Vaccines for Human Leishmaniasis: Where Do We Stand and What Is Still Missing?

Responsible for up to 30,000 deaths annually, leishmaniasis is a complex spectrum of diseases endemic in 97 countries around the globe. Disease control relies heavily on the early diagnosis and treatment of the active cases (relevant for anthroponotic disease), although it is widely accepted that a prophylactic vaccine for human leishmaniasis is the way to achieve the successful elimination of human disease (taking in consideration the vast list of non-human reservoirs that enable the perpetuation of parasites all around the globe). The notion that infection leads to strong and long-lasting immunity against leishmaniasis supports vaccination as an achievable goal. However, and in spite of the different candidates tested along the years, till date, we still do not have an approved vaccine for humans. In this chapter, we will explore the last advances made in the field of vaccines against Leishmania without forgetting the historical perspective, essential to the understanding of the road already undergone. We will then discuss the correlates of disease and protection, still neither consensual nor definitive, as well as the issue of pre-clinical to clinical translation. The complete understanding of these issues will be essential for the approval of a successful vaccine for human leishmaniasis

Can Attenuated Leishmania Induce Equally Effective Protection as Virulent Strains in Visceral Leishmaniasis?

Metals technology / metallurg

Host Cell Phenotypic Variability Induced by Trypanosomatid-Parasite-Released Immunomodulatory Factors: Physiopathological Implications

The parasitic protozoa Trypanosoma cruzi and Leishmania sp release a variety of molecules into their mammalian hosts (ESA: excretory-secretory products). The effects of these ESA on the host cell function may participate in the establishment of a successful infection, in which the parasite persists for a sufficient period of time to complete its life cycle. A number of regulatory components or processes originating from the parasite that control or regulate the metabolism and the growth of host cell have been identified. The purpose of the present review is to analyze some of the current data related to the parasite ESA that interfere with the host cell physiology. Special attention is given to members of conserved protein families demonstrating remarkable diversity and plasticity of function (ie, glutathione S-transferases and related molecules; members of the trans-sialidase and mucin family; and members of the ribosomal protein family). The identification of parasite target molecules and the elucidation of their mode of action toward the host cell represents a step forward in efforts aimed at an immunotherapeutic or pharmacological control of parasitic infection

Biomarkers in Leishmaniasis: From Basic Research to Clinical Application

Leishmania is an intracellular protozoan parasite and the etiological agent of a vector-borne disease known as leishmaniasis. This neglected tropical disease exhibits high morbidity and mortality putting at risk people from multiple countries worldwide. It is endemic in 97 countries and 700,000–1 million new cases are estimated to occur each year. Leishmaniasis management is very challenging, the symptoms are non-pathognomonic (in both human and canine populations) and the treatments are associated with significant toxicity. Therefore, the need for detection in symptomatic and asymptomatic hosts is important to tackle the dissemination of infection, increasing the need for highly specific biomarkers. In this complex the available disease biomarkers will be addressed in a retrospective manner, focusing on their development from laboratory to their direct use in clinical settings

Trypanosoma cruzi-induced host immune system dysfunction: a rationale for parasite immunosuppressive factor(s) encoding gene targeting

An intense suppression of T cell proliferation to mitogens and to antigens is observed in a large number of parasitic infections. The impairment of T cell proliferation also occurred during the acute phase of Chagas' disease, caused by the intracellular protozoan parasite Trypanosoma cruzi. A wealth of evidence has accumulated that illustrates the ability of T. cruzi released molecules to influence directly a variety of diverse immunological functions. In this paper, we review the data concerning the immunoregulatory effects of T. cruzi Tc24 (a B cell activator antigen) and Tc52 (an immunosuppressive protein) released molecules on the host immune system. The gene targeting approach developed to further explore the biological function(s) of Tc52 molecule, revealed interesting unexpected functional properties. Indeed, in addition to its immunusuppressive activity a direct or indirect involvement of Tc52 gene product alone or in combination with other cellular components in T. cruzi differentiation control mechanisms have been evidenced. Moreover, targeted Tc52 replacement allowed the obtention of parasite mutants exhibiting low virulence in vitro and in vivo. Thus, the generation of a complete deficiency state of virulence factors by gene targeting should provide a means to assess the importance of these factors in the pathophysiological processes and disease progression. It is hoped that such approaches might allow rational design of tools to control T. cruzi infections

