A Leishmania hypothetical protein-containing liposome-based formulation is highly immunogenic and induces protection against visceral leishmaniasis.

Leishmania proteins have been evaluated as vaccine candidates against leishmaniasis; however, most antigens present low immunogenicity and need to be added with immune adjuvants. A low number of licensed adjuvants exist on the market today; therefore, research conducted to produce new products is desirable. The present study sought to evaluate the immunogenicity and protective efficacy of a recombinant Leishmania hypothetical protein, namely LiHyR, administered with saponin or liposomes in BALB/c mice. Immunological and parasitological parameters were evaluated, and results showed significant protection against Leishmania infantum infection produced by both compositions in the immunized animals; however, this was not identified when the antigen was used alone. In addition, the liposomal formulation was more effective in inducing a polarized Th1 response in the vaccinated animals, which was maintained after challenge and reflected by lower parasitism found in all evaluated organs when the limiting dilution technique and RT-PCR assay were employed. The protected animals showed higher levels of protein and parasite-specific IFN-γ IL-2, IL-12, GM-CSF, and TNF-α, which were evaluated by capture ELISA and flow cytometry, in addition to a higher production of anti-protein and anti-parasite IgG2a antibodies, both before and after challenge. The Lip/rLiHyR combination induced higher IFN-γ production through both CD4+ and CD8+ T cell subtypes. Results indicate the possibility of using the LiHyR, containing a liposomal formulation, as a vaccine candidate against visceral leishmaniasis.

Comparing the therapeutic efficacy of different amphotericin B-carrying delivery systems against visceral leishmaniasis.

Amphotericin B (Amp) has been well-successfully used to treat against Leishmania infection, although high toxicity has been found in patients. In the present study, Amp was administered in Leishmania infantum-infected BALB/c mice by three distinct delivery systems aiming to compare their efficacy against challenge infection, as well as their side effects in a murine visceral leishmaniasis (VL) model. This product was administered in a Poloxamer P407 (Pluronic® F127)-based polymeric micelle system (Amp/M), in the Ambisome® formulation (Lip-Amp) or in a free format (free Amp). Glucantime® (Gluc) was used as a comparative drug. Aiming to evaluate different endpoints of the treatments, the efficacy of the compounds was investigated one and 15-days after the therapeutic regimens, determining the parasite load by a limiting dilution assay and a quantitative PCR (qPCR) technique, as well as evaluating the immune response generated in the infected and treated animals. In the results, Amp/M or Lip-Amp-treated mice presented the best outcomes, since significant parasite load reductions were found in the evaluated organs, as well as a parasite-specific Th1 immune response was observed in the animals. In addition, no hepatic or renal damage was found in these mice. On the other hand, free Amp or Gluc induced toxicity in the animals, which was associated with a low Th1 immune response. Comparatively, Amp/M was the most effective drug in our experimental model, and results showed that the Amp-carrying system could be considered as a future alternative in studies against VL.

1,3-Bis(aryloxy)propan-2-ols as potential antileishmanial agents.

We describe herein the synthesis and antileishmanial activity of 1,3-bis(aryloxy)propan-2-ols. Five compounds (2, 3, 13, 17, and 18) exhibited an effective antileishmanial activity against stationary promastigote forms of Leishmania amazonensis (IC50  < 15.0 µm), and an influence of compound lipophilicity on activity was suggested. Most of the compounds were poorly selective, as they showed toxicity toward murine macrophages, except 17 and 18, which presented good selective indexes (SI ≥ 10.0). The five more active compounds (2, 3, 13, 17, and 18) were selected for the treatment of infected macrophages, and all of them were able to reduce the number of internalized parasites by more than 80%, as well as the number of infected macrophages by more than 70% in at least one of the tested concentrations. Altogether, these results demonstrate the potential of these compounds as new hits of antileishmanial agents and open future possibilities for them to be tested in in vivo studies.

