Unveiling the Enigmatic nature of six neglected Amazonian Leishmania (Viannia) species using the hamster model: Virulence, Histopathology and prospection of LRV1.

American tegumentary leishmaniasis (ATL) is highly endemic in the Amazon basin and occurs in all South American countries, except Chile and Uruguay. Most Brazilian ATL cases are due to Leishmania (Viannia) braziliensis, however other neglected Amazonian species are being increasingly reported. They belong to the subgenus L. (Viannia) and information on suitable models to understand immunopathology are scarce. Here, we explored the use of the golden hamster Mesocricetus auratus and its macrophages as a model for L. (Viannia) species. We also studied the interaction of parasite glycoconjugates (LPGs and GIPLs) in murine macrophages. The following strains were used: L. (V.) braziliensis (MHOM/BR/2001/BA788), L. (V.) guyanensis (MHOM/BR/85/M9945), L. (V.) shawi (MHOM/BR/96/M15789), L. (V.) lindenbergi (MHOM/BR/98/M15733) and L. (V.) naiffi (MDAS/BR/79/M5533). In vivo infections were initiated by injecting parasites into the footpad and were followed up at 20- and 40-days PI. Parasites were mixed with salivary gland extract (SGE) from wild-captured Nyssomyia neivai prior to in vivo infections. Animals were euthanized for histopathological evaluation of the footpads, spleen, and liver. The parasite burden was evaluated in the skin and draining lymph nodes. In vitro infections used resident peritoneal macrophages and THP-1 monocytes infected with all species using a MOI (1:10). For biochemical studies, glycoconjugates (LPGs and GIPLs) were extracted, purified, and biochemically characterized using fluorophore-assisted carbohydrate electrophoresis (FACE). They were functionally evaluated after incubation with macrophages from C57BL/6 mice and knockouts (TLR2-/- and TLR4-/-) for nitric oxide (NO) and cytokine/chemokine production. All species, except L. (V.) guyanensis, failed to generate evident macroscopic lesions 40 days PI. The L. (V.) guyanensis lesions were swollen but did not ulcerate and microscopically were characterized by an intense inflammatory exudate. Despite the fact the other species did not produce visible skin lesions there was no or mild pro-inflammatory infiltration at the inoculation site and parasites survived in the hamster skin/lymph nodes and even visceralized. Although none of the species caused severe disease in the hamster, they differentially infected peritoneal macrophages in vitro. LPGs and GIPLs were able to differentially trigger NO and cytokine production via TLR2/TLR4 and TLR4, respectively. The presence of a sidechain in L. (V.) lainsoni LPG (type II) may be responsible for its higher proinflammatory activity. After Principal Component analyses using all phenotypic features, the clustering of L. (V.) lainsoni was separated from all the other L. (Viannia) species. We conclude that M. auratus was a suitable in vivo model for at least four dermotropic L. (Viannia) species. However, in vitro studies using peritoneal cells are a suitable alternative for understanding interactions of the six L. (Viannia) species used here. LRV1 presence was found in L. (V.) guyanensis and L. (V.) shawi with no apparent correlation with virulence in vitro and in vivo. Finally, parasite glycoconjugates were able to functionally trigger various innate immune responses in murine macrophages via TLRs consistent with their inflammatory profile in vivo.

Leishmania (Sauroleishmania) tarentolae versus pathogenic species: comparative evaluation of protease activity, glycoconjugates, resistance to complement and metabolome composition.

BACKGROUND: Leishmania tarentolae is a non-pathogenic species found in lizards representing an important model for Leishmania biology. However, several aspects of this Sauroleishmania remain unknown to explain its low level of virulence. OBJECTIVES: We reported several aspects of L. tarentolae biology including glycoconjugates, proteolytic activities and metabolome composition in comparison to pathogenic species (Leishmania amazonensis, Leishmania braziliensis, Leishmania infantum and Leishmania major). METHODS: Parasites were cultured for extraction and purification of lipophosphoglycan (LPG), immunofluorescence probing with anti-gp63 and resistance against complement. Parasite extracts were also tested for proteases activity and metabolome composition. FINDINGS: Leishmania tarentolae does not express LPG on its surface. It expresses gp63 at lower levels compared to pathogenic species and, is highly sensitive to complement-mediated lysis. This species also lacks intracellular/extracellular activities of proteolytic enzymes. It has metabolic differences with pathogenic species, exhibiting a lower abundance of metabolites including ABC transporters, biosynthesis of unsaturated fatty acids and steroids, TCA cycle, glycine/serine/threonine metabolism, glyoxylate/dicarboxylate metabolism and pentose-phosphate pathways. MAIN CONCLUSIONS: The non-pathogenic phenotype of L. tarentolae is associated with alterations in several biochemical and molecular features. This reinforces the need of comparative studies between pathogenic and non-pathogenic species to elucidate the molecular mechanisms of virulence during host-parasite interactions.

