1. Investigación

Leishmaniasis a ects around 12 million people worldwide and is estimated to cause the ninth-largest disease burden. There are three main forms of the disease, visceral (VL), cutaneous (CL), and mucocutaneous (MCL), leading to more than one million new cases every year and several thousand deaths. Current treatments based on chemically synthesized molecules are far from ideal. In this study, we have tested the in vitro and in vivo e cacy of ursolic acid (UA), a multifunctional triterpenoid with well-known antitumoral, antioxidant, and antimicrobial e ects on di erent Leishmania strains. The in vitro antileishmanial activity against the intracellular forms was six and three-fold higher compared to extracellular forms of L. amazonensis and L. infantum, respectively. UA also showed to be a potent antileishmanial drug against both VL and CL manifestations of the disease in experimental models. UA parenterally administered at 5 mg/kg for seven days significantly reduced the parasite burden in liver and spleen not only in murine acute infection but also in a chronic-infection model against L. infantum. In addition, UA ointment (0.2%) topically administered for four weeks diminished (50%) lesion size progression in a chronic infection model of CL caused by L. amazonensis, which was much greater than the e ect of UA formulated as an O/W emulsion. UA played a key role in the immunological response modulating the Th1 response. The exposure of Leishmania-infected macrophages to UA led to a significant di erent production in the cytokine levels depending on the Leishmania strain causing the infection. In conclusion, UA can be a promising therapy against both CL and VL.

A stronger Th1 (cellular) immune response in canine leishmaniosis (CanL) leads to a better prognosis. Dietary nucleotides plus AHCC® have shown beneficial e ects in dogs with clinical leishmaniosis and in clinically healthy Leishmania-infected dogs. The potential leishmanicidal activity of nucleotides and AHCC was assessed by quantifying nitric oxide (NO) production and replication of parasites. Their e ects on lymphocyte proliferation were studied with and without soluble Leishmania infantum antigen (SLA) stimulation. Cytokine level variations were assessed using naïve and L. infantum-infected macrophages/lymphocytes cocultures. Promastigotes and amastigotes proliferation and NO macrophage production were not directly a ected. Lymphocyte proliferation was significantly enhanced by nucleotides, AHCC, and their combinations only after SLA stimulation. Nucleotides and AHCC significantly increased the production of IL-1 , IL-2, IL-5, IL-9, IL-10, and IL-12 by naïve immune cells. In naïve and L. infantum-infected macrophage/lymphocyte cocultures, nucleotides with or without AHCC led to significant increases in IFN- and TNF- . Given that these cytokines are involved in the e ective Th1 immune response against Leishmania parasites, these mechanisms of action could explain the previously reported in vivo clinical e cacy of such combination and further support the use of nucleotides with or without AHCC in the management of CanL patients.