A recombinant fusion protein displaying murine and human MHC class I- and II-specific epitopes protects against Leishmania amazonensis infection.

Tegumentary leishmaniasis (TL) constitutes a major public health problem with significant morbidity worldwide. Synthetic peptide-based vaccines are attractive candidates to protect against leishmaniasis, since T cell-specific epitopes can be delivery to antigen-presenting cells, leading to the generation of a Th1 cell-mediated immunity. In this context, the present study aims to evaluate the immunogenicity and protective efficacy of a vaccine composed of major histocompatibility complex class I and II-restricted epitopes derived from four Leishmania infantum proteins to protect mice against Leishmania amazonensis infection. This recombinant fusion protein was administered in BALB/c mice alone or with saponin. As controls, animals received saline or saponin. In the results, the administration of the recombinant protein plus saponin induced a specific IFN-γ, IL-12 and GM-CSF production, as well as high IgG2a isotype antibody levels, which protected mice against a challenge using L. amazonensis promastigotes. Lower parasite burden was found in the infected footpads, liver, spleen and draining lymph node of vaccinated mice, when compared to those from the control groups. In addition, protection was associated with a lower IL-4 and IL-10 response, which was accompanied by the antileishmanial nitrite production by spleen cells of the animals. Interestingly, the recombinant protein administered alone induced a partial protection against challenge. In conclusion, this study shows a new vaccine candidate based on T cell-specific epitopes that was able to induce protection against L. amazonensis infection.

Leishmania infantum mimotopes and a phage-ELISA assay as tools for a sensitive and specific serodiagnosis of human visceral leishmaniasis.

Serological methods used to diagnose visceral leishmaniasis (VL) are considered minimally invasive, but they present problems related with their sensitivity and/or specificity. In this study, a subtractive selection using the phage display technology against antibodies from healthy subjects living in endemic and non-endemic areas of disease, as well as from Chagas disease patients and those developing active VL, was developed. The aim of this study was to select bacteriophage-fused epitopes to be used in the serodiagnosis of human VL. Eight phage clones were selected after the bio-panning rounds, and their reactivity was evaluated in a phage-ELISA assay against a human serological panel. A wild-type clone and the recombinant K39-based immunochromatographic test were used as controls. In the results, it was shown that all clones showed an excellent performance to serologically identify VL patients, demonstrating the feasibility of the isolated phages for developing a specific and sensitive serodiagnosis of human VL.

Poloxamer 407 (Pluronic(®) F127)-based polymeric micelles for amphotericin B: In vitro biological activity, toxicity and in vivo therapeutic efficacy against murine tegumentary leishmaniasis.

In the present study, a Poloxamer 407-based amphotericin B (AmpB)-containing polymeric micelles system (AmpB/M) was employed in the treatment of Leishmania amazonensis-infected BALB/c mice. Initially, the in vitro antileishmanial activity (IC50 value) of AmpB/M and B-AmpB/M (empty micelles) against stationary promastigotes and amastigotes-like forms of the parasites was determined, and results were of 1.83 ± 0.4 and 22.1 ± 0.7 µM, respectively, for the promastigotes, and of 2.27 ± 0.5 and 33.98 ± 2.6 µM, respectively, for the amastigotes-like. The cytotoxic concentration (CC50) values of these products were also evaluated, and we found the results of 119.5 ± 9.6 and 134.7 ± 10.3 µM, respectively. With these values, the selectivity index (SI) was calculated and results were of 65.3 and 5.4, respectively, for the promastigotes, and of 59.3 and 3.96, respectively, for the amastigotes-like of the parasites. Free AmpB showed IC50 values of 1.2 ± 0.3 and 2.5 ± 0.5 µM for the promastigotes and amastigotes-like, respectively, whereas the CC50 value was of 9.5 ± 0.4 µM. The SI values of this drug were of 7.9 and 3.8, respectively, for the promastigote and amastigote-like stages of the parasites. After, animals were infected and received saline or were treated subcutaneously with free AmpB, AmpB/M or B-AmpB/M. In the results, free AmpB-treated and infected mice showed reductions in their body weight, which were associated with hepatic and renal damage; however, no organic alteration was observed in the AmpB/M-treated animals. In addition, these animals showed significant reductions in their lesion average size and in the parasite burden in all evaluated infected tissue and organs, when compared to the other groups; as well as significantly higher levels of antileishmanial IFN-γ, IL-12, GM-CSF and nitrite, which were associated with low production of IL-4, IL-10 and IgG1 isotype antibodies. In conclusion, this AmpB/M system could be considered as an alternative for future studies in the treatment of tegumentary leishmaniasis.

