Vaccine 21 (2003) 4668–4676 Immunotherapy against murine experimental visceral leishmaniasis with the FML-vaccine Wania Renata Santos a , Ivan Augusto Aguiar a , Edilma Paraguai de Souza a , Valéria M.F. de Lima b , Marcos Palatnik c , Clarisa Beatriz Palatnik-de-Sousa a,∗ a Instituto de Microbiologia, “Professor Paulo de Góes”, Universidade Federal do Rio de Janeiro (UFRJ), CCS, Cidade Universitária, Ilha do Fundão, CP 68040, CEP 21941-590, Rio de Janeiro, Brazil b Curso de Medicina Veterinária, Universidade Estadual Paulista, Araçatuba, CEP 16050-680, Brazil c Hospital Universitário Clementino Fraga Filho-Faculdade de Medicina UFRJ, Rio de Janeiro, Brazil Received 25 March 2003; accepted 3 July 2003 Abstract The fucose mannose ligand (Leishmania donovani FML)-saponin vaccine has earlier shown its immunoprophylactic potential against visceral leishmaniasis in the CB hamster (87.7% of parasite load reduction), Balb/c (84.4%) and Swiss albino mouse (85–93%) models. In this investigation its specific immunotherapeutic efficacy against L. donovani infection in Balb/c mice was studied. The effects of vaccine treatment on the humoral response, delayed type of hypersensitivity to promastigote lysate (DTH), cytokine levels in sera and reduction of the liver parasitic load of L. donovani infected mice, were examined. The types and subtypes of anti-FML antibodies increased significantly in the vaccinees over the saline and saponin controls. As expected for a saponin vaccine, the highest ratios were found in relation to IgG1, IgG2a and IgG2b (4.4, 5 and 2.5, respectively). The DTH response and the in vitro ganglion cell proliferative response against FML antigen were also significantly higher than controls (P< 0.005). Concomitantly, an impressive and specific decrease of liver parasitic burden was detected only in vaccine-treated animals (94.7%). Our results indicate that the therapeutic FML-vaccine has a potent effect on modulation of the murine infection leading to the reduction of parasitic load and signs of disease, being a new potential tool in the therapy and control of visceral leishmaniasis. © 2003 Elsevier Ltd. All rights reserved. Keywords: Visceral leishmaniasis; Kala-azar; FML-vaccine; Immunotherapy; Immunoprophylaxis; Saponin; Vaccination 1. Introduction Human visceral leishmaniasis or kala-azar is a severe and frequently lethal infectious disease against which chemotherapy treatment is very toxic, show failing in 5–10% of cases [1]. In addition, chemotherapy demands hospitalization for 30 days. Alternatively, immunotherapy or immunochemotherapy were assayed against tegumentar human leishmaniasis, a less severe form of disease [2–4]. Effective immunotherapy or immunochemotherapy against canine visceral leishmaniasis would also be a good tool for control of dissemination of human disease. Indeed, zoonotic visceral leishmaniasis is a re-emerging disease that causes 500,000 new human cases all over the world. Dogs, foxes and wild canids are the reservoir for visceral leishmaniasis in the Mediterranean, Asia, North Africa and South Amer- ∗ Corresponding author. Tel.: +55-21-256-26742; fax: +55-21-25608344/25608028. E-mail address: clarisaps@infolink.com.br (C.B. Palatnik-de-Sousa). ica. The etiological agent (Leishmania chagasi or Leishma- nia infantum) is introduced into the domestic cycle when infected foxes visit houses to scavenge poultry. Peridomes- tic sand flies acquire the parasite by feeding on the foxes’ skin and transmit it to dogs. The subsequent transmission to humans by sand flies causes human visceral leishmaniasis (reviewed in [5]). One of the tools used in epidemiological control of the disease is the sacrifice of seropositive infected dogs, since they expose the parasite to sandflies [5]. Despite the great number of investigations [6–9] no effective ch- emotherapy treatment against the canine disease is available [10–13]. Therapeutic failure has epidemiological implica- tions since treated animals became infectious after treat- ment although they might remain asymptomatic [12]. Since infectivity to sandflies is highly correlated to the loss of an effective cellular immune response [14], the immunotherapy or combined immunochemotherapy treatment of infected dogs is an alternative that has begun to be explored [15]. In previous reports, we described the isolation of a Leishmania donovani promastigote glycoproteic complex 0264-410X/$ – see front matter © 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0264-410X(03)00527-9