Improved Treatment Outcome Following the Use of a Wound Dressings in Cutaneous Leishmaniasis Lesions

Leishmaniasis, caused by Leishmania parasites, is a neglected tropical disease and Cutaneous Leishmaniasis (CL) is the most common form. Despite the associated toxicity and adverse effects, Meglumine antimoniate (MA) remains the first-choice treatment for CL in Brazil, pressing the need for the development of better alternatives. Bacterial NanoCellulose (BNC), a biocompatible nanomaterial, has unique properties regarding wound healing. In a previous study, we showed that use of topical BNC + systemic MA significantly increased the cure rate of CL patients, compared to treatment with MA alone. Herein, we performed a study comparing the combination of a wound dressing (BNC or placebo) plus systemic MA versus systemic MA alone, in CL caused by Leishmania braziliensis. We show that patients treated with the combination treatment (BNC or placebo) + MA showed improved cure rates and decreased need for rescue treatment, although differences compared to controls (systemic MA alone) were not significant. However, the overall time-to-cure was significantly lower in groups treated with the combination treatment (BNC+ systemic MA or placebo + systemic MA) in comparison to controls (MA alone), indicating that the use of a wound dressing improves CL treatment outcome. Assessment of the immune response in peripheral blood showed an overall downmodulation in the inflammatory landscape and a significant decrease in the production of IL-1a (p < 0.05) in patients treated with topical BNC + systemic MA. Our results show that the application of wound dressings to CL lesions can improve chemotherapy outcome in CL caused by L. braziliensis.

Pathogenic CD8 T cell responses are driven by neutrophil-mediated hypoxia in cutaneous leishmaniasis

Cutaneous leishmaniasis caused by Leishmania parasites exhibits a wide range of clinical manifestations. Although parasites influence disease severity, cytolytic CD8 T cell responses mediate disease. While these responses originate in the lymph node, we find that expression of the cytolytic effector molecule granzyme B is restricted to lesional CD8 T cells in Leishmania - infected mice, suggesting that local cues within inflamed skin induce cytolytic function. Expression of Blimp-1 ( Prdm1 ), a transcription factor necessary for cytolytic CD8 T cell differentiation, is driven by hypoxia within the inflamed skin. Hypoxia is further enhanced by the recruitment of neutrophils that consume oxygen to produce reactive oxygen species, ultimately increasing granzyme B expression in CD8 T cells. Importantly, lesions from cutaneous leishmaniasis patients exhibit hypoxia transcription signatures that correlate with the presence of neutrophils. Thus, targeting hypoxia-driven signals that support local differentiation of cytolytic CD8 T cells may improve the prognosis for patients with cutaneous leishmaniasis, as well as other inflammatory skin diseases where cytolytic CD8 T cells contribute to pathogenesis.

Clinical Profile and Diagnosis of Recurrent Cutaneous Leishmaniasis

This case-control study compared the clinical profile, parasite load, polymerase chain reaction positivity, and response to therapy in patients with recurrent cutaneous leishmaniasis (RCL) with primary cutaneous leishmaniasis (CL). The RCL patients had milder diseases with lower parasite loads, a lower number of lesions, and more self-healing diseases than primary CL patients.

Serodiagnosis and therapeutic monitoring of New-World tegumentary leishmaniasis using synthetic type-2 glycoinositolphospholipid-based neoglycoproteins

American tegumentary leishmaniasis (TL) caused by Leishmania braziliensis is characterized by a spectrum of clinical presentations, ranging from localized cutaneous ulcers (CL), mucosal (ML), or disseminated (DL) disease, to a subclinical (SC) asymptomatic form. Current diagnosis based on parasite culture and/or microscopy lacks sensitivity and specificity. Previous studies showed that patients with CL and ML have very high levels of Leishmania-specific anti-α-Gal antibodies. However, the native parasite α-Gal glycotope(s) is(are) still elusive, thus they have not yet been explored for a more accurate TL diagnosis. Using a chemiluminescent immunoassay, we evaluated the seroreactivity of TL patients across its clinical spectrum, and of endemic (EC) and nonendemic healthy controls (NEC) against three synthetic neoglycoproteins (NGP29b, NGP30b, and NGP28b), respectively comprising the L. major-derived type-2 glycoinositolphospholipid (GIPL)-1 (Galfβ1,3Manα), GIPL-2 (Galα1,3Galfβ1,3Manα), and GIPL-3 (Galα1,6Galα1,3Galfβ) glycotopes. Contrary to NGP29b and NGP30b, NGP28b exhibited high sensitivity and specificity to a CL serum pool. More importantly, NGP28b reacted strongly and specifically with individual sera from distinct clinical forms of TL, especially with SC sera, with 94% sensitivity and 97% specificity, by post-two-graph receiver-operating characteristic curve analysis. Contrary to NGP29b, NGP28b showed low cross-reactivity with Chagas disease and control (NEC/EC) sera. Additionally, seroreactivity of CL patients against NGP28b was significantly decreased after successful chemotherapy, indicating that L. braziliensis-specific anti-α-Gal antibodies may serve as an early biomarker of cure in CL. Our data also points towards the applicability of L. major type-2 GIPL-3-derived Galα1,6Galα1,3Galfβ glycotope for the serological diagnosis of American TL, particularly of the subclinical form.

Pioglitazone, a Peroxisome Proliferator-Activated Receptor-γ Agonist, Downregulates the Inflammatory Response in Cutaneous Leishmaniasis Patients Without Interfering in Leishmania braziliensis Killing by Monocytes

Patients with cutaneous leishmaniasis (CL) due to Leishmania braziliensis infection have an exacerbated inflammatory response associated with tissue damage and ulcer development. An increase in the rate of patients who fail therapy with pentavalent antimony has been documented. An adjuvant therapy with an anti-inflammatory drug with the potential of Leishmania killing would benefit CL patients. The aim of the present study was to investigate the contribution of peroxisome proliferator-activated receptor-γ (PPAR-γ) activation by pioglitazone in the regulation of the inflammatory response and L. braziliensis killing by monocytes. Pioglitazone is an oral drug used in the treatment of diabetes, and its main mechanism of action is through the activation of PPAR-γ, which is expressed in many cell types of the immune response. We found that activation of PPAR-γ by pioglitazone decreases the inflammatory response in CL patients without affecting L. braziliensis killing by monocytes. Our data suggest that pioglitazone may serve as an adjunctive treatment for CL caused by L. braziliensis.

Immune response to LinB13, a Lutzomyia intermedia salivary protein correlates with disease severity in tegumentary leishmaniasis

BACKGROUND

We have previously shown that seropositivity to rLinB-13, a salivary protein from Lutzomyia intermedia, predicted sand fly exposure and was associated with increased risk of developing cutaneous leishmaniasis (CL).

METHODS

Herein, we investigated the cellular immune response to saliva from Lu. intermedia, using rLinB-13 as a surrogate antigen in naturally exposed individuals presenting positive serology to LinB-13. We also investigated the response to rLinB-13 in leishmaniasis patients, displaying active ulcers and positive PCR for L. braziliensis.

RESULTS

Peripheral blood mononuclear cells (PBMCs) stimulated in vitro with rLinB-13 secreted elevated levels of IL-10, IL-4, IL-1β, IL-1α, IL-6 and chemokines (CCL3, CCL4, CCL5 and CXCL5). CL, and disseminated leishmaniasis (DL) patients displayed a significantly higher IgG response to rLinB-13, compared to healthy subjects and anti-rLinB-13 IgG was positively correlated with the number of lesions in DL patients. Positive serology to rLinB-13 was also associated with chemotherapy failure. PBMCs from DL patients stimulated with rLINB-13 secreted significantly higher levels IL-10 and IL-1β compared to CL individuals.

CONCLUSIONS

In this study, we observed an association between humoral and cellular immune response to the sand fly salivary protein rLinB-13 and disease severity in tegumentary leishmaniasis. This study brings evidence that immunity to rLinB-13 influences disease outcome in L. braziliensis infection and results indicate that positive serology to rLinB-13 IgG can be employed as marker of DL, an emerging and severe form of disease caused by L. braziliensis.