Immune Response Regulation by Leishmania Secreted and Nonsecreted Antigens

Leishmania infection consists in two sequential events, the host cell colonization followed by the proliferation/dissemination of the parasite. In this review, we discuss the importance of two distinct sets of molecules, the secreted and/or surface and the nonsecreted antigens. The importance of the immune response against secreted and surface antigens is noted in the establishment of the infection and we dissect the contribution of the nonsecreted antigens in the immunopathology associated with leishmaniasis, showing the importance of these panantigens during the course of the infection. As a further example of proteins belonging to these two different groups, we include several laboratorial observations on Leishmania Sir2 and LicTXNPx as excreted/secreted proteins and LmS3arp and LimTXNPx as nonsecreted/panantigens. The role of these two groups of antigens in the immune response observed during the infection is discussed

Evaluating the Role of Host AMPK in Leishmania Burden

Uncorrected proofThe study of host AMP-activated protein kinase (AMPK) activation during Leishmania infection imposes distinct types of techniques to measure protein expression and activation, as well as to quantify, at transcription and translational levels, its downstream targets. The investigation of host AMPK protein modulation during Leishmania infection should primarily be assessed during in vitro infections using as a host murine bone marrow-derived macrophages (BMMos). The infection outcome is assessed measuring the percentage of infected cells in the context of BMMos. To evaluate AMPK activity during infection, the expression of AMPK phosphorylated at Thr172 as well as the transcription and translational levels of its downstream targets are evaluated by quantitative PCR and immunoblotting. The modulation of AMPK activity in vivo is determined specifically in sorted splenic macrophages harboring Leishmania parasites recovered from infected mice using fluorescent-labeled parasites in the infectious inocolum. The modulation of AMPK activity was assessed by AMPK activators and inhibitors and also using AMPK, SIRT1, or LKB1 KO mice models. The infection outcome in BMMos and in vivo was further determined using these two different approaches. To finally understand the metabolic impact of AMPK during infection, in vitro metabolic assays in infected BMMos were measured in the bioenergetic profile using an extracellular flux analyzer.Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER) (NORTE-01-0145-FEDER-000013) and the Fundação para a Ciência e Tecnologia (FCT) (contract IF/00021/2014 to R.S.), by FEDER funds through the Operational Competitiveness Programme (COMPETE), and by national funds through FCT (Fundação para a Ciência e a Tecnologia) under the project FCOMP-01-0124-FEDER-011054 (PTDC/SAU-FCF/100749/2008) and PTDC/BIA-MIC/118644/2010. The research leading to these results has also received funding from the European community’s Seventh Framework Programme under grant agreement No.602773 to JE and ACS (Project KINDRED). DM was supported by SFRH/BD/91543/2012. JE thanks the Canada Research Chair program for their support

Silent Information Regulator 2 from Trypanosoma cruzi Is a Potential Target to Infection Control

Human trypanosomiasis is a neglected tropical disease caused by protozoan parasites of the genus Trypanosoma. Trypanosoma brucei is responsible for sleeping sickness, also called African trypanosomiasis, while Trypanosoma cruzi causes Chagas disease, or American trypanosomiasis. Together, these diseases are responsible for significant mortality, morbidity and lost productivity in the endemic regions. There are no vaccines and treatments rely on drugs with limited efficacy, high cost, serious side effects and long administration periods. Since these diseases affect mostly the poor, there is no economic interest in the development of new drugs by pharmaceutical companies, and hopes for new treatments rely on public initiatives, public-private partnerships or philanthropic programs. The first step in the discovery of new drugs involves the identification of active molecules as starting points for further development, by either employing whole cells or by specific molecular target screenings. Research efforts undertaken by the authors’ groups have focused on exploiting both strategies in the search for new molecules for trypanosomiasis drug discovery. In this chapter, we focus on Chagas disease and the recently uncovered potential of using sirtuins as targets for infection control