A vaccine combining two Leishmania braziliensis proteins offers heterologous protection against Leishmania infantum infection.

In the present study, two Leishmania braziliensis proteins, one hypothetical and the eukaryotic initiation factor 5a (EiF5a), were cloned and used as a polyproteins vaccine for the heterologous protection of BALB/c mice against infantum infection. Animals were immunized with the antigens separately or in association, and in both cases saponin was used as an adjuvant. In the results, spleen cells from mice inoculated with the individual or polyproteins vaccine and lately challenged produced significantly higher levels of protein- and parasite-specific IFN-γ, IL-12, and GM-CSF, when both a capture ELISA and flow cytometry assays were performed. Evaluating the parasite load by a limiting dilution as well as by RT-PCR, these animals presented significant reductions in the parasite number in all evaluated organs, when compared to the control (saline and saponin) groups. The best protection was reached when the polyproteins vaccine was employed. Protection was associated with the IFN-γ production against parasite extracts, which was mediated by both CD4(+) and CD8(+) T cells and correlated with the antileishmanial nitrite production. In this context, this vaccine combining two L. braziliensis proteins was able to induce a heterologous protection against VL, and could be considered in future studies to be tested against other Leishmania species or in other mammalian hosts.

New serological tools for improved diagnosis of human tegumentary leishmaniasis.

Human tegumentary leishmaniasis (HTL), characterized by skin ulcers that may spread and cause dreadful and massive tissue destruction of the nose and mouth, is considered a neglected tropical disease, and it is a serious threat to global health due to its continuous expansion, favored by the lifecycle of its causative organism that is maintained in domestic animal reservoirs and anthropophilic sand fly species. Serodiagnosis of HTL is a great challenge due to many biological factors, including hampered specificity and/or sensitivity. This investigation addresses the unmet need for new diagnostic markers of HTL, and describes a simple platform to improve the serodiagnosis. A constrained conformational phage display random peptide library combined with a magnetic microsphere-based subtraction strategy was used to identify ligands with potential diagnostic applications. Six clones were selected against IgG antibodies from HTL patients, characterized by sequencing and confirmed by a phage-ELISA using sera from patients developing visceral leishmaniasis (n=20), Chagas disease (n=10), mucosal (n=30) and cutaneous (n=20) leishmaniasis; as well as from healthy subjects living in endemic (n=20) and non-endemic (n=30) areas of leishmaniasis. A wild-type M13-phage clone and a soluble Leishmania antigenic extract were used as negative and positive controls, respectively. Three clones reached 100% sensitivity and specificity, without any cross-reactivity with sera from patients with leishmaniasis-related diseases. Briefly, we describe for the first time a set of serological markers based on three immunodominant mimotopes that showed 100% accuracy, and that could be used in a phage-ELISA assay for the HTL serodiagnosis.

Antileishmanial activity and mechanism of action from a purified fraction of Zingiber officinalis Roscoe against Leishmania amazonensis.