Targeted Deletion of Centrin in Leishmania braziliensis Using CRISPR-Cas9-Based Editing

Leishmania braziliensis is the main causative agent of Tegumentary Leishmaniasis in the Americas. However, difficulties related to genome manipulation, experimental infection, and parasite growth have so far limited studies with this species. CRISPR-Cas9-based technology has made genome editing more accessible, and here we have successfully employed the LeishGEdit approach to attenuate L. braziliensis. We generated a transgenic cell line expressing Cas9 and T7 RNA polymerase, which was employed for the targeted deletion of centrin, a calcium-binding cytoskeletal protein involved in the centrosome duplication in eukaryotes. Centrin-deficient Leishmania exhibit growth arrest at the amastigote stage. Whole-genome sequencing of centrin-deficient L. braziliensis (LbCen^−/−) did not indicate the presence of off-target mutations. In vitro, the growth rates of LbCen^−/− and wild-type promastigotes were similar, but axenic and intracellular LbCen^−/− amastigotes showed a multinucleated phenotype with impaired survival following macrophage infection. Upon inoculation into BALB/c mice, LbCen^−/− were detected at an early time point but failed to induce lesion formation, contrary to control animals, infected with wild-type L. braziliensis. A significantly lower parasite burden was also observed in mice inoculated with LbCen^−/−, differently from control mice. Given that centrin-deficient Leishmania sp. have become candidates for vaccine development, we propose that LbCen^−/− can be further explored for the purposes of immunoprophylaxis against American Tegumentary Leishmaniasis.

A Potential SARS-CoV-2 Variant of Interest (VOI) Harboring Mutation E484K in the Spike Protein Was Identified within Lineage B.1.1.33 Circulating in Brazil

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic in Brazil was dominated by two lineages designated as B.1.1.28 and B.1.1.33. The two SARS-CoV-2 variants harboring mutations at the receptor-binding domain of the Spike (S) protein, designated as lineages P.1 and P.2, evolved from lineage B.1.1.28 and are rapidly spreading in Brazil. Lineage P.1 is considered a Variant of Concern (VOC) because of the presence of multiple mutations in the S protein (including K417T, E484K, N501Y), while lineage P.2 only harbors mutation S:E484K and is considered a Variant of Interest (VOI). On the other hand, epidemiologically relevant B.1.1.33 deriving lineages have not been described so far. Here we report the identification of a new SARS-CoV-2 VOI within lineage B.1.1.33 that also harbors mutation S:E484K and was detected in Brazil between November 2020 and February 2021. This VOI displayed four non-synonymous lineage-defining mutations (NSP3:A1711V, NSP6:F36L, S:E484K, and NS7b:E33A) and was designated as lineage N.9. The VOI N.9 probably emerged in August 2020 and has spread across different Brazilian states from the Southeast, South, North, and Northeast regions.

The Long Pentraxin 3 (PTX3) Suppresses Immunity to Cutaneous Leishmaniasis by Regulating CD4+ T Helper Cell Response

The long pentraxin 3 (PTX3) plays a critical role in inflammation, tissue repair, and wound healing. Here, we show that PTX3 regulates disease pathogenesis in cutaneous leishmaniasis (CL). PTX3 expression increases in skin lesions in patients and mice during CL, with higher expression correlating with severe disease. PTX3-deficient (PTX3^-/-) mice are highly resistant to L. major and L. braziliensis infections. This enhanced resistance is associated with increases in Th17 and IL-17A responses. The neutralization of IL-17A abolishes this enhanced resistance, while rPTX3 treatment results in decrease in Th17 and IL-17A responses and increases susceptibility. PTX3^-/- CD4⁺ T cells display increased differentiation to Th17 and expression of Th17-specific transcription factors. The addition of rPTX3 suppresses the expression of Th17 transcription factors, Th17 differentiation, and IL-17A production by CD4⁺ T cells from PTX3^-/- mice. Collectively, our results show that PTX3 contributes to the pathogenesis of CL by negatively regulating Th17 and IL-17A responses.

Evaluation of in vitro and in vivo Efficacy of a Novel Amphotericin B-Loaded Nanostructured Lipid Carrier in the Treatment of Leishmania braziliensis Infection

Background

Leishmaniasis is a neglected disease, and the current therapeutic arsenal for its treatment is seriously limited by high cost and toxicity. Nanostructured lipid carriers (NLCs) represent a promising approach due to high drug loading capacity, controlled drug release profiles and superior stability. Here, we explore the efficacy of a unique pH-sensitive amphotericin B-loaded NLC (AmB-NLC) in Leishmania braziliensis infection in vitro and in vivo.

Methods and Results

AmB-NLC was assessed by dynamic light scattering and atomic force microscopy assays. The carrier showed a spherical shape with a nanometric size of 242.0 ± 18.3 nm. Zeta potential was suggestive of high carrier stability (−42.5 ± 1.5 mV), and the NLC showed ~99% drug encapsulation efficiency (EE%). In biological assays, AmB-NLC presented a similar IC₅₀ as free AmB and conventional AmB deoxycholate (AmB-D) (11.7 ± 1.73; 5.3 ± 0.55 and 13 ± 0.57 ng/mL, respectively), while also presenting higher selectivity index and lower toxicity to host cells, with no observed production of nitric oxide or TNF-α by in vitro assay. Confocal microscopy revealed the rapid uptake of AmB-NLC by infected macrophages after 1h, which, in association with more rapid disruption of AmB-NLC at acidic pH levels, may directly affect intracellular parasites. Leishmanicidal effects were evaluated in vivo in BALB/c mice infected in the ear dermis with L. braziliensis and treated with a pentavalent antimonial (Sb⁵⁺), liposomal AmB (AmB-L) or AmB-NLC. After 6 weeks of infection, AmB-NLC treatment resulted in smaller ear lesion size in all treated mice, indicating the efficacy of the novel formulation.

Conclusion

Here, we preliminarily demonstrate the effectiveness of an innovative and cost-effective AmB-NLC formulation in promoting the killing of intracellular L. braziliensis. This novel carrier system could be a promising alternative for the future treatment of cutaneous leishmaniasis.

Mechanistic and biological characterisation of novel N5-substituted paullones targeting the biosynthesis of trypanothione in Leishmania

Trypanothione synthetase (TryS) produces N¹,N⁸-bis(glutathionyl)spermidine (or trypanothione) at the expense of ATP. Trypanothione is a metabolite unique and essential for survival and drug-resistance of trypanosomatid parasites. In this study, we report the mechanistic and biological characterisation of optimised N⁵-substituted paullone analogues with anti-TryS activity. Several of the new derivatives retained submicromolar IC₅₀ against leishmanial TryS. The binding mode to TryS of the most potent paullones has been revealed by means of kinetic, biophysical and molecular modelling approaches. A subset of analogues showed an improved potency (EC₅₀ 0.5–10 µM) and selectivity (20–35) against the clinically relevant stage of Leishmania braziliensis (mucocutaneous leishmaniasis) and L. infantum (visceral leishmaniasis). For a selected derivative, the mode of action involved intracellular depletion of trypanothione. Our findings shed light on the molecular interaction of TryS with rationally designed inhibitors and disclose a new set of compounds with on-target activity against different Leishmania species.

Generation and Characterization of a Dual-Reporter Transgenic Leishmania braziliensis Line Expressing eGFP and Luciferase

In this study, we generated a transgenic strain of Leishmania braziliensis, an etiological agent associated with a diversity of clinical manifestations of leishmaniasis ranging from localized cutaneous to mucocutaneous to disseminated disease. Transgenic parasites expressing reporter proteins are valuable tools for studies of parasite biology, host-pathogen interactions, and anti-parasitic drug development. To this end, we constructed an L. braziliensis line stably expressing the reporters eGFP and luciferase (eGFP-LUC L. braziliensis). The integration cassette co-expressing the two reporters was targeted to the ribosomal locus (SSU) of the parasite genome. Transgenic parasites were characterized for their infectivity and stability both in vitro and in vivo. Parasite maintenance in axenic long-term culture in the absence of selective drugs did not alter expression of the two reporters or infection of BALB/c mice, indicating stability of the integrated cassette. Infectivity of eGFP-LUC, L. braziliensis, both in vivo and in vitro was similar to that obtained with the parental wild type strain. The possibility of L. braziliensis tracking and quantification using fluorescence and luminescence broadens the scope of research involving this neglected species, despite its importance in terms of public health concerning the leishmaniasis burden.

