T-cell-derived cytokines, nitric oxide production by peripheral blood monocytes and seric anti-Leishmania (Leishmania) chagasi IgG subclass patterns following immunization against canine visceral leishmaniasis using Leishvaccine and Leishmune®

Abstract

It is generally accepted that distinct cytokine expression by the cellular immune response plays a critical role during the outcome of experimental as well as natural canine visceral Leishmaniasis (CVL). Despite the fact that immunoprophylaxis of CVL has become an important control strategy and protective immunity has been reported upon immunization with whole as well as purified Leishmania antigens, the cytokine profile of T-cells triggered by anti-CVL vaccines still remain to be determined. Herein, we have developed a cross-sectional analysis of German Shepherd dogs submitted to vaccination protocols with Leishvaccine (n=6) and Leishmune (n=6). Our data identified distinct immunological profiles elicited by Leishvaccine and Leishmune, with the Leishvaccine triggering a mixed, IFN-gamma and IL-4, cytokine pattern in addition to high levels of anti-Leishmania IgG1, whereas the Leishmune induced an immunological pattern characterized by enhanced levels of IFN-gamma, NO and anti-Leishmania chagasi IgG2. It was important to notice that despite the distinct immunological patterns triggered by Leishvaccine and Leishmune, the ability of both immunobiologicals to activate T-cell-derived IFN-gamma synthesis further suggesting their immunogenic potential against CVL. These findings added support to our hypothesis that both antigenic composition (whole antigen in Leishvaccine versus purified antigen in Leishmune) as well as the adjuvant nature (BGC and saponin) used for the vaccine formulation may count for the distinct activation pattern observed.

Vaccines for Canine Leishmaniasis

“…Leishmune ® induced an immunological pattern characterized by enhanced levels of IFN-γ, NO, and anti- L. chagasi IgG2 (Araújo et al, 2009), the early and persistent activation of neutrophils and monocytes, and increased the CD8+ T-cells expressing IFN-γ (Araújo et al, 2008; Table 1). This increase of CD8+ T-cells is expected for the QS21 saponin adjuvant of Leishmune ® (Oliveira-Freitas et al, 2006) and it was also described in the immunotherapy assays against naturally (Borja-Cabrera et al, 2004) and experimentally acquired ZVL (Santos et al, 2007).…”

“…It is composed of the recombinant A2-antigen of Leishmania amastigotes and is adjuvanted by saponin (Fernandes et al, 2008). While protection due to the Leishmune ® vaccine has been extensively investigated in laboratory models (reviewed by Palatnik-de-Sousa et al, 2008), explained through an immunological approach (Araújo et al, 2008, 2009, 2011), and reported in: control versus trial-field assays with cohorts including 117 (da Silva et al, 2001), 85 (Borja-Cabrera et al, 2002), 72 (Nogueira et al, 2005), and 1138 dogs (Parra et al, 2007; Borja-Cabrera et al, 2008); immunotherapy assays with 66 (Borja-Cabrera et al, 2010) and 24 dogs (Santos et al, 2007); and in 19,392 vaccinated dogs in two Brazilian towns (Palatnik-de-Sousa et al, 2009), there is only one report of an experimental kennel assay with Leish-Tec ® which was tested on seven dogs and compared with four untreated controls (Fernandes et al, 2008). There is no information about the infectivity of the strain used for challenge in that study and the lack of deaths in the control animals suggests that the challenge was mild.…”

Vaccine candidates for leishmaniasis: A review

“…The strong immunogenicity induced by Leishmune® vaccine was demonstrated by the seropositivity, increased positive DTH responses and average increase in CD8 + and CD21 + cells. Recently, immunization with Leishmune® induced an immunological pattern characterized by activation of CD8 + cells and enhanced levels of IFN-γ, NO and IgG2 [167,168]. The potential effect of Leishmune® vaccine to block the transmission of Leishmania parasite in dogs was also investigated [169].…”

Leishmania donovani Nucleoside Hydrolase Terminal Domains in Cross-Protective Immunotherapy Against Leishmania amazonensis Murine Infection

“…Recently, we developed the first licensed second generation vaccine against canine VL leishmaniasis (Leishmune ® ), which contains the fucose–mannose ligand (FML) antigen of L. donovani in formulation with saponin (16–19), is a transmission blocking vaccine (18, 19) and has already determined a reduction in the incidence of the human and canine disease in Brazilian endemic areas (20). Prophylactic vaccination of dogs with Leishmune ® promoted increases in the production of NO, IgG2 antibodies against FML and L. chagasi , intradermal reactions and proportions of CD8 + lymphocytes, which secrete more IFN-γ than IL-4 (21, 22) expressing a selective pro-inflammatory pattern (IFN-γ/NO) (23). The early and persistent activation of neutrophils and monocytes have also been described (23).…”