In recent years, considerable attention has been given to identify new antileishmanial products derived from medicinal plants, although, to date, no new effective compound has been recently applied to treat leishmaniasis. In the present study, the antileishmanial activity of a water extract from Zingiber officinalis Roscoe (ginger) was investigated and a purified fraction, named F10, was identified as responsible by this biological activity. The chemical characterization performed for this fraction showed that it is mainly composed by flavonoids and saponins. The water extract and the F10 fraction presented IC50 values of 125.5 and 49.8 µg/mL, respectively. Their selectivity indexes (SI) were calculated and values were seven and 40 times higher, respectively, in relation to the value found for amphotericin B, which was used as a control. Additional studies were performed to evaluate the toxicity of these compounds in human red blood cells, besides of the production of nitrite, as an indicator of nitric oxide (NO), in treated and infected macrophages. The results showed that both F10 fraction and water extract were not toxic to human cells, and they were able to stimulate the nitrite production, with values of 13.6 and 5.4 µM, respectively, suggesting that their biological activity could be due to macrophages activation via NO production. In conclusion, the present study shows that a purified fraction from ginger could be evaluated in future works as a therapeutic alternative, on its own or in association with other drugs, to treat disease caused by L. amazonensis.

A new Leishmania-specific hypothetical protein and its non-described specific B cell conformational epitope applied in the serodiagnosis of canine visceral leishmaniasis.

The serodiagnosis of canine visceral leishmaniasis (CVL) presents problems related to its sensitivity and/or specificity. In the present study, a new Leishmania-specific hypothetical protein, LiHyD, was produced as a recombinant protein (rLiHyD) and evaluated in ELISA experiments for the CVL serodiagnosis. LiHyD was characterized as antigenic in a recent immunoproteomic search performed with Leishmania infantum proteins and the sera of dogs developing visceral leishmaniasis (VL). Aiming to compare the efficacy between whole proteins and synthetic peptides, two linear and one conformational B cell epitopes of LiHyD were synthesized and also evaluated as diagnostic markers. The four antigens were recognized by the sera of dogs suffering VL. On the contrary, low reactivity was observed when they were assayed with sera from non-infected healthy dogs living in endemic or non-endemic areas of leishmaniasis. In addition, no reactivity was found against them using sera from dogs experimentally infected by Trypanosoma cruzi, Babesia canis, or Ehrlichia canis, or sera from animals vaccinated with the Leish-Tec® vaccine, a prophylactic preparation commercially available for CVL prevention in Brazil. As comparative diagnostic tools, a recombinant version of the amastigote-specific A2 protein and a soluble crude Leishmania extract were studied. Both antigens presented lower sensitivity and/or specificity values than the LiHyD-based products. The rLiHyD presented better results for the CVL serodiagnosis than its linear epitopes, although the peptide recreating the conformational epitope resulted also appropriate as a diagnostic marker of CVL. To the best of our knowledge, this is the first study showing the use of a conformational epitope derived from a Leishmania protein for serodiagnosis of CVL.

Antileishmanial activity and evaluation of the mechanism of action of strychnobiflavone flavonoid isolated from Strychnos pseudoquina against Leishmania infantum.

The present study aimed to investigate the in vitro antileishmanial activity of strychnobiflavone flavonoid against Leishmania infantum, as well as its mechanism of action, and evaluate the ex vivo biodistribution profile of the flavonoid in naive BALB/c mice. The antileishmanial activity (IC50 value) of strychnobiflavone against stationary promastigote and amastigote-like stages of the parasites was of 5.4 and 18.9 µM, respectively; with a 50% cytotoxic concentration (CC50) value of 125.0 µM on murine macrophages, resulting in selectivity index (SI) of 23.2 and 6.6, respectively. Amphotericin B, used as a positive control, presented SI values of 7.6 and 3.3 for promastigote and amastigote-like stages of L. infantum, respectively. The strychnobiflavone was also effective in reducing in significant levels the percentage of infected macrophages, as well as the number of amastigotes per macrophage, after the treatment of infected macrophages using the flavonoid. By using different fluorescent probes, we investigated the bioenergetics metabolism of L. infantum promastigotes and demonstrated that the flavonoid caused the depolarization of the mitochondrial membrane potential, without affecting the production of reactive oxygen species. In addition, using SYTOX(®) green as a fluorescent probe, the strychnobiflavone demonstrated no interference in plasma membrane permeability. For the ex vivo biodistribution assays, the flavonoid was labeled with technetium-(99m) and studied in a mouse model by intraperitoneal route. After a single dose administration, the scintigraphic images demonstrated a highest uptake by the liver and spleen of the animals within 60 min, resulting in low concentrations after 24 h. The present study therefore demonstrated, for the first time, the antileishmanial activity of the strychnobiflavone against L. infantum, and suggests that the mitochondria of the parasites may be the possible target organelle. The preferential distribution of this compound into the liver and spleen of the animals could warrant its employ in the treatment of visceral leishmaniasis.

