Trypanocidal Activity of Four Sesquiterpene Lactones Isolated from Asteraceae Species.

The sesquiterpene lactones eupatoriopicrin, estafietin, eupahakonenin B and minimolide have been isolated from Argentinean Astearaceae species and have been found to be active against Trypanosoma cruzi epimastigotes. The aim of this work was to evaluate the activity of these compounds by analyzing their effect against the stages of the parasites that are infective for the human. Even more interesting, we aimed to determine the effect of the most active and selective compound on an in vivo model of T. cruzi infection. Eupatoriopicrin was the most active against amastigotes and tripomastigotes (IC50 = 2.3 µg/mL, and 7.2 µg/mL, respectively) and displayed a high selectivity index. This compound was selected to study on an in vivo model of T. cruzi infection. The administration of 1 mg/kg/day of eupatoriopicrin for five consecutive days to infected mice produced a significant reduction in the parasitaemia levels in comparison with non-treated animals (area under parasitaemia curves 4.48 vs. 30.47, respectively). Skeletal muscular tissues from eupatopicrin-treated mice displayed only focal and interstitial lymphocyte inflammatory infiltrates and small areas of necrotic; by contrast, skeletal tissues from T. cruzi infected mice treated with the vehicle showed severe lymphocyte inflammatory infiltrates with necrosis of the adjacent myocytes. The results indicate that eupatoriopicrin could be considered a promising candidate for the development of new therapeutic agents for Chagas disease.

Activity of Estafietin and Analogues on Trypanosoma cruzi and Leishmania braziliensis.

Sesquiterpene lactones are naturally occurring compounds mainly found in the Asteraceae family. These types of plant metabolites display a wide range of biological activities, including antiprotozoal activity and are considered interesting structures for drug discovery. Four derivatives were synthesized from estafietin (1), isolated from Stevia alpina (Asteraceae): 11ßH,13-dihydroestafietin (2), epoxyestafietin (3a and 3b), 11ßH,13-methoxyestafietin, (4) and 11ßH,13-cianoestafietin. The antiprotozoal activity against Trypanosoma cruzi and Leishmania braziliensis of these compounds was evaluated. Epoxyestafietin was the most active compound against T. cruzi trypomastigotes and amastigotes (IC50 values of 18.7 and 2.0 µg/mL, respectively). Estafietin (1) and 11ßH,13-dihydroestafietin (2) were the most active and selective compounds on L. braziliensis promastigotes (IC50 values of 1.0 and 1.3 µg/mL, respectively). The antiparasitic activity demonstrated by estafietin and some of its derivatives make them promising candidates for the development of effective compounds for the treatment of Chagas disease and leihsmaniasis.

Oral multicomponent DNA vaccine delivered by attenuated Salmonella elicited immunoprotection against American trypanosomiasis.

We have reported that attenuated Salmonella (S) carrying plasmids encoding the cysteine protease cruzipain (Cz) protects against Trypanosoma cruzi infection. Here, we determined whether immunoprotection could be improved by the oral coadministration of 3 Salmonella carrying the plasmids that encode the antigens Cz, Tc52, and Tc24. SCz+STc52+STc24-immunized mice presented an increased antibody response against each antigen compared with those in the single antigen-immunized groups, as well as higher trypomastigotes antibody-mediated lyses and cell invasion inhibition compared with controls. SCz+STc52+STc24-immunized and -challenged mice rendered lower parasitemia. Weight loss after infection was detected in all mice except those in the SCz+STc52+STc24 group. Moreover, cardiomyopathy-associated enzyme activity was significantly lower in SCz+STc24+STc52-immunized mice compared with controls. Few or no abnormalities were found in muscle tissues of SCz+STc24+STc52-immunized mice, whereas controls presented with inflammatory foci, necrosis, and amastigote nests. We conclude that a multicomponent approach that targets several invasion and metabolic mechanisms improves protection compared with single-component vaccines.

Tc52 amino-terminal-domain DNA carried by attenuated Salmonella enterica serovar Typhimurium induces protection against a Trypanosoma cruzi lethal challenge.