The Paradoxical Leishmanicidal Effects of Superoxide Dismutase (SOD)-Mimetic Tempol in Leishmania braziliensis Infection in vitro

Leishmaniasis is an infectious disease caused by protozoans of the genus Leishmania. The macrophage is the resident cell in which the parasite replicates and it is important to identify new compounds that can aid in parasite elimination since the drugs used to treat leishmaniasis are toxic and present side effects. We have previously shown that treatment of Leishmania braziliensis-infected macrophages with DETC (Diethyldithiocarbamate) induces parasite killing, in vivo. Thus, the objective of this study was to further evaluate the effect of oxidants and antioxidants in L. braziliensis-infected macrophages, following treatment with either oxidizing Hydrogen Peroxide, Menadione, DETC, or antioxidant [NAC (N-Acetyl-Cyteine), Apocynin, and Tempol] compounds. We determined the percentage of infected macrophages and number of amastigotes. Promastigote survival was also evaluated. Both DETC (SOD-inhibitor) and Tempol (SOD-mimetic) decreased the percentage of infected cells and parasite load. Hydrogen peroxide did not interfere with parasite burden, while superoxide-generator Menadione had a reducing effect. On the other hand, NAC (GSH-replenisher) and Apocynin (NADPH-oxidase inhibitor) increased parasite burden. Tempol surfaces as an interesting candidate for the chemotherapy of CL with an IC₅₀ of 0.66 ± 0.08 mM and selectivity index of 151. While it remains obscure how a SOD-mimetic may induce leishmanicidal effects, we suggest the possibility of developing Tempol-based topical applications for the treatment of cutaneous leishmaniasis caused by L. braziliensis.

Long Pentraxin 3 (PTX3) Regulates IL-17A Mediated Immunity to Primary and Secondary Leishmania major Infection

Resolution of cutaneous leishmaniasis (CL), caused by the protozoan parasite Leishmania (L) major, relies on the nature of the host immune response. The long pentraxin 3 (PTX3), a soluble pattern recognition molecule, is critical for wound healing by regulating tissue repair and also in innate and adaptive responses during infection and inflammation. Here, we show that PTX3 regulates disease pathogenesis and immunity to CL. PTX3 expression is increased in active skin lesions in patients and mice during CL, with higher levels being expressed in individuals with severe disease. PTX3−/− mice were highly resistant to primary and secondary L. major infection. Interestingly, the enhanced resistance of PTX3−/− mice to primary or secondary L. major infection was not associated with enhanced IFN-γ or decreased IL-10 response. Instead, L. major-infected PTX3−/− mice displayed strong IL-17 response and in vivo neutralization of IL-17A abolished their enhanced resistance. Naïve CD4+ T cells from PTX3−/− mice displayed increased differentiation into Th17 cells and this was associated with increased expression of Th17-specific transcription factors including RORγt, AhR and STAT3. Addition of recombinant PTX3 significantly inhibited the expression of Th17-specific transcription factors and the frequency of Th17 cells in Th17 polarizing cultures of PTX3−/− CD4+ T cells. Similarly, healed PTX3−/− mice had higher frequencies of effector memory CD4+ T cells that rapidly proliferate and differentiate into IL-17A-producing CD4+ T cells upon secondary challenge. Collectively, our results show that PTX3 contributes to pathogenesis of CL by negatively regulating protective Th17 and IL-17 responses.

Lutzomyia longipalpis Saliva Induces Heme Oxygenase-1 Expression at Bite Sites

Sand flies bite mammalian hosts to obtain a blood meal, driving changes in the host inflammatory response that support the establishment of Leishmania infection. This effect is partially attributed to components of sand fly saliva, which are able to recruit and activate leukocytes. Our group has shown that heme oxygenase-1 (HO-1) favors Leishmania survival in infected cells by reducing inflammatory responses. Here, we show that exposure to sand fly bites is associated with induction of HO-1 in vivo. Histopathological analyses of skin specimens from human volunteers experimentally exposed to sand fly bites revealed that HO-1 and Nrf2 are produced at bite sites in the skin. These results were recapitulated in mice ears injected with a salivary gland sonicate (SGS) or exposed to sand fly bites, indicating that vector saliva may be a key factor in triggering HO-1 expression. Resident skin macrophages were the main source HO-1 at 24–48 h after bites. Additionally, assays in vivo after bites and in vitro after stimulation with saliva both demonstrated that HO-1 production by macrophages was Nrf2-dependent. Collectively, our data demonstrates that vector saliva induces early HO-1 production at the bite sites, representing a major event associated with establishment of naturally-transmitted Leishmania infections.

In situ Immune Signatures and Microbial Load at the Nasopharyngeal Interface in Children With Acute Respiratory Infection

Acute respiratory infection (ARI) is the most frequent cause for hospitalization in infants and young children. Using multiplexed nCounter technology to digitally quantify 600 human mRNAs in parallel with 14 virus- and 5 bacterium-specific RNAs, we characterized viral and bacterial presence in nasopharyngeal aspirates (NPA) of 58 children with ARI and determined the corresponding in situ immune profiles. NPA contained different groups of organisms and these were classified into bacterial (n = 27), viral (n = 5), codetection [containing both viral and bacterial transcripts (n = 21), or indeterminate intermediate where microbial load is below threshold (n = 5)]. We then identified differentially expressed immune transcripts (DEITs) comparing NPAs from symptomatic children vs. healthy controls, and comparing children presenting NPAs with detectable microbial load vs. indeterminate. We observed a strong innate immune response in NPAs, due to the presence of evolutionarily conserved type I Interferon (IFN)-stimulated genes (ISG), which was correlated with total bacterial and/or viral load. In comparison with indeterminate NPAs, adaptive immunity transcripts discriminated among viral, bacterial, and codetected microbial profiles. In viral NPAs, B cell transcripts were significantly enriched among DEITs, while only type III IFN was correlated with viral load. In bacterial NPAs, myeloid cells and coinhibitory transcripts were enriched and significantly correlated with bacterial load. In conclusion, digital nCounter transcriptomics provide a microbial and immunological in situ “snapshot” of the nasopharyngeal interface in children with ARI. This enabled discrimination among viral, bacterial, codetection, and indeterminate transcripts in the samples using non-invasive sampling.

Photodynamic Vaccination of BALB/c Mice for Prophylaxis of Cutaneous Leishmaniasis Caused by Leishmania amazonensis

Background: Photosensitizers (PS), like porphyrins and phthalocyanines (PC) are excitable by light to generate cytotoxic singlet oxygen and other reactive oxygen species in the presence of atmospheric O₂. Photodynamic inactivation of Leishmania by this means renders them non-viable, but preserves their effective use as vaccines. Leishmania can be photo-inactivated after PS-sensitization by loading via their endocytic uptake of PC or endogenous induction of transgenic mutants with delta-aminolevulinate (ALA) to accumulate cytosolic uroporphyrin I (URO). Here, PS-sensitization and photo-inactivation of Leishmaniaamazonensis was further examined in vitro and in vivo for vaccination against cutaneous leishmaniasis (CL).

Methods and Results:Leishmania amazonensis promastigotes were photodynamically inactivated in vitro by PC-loading followed by exposure to red light (1–2 J/cm²) or ALA-induction of uroporphyrinogenic transfectants to accumulate cytosolic URO followed by longwave UV exposure. When applied individually, both strategies of photodynamic inactivation were found to significantly, albeit incompletely abolish the MTT reduction activities of the promastigotes, their uptake by mouse bone marrow-derived macrophages in vitro and their infectivity to mouse ear dermis in vivo. Inactivation of Leishmania to completion by using a combination of both strategies was thus used for the sake of safety as whole-cell vaccines for immunization of BALB/c mice. Different cutaneous sites were assessed for the efficacy of such photodynamic vaccination in vivo. Each site was inoculated first with in vitro doubly PS-sensitized promastigotes and then spot-illuminated with white light (50 J/cm²) for their photo-inactivation in situ. Only in ear dermis parasites were photo-inactivated beyond detection. Mice were thus immunized once in the ear and challenged 3 weeks later at the tail base with virulent L. amazonensis. Prophylaxis was noted in mice photodynamically vaccinated with doubly photo-inactivated parasites, as indicated by a significant delay in the onset of lesion development and a substantial decrease in the parasite loads.

Conclusion: Leishmania doubly PS-sensitized and in situ photo-inactivated as described proved to be safe and effective when used for one-time immunization of ear dermis, as indicated by its significant protection of the inherently very susceptible BALB/c mice against CL.