Proteins Selected in Leishmania (Viannia) braziliensis by an Immunoproteomic Approach with Potential Serodiagnosis Applications for Tegumentary Leishmaniasis.

The serodiagnosis of human tegumentary leishmaniasis (TL) presents some problems, such as the low level of antileishmanial antibodies found in most of the patients, as well as the cross-reactivity in subjects infected by other trypanosomatids. In the present study, an immunoproteomic approach was performed aimed at identification of antigens in total extracts of stationary-phase promastigote and amastigote-like forms of Leishmania (Viannia) braziliensis using sera from TL patients. With the purpose of reducing the cross-reactivity of the identified proteins, spots recognized by sera from TL patients, as well as those recognized by antibodies present in sera from noninfected patients living in areas where TL is endemic and sera from Chagas disease patients, were discarded. Two Leishmania hypothetical proteins and 18 proteins with known functions were identified as antigenic. The study was extended with some of them to validate the results of the immunoscreening. The coding regions of five of the characterized antigens (enolase, tryparedoxin peroxidase, eukaryotic initiation factor 5a, ß-tubulin, and one of the hypothetical proteins) were cloned in a prokaryotic expression vector, and the corresponding recombinant proteins were purified and evaluated for the serodiagnosis of TL. The antigens presented sensitivity and specificity values ranging from 95.4 to 100% and 82.5 to 100%, respectively. As a comparative antigen, a preparation of Leishmania extract showed sensitivity and specificity values of 65.1 and 57.5%, respectively. The present study has enabled the identification of proteins able to be employed for the serodiagnosis of TL.

A Leishmania-specific hypothetical protein expressed in both promastigote and amastigote stages of Leishmania infantum employed for the serodiagnosis of, and as a vaccine candidate against, visceral leishmaniasis.

BACKGROUND: LiHyV is an antigenic hypothetical protein present in both promastigote and amastigote stages of Leishmania infantum, which was recently identified by an immunoproteomic approach. A recombinant version of this protein (rLiHyV) was evaluated as a diagnostic marker for canine VL (CVL). In addition, the prophylactic efficacy of the rLiHyV protein, and two of its CD8(+) T cell epitopes, has been analyzed in a murine model of visceral leishmaniasis (VL). METHODS: Initially, the rLiHyV protein was evaluated by an ELISA technique for the serodiagnosis of CVL. Secondly, vaccines composed of the recombinant protein and both chemically synthesized peptides, combined with saponin as an adjuvant; were administered subcutaneously into BALB/c mice. The cellular and humoral responses generated by vaccination were evaluated. In addition, the parasite burden and immune response were studied 10 weeks after L. infantum infection. RESULTS: The rLiHyV protein was recognized by antibodies of VL dogs. No cross-reactivity was obtained with sera from dogs vaccinated with a Brazilian commercial vaccine, with sera from animals infected with Trypanosoma cruzi, Babesia canis and Ehrlichia canis, or those from non-infected animals living in an endemic area for leishmaniasis. After challenge with L. infantum, spleen cells of BALB/c mice vaccinated with rLiHyV/saponin stimulated with parasite antigens showed a higher production of IFN-γ, IL-12 and GM-CSF, than the same cells obtained from mice vaccinated with the individual peptides, or mice from control (inoculated with saline or saponin) groups. This Th1-type cellular response observed in rLiHyV/saponin vaccinated mice was accompanied by the induction of parasite-specific IgG2a isotype antibodies. Animals immunized with rLiHyV/saponin showed significant reductions in the parasite burden in the liver, spleen, bone marrow and in the lymph nodes draining the paws relative to control mice. CONCLUSIONS: The present study showed for the first time that the L. infantum LiHyV protein could be considered as a vaccine candidate against L. infantum infection, as well as a diagnostic marker for CVL.

