Enhancement of experimental cutaneous leishmaniasis by Leishmania extract: identification of a disease-associated antibody specificity

Treatment using vanillin-derived synthetic molecules incorporated into polymeric micelles is effective against infection caused by Leishmania amazonensis species

Treatment against leishmaniasis presents problems, mainly due to the toxicity of the drugs, high cost, and the emergence of resistant strains. A previous study showed that two vanillin-derived synthetic molecules, 3s [4-(2-hydroxy-3-(4-octyl-1H-1,2,3-triazol-1-yl)propoxy)-3-methoxybenzaldehyde] and 3t [4-(3-(4-decyl-1H-1,2,3-triazol-1-yl)-2-hydroxypropoxy)-3-methoxybenzaldehyde], presented antileishmanial activity against Leishmania infantum, L. amazonensis, and L. braziliensis species. In the present work, 3s and 3t were evaluated to treat L. amazonensis-infected mice. Molecules were used pure or incorporated into Poloxamer 407-based micelles. In addition, amphotericin B (AmpB) and its liposomal formulation, Ambisome®, were used as control. Animals received the treatment and, one and 30 days after, they were euthanized to evaluate immunological, parasitological, and biochemical parameters. Results showed that the micellar compositions (3s/Mic and 3t/Mic) induced significant reductions in the lesion mean diameter and parasite load in the infected tissue and distinct organs, as well as a specific and significant antileishmanial Th1-type immune response, which was based on significantly higher levels of IFN-γ, IL-12, nitrite, and IgG2a isotype antibodies. Drug controls showed also antileishmanial action; although 3s/Mic and 3t/Mic have presented better and more significant parasitological and immunological data, which were based on significantly higher IFN-γ production and lower parasite burden in treated animals. In addition, significantly lower levels of urea, creatinine, alanine transaminase, and aspartate transaminase were found in mice treated with 3s/Mic and 3t/Mic, when compared to the others. In conclusion, results suggest that 3s/Mic and 3t/Mic could be considered as therapeutic candidates to treat against L. amazonensis infection.

Investigations on the effects of anti-Leishmania major serum on the progression of Leishmania infantum infection in vivo and in vitro - implications of heterologous exposure to Leishmania spp

Leishmaniasis is a vector-borne parasitic disease caused by protozoa of the genus Leishmania. Twenty different species are known to cause disease in humans with varying degrees of pathology. These diseases are transmitted throughout the geographic range of phlebotomine sandflies, found between the latitudes 50°N and 40°S. This study explores antibody dependent enhancement (ADE) as the cause of disease exacerbation in heterologous exposure of L. major primed mice to L. infantum challenge. BALB/c mice received serum from L. major infected or naive mice. All mice were challenged with L. infantum and tissue parasite burdens were recorded. Animals that received anti-L. major serum exhibited significantly higher parasite burdens. Surprisingly, these parasite burdens were higher than those of mice infected with L. major and challenged with L. infantum. In vitro phagocytosis assays were carried out to measure parasite uptake in the presence of naive vs. anti-L. major serum. J774A.1 murine monocytes were cultured with either L. major or L. infantum in the presence of anti-L. major serum, naive serum, or no serum. Significantly higher rates of L. major uptake by J774A.1 cells occurred in the presence of anti-L. major serum, but no measurable increase of L. infantum phagocytosis was seen. Our results suggest that increased disease severity observed in vivo in mice previously exposed to L. major and challenged with L infantum is not a result of extrinsic ADE. We speculate that intrinsic ADE, due to biased memory T cell responses caused by Fcγ signaling, could account for disease exacerbation seen in the animal model.

Immunity to vector saliva is compromised by short sand fly seasons in endemic regions with temperate climates

Individuals exposed to sand fly bites develop humoral and cellular immune responses to sand fly salivary proteins. Moreover, cellular immunity to saliva or distinct salivary proteins protects against leishmaniasis in various animal models. In Tbilisi, Georgia, an endemic area for visceral leishmaniasis (VL), sand flies are abundant for a short period of ≤3 months. Here, we demonstrate that humans and dogs residing in Tbilisi have little immunological memory to saliva of P. kandelakii, the principal vector of VL. Only 30% of humans and 50% of dogs displayed a weak antibody response to saliva after the end of the sand fly season. Likewise, their peripheral blood mononuclear cells mounted a negligible cellular immune response after stimulation with saliva. RNA seq analysis of wild-caught P. kandelakii salivary glands established the presence of a typical salivary repertoire that included proteins commonly found in other sand fly species such as the yellow, SP15 and apyrase protein families. This indicates that the absence of immunity to P. kandelakii saliva in humans and dogs from Tbilisi is probably caused by insufficient exposure to sand fly bites. This absence of immunity to vector saliva will influence the dynamics of VL transmission in Tbilisi and other endemic areas with brief sand fly seasons.

Pathophysiology of Leishmania Infection during Pregnancy

The pathological processes resulting from parasitic infection are known to have important impacts on the mother child dyad during pregnancy. The roles of parasite transmission and the maternal immune response have been described in diseases such as malaria, toxoplasmosis, and trypanosomiasis. However, the impact of parasites of the genus Leishmania, etiological agents of the neglected tropical diseases tegumentary leishmaniasis (TL) and visceral leishmaniasis (VL), is comparatively less well known, though it is an increasingly recognized concern for infected mothers and their fetuses. In this review, we first consider the pathophysiology of placental infection and transplacental transmission of this parasite, and then discuss the role and mechanisms of the maternal immune system in simultaneously mediating maternal-fetal infection and adverse pregnancy outcomes.

Cross-protective efficacy of Leishmania infantum LiHyD protein against tegumentary leishmaniasis caused by Leishmania major and Leishmania braziliensis species

Vaccination can be considered the most cost-effective strategy to control neglected diseases, but nowadays there is not an effective vaccine available against leishmaniasis. In the present study, a vaccine based on the combination of the Leishmania-specific hypothetical protein (LiHyD) with saponin was tested in BALB/c mice against infection caused by Leishmania major and Leishmania braziliensis species. This antigen was firstly identified in Leishmania infantum and showed to be protective against infection of BALB/c mice using this parasite species. The immunogenicity of rLiHyD/saponin vaccine was evaluated, and the results showed that immunized mice produced high levels of IFN-γ, IL-12 and GM-CSF after in vitro stimulation with rLiHyD, as well as by using L. major or L. braziliensis protein extracts. After challenge, vaccinated animals showed significant reductions in the infected footpad swellings, as well as in the parasite burden in the infection site, liver, spleen, and infected paws draining lymph nodes, when compared to those that were inoculated with the vaccine diluent (saline) or immunized with saponin. The immunization of rLiHyD without adjuvant was not protective against both challenges. The partial protection obtained by the rLiHyD/saponin vaccine was associated with a parasite-specific IL-12-dependent IFN-γ secretion, which was produced mainly by CD4(+) T cells. In these animals, a decrease in the parasite-mediated IL-4 and IL-10 responses, associated with the presence of high levels of LiHyD- and parasite-specific IgG2a isotype antibodies, were also observed. The present study showed that a hypothetical protein that was firstly identified in L. infantum, when combined to a Th1 adjuvant, was able to confer a cross-protection against highly infective stationary-phase promastigotes of two Leishmania species causing tegumentary leishmaniasis.