Sensitive and specific serodiagnosis of tegumentary leishmaniasis using a new chimeric protein based on specific B-cell epitopes of Leishmania antigenic proteins.

Serological tests used for the diagnosis of tegumentary leishmaniasis (TL) presents problems, mainly related to their variable sensitivity and/or specificity, which can be caused by low levels of antileishmanial antibodies or by presence of cross-reactive diseases, respectively. In this context, the search for new antigenic candidates presenting higher sensitivity and specificity is urgently required. In the present study, the amino acid sequences of the LiHyT, LiHyD, LiHyV, and LiHyP proteins, which were previously showed to be antigenic in the visceral leishmaniasis (VL), were evaluated and eight B-cell epitopes were predicted and used for construction of gene codifying a chimeric protein called ChimLeish. The protein was expressed, purified and evaluated as a recombinant antigen in ELISA (Enzyme-Linked Immunosorbent Assay) for the diagnosis of TL. The own B cell epitopes used to construct the chimera were synthetized and also evaluated as antigens, as well as a soluble Leishmania braziliensis antigenic extract (SLA). Results showed that ChimLeish presented 100% sensitivity and specificity to diagnose TL, while synthetic peptides showed sensitivity varying from 9.1% to 90.9%, while specificity reached from 98.3% to 99.1%. SLA showed sensitivity and specificity of 18.2% and 98.3%, respectively. A preliminary prognostic evaluation showed that anti-ChimLeish IgG antibodies declined in significant levels, when serological reactivity was compared before and six months after treatment, suggesting also a possible prognostic role of this antigen for TL.

Flau-A, a naphthoquinone derivative, is a promising therapeutic candidate against visceral leishmaniasis: A preliminary study.

Visceral leishmaniasis (VL) is a neglected tropical disease found in tropical and subtropical regions in the world. The therapeutics used for the treatment against disease presents problems, mainly related to drug toxicity, route of administration, high cost and/or by emergence of resistant strains. In this context, the search for alternative antileishmanial candidates is desirable. Recently, a naphthoquinone derivative namely 2-(2,3,4-tri-O-acetyl-6-deoxy-ß-L-galactopyranosyloxy)-1,4-naphthoquinone or Flau-A showed an effective in vitro biological action against Leishmania infantum. In the present study, the efficacy of this naphthoquinone derivative was evaluated in an in vivo infection model. BALB/c mice (n = 12 per group) were infected and later received saline or were treated with empty micelles (B/Mic), free Flau-A or it incorporated in Poloxamer 407-based micelles (Flau-A/Mic). The products were administered subcutaneously in the infected animals, which were then euthanized one (n = 6 per group) and 15 (n = 6 per group) days post-therapy, when immunological and parasitological evaluations were performed. Results showed that animals treated with Flau-A or Flau-A/Mic produced significantly higher levels of antileishmanial IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and IgG2a isotype antibody, when compared to data found in the control (saline and B/Mic) groups; which showed significantly higher levels of parasite-specific IL-4, IL-10 and IgG1 antibody. In addition, animals receiving free Flau-A or Flau-A/Mic presented also significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes, when compared to the controls. A low hepatic and renal toxicity was also found. Overall, Flau-A/Mic showed better immunological and parasitological results, when compared to the use of free molecule. In conclusion, preliminary data suggest that this composition could be considered in future studies as promising therapeutic candidate against VL.

Leishmania eukaryotic elongation Factor-1 beta protein is immunogenic and induces parasitological protection in mice against Leishmania infantum infection.

Treatment for visceral leishmaniasis (VL) is hampered mainly by the toxicity and/or high cost of antileishmanial drugs. What is more, variability on sensitivity and/or specificity of diagnostic tests hinders effective disease management. In this context, prophylactic vaccination should be considered as a strategy to prevent disease. In the present study, immunogenicity of the Leishmania eukaryotic Elongation Factor-1 beta (EF1b) protein, classified as a Leishmania virulence factor, was evaluated in vitro and in vivo and tested, for the first time, as a vaccine candidate against Leishmania infantum infection. The antigen was administered as DNA vaccine or as recombinant protein (rEF1b) delivered in saponin. BALB/c mice immunization with a DNA plasmid and recombinant protein plus saponin induced development of specific Th1-type immunity, characterized by high levels of IFN-γ, IL-12, GM-CSF, both T cell subtypes and antileishmanial IgG2a isotype antibodies, before and after infection. This immunological response to the vaccines was corroborated further by parasitological analysis of the vaccinated and then challenged mice, which showed significant reductions in the parasite load in their liver, spleen, bone marrow and draining lymph nodes, when compared to the controls. Vaccination using rEF1b/saponin induced a more robust Th1 response and parasitological protection when compared to the DNA vaccine. Furthermore, in vitro analysis of lymphoproliferation, IFN-γ and IL-10 levels in human PBMC cultures showed as well development of a specific Th1-type response. In conclusion, data suggest that EF1b could be a promising vaccine candidate to protect against L. infantum infection.