Intricate balance of dually-localized catalase modulates infectivity of Leptomonas seymouri (Kinetoplastea: Trypanosomatidae).

Nearly all aerobic organisms are equipped with catalases, powerful enzymes scavenging hydrogen peroxide and facilitating defense against harmful reactive oxygen species. In trypanosomatids, this enzyme was not present in the common ancestor, yet it had been independently acquired by different lineages of monoxenous trypanosomatids from different bacteria at least three times. This observation posited an obvious question: why was catalase so "sought after" if many trypanosomatid groups do just fine without it? In this work, we analyzed subcellular localization and function of catalase in Leptomonas seymouri. We demonstrated that this enzyme is present in the cytoplasm and a subset of glycosomes, and that its cytoplasmic retention is H2O2-dependent. The ablation of catalase in this parasite is not detrimental in vivo, while its overexpression resulted in a substantially higher parasite load in the experimental infection of Dysdercus peruvianus. We propose that the capacity of studied flagellates to modulate the catalase activity in the midgut of its insect host facilitates their development and protects them from oxidative damage at elevated temperatures.

Pathogen-associated molecular patterns (PAMPs) derived from Leishmania and bacteria increase gene expression of antimicrobial peptides and gut surface proteins in sand flies.

The interaction between pathogens and vectors' physiology can impact parasite transmission. Studying this interaction at the molecular level can help in developing control strategies. We study leishmaniases, diseases caused by Leishmania parasites transmitted by sand fly vectors, posing a significant global public health concern. Lipophosphoglycan (LPG), the major surface glycoconjugate of Leishmania, has been described to have several roles throughout the parasite's life cycle, both in the insect and vertebrate hosts. In addition, the sand fly midgut possesses a rich microbiota expressing lipopolysaccharides (LPS). However, the effect of LPG and LPS on the gene expression of sand fly midgut proteins or immunity effectors has not yet been documented. We experimentally fed Lutzomyia longipalpis and Phlebotomus papatasi sand flies with blood containing purified LPG from Leishmania infantum, Leishmania major, or LPS from Escherichia coli. The effect on the expression of genes encoding gut proteins galectin and mucin, digestive enzymes trypsin and chymotrypsin, and antimicrobial peptides (AMPs) attacin and defensins was assessed by quantitative PCR (qPCR). The gene expression of a mucin-like protein in L. longipalpis was increased by L. infantum LPG and E. coli LPS. The gene expression of a galectin was increased in L. longipalpis by L. major LPG, and in P. papatasi by E. coli LPS. Nevertheless, the gene expression of trypsins and chymotrypsins did not significantly change. On the other hand, both L. infantum and L. major LPG significantly enhanced expression of the AMP attacin in both sand fly species and defensin in L. longipalpis. In addition, E. coli LPS increased the expression of attacin and defensin in L. longipalpis. Our study showed that Leishmania LPG and E. coli LPS differentially modulate the expression of sand fly genes involved in gut maintenance and defence. This suggests that the glycoconjugates from microbiota or Leishmania may increase the vector's immune response and the gene expression of a gut coating protein in a permissive vector.

The absence of eosinophils is associated with early metastatic lesions in Leishmania amazonensis-infected mice.