Meta-Analysis of Aedes aegypti Expression Datasets: Comparing Virus Infection and Blood-Fed Transcriptomes to Identify Markers of Virus Presence

The mosquito Aedes aegypti (L.) is vector of several arboviruses including dengue, yellow fever, chikungunya, and more recently zika. Previous transcriptomic studies have been performed to elucidate altered pathways in response to viral infection. However, the intrinsic coupling between alimentation and infection were unappreciated in these studies. Feeding is required for the initial mosquito contact with the virus and these events are highly dependent. Addressing this relationship, we reinterrogated datasets of virus-infected mosquitoes with two different diet schemes (fed and unfed mosquitoes), evaluating the metabolic cross-talk during both processes. We constructed coexpression networks with the differentially expressed genes of these comparison: virus-infected versus blood-fed mosquitoes and virus-infected versus unfed mosquitoes. Our analysis identified one module with 110 genes that correlated with infection status (representing ~0.7% of the A. aegypti genome). Furthermore, we performed a machine-learning approach and summarized the infection status using only four genes (AAEL012128, AAEL014210, AAEL002477, and AAEL005350). While three of the four genes were annotated as hypothetical proteins, AAEL012128 gene is a membrane amino acid transporter correlated with viral envelope binding. This gene alone is able to discriminate all infected samples and thus should have a key role to discriminate viral infection in the A. aegypti mosquito. Moreover, validation using external datasets found this gene as differentially expressed in four transcriptomic experiments. Therefore, these genes may serve as a proxy of viral infection in the mosquito and the others 106 identified genes provides a framework to future studies.

Heme Drives Oxidative Stress-Associated Cell Death in Human Neutrophils Infected with Leishmania infantum

Free heme is an inflammatory molecule capable of inducing migration and activation of neutrophils. Here, we examine the heme-driven oxidative stress-associated cell death mechanisms in human neutrophils infected with Leishmania infantum, an etiologic agent of visceral leishmaniasis (VL). We first performed exploratory analyses in a population of well characterized treatment-naïve VL patients as well as uninfected controls, who were part of previously reported studies. We noted a positive correlation between serum concentrations of heme with heme oxygenase-1 (HO-1) and lactate deydrogenase, as well as, a negative correlation between heme values and peripheral blood neutrophils counts. Moreover, in vitro infection with L. infantum in the presence of heme enhanced parasite burden in neutrophils, while increasing the production of reactive oxygen species and release of neutrophilic enzymes. Additional experiments demonstrated that treatment of infected neutrophils with ferrous iron (Fe⁺²), a key component of the heme molecule, resulted in increased parasite survival without affecting neutrophil activation status. Furthermore, stimulation of infected neutrophils with heme triggered substantial increases in HO-1 mRNA expression as well as in superoxide dismutase-1 enzymatic activity. Heme, but not Fe⁺², induced oxidative stress-associated cell death. These findings indicate that heme promotes intracellular L. infantum survival via activation of neutrophil function and oxidative stress. This study opens new perspectives for the understanding of immunopathogenic mechanisms involving neutrophils in VL.

Insights into the sand fly saliva: Blood-feeding and immune interactions between sand flies, hosts, and Leishmania

Background

Leishmaniases are parasitic diseases present worldwide that are transmitted to the vertebrate host by the bite of an infected sand fly during a blood feeding. Phlebotomine sand flies inoculate into the mammalian host Leishmania parasites embedded in promastigote secretory gel (PSG) with saliva, which is composed of a diverse group of molecules with pharmacological and immunomodulatory properties.

Methods and findings

In this review, we focus on 3 main aspects of sand fly salivary molecules: (1) structure and composition of salivary glands, including the properties of salivary molecules related to hemostasis and blood feeding, (2) immunomodulatory properties of salivary molecules and the diverse impacts of these molecules on leishmaniasis, ranging from disease exacerbation to vaccine development, and (3) use of salivary molecules for field applications, including monitoring host exposure to sand flies and the risk of Leishmania transmission. Studies showed interesting differences between salivary proteins of Phlebotomus and Lutzomyia species, however, no data were ever published on salivary proteins of Sergentomyia species.

Conclusions

In the last 15 years, numerous studies have characterized sand fly salivary proteins and, in parallel, have addressed the impact of such molecules on the biology of the host–sand fly–parasite interaction. The results obtained shall pave the way for the development of field-application tools that could contribute to the management of leishmaniasis in endemic areas.

Seroconversion to Lutzomyia intermedia LinB-13 as a biomarker for developing cutaneous leishmaniasis

Sand flies inject saliva while feeding in the vertebrate host and anti-saliva antibodies can be used as biomarkers of exposure to Leishmania vectors. We expressed recombinant salivary proteins from Lutzomyia intermedia, a vector of Leishmania braziliensis, and evaluated the seroreactivity in exposed individuals in search for exposure markers. We found a strong correlation among positive serology to recombinant proteins LinB-13, 26, 15, 21 and to salivary proteins: rLinB-13 was the top performing molecule; IgG4 was the most predominant antibody subclass and antibodies to rLinB-13 did not cross react with Lu. longipalpis salivary proteins. By evaluating a cohort of contacts of CL patients, we confirmed that rLinB-13, an antigen 5-related protein, is a marker of exposure to Lu. intermedia with high degree of accuracy. In a 5-year follow up, we determined that individuals who developed CL presented higher anti-rLinB13 IgG responses, before the appearance of clinical symptoms. They also presented a lower frequency of cellular responses to the parasite (DTH). Our results show that seroconversion to a salivary molecule, rLinB-13, is a marker of risk for CL development caused by Leishmania braziliensis. This highlight the possibility of developing tools based on vector molecules to manage the disease in endemic areas.

DETC-based bacterial cellulose bio-curatives for topical treatment of cutaneous leishmaniasis

The treatment of leishmaniasis still relies on drugs with potentially serious adverse effects. Herein, we tested a topical formulation of bacterial cellulose (BC) membranes containing Diethyldithiocarbamate (DETC), a superoxide dismutase 1 inhibitor. Leishmania-infected macrophages exposed to BC-DETC resulted in parasite killing, without pronounced toxic effects to host cells. This outcome was associated with lower SOD1 activity and higher production of superoxide and cytokine mediators. Topical application of BC-DETC significantly decreased lesion size, parasite load and the inflammatory response at the infection site, as well as the production of both IFN-γ and TNF. Combination of topical BC-DETC plus intraperitoneal Sb^v also significantly reduced disease development and parasite load. The leishmanicidal effect of BC-DETC was extended to human macrophages infected with L. braziliensis, highlighting the feasibility of BC-DETC as a topical formulation for chemotherapy of cutaneous leishmaniasis caused by L. braziliensis.

Gene Expression Profile of High IFN-γ Producers Stimulated with Leishmania braziliensis Identifies Genes Associated with Cutaneous Leishmaniasis

Background

The initial response to Leishmania parasites is essential in determining disease development or resistance. In vitro, a divergent response to Leishmania, characterized by high or low IFN-γ production has been described as a potential tool to predict both vaccine response and disease susceptibility in vivo.

Methods and findings

We identified uninfected and healthy individuals that were shown to be either high- or low IFN-γ producers (HPs and LPs, respectively) following stimulation of peripheral blood cells with Leishmania braziliensis. Following stimulation, RNA was processed for gene expression analysis using immune gene arrays. Both HPs and LPs were shown to upregulate the expression of CXCL10, IFI27, IL6 and LTA. Genes expressed in HPs only (CCL7, IL8, IFI44L and IL1B) were associated with pathways related to IL17 and TREM 1 signaling. In LPs, uniquely expressed genes (for example IL9, IFI44, IFIT1 and IL2RA) were associated with pathways related to pattern recognition receptors and interferon signaling. We then investigated whether the unique gene expression profiles described here could be recapitulated in vivo, in individuals with active Cutaneous Leishmaniasis or with subclinical infection. Indeed, using a set of six genes (TLR2, JAK2, IFI27, IFIT1, IRF1 and IL6) modulated in HPs and LPs, we could successfully discriminate these two clinical groups. Finally, we demonstrate that these six genes are significantly overexpressed in CL lesions.

Conclusion

Upon interrogation of the peripheral response of naive individuals with diverging IFN-γ production to L. braziliensis, we identified differences in the innate response to the parasite that are recapitulated in vivo and that discriminate CL patients from individuals presenting a subclinical infection.

Control and development of Cutaneous Leishmaniasis (CL) are dependent on the host immunological response. One of the key molecules in determining elimination of Leishmania parasites from the infected host cell is the cytokine interferon gamma (IFN-γ). The aim of this study was to investigate which immune response genes are associated with the production of IFN-γ in the context of Leishmania infection. We identified individuals that are high- or low IFN-γ producers upon stimulation of their peripheral blood cells with Leishmania parasites. We then determined the immune gene expression profile of these individuals and we identified a set of genes that are differentially expressed comparing high- and low IFN-γ producers. The expression of these genes was also evaluated in patients with CL and in individuals with a subclinical Leishmania infection (SC). In this setting, the overall pattern of expression of this particular gene combination discriminated the CL patients x from SC individuals. Understanding the initial response to Leishmania may lead to the identification of markers that are associated with development of CL.

