Leishmania infantum released proteins specifically regulate cytokine expression and production patterns by CD4+ and CD8+ T cells

Leishmania infantum-specific IFN-γ production in stimulated blood from dogs with clinical leishmaniosis at diagnosis and during treatment

There is limited data regarding Leishmania infantum specific T cell mediated immunity in naturally infected sick dogs at the time of diagnosis and during anti-Leishmania treatment. Our aim was to investigate the kinetics of L. infantum specific IFN-γ production in dogs with leishmaniosis at the time of diagnosis and during treatment and to correlate it with specific L. infantum antibodies, blood parasitemia and clinicopathological findings. Thirty-four dogs were diagnosed with leishmaniosis based on physical examination, routine laboratory tests and L. infantum-specific antibody levels by quantitative ELISA. Heparinized whole blood was stimulated with L. infantum soluble antigen (LSA) and concanavalin A (ConA) and incubated for 5days. IFN-γ concentration was evaluated in supernatants of stimulated blood using a commercial sandwich ELISA. Leishmania real-time PCR was also performed for assessing blood parasitemia. Dogs were treated with meglumine antimoniate and allopurinol. Sixteen dogs were classified as IFN-γ non-producers after LSA stimulation (mean±SD: 0±0pg/mL) and 18 dogs as IFN-γ producers (mean±SD: 2885.3±4436.1pg/mL) at the time of diagnosis (P<0.0001). IFN-γ non-producers were classified in a more severe clinical staging than IFN-γ producers that presented a mild to moderate clinical staging (P=0.03). In the IFN-γ non-producer group, production of IFN-γ after LSA stimulation was significantly increased during treatment especially at day 365 (P=0.018) together with clinical improvement when compared with day 0. In contrast, IFN-γ producers maintained their IFN-γ production after LSA stimulation and no statistically significant changes were found during treatment follow-up. At diagnosis, IFN-γ non-producers showed a significantly higher blood parasitemia versus IFN-γ -producers (P=0.005). IFN-γ non-producers drastically reduced blood parasitemia to minimum values at day 365 when compared with day 0 (P=0.017). No significant differences were found at day 365 in blood parasitemia of IFN-γ producers compared to pre-treatment. At diagnosis, L. infantum specific antibodies were higher in IFN-γ non-producers than IFN-γ producers (P=0.014). A marked reduction of antibody levels was found at day 365 when compared with day 0 in IFN-γ non-producers (P=0.005) and producers (P=0.001). These results demonstrate that IFN-γ concentration increases with long-term anti-Leishmania treatment together with clinical improvement in dogs that do not produce IFN-γ at diagnosis. Together with clinical recovery, reduction in blood parasitemia and L. infantum specific antibodies, tracking IFN-γ concentration could constitute an important prognostic tool for immune monitoring in CanL.

Finding of leishmanicidal activity of 14-hydroxylunularin in mice experimentally infected with Leishmania infantum

In this study, we report the in vivo efficacy of 14-hydroxylunularin evaluated in BALB/c mice experimentally infected with promastigotes of Leishmania infantum (syn L. chagasi), the major causative agent of visceral leishmaniasis in Latin America. Seven days post-infection, treatment with 14-hydroxylunularin started and it was administered by oral and subcutaneous routes in doses of 10 and 25 mg/kg of weight for ten days using Glucantime® as reference drug. In the liver, the evaluated compound showed parasite reduction above 90% by both administration routes being the oral route the most effective at both doses. Significant decreased numbers of parasites were also observed when the treated group was compared with the control group (p≤0.05). The subcutaneous route presented a remarkable difference with at least 80% parasite suppression in liver and spleen at 10 mg/kg dose and 90% in liver at 25 mg/kg. The leishmanicidal activity of 14-hydroxylunularin against L. infantum revealed by this study is another evidence in favor of this compound as a potential candidate for the development of a new oral treatment for leishmaniasis.

Immunization with Leishmania infantum released proteins confers partial protection against parasite infection with a predominant Th1 specific immune response

In this study, protective effect and immune response elicited by protein fractions LiRic1 (>75 kDa) and LiRic2 (<37 kDa) released by Leishmania infantum promastigotes were analysed in challenged BALB/c mice. Viable parasites were quantified in spleen and isolated CD4(+) and CD8(+) T cells were stimulated for evaluation of proliferative response and cytokine production. Immunization triggered 50.4-66.9% of parasite reduction. Stimulated CD4(+) T cells from challenged animals revealed high proliferation. IL-12 and IFN-gamma were released by CD4(+) T cells whereas IL-4 and IL-10 were impaired. LiRic1 and LiRic2 immunization gave partial protection and a CD4(+) Th1 response. LiRic2 generated IL-12 by CD8(+) T cells pointing to its participation in protective response. These results encourage further research on the development of a vaccine that provides long-lasting protection against zoonotic visceral leishmaniasis.