BACKGROUND: Eosinophils are granulocytes that rapidly increase frequency in the bloodstream during helminthic infections and allergic responses. They are found in tissue infected by Leishmania during early disease, but their role during infection is not entirely understood. OBJECTIVES: We aim to compare the disease due to Leishmania amazonensis in BALB/c and Δdbl-GATA1 mice, which lack eosinophils. METHODS: BALB/c and Δdbl-GATA1 mice infected with L. amazonensis were observed for several weeks. The parasite load and dissemination pattern were assessed. FINDINGS: The Δdbl-GATA1 mice developed an anticipated dissemination of L. amazonensis and a worsening disease. No differences were found in the lesion development or the parasite load in the footpad among Δdbl-GATA1 mice and BALB/c eight weeks after infection. However, nine weeks after infection, massive growth of metastatic lesions appeared in several parts of the skin in Δdbl-GATA1 mice, weeks earlier than BALB/c. We observed increased parasites in the bloodstream, probably an essential dissemination route. Thirteen weeks after infection, metastatic lesions were found in all Δdbl-GATA1 mice. MAIN CONCLUSION: These results suggest a protective role of eosinophils in delaying the disease caused by L. amazonensis, although several limitations of this mice strain must be considered.

The absence of eosinophils is associated with early metastatic lesions in Leishmania amazonensis-infected mice

BACKGROUND Eosinophils are granulocytes that rapidly increase frequency in the bloodstream during helminthic infections and allergic responses. They are found in tissue infected by Leishmania during early disease, but their role during infection is not entirely understood. OBJECTIVES We aim to compare the disease due to Leishmania amazonensis in BALB/c and Δdbl-GATA1 mice, which lack eosinophils. METHODS BALB/c and Δdbl-GATA1 mice infected with L. amazonensis were observed for several weeks. The parasite load and dissemination pattern were assessed. FINDINGS The Δdbl-GATA1 mice developed an anticipated dissemination of L. amazonensis and a worsening disease. No differences were found in the lesion development or the parasite load in the footpad among Δdbl-GATA1 mice and BALB/c eight weeks after infection. However, nine weeks after infection, massive growth of metastatic lesions appeared in several parts of the skin in Δdbl-GATA1 mice, weeks earlier than BALB/c. We observed increased parasites in the bloodstream, probably an essential dissemination route. Thirteen weeks after infection, metastatic lesions were found in all Δdbl-GATA1 mice. MAIN CONCLUSION These results suggest a protective role of eosinophils in delaying the disease caused by L. amazonensis, although several limitations of this mice strain must be considered.

Leishmania (Sauroleishmania) tarentolae versus pathogenic species: comparative evaluation of protease activity, glycoconjugates, resistance to complement and metabolome composition

BACKGROUND Leishmania tarentolae is a non-pathogenic species found in lizards representing an important model for Leishmania biology. However, several aspects of this Sauroleishmania remain unknown to explain its low level of virulence. OBJECTIVES We reported several aspects of L. tarentolae biology including glycoconjugates, proteolytic activities and metabolome composition in comparison to pathogenic species (Leishmania amazonensis, Leishmania braziliensis, Leishmania infantum and Leishmania major). METHODS Parasites were cultured for extraction and purification of lipophosphoglycan (LPG), immunofluorescence probing with anti-gp63 and resistance against complement. Parasite extracts were also tested for proteases activity and metabolome composition. FINDINGS Leishmania tarentolae does not express LPG on its surface. It expresses gp63 at lower levels compared to pathogenic species and, is highly sensitive to complement-mediated lysis. This species also lacks intracellular/extracellular activities of proteolytic enzymes. It has metabolic differences with pathogenic species, exhibiting a lower abundance of metabolites including ABC transporters, biosynthesis of unsaturated fatty acids and steroids, TCA cycle, glycine/serine/threonine metabolism, glyoxylate/dicarboxylate metabolism and pentose-phosphate pathways. MAIN CONCLUSIONS The non-pathogenic phenotype of L. tarentolae is associated with alterations in several biochemical and molecular features. This reinforces the need of comparative studies between pathogenic and non-pathogenic species to elucidate the molecular mechanisms of virulence during host-parasite interactions.

Extracellular Vesicles Released by Leishmania (Leishmania) amazonensis Promastigotes with Distinct Virulence Profile Differently Modulate the Macrophage Functions.