The microbiological signature of human cutaneous leishmaniasis lesions exhibits restricted bacterial diversity compared to healthy skin

Localised cutaneous leishmaniasis (LCL) is the most common form of cutaneous leishmaniasis characterised by single or multiple painless chronic ulcers, which commonly presents with secondary bacterial infection. Previous culture-based studies have found staphylococci, streptococci, and opportunistic pathogenic bacteria in LCL lesions, but there have been no comparisons to normal skin. In addition, this approach has strong bias for determining bacterial composition. The present study tested the hypothesis that bacterial communities in LCL lesions differ from those found on healthy skin (HS). Using a high throughput amplicon sequencing approach, which allows for better populational evaluation due to greater depth coverage and the Quantitative Insights Into Microbial Ecology pipeline, we compared the microbiological signature of LCL lesions with that of contralateral HS from the same individuals.Streptococcus, Staphylococcus,Fusobacterium and other strict or facultative anaerobic bacteria composed the LCL microbiome. Aerobic and facultative anaerobic bacteria found in HS, including environmental bacteria, were significantly decreased in LCL lesions (p < 0.01). This paper presents the first comprehensive microbiome identification from LCL lesions with next generation sequence methodology and shows a marked reduction of bacterial diversity in the lesions.

Respiratory syncytial virus a and b display different temporal patterns in a 4-year prospective cross-sectional study among children with acute respiratory infection in a tropical city

Respiratory syncytial virus (RSV) is one of the most common etiological agents of childhood respiratory infections globally. Information on seasonality of different antigenic groups is scarce. We aimed to describe the frequency, seasonality, and age of children infected by RSV antigenic groups A (RSVA) and B (RSVB) among children with ARI in a 4-year period.Children (6-23 months old) with respiratory infection for ≤7 days were enrolled in a prospective cross-sectional study, from September, 2009 to October, 2013, in Salvador, in a tropical region of Brazil. Upon recruitment, demographic, clinical data, and nasopharyngeal aspirates (NPA) were collected. A multiplex quantitative real-time polymerase chain reaction (RT-PCR) with a group-specific primer and probeset for RSVA and RSVB was used. Seasonal distribution of infection by RSV different antigenic groups was evaluated by Prais-Wisten regression.Of 560 cases, the mean age was 11.4 ± 4.5 months and there were 287 (51.3%) girls. Overall, RSV was detected in 139 (24.8%; 95% CI: 21.4%-28.5%) cases, RSVA in 74 (13.2%; 95% CI: 10.6%-16.2%) cases, and RSVB in 67 (12.0%; 95% CI: 9.5%-14.9%) cases. Two (0.4%; 95% CI: 0.06%-1.2%) cases had coinfection. RSVA frequency was 9.6%, 18.4%, 21.6%, and 3.1% in 2010, 2011, 2012, and 2013, respectively. RSVB frequency was 19.2%, 0.7%, 1.4%, and 35.4% in the same years. RSVA was more frequently found from August to January than February to July (18.2% vs. 6.4%, P < 0.001). RSVB was more frequently found (P < 0.001) between March and June (36.0%) than July to October (1.0%) or November to February (1.6%). RSVB infection showed seasonal distribution and positive association with humidity (P = 0.02) whereas RSVA did not. RSVA was more common among children ≥1-year-old (17.8% vs. 1.8%; P = 0.02), as opposed to RSVB (11.5% vs. 12.2%; P = 0.8).One quarter of patients had RSV infection. RSVA compromised more frequently children aged ≥1 year. RSVA predominated in 2011 and 2012 whereas RSVB predominated in 2010 and 2013. In regard to months, RSVA was more frequent from August to January whereas RSVB was more often detected between March and June. Markedly different monthly as well as yearly patterns for RSVA and RSVB reveal independent RSV antigenic groups' epidemics.

Pathogen transcriptional profile in nasopharyngeal aspirates of children with acute respiratory tract infection

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nCounter enables detection of pathogen transcripts in NPA with low RNA input.

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nCounter detects, in a single reaction, the presence of multiple pathogens in NPA.

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nCounter displayed a good agreement with Real-Time PCR for RSV.

Background

Acute respiratory tract infections (ARI) present a significant morbidity and pose a global health burden. Patients are frequently treated with antibiotics although ARI are most commonly caused by virus, strengthening the need for improved diagnostic methods.

Objectives

Detect viral and bacterial RNA in nasopharyngeal aspirates (NPA) from children aged 6–23 months with ARI using nCounter.

Study design

A custom-designed nCounter probeset containing viral and bacterial targets was tested in NPA of ARI patients.

Results

Initially, spiked control viral RNAs were detectable in ≥6.25 ng input RNA, indicating absence of inhibitors in NPA. nCounter applied to a larger NPA sample (n = 61) enabled the multiplex detection of different pathogens: RNA viruses Parainfluenza virus (PIV 1–3) and RSV A-B in 21%, Human metapneumovirus (hMPV) in 5%, Bocavirus (BoV), CoV, Influenza virus (IV) A in 3% and, Rhinovirus (RV) in 2% of samples, respectively. RSV A-B was confirmed by Real Time PCR (86.2–96.9% agreement). DNA virus (AV) was detected at RNA level, reflecting viral replication, in 10% of samples. Bacterial transcripts from Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Mycoplasma pneumoniae and Chlamydophila pneumoniae were detected in 77, 69, 26, 8, 3 and 2% of samples, respectively.

Conclusion

nCounter is robust and sensitive for the simultaneous detection of viral (both RNA and DNA) and bacterial transcripts in NPA with low RNA input (<10 ng). This medium-throughput technique will increase our understanding of ARI pathogenesis and may provide an evidence-based approach for the targeted and rational use of antibiotics in pediatric ARI.

Prediction of CD8+ Epitopes in Leishmania braziliensis Proteins Using EPIBOT: In Silico Search and In Vivo Validation

Background

Leishmaniasis is caused by intracellular Leishmania parasites that induce a T-cell mediated response associated with recognition of CD4⁺ and CD8⁺ T cell Line 1Lineepitopes. Identification of CD8⁺ antigenic determinants is crucial for vaccine and therapy development. Herein, we developed an open-source software dedicated to search and compile data obtained from currently available on line prediction algorithms.

Methodology/Principal Findings

We developed a two-phase algorithm and implemented in an open source software called EPIBOT, that consolidates the results obtained with single prediction algorithms, generating a final output in which epitopes are ranked. EPIBOT was initially trained using a set of 831 known epitopes from 397 proteins from IEDB. We then screened 63 Leishmania braziliensis vaccine candidates with the EPIBOT trained tool to search for CD8⁺ T cell epitopes. A proof-of-concept experiment was conducted with the top eight CD8⁺ epitopes, elected by EPIBOT. To do this, the elected peptides were synthesized and validated for their in vivo cytotoxicity. Among the tested epitopes, three were able to induce lysis of pulsed-target cells.

Conclusion

Our results show that EPIBOT can successfully search across existing prediction tools, generating a compiled list of candidate CD8⁺ epitopes. This software is fast and a simple search engine that can be customized to search over different MHC alleles or HLA haplotypes.

Exposure to Leishmania braziliensis triggers neutrophil activation and apoptosis

Background

Neutrophils are the first line of defense against invading pathogens and are rapidly recruited to the sites of Leishmania inoculation. During Leishmania braziliensis infection, depletion of inflammatory cells significantly increases the parasite load whereas co-inoculation of neutrophils plus L. braziliensis had an opposite effect. Moreover, the co-culture of infected macrophages and neutrophils also induced parasite killing leading us to ask how neutrophils alone respond to an L. braziliensis exposure. Herein we focused on understanding the interaction between neutrophils and L. braziliensis, exploring cell activation and apoptotic fate.

Methods and Findings

Inoculation of serum-opsonized L. braziliensis promastigotes in mice induced neutrophil accumulation in vivo, peaking at 24 h. In vitro, exposure of thyoglycollate-elicited inflammatory or bone marrow neutrophils to L. braziliensis modulated the expression of surface molecules such as CD18 and CD62L, and induced the oxidative burst. Using mCherry-expressing L. braziliensis, we determined that such effects were mainly observed in infected and not in bystander cells. Neutrophil activation following contact with L. braziliensis was also confirmed by the release of TNF-α and neutrophil elastase. Lastly, neutrophils infected with L. braziliensis but not with L. major displayed markers of early apoptosis.

Conclusions

We show that L. braziliensis induces neutrophil recruitment in vivo and that neutrophils exposed to the parasite in vitro respond through activation and release of inflammatory mediators. This outcome may impact on parasite elimination, particularly at the early stages of infection.