An optimized nanoparticle delivery system based on chitosan and chondroitin sulfate molecules reduces the toxicity of amphotericin B and is effective in treating tegumentary leishmaniasis.

Amphotericin B (AmpB) is active against leishmaniasis, but its use is hampered due to its high toxicity observed in patients. In this study, a nanoparticles-delivery system for AmpB (NQC-AmpB), containing chitosan and chondroitin sulfate molecules, was evaluated in BALB/c mice against Leishmania amazonensis. An in vivo biodistribution study, including biochemical and toxicological evaluations, was performed to evaluate the toxicity of AmpB. Nanoparticles were radiolabeled with technetium-99m and injected in mice. The products presented a similar biodistribution in the liver, spleen, and kidneys of the animals. Free AmpB induced alterations in the body weight of the mice, which, in the biochemical analysis, indicated hepatic and renal injury, as well as morphological damage to the kidneys of the animals. In general, no significant organic alteration was observed in the animals treated with NQC-AmpB. Mice were infected with L. amazonensis and treated with the nanoparticles or free AmpB; then, parasitological and immunological analyses were performed. The NQC-AmpB group, as compared to the control groups, presented significant reductions in the lesion size and in the parasite burden in all evaluated organs. These animals presented significantly higher levels of IFN-γ and IL-12, and low levels of IL-4 and IL-10, when compared to the control groups. The NQC-AmpB system was effective in reducing the infection in the animals, and proved to be effective in diminishing the toxicity evoked by AmpB, which was observed when it was administered alone. In conclusion, NQC-AmpB could be considered a viable possibility for future studies in the treatment of leishmaniasis.

Identification of differentially expressed proteins from Leishmania amazonensis associated with the loss of virulence of the parasites.

BACKGROUND: The present study analyzed whether or not the in vitro cultivation for long periods of time of pre-isolated Leishmania amazonensis from lesions of chronically infected BALB/c mice was able to interfere in the parasites' infectivity using in vivo and in vitro experiments. In addition, the proteins that presented a significant decrease or increase in their protein expression content were identified applying a proteomic approach. METHODOLOGY/PRINCIPAL FINDINGS: Parasites were cultured in vitro for 150 days. Aliquots were collected on the day 0 of culture (R0), as well as after ten (R10; 50 days of culture), twenty (R20; 100 days of culture), and thirty (R30; 150 days of culture) passages, and were used to analyze the parasites' in vitro and in vivo infectivity, as well as to perform the proteomic approach. Approximately 837, 967, 935, and 872 spots were found in 2-DE gels prepared from R0, R10, R20, and R30 samples, respectively. A total of 37 spots presented a significant decrease in their intensity of expression, whereas a significant increase in protein content during cultivation could be observed for 19 proteins (both cases >2.0 folds). Some of these identified proteins can be described, such as diagnosis and/or vaccine candidates, while others are involved in the infectivity of Leishmania. It is interesting to note that six proteins, considered hypothetical in Leishmania, showed a significant decrease in their expression and were also identified. CONCLUSIONS/SIGNIFICANCE: The present study contributes to the understanding that the cultivation of parasites over long periods of time may well be related to the possible loss of infectivity of L. amazonensis. The identified proteins that presented a significant decrease in their expression during cultivation, including the hypothetical, may also be related to this loss of parasites' infectivity, and applied in future studies, including vaccine candidates and/or immunotherapeutic targets against leishmaniasis.