Leishmania spp. is the aetiologic agent of leishmaniasis, a disease endemic in several developing countries. The parasite expresses and secretes several virulence factors that subvert the macrophage function and immune response. Extracellular vesicles (EVs) can carry molecules of the parasites that show immunomodulatory effects on macrophage activation and disease progression. In the present work, we detected a significantly higher expression of lpg3 and gp63 genes in Leishmania amazonensis promastigotes recovered after successive experimental infections (IVD-P) compared to those cultured for a long period (LT-P). In addition, we observed a significantly higher percentage of infection and internalized parasites in groups of macrophages infected with IVD-P. Macrophages previously treated with EVs from LT-P showed higher percentages of infection and production of inflammatory cytokines after the parasite challenge compared to the untreated ones. However, macrophages infected with parasites and treated with EVs did not reduce the parasite load. In addition, no synergistic effects were observed in the infected macrophages treated with EVs and reference drugs. In conclusion, parasites cultured for a long period in vitro and recovered from animals' infections, differently affected the macrophage response. Furthermore, EVs produced by these parasites affected the macrophage response in the early infection of these cells.

First report of putative Leishmania RNA virus 2 (LRV2) in Leishmania infantum strains from canine and human visceral leishmaniasis cases in the southeast of Brazil.

BACKGROUND: Leishmania RNA virus 1 (LRV1) is commonly found in South American Leishmania parasites belonging to the subgenus Viannia, whereas Leishmania RNA virus 2 (LRV2) was previously thought to be restricted to the Old-World pathogens of the subgenus Leishmania. OBJECTIVES: In this study, we investigated the presence of LRV2 in strains of Leishmania (L.) infantum, the causative agent of visceral leishmaniasis (VL), originating from different hosts, clinical forms, and geographical regions. METHODS: A total of seventy-one isolates were screened for LRV2 using semi-nested reverse transcription-polymerase chain reaction (RT-PCR) targeting the RNA-dependent RNA polymerase (RdRp) gene. FINDINGS: We detected LRV2 in two L. infantum isolates (CUR268 and HP-EMO) from canine and human cases, respectively. MAIN CONCLUSIONS: To the best of our knowledge, this is the first detection of LRV2 in the New World.

Clinical evolution of equine leishmaniasis with self-limiting cutaneous disease caused by Leishmania infantum in northeastern Brazil: A case report.

Leishmania infantum infections have long been described in humans and dogs worldwide, but characterization of equine cases remains scarce. We describe the clinical evolution of a natural L. infantum infection to contribute to the diagnostic knowledge and epidemiology of equine leishmaniasis (EL). An auction-acquired four-year-old Mangalarga Marchador mare from Pernambuco state, presented a few subcutaneous nodules on the head and neck upon arrival at the purchaser's stud at Bahia state, in November of 2019. They progressed to multiple ulcerated and non-ulcerated nodules and spread to both right limbs in seven weeks. Hematology revealed anemia, lymphocytosis, monocytosis, and elevated plasma fibrinogen. Histopathology of the biopsied nodules identified a granulomatous dermatitis with macrophages containing Leishmania amastigotes. PCR detected Leishmania in skin lesions, but not in blood or spleen aspirate samples; ITS1 PCR-RFLP and DNA sequencing confirmed L. infantum species. A topical antiseptic and insect-repellent therapy and a monthly follow-up were established. All lesions improved progressively, without specific anti-Leishmania treatment, and 14 months later there was a consistent resolution. This first description of EL by L. infantum in an endemic area is relevant to emphasize the need for epidemiological studies, and to enhance clinicians' awareness for differential diagnosis.

Phenotypical Differences between Leishmania (Leishmania) amazonensis PH8 and LV79 Strains May Impact Survival in Mammal Host and in Phlebotomine Sand Flies.