Leishmania is the parasite responsible for the disease leishmaniasis, present in all continents. Leishmania parasites are spread through infected sand-flies and, during transmission into the vertebrate host, neutrophils are among the first cells to arrive at the infection site. Since neutrophils are key players at the frontline of defense against invading organisms, we investigated their response to Leishmania braziliensis. Importantly, L. braziliensis causes both Cutaneous and Mucocutaneous Leishmaniasis, two clinical manifestations characterized by their chronic development and by the presence of skin lesions with tissue destruction. Upon inoculation of mice with L. braziliensis, neutrophils rapidly arrive at the site of infection. We then observed that culture of mouse neutrophils with L. braziliensis induced the expression of adhesion molecules, production of Reactive Oxygen Species and secretion of elastase and TNF-α, two important inflammatory mediators. Also, infection with L. braziliensis induced neutrophil apoptosis, a cell death mechanism key for regulating inflammation. Our results show that neutrophils respond to presence of the L. braziliensis parasites by becoming activated and undergoing apoptosis. We suggest that this outcome modifies the local environment at the site of parasite inoculation and thus contributes with parasite killing in the infected host.

Interleukin 10-Dominant Immune Response and Increased Risk of Cutaneous Leishmaniasis After Natural Exposure to Lutzomyia intermedia Sand Flies

BACKGROUND

Leishmaniasis is caused by parasites transmitted to the vertebrate host by infected sand flies. During transmission, the vertebrate host is also inoculated with sand fly saliva, which exerts powerful immunomodulatory effects on the host's immune response.

METHODS

We conducted a prospective cohort analysis to characterize the human immune response to Lutzomyia intermedia saliva in 264 individuals, from an area for cutaneous leishmaniasis (CL) caused by Leishmania braziliensis.

RESULTS

Antibodies were found in 150 individuals (56.8%); immunoglobulin G1 and G4 were the predominant subclasses. Recall responses to salivary gland sonicate showed elevated production of interleukin 10 (IL-10), interleukin 13, interferon γ, CXCL9, and CCL2 compared with controls. CD4(+)CD25(+) T cells, including Foxp3(+) cells, were the main source of IL-10. L. braziliensis replication was increased (P < .05) in macrophages cocultured with saliva-stimulated lymphocytes from exposed individuals and addition of anti-IL-10 reverted this effect. Positive correlation between antibody response to saliva and cellular response to Leishmania was not found. Importantly, individuals seropositive to saliva are 2.1 times more likely to develop CL (relative risk, 2.1; 95% confidence interval, 1.07-4.2; P < .05).

CONCLUSIONS

Exposure to L. intermedia sand flies skews the human immune response, facilitating L. braziliensis survival in vitro, and increases the risk of developing CL.

Chemotherapeutic potential of 17-AAG against cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis

BACKGROUND

Leishmaniasis remains a worldwide public health problem. The limited therapeutic options, drug toxicity and reports of resistance, reinforce the need for the development of new treatment options. Previously, we showed that 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), a Heat Shock Protein 90 (HSP90)-specific inhibitor, reduces L. (L.) amazonensis infection in vitro. Herein, we expand the current knowledge on the leishmanicidal activity of 17-AAG against cutaneous leishmaniasis, employing an experimental model of infection with L. (V.) braziliensis.

METHODOLOGY/PRINCIPAL FINDINGS

Exposure of axenic L. (V.) braziliensis promastigotes to 17-AAG resulted in direct dose-dependent parasite killing. These results were extended to L. (V.) braziliensis-infected macrophages, an effect that was dissociated from the production of nitric oxide (NO), superoxide (O(-2)) or inflammatory mediators such as TNF-α, IL-6 and MCP-1. The leishmanicidal effect was then demonstrated in vivo, employing BALB/c mice infected with L. braziliensis. In this model, 17-AAG treatment resulted in smaller skin lesions and parasite counts were also significantly reduced. Lastly, 17-AAG showed a similar effect to amphotericin B regarding the ability to reduce parasite viability.

CONCLUSION/SIGNIFICANCE

17-AAG effectively inhibited the growth of L. braziliensis, both in vitro and in vivo. Given the chronicity of L. (V.) braziliensis infection and its association with mucocutaneous leishmaniasis, 17-AAG can be envisaged as a new chemotherapeutic alternative for cutaneous Leishmaniasis.

Serological survey of Leishmania infection in blood donors in Salvador, Northeastern Brazil

BACKGROUND

Visceral Leishmaniasis is endemic to Brazil, where it is caused by Leishmania infantum (syn. Leishmania chagasi). Following parasite inoculation, individuals may experience asymptomatic infection, raising the possibility of parasite transmission through the transfusion of contaminated blood products. In the present work, we evaluated the prevalence of asymptomatic Leishmania infection among blood donors in Salvador, northeastern Brazil.

METHODS

Peripheral blood was collected from 700 blood donors attending the Blood Bank of Bahia (HEMOBA/SESAB), from January to September 2010. We evaluated anti-Leishmania serology by ELISA, employing Soluble Leishmania Antigen (sensitivity 90% and specificity 95%). The presence of parasite DNA was determined by qPCR, targeting a single copy gene (G6PD), and by end-point PCR, targeting multiple targets, namely a segment located in the Leishmania rRNA locus (ITS) and the conserved region of kinetoplastid DNA (kDNA) minicircles.

RESULTS

The blood-donor population was comprised of 74.5% of males with a mean age of 34 years. Anti-Leishmania serology by ELISA was positive in 5.4% (38/700) individuals. One individual was also positive for Chagas' disease and another tested positive for Syphilis. Employing qPCR, parasite DNA was not found in any of 38 seropositive samples. However, by ITS PCR, 8/38 (21%) samples were positive and this positivity increased to 26/38 (68%) when we targeted kDNA amplification. Agreement between both techniques (ITS and kDNA PCR) was fair (kappa = 0.219).

CONCLUSIONS

These results indicate that asymptomatic infection is present among the blood donor population of Salvador, a finding that warrants a broader discussion regarding the need to implement specific screening strategies.

Vaccines in leishmaniasis: advances in the last five years

The leishmaniases are a group of diseases caused by protozoa of the genus Leishmania which affects millions of people worldwide. The leishmaniases are transmitted to the vertebrate hosts by phlebotomine sand flies. In this review, we focus on clinical aspects of the leishmaniases and on the immune response against the parasite, both in animal models and humans. These aspects are of key importance to understand the many attempts to obtain an effective vaccine against Leishmania. We considered the last advances in new generation vaccines, including the use of new adjuvants to improve the protective response against the parasite. Finally, the possibility to use components of the sand fly saliva as part of vaccines against the infection by Leishmania is mentioned.

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.

Sand-fly saliva-leishmania-man: the trigger trio

Leishmaniases are worldwide diseases transmitted to the vertebrate host by the bite of an infected sand-fly. Sand-fly biting and parasite inoculation are accompanied by the injection of salivary molecules, whose immunomodulatory properties are actively being studied. This mini review focuses on how the interactions between sand-fly saliva and the immune system may shape the outcome of infection, given its immunomodulatory properties, in experimental models and in the endemic area. Additionally, we approach the recent contributions regarding the identification of individual salivary components and how these are currently being considered as additional components of a vaccine against leishmaniasis.

Cytotoxic T cells mediate pathology and metastasis in cutaneous leishmaniasis

Disease progression in response to infection can be strongly influenced by both pathogen burden and infection-induced immunopathology. While current therapeutics focus on augmenting protective immune responses, identifying therapeutics that reduce infection-induced immunopathology are clearly warranted. Despite the apparent protective role for murine CD8⁺ T cells following infection with the intracellular parasite Leishmania, CD8⁺ T cells have been paradoxically linked to immunopathological responses in human cutaneous leishmaniasis. Transcriptome analysis of lesions from Leishmania braziliensis patients revealed that genes associated with the cytolytic pathway are highly expressed and CD8⁺ T cells from lesions exhibited a cytolytic phenotype. To determine if CD8⁺ T cells play a causal role in disease, we turned to a murine model. These studies revealed that disease progression and metastasis in L. braziliensis infected mice was independent of parasite burden and was instead directly associated with the presence of CD8⁺ T cells. In mice with severe pathology, we visualized CD8⁺ T cell degranulation and lysis of L. braziliensis infected cells. Finally, in contrast to wild-type CD8⁺ T cells, perforin-deficient cells failed to induce disease. Thus, we show for the first time that cytolytic CD8⁺ T cells mediate immunopathology and drive the development of metastatic lesions in cutaneous leishmaniasis.

Towards a more precise serological diagnosis of human tegumentary leishmaniasis using Leishmania recombinant proteins

Background

Exposure to Leishmania induces a humoral immune response that can be used as a marker of parasite exposure.

