma production by T-cells, when L. infantum-infected CM-DM were co-cultured with autologous lymphocytes. Overall, our results support the view that a LiESAp vaccine might be useful in a promising vaccination approach against natural L. infantum infection.
authors.affiliation: Institut de Recherche pour le Développement, UR 008 Pathogénie des Trypanosomatidae, 911 Avenue Agropolis, BP 64501, 34394 Montpellier cedex 5, France. lemesre@mpl.ird.fr
authors.forename: Jean-Loup
authors.initials: JL
authors.lastname: Lemesre
authors.forename: Philippe
authors.initials: P
authors.lastname: Holzmuller
authors.forename: Mireille
authors.initials: M
authors.lastname: Cavaleyra
authors.forename: Rachel Bras
authors.initials: RB
authors.lastname: Gonçalves
authors.forename: Grégory
authors.initials: G
authors.lastname: Hottin
authors.forename: Gérard
authors.initials: G
authors.lastname: Papierok
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis; D000953:Antigens, Protozoan / Q000276:immunology*; D015153:Blotting, Western; D004283:Dog Diseases / Q000276:immunology / Q000517:prevention & control*; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007371:Interferon-gamma / Q000096:biosynthesis; D018314:Leishmania infantum / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000276:immunology / Q000517:prevention & control* / Q000662:veterinary; D008297:Male; D016052:Protozoan Vaccines / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016052:Protozoan Vaccines; D007371:Interferon-gamma