In this work we immunized mice with DNA encoding full-length Tc52 or its amino- or carboxy-terminal (N- and C-term, respectively) domain carried by attenuated Salmonella as a DNA delivery system. As expected, Salmonella-mediated DNA delivery resulted in low antibody titers and a predominantly Th1 response, as shown by the ratio of IgG2a/IgG1-specific antibodies. Despite modest expression of Tc52 in trypomastigotes, the antibodies elicited by vaccination were able to mediate lysis of the trypomastigotes in the presence of complement and inhibit their invasion of mammal cells in vitro. The strongest functional activity was observed with sera from mice immunized with Salmonella carrying the N-term domain (SN-term), followed by Tc52 (STc52), and the C-term domain (SC-term). All immunized groups developed strong cellular responses, with predominant activation of Th1 cells. However, mice immunized with SN-term showed higher levels of interleukin-10 (IL-10), counterbalancing the inflammatory reaction, and also strong activation of Tc52-specific gamma interferon-positive (IFN-γ(+)) CD8(+) T cells. In agreement with this, although all prototypes conferred protection against infection, immunization with SN-term promoted greater protection than that with SC-term for all parameters tested and slightly better protection than that with STc52, especially in the acute stage of infection. We conclude that the N-terminal domain of Tc52 is the section of the protein that confers maximal protection against infection and propose it as a promising candidate for vaccine development.

Lacticaseibacillus rhamnosus CRL 2244 secreted metabolites display killing and antibiotic synergistic activity against multi-drug resistant pathogens.

A growing increase in the number of serious infections caused by multidrug resistant bacteria (MDR) is challenging our society. Despite efforts to discover novel therapeutic options, few antibiotics targeting MDR have been approved by the Food and Drug Administration (FDA). Lactic acid bacteria have emerged as a promising therapeutic alternative due to their demonstrated ability to combat MDR pathogens in vitro. Our previous co-culture studies showed Lacticaseibacillus rhamnosus CRL 2244 as having a potent killing effect against carbapenem-resistant Acinetobacter baumannii (CRAB) strains. Here we report that cell-free conditioned media (CFCM) samples obtained from Lcb. rhamnosus CRL 2244 cultures incubated at different times display antimicrobial activity against 43 different pathogens, including CRAB, methicillin-resistant Staphylococcus aureus (MRSA) and carbapenemase Klebsiella pneumoniae (KPC)-positive strains. Furthermore, transwell and ultrafiltration analyses together with physical and chemical/biochemical tests showed that Lcb. rhamnosus CRL 2244 secretes a <3 kDa metabolite(s) whose antimicrobial activity is not significantly impaired by mild changes in pH, temperature and various enzymatic treatments. Furthermore, sensitivity and time-kill assays showed that the bactericidal activity of the Lcb. rhamnosus CRL 2244 metabolite(s) enhances the activity of some current FDA approved antibiotics. We hypothesize that this observation could be due to the effects of Lcb. rhamnosus CRL 2244 metabolite(s) on cell morphology and the enhanced transcriptional expression of genes coding for the phenylacetate (PAA) and histidine catabolic Hut pathways, metal acquisition and biofilm formation, all of which are associated with bacterial virulence. Interestingly, the extracellular presence of Lcb. rhamnosus CRL 2244 induced the transcription of the gene coding for the CidA/LgrA protein, which is involved in programmed cell death in some bacteria. Overall, the findings presented in this report underscore the promising potential of the compound(s) released by Lcb. rhamnosus CRL2244 as an alternative and/or complementary option to treat infections caused by A. baumannii as well as other MDR bacterial pathogens.

Antiprotozoal compounds from Mikania periplocifolia (Asteraceae).

Chagas disease, African trypanosomiasis and Leishmaniasis are neglected parasitic diseases which affect millions of people worldwide. In a previous work, we report the antiprotozoal activity of the dichloromethane extract of Mikania periplocifolia Hook. & Arn. (Asteraceae). The aim of this work was to isolate and identify the bioactive compounds present in the extract. The fractionation of the dichloromethane extract has led to the isolation of the sesquiterpene lactone miscandenin and the flavonoid onopordin, together with the sesquiterpene lactones mikanolide, dihydromikanolide and deoxymikanolide, which have previously shown antiprotozoal activity. Miscandenin and onopordin were assayed in vitro against Trypanosoma cruzi, T. brucei and Leishmania braziliensis. Miscandenin was active against T. cruzi trypomastigotes and amastigotes with IC50 values of 9.1 and 7.7 µg/ml, respectively. This sesquiterpene lactone and the flavonoid onopordin showed activity against T. brucei trypomastigotes (IC50 = 0.16 and 0.37 µg/ml) and L. braziliensis promastigotes (IC50 = 0.6 and 1.2 µg/ml), respectively. The CC50 values on mammalian cells were 37.9 and 53.4 µg/ml for miscandenin and onopordin, respectively. Besides, the pharmacokinetic and physicochemical properties of miscandenin were assessed in silico, showing a good drug-likeness profile. Our results highlight this compound as a promising candidate for further preclinical studies in the search of new drugs for the treatment of trypanosomiasis and leishmaniasis.