Methodology/Principal Findings

Herein, ELISA was used to screen sera from patients with Tegumentary Leishmaniasis (TL) against different L. infantum-chagasi-derived recombinant proteins (rHSP70, rH2A, rH2B, rH3, rH4 and rKMP11). Among the recombinant proteins, rHSP70 and rH2A showed the best reactivity against human sera obtained from endemic areas of TL. Receiver-Operator Characteristics (ROC) curve analysis was used to identify the effectiveness of these proteins for serodiagnosis of TL. ROC curves confirmed the superior performance of rHSP70 and rH2A, in comparison to the other tested recombinant proteins. Additionally, we evaluated the specificity of the response to rHSP70 and rH2A by testing sera obtained from patients with Chagas' disease, Tuberculosis, Leprosy or Systemic Lupus Erythematosus. In this case, rHSP70 displayed an increased ability to discriminate diseases, in comparison to SLA.

Conclusion

Our results raise possibility of using rHSP70 for the serodiagnosis of TL

Functional transcriptomics of wild-caught Lutzomyia intermedia salivary glands: identification of a protective salivary protein against Leishmania braziliensis infection

Background

Leishmania parasites are transmitted in the presence of sand fly saliva. Together with the parasite, the sand fly injects salivary components that change the environment at the feeding site. Mice immunized with Phlebotomus papatasi salivary gland (SG) homogenate are protected against Leishmania major infection, while immunity to Lutzomyia intermedia SG homogenate exacerbated experimental Leishmania braziliensis infection. In humans, antibodies to Lu. intermedia saliva are associated with risk of acquiring L. braziliensis infection. Despite these important findings, there is no information regarding the repertoire of Lu. intermedia salivary proteins.

Methods and Findings

A cDNA library from the Salivary Glands (SGs) of wild-caught Lu. intermedia was constructed, sequenced, and complemented by a proteomic approach based on 1D SDS PAGE and mass/mass spectrometry to validate the transcripts present in this cDNA library. We identified the most abundant transcripts and proteins reported in other sand fly species as well as novel proteins such as neurotoxin-like proteins, peptides with ML domain, and three small peptides found so far only in this sand fly species. DNA plasmids coding for ten selected transcripts were constructed and used to immunize BALB/c mice to study their immunogenicity. Plasmid Linb-11—coding for a 4.5-kDa protein—induced a cellular immune response and conferred protection against L. braziliensis infection. This protection correlated with a decreased parasite load and an increased frequency of IFN-γ-producing cells.

Conclusions

We identified the most abundant and novel proteins present in the SGs of Lu. intermedia, a vector of cutaneous leishmaniasis in the Americas. We also show for the first time that immunity to a single salivary protein from Lu. intermedia can protect against cutaneous leishmaniasis caused by L. braziliensis.

Sand fly saliva contains potent, biologically active proteins that allow the insect to stop host responses to acquire a blood meal. After repeated exposures, a number of these salivary proteins also induce a response in the host such as antibody production and/or cellular-mediated immunity. In animal models, these immune responses affect Leishmania infection. On one hand, immunity to Phlebotomus papatasi saliva protected animals against cutaneous leishmaniasis, while on the other hand, immunity to Lutzomyia intermedia saliva did not protect but exacerbated this disease. These differences are probably due to the types of proteins present in the saliva of these different sand fly species. The present work focused on isolation and identification of the secreted proteins present in the salivary glands of Lu. intermedia, an important vector of L. braziliensis, the agent of mucocutaneous leishmaniasis. Saliva from this sand fly contains a number of proteins not present in P. papatasi saliva and, with some exceptions; proteins that are homologous between the two species are very divergent. Furthermore, we identified one protein that, after vaccination, induced a cellular immune response able to protect mice against Leishmania braziliensis infection. This is the first evidence that a single salivary protein from Lu. intermedia can protect mice against this cutaneous leishmaniasis.

PLGA nanoparticles loaded with KMP-11 stimulate innate immunity and induce the killing of Leishmania

We recently demonstrated that immunization with polyester poly(lactide-co-glycolide acid) (PLGA) nanoparticles loaded with the 11-kDa Leishmania vaccine candidate kinetoplastid membrane protein 11 (KMP-11) significantly reduced parasite load in vivo. Presently, we explored the ability of the recombinant PLGA nanoparticles to stimulate innate responses in macrophages and the outcome of infection with Leishmania braziliensis in vitro. Incubation of macrophages with KMP-11-loaded PLGA nanoparticles significantly decreased parasite load. In parallel, we observed the augmented production of nitric oxide, superoxide, TNF-α and IL-6. An increased release of CCL2/MCP-1 and CXCL1/KC was also observed, resulting in macrophage and neutrophil recruitment in vitro. Lastly, the incubation of macrophages with KMP-11-loaded PLGA nanoparticles triggered the activation of caspase-1 and the secretion of IL-1β and IL-18, suggesting inflammasome participation. Inhibition of caspase-1 significantly increased the parasite load. We conclude that KMP-11-loaded PLGA nanoparticles promote the killing of intracellular Leishmania parasites through the induction of potent innate responses.

FROM THE CLINICAL EDITOR

In this novel study, KMP-11-loaded PLGA nanoparticles are demonstrated to promote the killing of intracellular Leishmania parasites through enhanced innate immune responses by multiple mechanisms. Future clinical applications would have a major effect on our efforts to address parasitic infections.

Experimental infection of dogs with Leishmania and saliva as a model to study Canine Visceral Leishmaniasis

Background

Canine Visceral Leishmaniasis (CVL) is a zoonotic disease caused by Leishmania infantum, transmitted by the bite of Lutzomyia longipalpis sand flies. Dogs are the main domestic reservoir of the parasite. The establishment of an experimental model that partially reproduces natural infection in dogs is very important to test vaccine candidates, mainly regarding those that use salivary proteins from the vector and new therapeutical approaches.

Methodology/Principal Findings

In this report, we describe an experimental infection in dogs, using intradermal injection of Leishmania infantum plus salivary gland homogenate (SGH) of Lutzomyia longipalpis. Thirty-five dogs were infected with 1×10⁷ parasites combined with five pairs of Lutzomyia longipalpis salivary glands and followed for 450 days after infection and clinical, immunological and parasitological parameters were evaluated. Two hundred and ten days after infection we observed that 31,4% of dogs did not display detectable levels of anti-Leishmania antibodies but all presented different numbers of parasites in the lymph nodes. Animals with a positive xenodiagnosis had at least 3,35×10⁵ parasites in their lymph nodes. An increase of IFN-γ and IL-10 levels was detected during infection. Twenty two percent of dogs developed symptoms of CVL during infection.

Conclusion

The infection model described here shows some degree of similarity when compared with naturally infected dogs opening new perspectives for the study of CVL using an experimental model that employs the combination of parasites and sand fly saliva both present during natural transmission.

CD8(+) granzyme B(+)-mediated tissue injury vs. CD4(+)IFNγ(+)-mediated parasite killing in human cutaneous leishmaniasis

A protective or deleterious role of CD8⁺T cells in human cutaneous leishmaniasis (CL) has been debated. The present report explores the participation of CD8⁺T cells in disease pathogenesis as well as in parasite killing. CD8⁺T cells accumulated in CL lesions as suggested by a higher frequency of CD8⁺CD45RO⁺T cells and CD8⁺CLA⁺T cells compared with peripheral blood mononuclear cells. Upon Leishmania braziliensis restimulation, most of the CD8⁺T cells from the lesion expressed cytolytic markers, CD107a and granzyme B. Granzyme B expression in CL lesions positively correlated with lesion size and percentage of TUNEL-positive cells. We also observed a significantly higher percentage of TUNEL-positive cells and granzyme B expression in the biopsies of patients showing a more intense necrotic process. Furthermore, coculture of infected macrophages and CD8⁺T lymphocytes resulted in the release of granzyme B, and the use of granzyme B inhibitor, as well as z-VAD, Fas:Fc, or anti-IFN-γ, had no effect upon parasite killing. However, coculture of infected macrophages with CD4⁺T cells strongly increased parasite killing, which was completely reversed by anti-IFN-γ. Our results reveal a dichotomy in human CL: CD8⁺ granzyme B⁺T cells mediate tissue injury, whereas CD4⁺IFN-γ⁺T cells mediate parasite killing.