Acarbose presents in vitro and in vivo antileishmanial activity against Leishmania infantum and is a promising therapeutic candidate against visceral leishmaniasis.

Treatment against visceral leishmaniasis (VL) is mainly hampered by drug toxicity, long treatment regimens and/or high costs. Thus, the identification of novel and low-cost antileishmanial agents is urgent. Acarbose (ACA) is a specific inhibitor of glucosidase-like proteins, which has been used for treating diabetes. In the present study, we show that this molecule also presents in vitro and in vivo specific antileishmanial activity against Leishmania infantum. Results showed an in vitro direct action against L. infantum promastigotes and amastigotes, and low toxicity to mammalian cells. In addition, in vivo experiments performed using free ACA or incorporated in a Pluronic® F127-based polymeric micelle system called ACA/Mic proved effective for the treatment of L. infantum-infected BALB/c mice. Treated animals presented significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes when compared to the controls, as well as the development of antileishmanial Th1-type humoral and cellular responses based on high levels of IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and IgG2a isotype antibodies. In addition, ACA or ACA-treated animals suffered from low organ toxicity. Treatment with ACA/Mic outperformed treatments using either Miltefosine or free ACA based on parasitological and immunological evaluations performed one and 15 days post-therapy. In conclusion, data suggest that the ACA/Mic is a potential therapeutic agent against L. infantum and merits further consideration for VL treatment.

Ivermectin presents effective and selective antileishmanial activity in vitro and in vivo against Leishmania infantum and is therapeutic against visceral leishmaniasis.

Treatment for visceral leishmaniasis (VL) is hindered mainly by the toxicity and/or high cost of therapeutic drugs. In addition, parasite resistance has been registered. Thus, there is an urgent need for the identification of novel, effective and low-cost antileishmanial agents. Since drug discovery is a long and expensive process, drug repositioning for treatment of leishmaniasis should be considered. In the present study, Ivermectin (IVE), a broad-spectrum drug used for treatment of parasitic diseases, was evaluated in vitro and in vivo against Leishmania infantum species. Results in vitro showed that IVE presented 50% Leishmania and macrophage inhibitory concentrations (IC50 and CC50, respectively) of 3.64 ± 0.48 µM and 427.50 ± 17.60 µM, respectively, with a selectivity index (SI) of 117.45; whereas Amphotericin B (AmpB), which was used as control, showed IC50 and CC50 values of 0.12 ± 0.05 µM and 1.06 ± 0.23 µM, respectively, with a corresponding SI of 8.90. Treatment with IVE effectively reduced the infection percentage and parasite burden in infected and treated macrophages and displayed a prophylactic activity by inhibiting macrophage infection with pre-treated parasites. Furthermore, preliminary studies suggested that IVE targets the parasite's mitochondria. Activity of IVE in its free format or incorporated into Pluronic® F127-based polymeric micelles (IVE/Mic) was also evaluated in vivo as a treating drug for L. infantum-infected BALB/c mice. Miltefosine was used as a control. Results showed that Miltefosine, IVE and IVE/Mic-treated animals presented significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes, as well as development of an antileishmanial Th1-type immune response one and 15 days after treatment. Notably, IVE/Mic showed a better parasitological and immunological response in comparison to other alternative treatments. In conclusion, results suggest that IVE/Mic could be considered in future studies as a therapeutic alternative to treat VL.

ChimLeish, a new recombinant chimeric protein evaluated as a diagnostic and prognostic marker for visceral leishmaniasis and human immunodeficiency virus coinfection.