In vitro evaluation of antiprotozoal and antiviral activities of extracts from Argentinean Mikania species.

The aim of this study was to investigate the antiprotozoal and antiviral activities of four Argentinean Mikania species. The organic and aqueous extracts of Mikania micrantha, M. parodii, M. periplocifolia, and M. cordifolia were tested on Trypanosoma cruzi epimastigotes, Leishmania braziliensis promastigotes, and dengue virus type 2. The organic extract of M. micrantha was the most active against T. cruzi and L. braziliensis exhibiting a growth inhibition of 77.6 ± 4.5% and 84.9 ± 6.1%, respectively, at a concentration of 10 µg/ml. The bioguided fractionation of M. micrantha organic extract led to the identification of two active fractions. The chromatographic profile and infrared analysis of these fractions revealed the presence of sesquiterpene lactones. None of the tested extracts were active against dengue virus type 2.

Redirection of the immune response to the functional catalytic domain of the cystein proteinase cruzipain improves protective immunity against Trypanosoma cruzi infection.

Despite the strong immune responses elicited after natural infection with Trypanosoma cruzi or vaccination against it, parasite survival suggests that these responses are insufficient or inherently inadequate. T. cruzi contains a major cystein proteinase, cruzipain, which has a catalytic N-terminal domain and a C-terminal extension. Immunizations that employed recombinant cruzipain or its N- and C-terminal domains allowed evaluation of the ability of cruzipain to circumvent responses against the catalytic domain. This phenomenon is not a property of the parasite but of cruzipain itself, because recombinant cruzipain triggers a response similar to that of cruzipain during natural or experimental infection. Cruzipain is not the only antigen with a highly immunogenic region of unknown function that somehow protects an essential domain for parasite survival. However, our studies show that this can be reverted by using the N-terminal domain as a tailored immunogen able to redirect host responses to provide enhanced protection.

Mucosal Heterologous Prime/Boost Vaccination Induces Polyfunctional Systemic Immunity, Improving Protection Against Trypanosoma cruzi.

There are several unmet needs in modern immunology. Among them, vaccines against parasitic diseases and chronic infections lead. Trypanosoma cruzi, the causative agent of Chagas disease, is an excellent example of a silent parasitic invasion that affects millions of people worldwide due to its progression into the symptomatic chronic phase of infection. In search for novel vaccine candidates, we have previously introduced Traspain, an engineered trivalent immunogen that was designed to address some of the known mechanisms of T. cruzi immune evasion. Here, we analyzed its performance in different DNA prime/protein boost protocols and characterized the systemic immune response associated with diverse levels of protection. Formulations that include a STING agonist, like c-di-AMP in the boost doses, were able to prime a Th1/Th17 immune response. Moreover, comparison between them showed that vaccines that were able to prime polyfunctional cell-mediated immunity at the CD4 and CD8 compartment enhanced protection levels in the murine model. These findings contribute to a better knowledge of the desired vaccine-elicited immunity against T. cruzi and promote the definition of a vaccine correlate of protection against the infection.

Anti-Trypanosoma cruzi Activity of Extracts from Argentinean Asteraceae Species.

The anti-Trypanosoma cruzi activity of extracts from 13 Argentinean Asteraceae species was determined. Dichloromethane and methanol extracts of Acmella bellidioides, Aspilia silphioides, Viguiera tuberosa, Calyptocarpus biaristatus, Hyalis argentea, Helenium radiatum, Gaillardia megapotamica, Verbesina subcordata, Gymnocoronis spilanthoides, Viguiera anchusaefolia, Thelesperma megapotamicum, Zexmenia buphtalmiflora, and Vernonia plantaginoides were evaluated in-vitro against Trypanosoma cruzi epimastigotes. A. silphioides, V. tuberosa, V. subcordata, G. spilanthoides, G. megapotamica, T. megapotamicum and Z. buphtalmiflora dichloromethane extracts showed trypanocidal activity with inhibitions higher than 60% at a concentration of 10 µg/mL. The methanol extracts of H. radiatum and G. megapotamica were the most active with inhibitions of 70.1 and 77.7%, respectively at 10 µg/mL. The chromatographic profiles of the most active extracts showed bands and major peaks that could be attributed to flavonoids and terpenoid compounds.