Novel targeting using nanoparticles: an approach to the development of an effective anti-leishmanial drug-delivery system.

The study reported here aimed to develop an optimized nanoparticle delivery system for amphotericin B (AmpB) using a polyelectrolyte complexation technique. For this, two oppositely charged polymers presenting anti-leishmanial activity - chitosan (Cs) and chondroitin sulfate (ChS) - were used: Cs as a positively charged polymer and ChS as a negatively charged polymer. The chitosan (NQ) nanoparticles, chitosan-chondroitin sulfate (NQC) nanoparticles, and chitosan-chondroitin sulfate-amphotericin B (NQC-AmpB) nanoparticles presented a mean particle size of 79, 104, and 136 nm, respectively; and a polydispersity index of 0.2. The measured zeta potential of the nanoparticles indicated a positive charge in their surface, while scanning and transmission electron microscopy revealed spherical nanoparticles with a smooth surface. Attenuated total reflectance-Fourier transform infrared spectroscopy analysis showed an electrostatic interaction between the polymers, whereas the release profile of AmpB from the NQC-AmpB nanoparticles showed a controlled release. In addition, the Cs; ChS; and NQ, NQC, and NQC-AmpB nanoparticles proved to be effective against promastigotes of Leishmania amazonensis and Leishmania chagasi, with a synergistic effect observed between Cs and ChS. Moreover, the applied NQ, NQC, and NQC-AmpB compounds demonstrated low toxicity in murine macrophages, as well as null hemolytic activity in type O(+) human red blood cells. Pure AmpB demonstrated high toxicity in the macrophages. The results show that cells infected with L. amazonensis and later treated with Cs, ChS, NQ, NQC, NQC-AmpB nanoparticles, or pure AmpB presented with a significant reduction in parasite number in the order of 24%, 31%, 55%, 66%, 90%, and 89%, respectively. The data presented indicate that the engineered NQC-AmpB nanoparticles could potentially be used as an alternative therapy to treat leishmaniasis, mainly due its low toxicity to mammals' cells.

Cross-protective effect of a combined L5 plus L3 Leishmania major ribosomal protein based vaccine combined with a Th1 adjuvant in murine cutaneous and visceral leishmaniasis.

BACKGROUND: Two Leishmania major ribosomal proteins L3 (LmL3) and L5 (LmL5) have been described as protective molecules against cutaneous leishmaniasis due to infection with L. major and Leishmania braziliensis in BALB/c mice when immunized with a Th1 adjuvant (non-methylated CpG-oligodeoxynucleotides; CpG-ODN). In the present study we analyzed the cross-protective efficacy of an LmL3-LmL5-CpG ODN combined vaccine against infection with Leishmania amazonensis and Leishmania chagasi (syn. Leishmania infantum) the etiologic agents of different clinical forms of human leishmaniasis in South America. METHODS: The combined vaccine was administered subcutaneously to BALB/c mice. After immunization the cellular and humoral responses elicited were analyzed. Mice were independently challenged with L. amazonensis and L. chagasi. The size of the cutaneous lesions caused by the infection with the first species, the parasite loads and the immune response in both infection models were analyzed nine weeks after challenge. RESULTS: Mice vaccinated with the combined vaccine showed a Th1-like response against LmL3 and LmL5. Vaccinated mice were able to delay lesion development due to L. amazonensis infection and to control parasite loads in the site of infection. A reduction of the parasite burden in the lymph nodes draining the site of infection and in the liver and spleen was observed in the vaccinated mice after a subcutaneous infection with L. chagasi. In both models of infection, protection was correlated to parasite antigen-specific production of IFN-γ and down-regulation of parasite-mediated IL-4 and IL-10 responses. CONCLUSIONS: The data presented here demonstrate the potential use of L. major L3 and L5 recombinant ribosomal proteins for the development of vaccines against various Leishmania species.

