Protection against experimental visceral leishmaniasis infection in dogs immunized with purified excreted secreted antigens of Leishmania infantum promastigotes

• Published in: Vaccine 2005-04, Vol.23 (22), p.2825-2840
• Main Authors: Lemesre, Jean-Loup, Holzmuller, Philippe, Cavaleyra, Mireille, Gonçalves, Rachel Bras, Hottin, Grégory, Papierok, Gérard
• Format: Article
• Language: English
• Subjects: Animals; Anti- Leishmania vaccine; Antibodies, Protozoan - biosynthesis; Antigens, Protozoan - immunology; Applied microbiology; Biological and medical sciences; Blotting, Western; Dog Diseases - immunology; Dog Diseases - prevention & control; Dogs; Electrophoresis, Polyacrylamide Gel; Female; Fundamental and applied biological sciences. Psychology; Human protozoal diseases; Infectious diseases; Interferon-gamma - biosynthesis; Leishmania infantum; Leishmania infantum - immunology; Leishmania infantum promastigotes; Leishmaniasis, Visceral - immunology; Leishmaniasis, Visceral - prevention & control; Leishmaniasis, Visceral - veterinary; Leshmaniasis; Male; Medical sciences; Microbiology; Parasitic diseases; Protozoal diseases; Protozoan Vaccines - immunology; T-Lymphocytes - immunology; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects); Visceral leishmaniasis
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2004.11.061

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 μg (group 2, n = 3), 100 μg (group3, n = 6) and 200 μg (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 IFNγ 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