Characterization of the biology and infectivity of Leishmania infantum viscerotropic and dermotropic strains isolated from HIV+ and HIV- patients in the murine model of visceral leishmaniasis

BACKGROUND: Leishmaniasis is a group of diseases with a variety of clinical manifestations. The form of the disease is highly dependent on the infective Leishmania species and the immunological status of the host. The infectivity of the parasite strain also plays an important role in the progression of the infection. The aim of this work is to understand the influence of the natural infectivity of Leishmania strains in the outcome of visceral leishmaniasis. METHODS: In this study we have characterized four strains of L. infantum in terms of molecular typing, in vitro cultivation and differentiation. Two strains were isolated from HIV+ patients with visceral leishmaniasis (Bibiano and E390M), one strain was isolated from a cutaneous lesion in an immunocompetent patient (HL) and another internal reference strain causative of visceral leishmaniasis (ST) also from an immunocompetent patient was used for comparison. For this objective, we have compared their virulence by in vitro and in vivo infectivity in a murine model of visceral leishmaniasis. RESULTS: Molecular typing unraveled a new k26 sequence attributed to MON-284 zymodeme and allowed the generation of a molecular signature for the identification of each strain. In vitro cultivation enabled the production of promastigotes with comparable growth curves and metacyclogenesis development. The HL strain was the most infective, showing the highest parasite loads in vitro that were corroborated with the in vivo assays, 6 weeks post-infection in BALB/c mice. The two strains isolated from HIV+ patients, both belonging to two different zymodemes, revealed different kinetics of infection. CONCLUSION: Differences in in vitro and in vivo infectivity found in the murine model were then attributed to intrinsic characteristics of each strain. This work is supported by other studies that present the parasite's inherent features as factors for the multiplicity of clinical manifestations and severity of leishmaniasis.This work was supported by FCT project number PTDC/BIA‒MIC/11866/2011, FEDER Ciência 2010 project number PTDC/SAU‒FCF/101017/2008 and MICINN project number PIM2010‒ENI00627. JC was supported by fellowship from FCT code SFRH/BD/48626/2008 and CS by Contratos de Técnicos de apoyo a la investigación en el SNS code AES-FIS-2011.S

Evaluation of the immune response following a short oral vaccination schedule with hepatitis B antigen encapsulated into alginate-coated chitosan nanoparticles

The purpose of this work was to assess the ability of recombinant hepatitis B vaccine, encapsulated in alginate-coated chitosan nanoparticles, to induce local and systemic immune responses following oral vaccination. The antigen was administered either alone or in combination with the immunopotentiator, synthetic oligodeoxynucleotide containing immunostimulatory CpG motif (CpG ODN) as adjuvant, and associated or not with the alginate-coated chitosan nanoparticles. After two immunizations the group I (HBsAg associated with nanoparticles) and the group VI (HBsAg and CpG, both associated with nanoparticles) showed enhanced immune responses. Both groups showed significant higher values of the CD69 expression in CD4+ and CD8+ T-lymphocytes and lower values of this marker in B lymphocytes. Moreover, a strongest proliferative response of the splenocytes, ex vivo stimulated with concanavalin A, was observed in the same groups. Although with a presence of non-responder mice within the groups, only mice of the groups I and VI elicited the generation of anti-HBsAg antibodies detected in serum (IgG) and in the intestinal washings (sIgA). The results demonstrated that coated chitosan nanoparticles might have potential for being used as a deliver system for oral vaccination with the recombinant hepatitis B surface antigen.http://www.sciencedirect.com/science/article/B6T25-4PF1WCM-2/1/3fe2a6633c054a684fa0fafa7bb4a8b