Subtractive phage display selection from canine visceral leishmaniasis identifies novel epitopes that mimic Leishmania infantum antigens with potential serodiagnosis applications.

Visceral leishmaniasis (VL) is a zoonotic disease that is endemic to Brazil, where dogs are the main domestic parasite reservoirs, and the percentages of infected dogs living in regions where canine VL (CVL) is endemic have ranged from 10% to 62%. Despite technological advances, some problems have been reported with CVL serodiagnosis. The present study describes a sequential subtractive selection through phage display technology from polyclonal antibodies of negative and positive sera that resulted in the identification of potential bacteriophage-fused peptides that were highly sensitive and specific to antibodies of CVL. A negative selection was performed in which phage clones were adhered to purified IgGs from healthy and Trypanosoma cruzi-infected dogs to eliminate cross-reactive phages. The remaining supernatant nonadhered phages were submitted to positive selection against IgG from the blood serum of dogs that were infected with Leishmania infantum. Phage clones that adhered to purified IgGs from the CVL-infected serum samples were selected. Eighteen clones were identified and their reactivities tested by a phage enzyme-linked immunosorbent assay (phage-ELISA) against the serum samples from infected dogs (n = 31) compared to those from vaccinated dogs (n = 21), experimentally infected dogs with cross-reactive parasites (n = 23), and healthy controls (n = 17). Eight clones presented sensitivity, specificity, and positive and negative predictive values of 100%, and they showed no cross-reactivity with T. cruzi- or Ehrlichia canis-infected dogs or with dogs vaccinated with two different commercial CVL vaccines in Brazil. Our study identified eight mimotopes of L. infantum antigens with 100% accuracy for CVL serodiagnosis. The use of these mimotopes by phage-ELISA proved to be an excellent assay that was reproducible, simple, fast, and inexpensive, and it can be applied in CVL-monitoring programs.

Correction: Antigenicity and Protective Efficacy of a Leishmania Amastigote-specific Protein, Member of the Super-oxygenase Family, against Visceral Leishmaniasis.

[This corrects the article on p. e2148 in vol. 7.].

Sensitive and specific serodiagnosis of Leishmania infantum infection in dogs by using peptides selected from hypothetical proteins identified by an immunoproteomic approach.

In Brazil, the percentage of infected dogs living in areas where canine visceral leishmaniasis (CVL) is endemic ranges from 10 to 62%; however, the prevalence of infection in dogs is probably higher than figures reported from serological studies. In addition, problems with the occurrence of false-positive or false-negative results in the serodiagnosis of CVL have been reported. The present work analyzed the potential of synthetic peptides mapped from hypothetical proteins for improvement of the serodiagnosis of Leishmania infantum infection in dogs. From 26 identified leishmanial proteins, eight were selected, considering that no homologies between these proteins and others from trypanosomatide sequence databases were encountered. The sequences of these proteins were mapped to identify linear B-cell epitopes, and 17 peptides were synthesized and tested in enzyme-linked immunosorbent assays (ELISAs) for the serodiagnosis of L. infantum infection in dogs. Of these, three exhibited sensitivity and specificity values higher than 75% and 90%, respectively, to differentiate L. infantum-infected animals from Trypanosoma cruzi-infected animals and healthy animals. Soluble Leishmania antigen (SLA) showed poor sensitivity (4%) and specificity (36%) to differentiate L. infantum-infected dogs from healthy and T. cruzi-infected dogs. Lastly, the three selected peptides were combined in different mixtures and higher sensitivity and specificity values were obtained, even when sera from T. cruzi-infected dogs were used. The study's findings suggest that these three peptides can constitute a potential tool for more sensitive and specific serodiagnosis of L. infantum infection in dogs.