Visceral leishmaniasis (VL) is a neglected tropical disease of global importance caused by parasites of the genus Leishmania, and coinfection with human immunodeficiency virus (HIV) is common in countries where both diseases are endemic. In particular, widely used immunological tests for VL diagnosis have impaired sensitivity (Se) and specificity (Sp) in VL/HIV coinfected patients and there is also cross-reactivity with other endemic diseases, e.g., Chagas disease, malaria, and tuberculosis. To develop new antigens to improve the diagnosis of VL and VL/HIV coinfection, we predicted eight specific B-cell epitopes of four Leishmania infantum antigens and constructed a recombinant polypeptide chimera antigen called ChimLeish. A serological panel of 195 serum samples was used to compare the diagnostic capabilities of ChimLeish alongside the individual synthetic peptides. ChimLeish reacted with sera from all VL and VL/HIV coinfected patients [Se = 100%; Sp = 100%; area under the curve (AUC) = 1.0]. Peptides showed lower reactivities (Se = 76.8 to 99.2%; Sp = 67.1 to 95.7%; AUC between 0.87 and 0.98) as did a L. infantum antigenic preparation used as an antigen control (Se = 56.8%; Sp = 69.5%: AUC = 0.45). Notably, ChimLeish demonstrated a significant reduction (p < 0.05) of anti-ChimLeish antibodies after treatment and cure of a small number of patients. Although only a limited serological panel was tested, preliminary data suggest that ChimLeish should be evaluated in larger sample studies for the diagnosis of VL and VL/HIV coinfection.

Digitoxigenin presents an effective and selective antileishmanial action against Leishmania infantum and is a potential therapeutic agent for visceral leishmaniasis.

Treatment for visceral leishmaniasis (VL) is hampered mainly by drug toxicity, their high cost, and parasite resistance. Drug development is a long and pricey process, and therefore, drug repositioning may be an alternative worth pursuing. Cardenolides are used to treat cardiac diseases, especially those obtained from Digitalis species. In the present study, cardenolide digitoxigenin (DIGI) obtained from a methanolic extract of Digitalis lanata leaves was tested for its antileishmanial activity against Leishmania infantum species. Results showed that 50% Leishmania and murine macrophage inhibitory concentrations (IC50 and CC50, respectively) were of 6.9 ± 1.5 and 295.3 ± 14.5 µg/mL, respectively. With amphotericin B (AmpB) deoxycholate, used as a control drug, values of 0.13 ± 0.02 and 0.79 ± 0.12 µg/mL, respectively, were observed. Selectivity index (SI) values were of 42.8 and 6.1 for DIGI and AmpB, respectively. Preliminary studies suggested that the mechanism of action for DIGI is to cause alterations in the mitochondrial membrane potential, to increase the levels of reactive oxygen species and induce accumulation of lipid bodies in the parasites. DIGI was incorporated into Pluronic® F127-based polymeric micelles, and the formula (DIGI/Mic) was used to treat L. infantum-infected mice. Miltefosine was used as a control drug. Results showed that animals treated with either miltefosine, DIGI, or DIGI/Mic presented significant reductions in the parasite load in their spleens, livers, bone marrows, and draining lymph nodes, as well as the development of a specific Th1-type response, when compared with the controls. Results obtained 1 day after treatment were corroborated with data corresponding to 15 days after therapy. Importantly, treatment with DIGI/Mic induced better parasitological and immunological responses when compared with miltefosine- and DIGI-treated mice. In conclusion, DIGI/Mic has the potential to be used as a therapeutic agent to protect against L. infantum infection, and it is therefore worth of consideration in future studies addressing VL treatment.

Parasitological and immunological evaluation of a novel chemotherapeutic agent against visceral leishmaniasis.

AIMS: Treatment for visceral leishmaniasis (VL) is hampered by the toxicity and/or high cost of drugs, as well as by emergence of parasite resistance. Therefore, there is an urgent need for new antileishmanial agents. METHODS AND RESULTS: In this study, the antileishmanial activity of a diprenylated flavonoid called 5,7,3,4'-tetrahydroxy-6,8-diprenylisoflavone (CMt) was tested against Leishmania infantum and L amazonensis species. Results showed that CMt presented selectivity index (SI) of 70.0 and 165.0 against L infantum and L amazonensis promastigotes, respectively, and of 181.9 and 397.8 against respective axenic amastigotes. Amphotericin B (AmpB) showed lower SI values of 9.1 and 11.1 against L infantum and L amazonensis promastigotes, respectively, and of 12.5 and 14.3 against amastigotes, respectively. CMt was effective in the treatment of infected macrophages and caused alterations in the parasite mitochondria. L infantum-infected mice treated with miltefosine, CMt alone or incorporated in polymeric micelles (CMt/Mic) presented significant reductions in the parasite load in distinct organs, when compared to the control groups. An antileishmanial Th1-type cellular and humoral immune response were developed one and 15 days after treatment, with CMt/Mic-treated mice presenting a better protective response. CONCLUSION: Our data suggest that CMt/Mic could be evaluated as a chemotherapeutic agent against VL.