We previously showed that L. (Leishmania) amazonensis promastigotes and amastigotes of the PH8 strain generated larger lesions in mice than LV79, and that lesion-derived amastigotes from the two strains differ in their proteomes. We recently reported that PH8 promastigotes are more phagocytized by macrophages. Promastigotes' membrane-enriched proteomes showed several differences, and samples of each strain clustered based on proteomes. In this paper, we show phenotypic differences between PH8 and LV79 promastigotes that may explain the higher virulence of PH8. We compared in vitro macrophage infections by day 4 (early) and day 6 (late stationary phase) cultures, resistance to complement, and LPG characteristics. PH8 promastigotes showed a higher infectivity and were more resistant to murine complement. LPG was different between the strains, which may influence the interaction with macrophages and survival to complement. We compared the infection of the permissive vector Lutzomyia longipalpis. PH8 was more abundant in the vector's gut 72 h after feeding, which is a moment where blood digestion is finished and the parasites are exposed to the gut environment. Our results indicate that PH8 promastigotes are more infective, more resistant to complement, and infect the permissive vector more efficiently. These data suggest that PH8 is probably better adapted to the sand fly and more prone to survive in the vertebrate host.

Guidelines for the purification and characterization of extracellular vesicles of parasites.

Parasites are responsible for the most neglected tropical diseases, affecting over a billion people worldwide (WHO, 2015) and accounting for billions of cases a year and responsible for several millions of deaths. Research on extracellular vesicles (EVs) has increased in recent years and demonstrated that EVs shed by pathogenic parasites interact with host cells playing an important role in the parasite's survival, such as facilitation of infection, immunomodulation, parasite adaptation to the host environment and the transfer of drug resistance factors. Thus, EVs released by parasites mediate parasite-parasite and parasite-host intercellular communication. In addition, they are being explored as biomarkers of asymptomatic infections and disease prognosis after drug treatment. However, most current protocols used for the isolation, size determination, quantification and characterization of molecular cargo of EVs lack greater rigor, standardization, and adequate quality controls to certify the enrichment or purity of the ensuing bioproducts. We are now initiating major guidelines based on the evolution of collective knowledge in recent years. The main points covered in this position paper are methods for the isolation and molecular characterization of EVs obtained from parasite-infected cell cultures, experimental animals, and patients. The guideline also includes a discussion of suggested protocols and functional assays in host cells.

First report of putative Leishmania RNA virus 2 (LRV2) in Leishmania infantum strains from canine and human visceral leishmaniasis cases in the southeast of Brazil

BACKGROUND Leishmania RNA virus 1 (LRV1) is commonly found in South American Leishmania parasites belonging to the subgenus Viannia, whereas Leishmania RNA virus 2 (LRV2) was previously thought to be restricted to the Old-World pathogens of the subgenus Leishmania. OBJECTIVES In this study, we investigated the presence of LRV2 in strains of Leishmania (L.) infantum, the causative agent of visceral leishmaniasis (VL), originating from different hosts, clinical forms, and geographical regions. METHODS A total of seventy-one isolates were screened for LRV2 using semi-nested reverse transcription-polymerase chain reaction (RT-PCR) targeting the RNA-dependent RNA polymerase (RdRp) gene. FINDINGS We detected LRV2 in two L. infantum isolates (CUR268 and HP-EMO) from canine and human cases, respectively. MAIN CONCLUSIONS To the best of our knowledge, this is the first detection of LRV2 in the New World.

Leishmania enriettii visceralises in the trachea, lungs, and spleen of Cavia porcellus.

BACKGROUND: Leishmania (Mundinia) enriettii is a species commonly found in the guinea pig, Cavia porcellus. Although it is a dermotropic species, there is still an uncertainty regarding its ability to visceralise during Leishmania life cycle. OBJECTIVE: Here, we investigated the ability of L. enriettii (strain L88) to visceralise in lungs, trachea, spleen, and liver of C. porcellus, its natural vertebrate host. METHODS: Animals were infected sub-cutaneously in the nose and followed for 12 weeks using histological (hematoxilin-eosin) and molecular tools (polymerase chain reaction-restriction fragment length polymorphism - PCR-RFLP). To isolate parasite from C. porcellus, animals were experimentally infected for viscera removal and PCR typing targeting hsp70 gene. FINDINGS: Histological analysis revealed intense and diffuse inflammation with the presence of amastigotes in the trachea, lung, and spleen up to 12 weeks post-infection (PI). Molecular analysis of paraffin-embedded tissues detected parasite DNA in the trachea and spleen between the 4th and 8th weeks PI. At the 12th PI, no parasite DNA was detected in any of the organs. To confirm that the spleen could serve as a temporary site for L. enriettii, we performed additional in vivo experiments. During 6th week PI, the parasite was isolated from the spleen confirming previous histopathological and PCR observations. MAIN CONCLUSION: Leishmania enriettii (strain L88) was able to visceralise in the trachea, lung, and spleen of C. porcellus.