Oral vaccination with Salmonella enterica as a cruzipain-DNA delivery system confers protective immunity against Trypanosoma cruzi.

To stimulate both local and systemic immune responses against Trypanosoma cruzi, Salmonella enterica serovar Typhimurium aroA was exploited as a DNA delivery system for cruzipain (SCz). In a murine model we compared SCz alone (GI) or coadministered with Salmonella carrying a plasmid encoding granulocyte-macrophage colony-stimulating factor (GII), as well as protocols in which SCz priming was followed by boosting with recombinant cruzipain (rCz) admixed with either CpG-ODN (GIII) or MALP-2, a synthetic derivative of a macrophage-activating lipopeptide of 2 kDa from Mycoplasma fermentans (GIV). The results showed that protocols that included four oral doses of SCz (GI) elicited mainly a mucosal response characterized by immunoglobulin A (IgA) secretion and proliferation of gut-associated lymphoid tissue cells, with weak systemic responses. In contrast, the protocol that included a boost with rCz plus CpG (GIII) triggered stronger systemic responses in terms of Cz-specific serum IgG titers, splenocyte proliferation, gamma interferon (IFN-gamma) secretion, and delayed-type hypersensitivity response. Trypomastigote challenge of vaccinated mice resulted in significantly lower levels of parasitemia compared to controls. Protection was abolished by depletion of either CD4+ or CD8+ T cells. Parasite control was also evident from the reduction of tissue damage, as revealed by histopathologic studies and serum levels of enzymes that are markers of muscle injury in chronic Chagas' disease (i.e., creatine kinase, aspartate aminotransferase, and lactate dehydrogenase). Enhanced release of IFN-gamma and interleukin-2 was observed in GI and GII upon restimulation of splenocytes in the nonparasitic phase of infection. Our results indicate that Salmonella-mediated delivery of Cz-DNA by itself promotes the elicitation of an immune response that controls T. cruzi infection, thereby reducing parasite loads and subsequent damage to muscle tissues.

Trypanocidal and leishmanicidal activities of sesquiterpene lactones from Ambrosia tenuifolia Sprengel (Asteraceae).

Bioassay-guided fractionation of the organic extract of Ambrosia tenuifolia Sprengel (Asteraceae) led to the isolation of two bioactive sesquiterpene lactones with significant trypanocidal and leishmanicidal activities. By spectroscopic methods ((1)H- and (13)C-nuclear magnetic resonance, distortionless enhancement by polarization transfer, correlated spectroscopy, heteronuclear multiple-quantum coherence, electron impact-mass spectrometry, and infrared spectroscopy), these compounds were identified as psilostachyin and peruvin. Both compounds showed a marked in vitro trypanocidal activity against Trypanosoma cruzi epimastigotes with 50% inhibitory concentration (IC(50)) values of less than 2 microg/ml. Psilostachyin exerted a significant in vitro activity against the trypomastigote forms of T. cruzi (IC(50), 0.76 microg/ml) and was selected for in vivo testing. Psilostachyin-treated mice had a survival of 100% and lower parasitemia values than control mice. Both compounds were also tested on Leishmania sp. promastigotes: psilostachyin (IC(50), 0.12 microg/ml) and peruvin (IC(50), 0.39 microg/ml) exerted significant leishmanicidal activities. This is the first time that the trypanocidal and leishmanicidal activities of these compounds have been reported. The selectivity index (SI) was employed to evaluate the cytotoxic effect of lactones on T lymphocytes. Although the SIs of both compounds were high for T. cruzi epimastigotes, psilostachyin was more selective against trypomastigotes (SI, 33.8) while peruvin showed no specificity for this parasite. Both compounds presented high selectivity for Leishmania spp. The results shown herein suggest that psilostachyin and peruvin could be considered potential candidates for the development of new antiprotozoal agents against Chagas' disease and leishmaniasis.