Protein signatures that promote operator selectivity among paralog MerR monovalent metal ion regulators.

Two paralog transcriptional regulators of the MerR family, CueR and GolS, are responsible for monovalent metal ion sensing and resistance in Salmonella enterica. Although similar in sequence and also in their target binding sites, these proteins differ in signal detection and in the set of target genes they control. Recently, we demonstrated that selective promoter recognition depends on the presence of specific bases located at positions 3' and 3 within the operators they interact with. Here, we identify the amino acid residues within the N-terminal DNA-binding domain of these sensor proteins that are directly involved in operator discrimination. We demonstrate that a methionine residue at position 16 of GolS, absolutely conserved among GolS-like proteins but absent in all CueR-like xenologs, is the key to selectively recognize operators that harbor the distinctive GolS-operator signature, whereas the residue at position 19 finely tunes the regulator/operator interaction. Furthermore, swapping these residues switches the set of genes recognized by these transcription factors. These results indicate that co-evolution of a regulator and its cognate operators within the bacterial cell provides the conditions to avoid cross-recognition and guarantees the proper response to metal injury.

Mechanisms of SARS-CoV-2 Inactivation Using UVC Laser Radiation.

Severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) has had a tremendous impact on humanity. Prevention of transmission by disinfection of surfaces and aerosols through a chemical-free method is highly desirable. Ultraviolet C (UVC) light is uniquely positioned to achieve inactivation of pathogens. We report the inactivation of SARS-CoV-2 virus by UVC radiation and explore its mechanisms. A dose of 50 mJ/cm2 using a UVC laser at 266 nm achieved an inactivation efficiency of 99.89%, while infectious virions were undetectable at 75 mJ/cm2 indicating >99.99% inactivation. Infection by SARS-CoV-2 involves viral entry mediated by the spike glycoprotein (S), and viral reproduction, reliant on translation of its genome. We demonstrate that UVC radiation damages ribonucleic acid (RNA) and provide in-depth characterization of UVC-induced damage of the S protein. We find that UVC severely impacts SARS-CoV- 2 spike protein's ability to bind human angiotensin-converting enzyme 2 (hACE2) and this correlates with loss of native protein conformation and aromatic amino acid integrity. This report has important implications for the design and development of rapid and effective disinfection systems against the SARS-CoV-2 virus and other pathogens.

Development of an Affordable ELISA Targeting the SARS-CoV-2 Nucleocapsid and Its Application to Samples from the Ongoing COVID-19 Epidemic in Ghana.

INTRODUCTION: The true nature of the population spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in populations is often not fully known as most cases, particularly in Africa, are asymptomatic. Finding the true magnitude of SARS-CoV-2 spread is crucial to provide actionable data about the epidemiological progress of the disease for researchers and policymakers. This study developed and optimized an antibody enzyme-linked immunosorbent assay (ELISA) using recombinant nucleocapsid antigen expressed in-house using a simple bacterial expression system. METHODS: Nucleocapsid protein from SARS-CoV-2 was expressed and purified from Escherichia coli. Plasma samples used for the assay development were obtained from Ghanaian SARS-CoV-2 seropositive individuals during the pandemic, while seronegative controls were plasma samples collected from blood donors before the coronavirus disease 2019 (COVID-19) pandemic. Another set of seronegative controls was collected during the COVID-19 pandemic. Antibody detection and levels within the samples were validated using commercial kits and Luminex. Analyses were performed using GraphPad Prism, and the sensitivity, specificity and background cut-off were calculated. RESULTS AND DISCUSSION: This low-cost ELISA (£0.96/test) assay has a high prediction of 98.9%, and sensitivity and specificity of 97% and 99%, respectively. The assay was subsequently used to screen plasma from SARS-CoV-2 RT-PCR-positive Ghanaians. The assay showed no significant difference in nucleocapsid antibody levels between symptomatic and asymptomatic, with an increase of the levels over time. This is in line with our previous publication. CONCLUSION: This study developed a low-cost and transferable assay that enables highly sensitive and specific detection of human anti-SARS-CoV-2 IgG antibodies. This assay can be modified to include additional antigens and used for continuous monitoring of sero-exposure to SARS-CoV-2 in West Africa.

Synthetic Heparan Sulfate Mimetic Pixatimod (PG545) Potently Inhibits SARS-CoV-2 by Disrupting the Spike-ACE2 Interaction.