Lipophosphoglycan From Dermotropic New World Leishmania Upregulates Interleukin-32 and Proinflammatory Cytokines Through TLR4 and NOD2 Receptors.

Interleukin-32 (IL-32) is produced during Leishmania infection, but the components of the parasite that induce its production are unknown. An important multivirulence factor of Leishmania spp. protozoa is the lipophosphoglycan (LPG), which plays a crucial role in the host-parasite interaction. Here, the ability of LPGs from two dermotropic Leishmania species to induce IL-32 production was evaluated in human peripheral blood mononuclear cells (PBMCs). Additionally, the potential receptors involved in this activation were assessed. PBMCs from healthy individuals were stimulated with LPGs from L. amazonensis (La) or L. braziliensis (Lb), live promastigotes of La or Lb and E. coli lipopolysaccharide (LPS, TLR4 agonist) as control. Blockers of TLR4 (Bartonella quintana LPS or monoclonal antibody) and Ponatinib (RIPK2 inhibitor, NOD2 pathway) were used to evaluate the receptors. ELISA was performed for IL-32 expression and cytokine (IL-1ß and IL-6) production in cell lysates and in supernatants, respectively. Expression of TLR4 (2 h, 24 h) was assessed by flow cytometry. IL-32γ mRNA transcript was analyzed by qPCR. It was observed that LPG from Leishmania, like whole parasites, induced the production of IL-32, IL-1ß and IL-6. Both LPGs induced the expression of IL32γ mRNA. The production of IL-32 was earlier detected (6 h) and positively associated with the production of IL-1ß and IL-6. The induction of cytokines (IL-32, IL-1ß and IL-6) was dependent on TLR4 and NOD2. The TLR4 was internalized after interaction with LPG. Therefore, our data suggest that LPGs from La and Lb are components of Leishmania able to upregulate IL-32 and other pro-inflammatory cytokines in a TLR4- and NOD2-dependent manner. In addition, LPG-induced IL-32 seems to be necessary for IL-1ß and IL-6 production. To identify the parasite factors and host receptors involved in IL-32 induction is crucial to reveal potential targets for novel strategies to control leishmaniasis.

Leishmania enriettii visceralises in the trachea, lungs, and spleen of Cavia porcellus

BACKGROUND Leishmania (Mundinia) enriettii is a species commonly found in the guinea pig, Cavia porcellus. Although it is a dermotropic species, there is still an uncertainty regarding its ability to visceralise during Leishmania life cycle. OBJECTIVE Here, we investigated the ability of L. enriettii (strain L88) to visceralise in lungs, trachea, spleen, and liver of C. porcellus, its natural vertebrate host. METHODS Animals were infected sub-cutaneously in the nose and followed for 12 weeks using histological (hematoxilin-eosin) and molecular tools (polymerase chain reaction-restriction fragment length polymorphism - PCR-RFLP). To isolate parasite from C. porcellus, animals were experimentally infected for viscera removal and PCR typing targeting hsp70 gene. FINDINGS Histological analysis revealed intense and diffuse inflammation with the presence of amastigotes in the trachea, lung, and spleen up to 12 weeks post-infection (PI). Molecular analysis of paraffin-embedded tissues detected parasite DNA in the trachea and spleen between the 4th and 8th weeks PI. At the 12th PI, no parasite DNA was detected in any of the organs. To confirm that the spleen could serve as a temporary site for L. enriettii, we performed additional in vivo experiments. During 6th week PI, the parasite was isolated from the spleen confirming previous histopathological and PCR observations. MAIN CONCLUSION Leishmania enriettii (strain L88) was able to visceralise in the trachea, lung, and spleen of C. porcellus.

Stress Induces Release of Extracellular Vesicles by Trypanosoma cruzi Trypomastigotes.