Oral Administration of Probiotics Increases Paneth Cells and Intestinal Antimicrobial Activity.

The huge amount of intestinal bacteria represents a continuing threat to the intestinal barrier. To meet this challenge, gut epithelial cells produce antimicrobial peptides (AMP) that act at the forefront of innate immunity. We explore whether this antimicrobial activity and Paneth cells, the main intestinal cell responsible of AMP production, are influenced by probiotics administration, to avoid the imbalance of intestinal microbiota and preserve intestinal barrier. Administration of Lactobacillus casei CRL 431 (Lc 431) and L. paracasei CNCM I-1518 (Lp 1518) to 42 days old mice, increases the number of Paneth cells on small intestine, and the antimicrobial activity against the pathogens Staphylococcus aureus and Salmonella Typhimurium in the intestinal fluids. Specifically, strong damage of the bacterial cell with leakage of cytoplasmic content, and cellular fragmentation were observed in S. Typhimurium and S. aureus. Even more important, probiotics increase the antimicrobial activity of the intestinal fluids at the different ages, from weaning (21 days old) to old age (180 days old). Intestinal antimicrobial activity stimulated by oral probiotics, do not influence significantly the composition of total anaerobic bacteria, lactobacilli and enterobacteria in the large intestine, at any age analyzed. This result, together with the antimicrobial activity observed against the same probiotic bacteria; endorse the regular consumption of probiotics without adverse effect on the intestinal homeostasis in healthy individuals. We demonstrate that oral probiotics increase intestinal antimicrobial activity and Paneth cells in order to strengthen epithelial barrier against pathogens. This effect would be another important mechanism by which probiotics protect the host mainly against infectious diseases.

Trypanosoma cruzi 80 kDa prolyl oligopeptidase (Tc80) as a novel immunogen for Chagas disease vaccine.

BACKGROUND: Chagas disease, also known as American Trypanosomiasis, is a chronic parasitic disease caused by the flagellated protozoan Trypanosoma cruzi that affects about 8 million people around the world where more than 25 million are at risk of contracting the infection. Despite of being endemic on 21 Latin-American countries, Chagas disease has become a global concern due to migratory movements. Unfortunately, available drugs for the treatment have several limitations and they are generally administered during the chronic phase of the infection, when its efficacy is considered controversial. Thus, prophylactic and/or therapeutic vaccines are emerging as interesting control alternatives. In this work, we proposed Trypanosoma cruzi 80 kDa prolyl oligopeptidase (Tc80) as a new antigen for vaccine development against Chagas disease. METHODOLOGY/PRINCIPAL FINDINGS: In a murine model, we analyzed the immune response triggered by different immunization protocols based on Tc80 and evaluated their ability to confer protection against a challenge with the parasite. Immunized mice developed Tc80-specific antibodies which were able to carry out different functions such as: enzymatic inhibition, neutralization of parasite infection and complement-mediated lysis of trypomastigotes. Furthermore, vaccinated mice elicited strong cell-mediated immunity. Spleen cells from immunized mice proliferated and secreted Th1 cytokines (IL-2, IFN-γ and TNF-α) upon re-stimulation with rTc80. Moreover, we found Tc80-specific polyfunctional CD4 T cells, and cytotoxic T lymphocyte activity against one Tc80 MHC-I peptide. Immunization protocols conferred protection against a T. cruzi lethal challenge. Immunized groups showed a decreased parasitemia and higher survival rate compared with non-immunized control mice. Moreover, during the chronic phase of the infection, immunized mice presented: lower levels of myopathy-linked enzymes, parasite burden, electrocardiographic disorders and inflammatory cells. CONCLUSIONS/SIGNIFICANCE: Considering that an early control of parasite burden and tissue damage might contribute to avoid the progression towards symptomatic forms of chronic Chagas disease, the efficacy of Tc80-based vaccines make this molecule a promising immunogen for a mono or multicomponent vaccine against T. cruzi infection.

Trypanocidal and leishmanicidal activities of flavonoids from Argentine medicinal plants.