Heparan sulfate (HS) is a cell surface polysaccharide recently identified as a coreceptor with the ACE2 protein for the S1 spike protein on SARS-CoV-2 virus, providing a tractable new therapeutic target. Clinically used heparins demonstrate an inhibitory activity but have an anticoagulant activity and are supply-limited, necessitating alternative solutions. Here, we show that synthetic HS mimetic pixatimod (PG545), a cancer drug candidate, binds and destabilizes the SARS-CoV-2 spike protein receptor binding domain and directly inhibits its binding to ACE2, consistent with molecular modeling identification of multiple molecular contacts and overlapping pixatimod and ACE2 binding sites. Assays with multiple clinical isolates of SARS-CoV-2 virus show that pixatimod potently inhibits the infection of monkey Vero E6 cells and physiologically relevant human bronchial epithelial cells at safe therapeutic concentrations. Pixatimod also retained broad potency against variants of concern (VOC) including B.1.1.7 (Alpha), B.1.351 (Beta), B.1.617.2 (Delta), and B.1.1.529 (Omicron). Furthermore, in a K18-hACE2 mouse model, pixatimod significantly reduced SARS-CoV-2 viral titers in the upper respiratory tract and virus-induced weight loss. This demonstration of potent anti-SARS-CoV-2 activity tolerant to emerging mutations establishes proof-of-concept for targeting the HS-Spike protein-ACE2 axis with synthetic HS mimetics and provides a strong rationale for clinical investigation of pixatimod as a potential multimodal therapeutic for COVID-19.

A candidate vaccine for human visceral leishmaniasis based on a specific T cell epitope-containing chimeric protein protects mice against Leishmania infantum infection.

Leishmaniases are neglected diseases caused by infection with Leishmania parasites and there are currently no prophylactic vaccines. In this study, we designed in silico a synthetic recombinant vaccine against visceral leishmaniasis (VL) called ChimeraT, which contains specific T-cell epitopes from Leishmania Prohibitin, Eukaryotic Initiation Factor 5a and the hypothetical LiHyp1 and LiHyp2 proteins. Subcutaneous delivery of ChimeraT plus saponin stimulated a Th1 cell-mediated immune response and protected mice against L. infantum infection, significantly reducing the parasite load in distinct organs. ChimeraT/saponin vaccine stimulated significantly higher levels of IFN-γ, IL-12, and GM-CSF cytokines by both murine CD4+ and CD8+ T cells, with correspondingly low levels of IL-4 and IL-10. Induced antibodies were predominantly IgG2a isotype and homologous antigen-stimulated spleen cells produced significant nitrite as a proxy for nitric oxide. ChimeraT also induced lymphoproliferative responses in peripheral blood mononuclear cells from VL patients after treatment and healthy subjects, as well as higher IFN-γ and lower IL-10 secretion into cell supernatants. Thus, ChimeraT associated with a Th1 adjuvant could be considered as a potential vaccine candidate to protect against human disease.

Liposomal Formulation of ChimeraT, a Multiple T-Cell Epitope-Containing Recombinant Protein, Is a Candidate Vaccine for Human Visceral Leishmaniasis.

Background: Leishmaniases are neglected diseases caused by infection with Leishmania parasites and there are no human vaccines in use routinely. The purpose of this study was to examine the immunogenicity of ChimeraT, a novel synthetic recombinant vaccine against visceral leishmaniasis (VL), incorporated into a human-compatible liposome formulation. Methods: BALB/c mice were immunized subcutaneously with ChimeraT/liposome vaccine, ChimeraT/saponin adjuvant, or ChimeraT/saline and immune responses examined in vitro and in vivo. Results: Immunization with the ChimeraT/liposome formulation induced a polarized Th1-type response and significant protection against L. infantum infection. ChimeraT/liposome vaccine stimulated significantly high levels of interferon (IFN)-γ, interleukin (IL)-12, and granulocyte macrophage-colony stimulating factor (GM-CSF) cytokines by both CD4 and CD8 T-cells, with correspondingly lower levels of IL-4 and IL-10 cytokines. Induced antibodies were predominantly IgG2a isotype, and homologous antigen-stimulated spleen cells produced significant nitrite as a proxy for nitric oxide (NO). Furthermore, we examined a small number of treated VL patients and found higher levels of circulating anti-ChimeraT protein IgG2 antibodies, compared to IgG1 levels. Conclusions: Overall, the liposomal formulation of ChimeraT induced a protective Th1-type immune response and thus could be considered in future studies as a vaccine candidate against human VL.