All extracellular forms of Trypanosoma cruzi, the causative agent of Chagas disease, release extracellular vesicles (EVs) containing major surface molecules of the parasite. EV release depends on several mechanisms (internal and external). However, most of the environmental conditions affecting this phenomenon are still unknown. In this work, we evaluated EV release under different stress conditions and their ability to be internalized by the parasites. In addition, we investigated whether the release conditions would affect their immunomodulatory properties in preactivated bone marrow-derived macrophages (BMDM). Sodium azide and methyl-cyclo-ß-dextrin (CDB) reduced EV release, indicating that this phenomenon relies on membrane organization. EV release was increased at low temperatures (4°C) and acidic conditions (pH 5.0). Under this pH, trypomastigotes differentiated into amastigotes. EVs are rapidly liberated and reabsorbed by the trypomastigotes in a concentration-dependent manner. Nitrosative stress caused by sodium nitrite in acid medium or S-nitrosoglutathione also stimulated the secretion of EVs. EVs released under all stress conditions also maintained their proinflammatory activity and increased the expression of iNOS, Arg 1, IL-12, and IL-23 genes in IFN-γ and LPS preactivated BMDM. In conclusion, our results suggest a budding mechanism of release, dependent on the membrane structure and parasite integrity. Stress conditions did not affect functional properties of EVs during interaction with host cells. EV release variations under stress conditions may be a physiological response against environmental changes.

Feline Leishmaniasis Caused by Leishmania infantum: Parasite Sequencing, Seropositivity, and Clinical Characterization in an Endemic Area From Brazil.

Zoonotic leishmaniasis caused by Leishmania infantum is a disease of One Health concern since human and animal cases and environmental damage are interconnected. L. infantum has a complex epidemiological cycle with multiple hosts, including mammals-humans, domestic, and wild animals-and arthropod vectors. Knowledge on mammal infections in endemic areas is crucial for developing control strategies. This work aimed to detect and characterize L. infantum infection in domestic cats from areas where human and canine leishmaniasis cases occur. No cases of feline leishmaniasis (FeL) had been previously reported in those areas. Five municipalities from Bahia state were chosen, comprising 2,480.8 km2 with 1,103,866 inhabitants. Ninety domiciliated and/or sheltered cats underwent clinical examination and serology by a rapid reference test recommended by the Brazilian government. Cytology, PCR, and parasite DNA sequencing were performed in bone marrow samples. Rapid tests detected antibodies in 5.6% (5/90) of the cats. Leishmania infantum infection was confirmed in 7.8% (7/90) of the cats by PCR, sequencing, and parasite isolation. Three out of the five municipalities (60%) had infected cats, and PCR positivity varied from 6.9 to 29%. One cat was categorized as harboring active L. infantum infection with amastigote forms in bone marrow smears. No clinical signs were detected at the first clinical exam, but 1 month later the cat developed severe FeL. The cat isolate was grown in culture, typed and its DNA sequence was homologous to the L. infantum reference strain (PP75). In conclusion, cats are potential hosts and may acquire L. infantum in endemic areas where canine and human cases occur. For cats, the need for surveillance, differential diagnosis and clinical care is highly recommended since a fast clinical progression of FeL developed in a subclinical animal. An accurate standardized immunodiagnostic assay for FeL is warranted.

α-Gal immunization positively impacts Trypanosoma cruzi colonization of heart tissue in a mouse model.

Chagas disease, caused by the parasite Trypanosoma cruzi, is considered endemic in more than 20 countries but lacks both an approved vaccine and limited treatment for its chronic stage. Chronic infection is most harmful to human health because of long-term parasitic infection of the heart. Here we show that immunization with a virus-like particle vaccine displaying a high density of the immunogenic α-Gal trisaccharide (Qß-αGal) induced several beneficial effects concerning acute and chronic T. cruzi infection in α1,3-galactosyltransferase knockout mice. Approximately 60% of these animals were protected from initial infection with high parasite loads. Vaccinated animals also produced high anti-αGal IgG antibody titers, improved IFN-γ and IL-12 cytokine production, and controlled parasitemia in the acute phase at 8 days post-infection (dpi) for the Y strain and 22 dpi for the Colombian strain. In the chronic stage of infection (36 and 190 dpi, respectively), all of the vaccinated group survived, showing significantly decreased heart inflammation and clearance of amastigote nests from the heart tissue.