Evaluation of immune responses and analysis of the effect of vaccination of the Leishmania major recombinant ribosomal proteins L3 or L5 in two different murine models of cutaneous leishmaniasis

Four new antigenic proteins located in Leishmania ribosomes have been characterized: S4, S6, L3 and L5. Recombinant versions of the four ribosomal proteins from Leishmania major were recognized by sera from human and canine patients suffering different clinical forms of leishmaniasis. The prophylactic properties of these proteins were first studied in the experimental model of cutaneous leishmaniasis caused by L. major inoculation into BALB/c mice. The administration of two of them, LmL3 or LmL5 combined with CpG-oligodeoxynucleotides (CpG-ODN) was able to protect BALB/c mice against L. major infection. Vaccinated mice showed smaller lesions and parasite burden compared to mice inoculated with vaccine diluent or vaccine adjuvant. Protection was correlated with an antigen-specific increased production of IFN-γ paralleled by a decrease of the antigen-specific IL-10 mediated response in protected mice relative to non-protected controls. Further, it was demonstrated that BALB/c mice vaccinated with recombinant LmL3 or LmL5 plus CpG-ODN were also protected against the development of cutaneous lesions following inoculation of L. braziliensis. Together, data presented here indicate that LmL3 or LmL5 ribosomal proteins combined with Th1 inducing adjuvants, may be relevant components of a vaccine against cutaneous leishmaniasis caused by distinct species.

Seroconversion of sentinel chickens as a biomarker for monitoring exposure to visceral leishmaniasis

Leishmania infantum chagasi causes visceral leishmaniasis (VL); it is transmitted by the sand fly Lutzomyia longipalpis that injects saliva and parasites into the host's skin during a blood meal. Chickens represent an important blood source for sand flies and their presence in the endemic area is often cited as a risk factor for VL transmission. However, the role of chickens in VL epidemiology has not been well defined. Here, we tested if chicken antibodies against Lu. longipalpis salivary gland sonicate (SGS) could be used as markers of exposure to sand fly bites. All naturally exposed chickens in a VL endemic area in Brazil developed anti-SGS IgY antibodies. Interestingly, Lu. longipalpis recombinant salivary proteins rLJM17 and rLJM11 were also able to detect anti-SGS IgY antibodies. Taken together, these results show that chickens can be used to monitor the presence of Lu. longipalpis in the peri-domiciliary area in VL endemic regions, when used as sentinel animals.

The presence of Tregs does not preclude immunity to reinfection with Leishmania braziliensis

Leishmania spp. cause a broad spectrum of diseases collectively known as leishmaniasis. Leishmania braziliensis is the main etiological agent of American cutaneous leishmaniasis and mucocutaneous leishmaniasis. During experimental infection with L. braziliensis, BALB/c mice develop an adaptive immune response that is associated with lesion healing and, in parallel, parasite persistence within draining lymph nodes (dLNs). In the Leishmania major model of cutaneous leishmaniasis, regulatory T cells (Tregs) play an important role in immune regulation, preventing pathological immune responses but at the same time precluding sterile cure. In this study we investigated the role of Tregs during experimental infection with L. braziliensis. CD4(+)CD25(+) T cells were detected throughout the duration of clinical disease both at the ear and in dLNs of infected mice. These cells expressed Treg markers such as glucocorticoid-induced TNF-receptor-related protein (GITR), the α chain of the αεβ7 integrin (CD103), and the forkhead/winged helix transcription factor, Foxp3, and were able to suppress the proliferation of CD4(+)CD25(-) cells. Importantly, a high frequency of Foxp3(+) cells accumulated at the site of infection and in dLNs. We next investigated the outcome of a reinfection with L. braziliensis in terms of Treg distribution and disease reactivation. Interestingly, a secondary inoculation with L. braziliensis did not preclude an efficient recall response to L. braziliensis at a distal site, despite the presence of Tregs. Within dLNs, reinfection did not promote parasite dissemination or a differential recruitment of either CD4(+)CD25(+)Foxp3(+) or CD4(+)IL-10(+) T cells. On the contrary, parasites were mainly detected in the LN draining the primary infection site where a high frequency of CD4(+)IFN-γ(+) T cells was also present. Collectively these data show that during experimental infection, Tregs are present in healed mice but this population does not compromise an effective immune response upon reinfection with L. braziliensis.

The immunobiology of Leishmania braziliensis infection

Leishmaniases are a group of diseases caused by protozoa of the genus Leishmania that affect millions of people worldwide. These diseases are caused by distinct Leishmania species, of which L. braziliensis, a New World representative of the Leishmania genus, has been the least studied. Although leishmaniasis caused by L. braziliensis induces a range of clinical manifestations ranging from mild localized lesions to severe mucosal involvement, few studies have focused on elucidating the immune mechanisms behind this pathology. In this review, we focus on the immunobiology of L. braziliensis infection, emphasizing the innate and adaptive immune responses and taking into consideration both studies performed in endemic areas and experimental models of infection. Additionally, we address recent findings regarding the role of sand fly saliva in disease immunopathogenesis and vaccine development.

Towards development of novel immunization strategies against leishmaniasis using PLGA nanoparticles loaded with kinetoplastid membrane protein-11

BACKGROUND

Vaccine development has been a priority in the fight against leishmaniases, which are vector-borne diseases caused by Leishmania protozoa. Among the different immunization strategies employed to date is inoculation of plasmid DNA coding for parasite antigens, which has a demonstrated ability to induce humoral and cellular immune responses. In this sense, inoculation of plasmid DNA encoding Leishmania kinetoplasmid membrane protein-11 (KMP-11) was able to confer protection against visceral leishmaniasis. However, recently the use of antigen delivery systems such as poly(lactic-co-glycolic acid) (PLGA) nanoparticles has also proven effective for eliciting protective immune responses.

METHODS

In the present work, we tested two immunization strategies with the goal of obtaining protection, in terms of lesion development and parasite load, against cutaneous leishmaniasis caused by L. braziliensis. One strategy involved immunization with plasmid DNA encoding L. infantum chagasi KMP-11. Alternatively, mice were primed with PLGA nanoparticles loaded with the recombinant plasmid DNA and boosted using PLGA nanoparticles loaded with recombinant KMP-11.

RESULTS

Both immunization strategies elicited detectable cellular immune responses with the presence of both proinflammatory and anti-inflammatory cytokines; mice receiving the recombinant PLGA nanoparticle formulations also demonstrated anti-KMP-11 IgG1 and IgG2a. Mice were then challenged with L. braziliensis, in the presence of sand fly saliva. Lesion development was not inhibited following either immunization strategy. However, immunization with PLGA nanoparticles resulted in a more prominent reduction in parasite load at the infection site when compared with immunization using plasmid DNA alone. This effect was associated with a local increase in interferon-gamma and in tumor necrosis factor-alpha. Both immunization strategies also resulted in a lower parasite load in the draining lymph nodes, albeit not significantly.

CONCLUSION

Our results encourage the pursuit of immunization strategies employing nanobased delivery systems for vaccine development against cutaneous leishmaniasis caused by L. braziliensis infection.

Low CXCL13 expression, splenic lymphoid tissue atrophy and germinal center disruption in severe canine visceral leishmaniasis

Visceral leishmaniasis is associated with atrophy and histological disorganization of splenic compartments. In this paper, we compared organized and disorganized splenic lymphoid tissue from dogs naturally infected with Leishmania infantum assessing the size of the white pulp compartments, the distribution of T, B and S100⁺ dendritic cells, using immunohistochemistry and morphometry and the expression of CCR7 and the cytokines, CXCL13, lymphotoxin (LT)-α, LT-β, CCL19, CCL21, TNF-α, IL-10, IFN-γ and TGF-β, using by real time RT-PCR. The lymphoid follicles and marginal zones were smaller (3.2 and 1.9 times, respectively; Mann-Whitney, P<0.02) in animals with disorganized splenic tissue in comparison to those with organized splenic lymphoid tissue. In spleens with disorganized lymphoid tissue, the numbers of T cells and S100⁺ dendritic cells were decreased in the follicles, and the numbers of B cells were reduced in both the follicles and marginal zones. CXCL13 mRNA expression was lower in animals with disorganized lymphoid tissue (0.5±0.4) compared to those with organized lymphoid tissue (2.7±2.9, both relative to 18S expression, P = 0.01). These changes in the spleen were associated with higher frequency of severe disease (7/12) in the animals with disorganized than in animals with organized (2/13, Chi-square, P = 0.01) splenic lymphoid tissue. The data presented herein suggest that natural infection with Leishmania infantum is associated with the impairment of follicular dendritic cells, CXCL13 expression, B cell migration and germinal center formation and associates these changes with severe clinical forms of visceral leishmaniasis. Furthermore the fact that this work uses dogs naturally infected with Leishmania infantum emphasizes the relevance of the data presented herein for the knowledge on the canine and human visceral leishmaniasis.