In vitro trypanocidal and leishmanicidal activities of the flavonoids hispidulin, from Ambrosia tenuifolia, and santin, from Eupatorium buniifolium, are reported. A sensitive technique that takes advantage of ((3)H)thymidine uptake by dividing trypanosomatids has been adjusted for quantification of the parasiticidal effect of the natural products. The IC(50) values for hispidulin and santin on Trypanosoma cruzi epimastigotes were 46.7 and 47.4 muM, respectively. On trypomastigotes, the IC(50) values were 62.3 microM for hispidulin and 42.1 microM for santin. Hispidulin was more active than santin on promastigotes of Leishmania mexicana (IC(50) = 6.0 microM versus 32.5 microM). No cytotoxic activity was observed on lymphoid cells, making hispidulin and santin potential lead compounds for the development of new natural drugs. This is the first report on the trypanocidal and leishmanicidal activities of these flavonoids and on the presence of santin in E. buniifolium.

Immunization with Tc52 or its amino terminal domain adjuvanted with c-di-AMP induces Th17+Th1 specific immune responses and confers protection against Trypanosoma cruzi.

The development of new adjuvants enables fine modulation of the elicited immune responses. Ideally, the use of one or more adjuvants should result in the induction of a protective immune response against the specific pathogen. We have evaluated the immune response and protection against Trypanosoma cruzi infection in mice vaccinated with recombinant Tc52 or its N- and C-terminal domains (NTc52 and CTc52) adjuvanted either with the STING (Stimulator of Interferon Genes) agonist cyclic di-AMP (c-di-AMP), a pegylated derivative of α-galactosylceramide (αGC-PEG), or oligodeoxynucleotides containing unmethylated CpG motifs (ODN-CpG). All groups immunized with the recombinant proteins plus adjuvant: Tc52+c-di-AMP, NTc52+c-di-AMP, CTc52+c-di-AMP, NTc52+c-di-AMP+αGC-PEG, NTc52+CpG, developed significantly higher anti-Tc52 IgG titers than controls. Groups immunized with c-di-AMP and Tc52, NTc52 or CTc52 showed the highest Tc52-specific IgA titers in nasal lavages. All groups immunized with the recombinant proteins plus adjuvant developed a strong specific cellular immune response in splenocytes and lymph node cells with significant differences for groups immunized with c-di-AMP and Tc52, NTc52 or CTc52. These groups also showed high levels of Tc52-specific IL-17 and IFN-γ producing cells, while NTc52+CpG group only showed significant difference with control in IFN-γ producing cells. Groups immunized with c-di-AMP and Tc52, NTc52 or CTc52 developed predominantly a Th17 and Th1immune response, whereas for NTc52+CpG it was a dominant Th1 response. It was previously described that αGC-PEG inhibits Th17 differentiation by activating NKT cells. Thus, in this work we have also included a group immunized with both adjuvants (NTc52+c-di-AMP+αGC-PEG) with the aim to modulate the Th17 response induced by c-di-AMP. This group showed a significant reduction in the number of Tc52-specific IL-17 producing splenocytes, as compared to the group NTc52+c-di-AMP, which has in turn correlated with a reduction in protection against infection. These results suggest that the Th17 immune response developed after immunizing with NTc52+c-di-AMP could have a protective role against T. cruzi infection. Groups NTc52+c-di-AMP, Tc52+c-di-AMP and NTc52PB, were the ones that showed better protection against infection with lower parasitemia and weight loss, and higher survival.

Assessment of sesquiterpene lactones isolated from Mikania plants species for their potential efficacy against Trypanosoma cruzi and Leishmania sp.

Four sesquiterpene lactones, mikanolide, deoxymikanolide, dihydromikanolide and scandenolide, were isolated by a bioassay-guided fractionation of Mikania variifolia and Mikania micrantha dichloromethane extracts. Mikanolide and deoxymikanolide were the major compounds in both extracts (2.2% and 0.4% for Mikania variifolia and 21.0% and 6.4% for Mikania micrantha respectively, calculated on extract dry weight). Mikanolide, deoxymikanolide and dihydromikanolide were active against Trypanosoma cruzi epimastigotes (50% inhibitory concentrations of 0.7, 0.08 and 2.5 µg/mL, for each compound respectively). These sesquiterpene lactones were also active against the bloodstream trypomastigotes (50% inhibitory concentrations for each compound were 2.1, 1.5 and 0.3 µg/mL, respectively) and against amastigotes (50% inhibitory concentrations for each compound were 4.5, 6.3 and 8.5 µg/mL, respectively). By contrast, scandenolide was not active on Trypanosoma cruzi. Besides, mikanolide and deoxymikanolide were also active on Leishmania braziliensis promastigotes (50% inhibitory concentrations of 5.1 and 11.5 µg/mL, respectively). The four sesquiterpene lactones were tested for their cytotoxicity on THP 1 cells. Deoxymikanolide presented the highest selectivity index for trypomastigotes (SI = 54) and amastigotes (SI = 12.5). In an in vivo model of Trypanosoma cruzi infection, deoxymikanolide was able to decrease the parasitemia and the weight loss associated to the acute phase of the parasite infection. More importantly, while 100% of control mice died by day 22 after receiving a lethal T. cruzi infection, 70% of deoxymikanolide-treated mice survived. We also observed that this compound increased TNF-α and IL-12 production by macrophages, which could contribute to control T. cruzi infection.

Engineered trivalent immunogen adjuvanted with a STING agonist confers protection against Trypanosoma cruzi infection.

The parasite Trypanosoma cruzi is the causative agent of Chagas disease, a potentially life-threatening infection that represents a major health problem in Latin America. Several characteristics of this protozoan contribute to the lack of an effective vaccine, among them: its silent invasion mechanism, T. cruzi antigen redundancy and immunodominance without protection. Taking into account these issues, we engineered Traspain, a chimeric antigen tailored to present a multivalent display of domains from key parasitic molecules, combined with stimulation of the STING pathway by c-di-AMP as a novel prophylactic strategy. This formulation proved to be effective for the priming of functional humoral responses and pathogen-specific CD8+ and CD4+ T cells, compatible with a Th1/Th17 bias. Interestingly, vaccine effectiveness assessed across the course of infection, showed a reduction in parasite load and chronic inflammation in different proof of concept assays. In conclusion, this approach represents a promising tool against parasitic chronic infections.

A prime-boost immunization with Tc52 N-terminal domain DNA and the recombinant protein expressed in Pichia pastoris protects against Trypanosoma cruzi infection.

We have previously reported that the N-terminal domain of the antigen Tc52 (NTc52) is the section of the protein that confers the strongest protection against Trypanosoma cruzi infection. To improve vaccine efficacy, we conducted here a prime-boost strategy (NTc52PB) by inoculating two doses of pcDNA3.1 encoding the NTc52 DNA carried by attenuated Salmonella (SNTc52), followed by two doses of recombinant NTc52 expressed in Picchia pastoris plus ODN-CpG as adjuvant. This strategy was comparatively analyzed with the following protocols: (1) two doses of NTc52+ODN-CpG by intranasal route followed by two doses of NTc52+ODN-CpG by intradermal route (NTc52CpG); (2) four doses of SNTc52; and (3) a control group with four doses of Salmonella carrying the empty plasmid. All immunized groups developed a predominant Th1 cellular immune response but with important differences in antibody development and protection against infection. Thus, immunization with just SNTc52 induces a strong specific cellular response, a specific systemic antibody response that is weak yet functional (considering lysis of trypomastigotes and inhibition of cell invasion), and IgA mucosal immunity, protecting in both the acute and chronic stages of infection. The group that received only recombinant protein (NTc52CpG) developed a strong antibody immune response but weaker cellular immunity than the other groups, and the protection against infection was clear in the acute phase of infection but not in chronicity. The prime-boost strategy, which combines DNA and protein vaccine and both mucosal and systemic immunizations routes, was the best assayed protocol, inducing strong cellular and humoral responses as well as specific mucosal IgA, thus conferring better protection in the acute and chronic stages of infection.

Attenuated Salmonella sp. as a DNA Delivery System for Trypanosoma cruzi Antigens.

Chagas disease is an important neglected disease affecting thousands of people in the Americas. Novel strategies for prophylactic and therapeutic vaccines against the etiological agent, the intracellular protozoan Trypanosoma cruzi, are urgently needed. Vaccines based on attenuated virus and bacteria as a foreign DNA delivery system represent a strong advantage over naked DNA-based vaccines. Here we describe the use of attenuated Salmonella carrying a eukaryotic expression plasmid encoding a T. cruzi antigen. The main advantages of the methodology are the oral administration of the Salmonella-based vaccine and the induction of a strong humoral and cell-mediated immune response at both mucosal and systemic level, favored by the adjuvant effect elicited by the bacteria pathogen-associated molecular patterns.