Murine infection with bioluminescent Leishmania infantum axenic amastigotes applied to drug discovery

Leishmaniasis is an important vector-borne neglected tropical disease caused by Leishmania parasites. Current anti-Leishmania chemotherapy is unsatisfactory, justifying the continued search for alternative treatment options. Herein, we demonstrate that luciferase-expressing Leishmania infantum axenic amastigotes, unlike promastigotes, are highly infectious to BALB/c mice and thus generate a robust bioluminescent signal in target organs, such as the liver and the spleen, as early as two weeks after infection. Treatment with the reference drugs amphotericin B and miltefosine was effective at reducing parasite burdens. This model allows the assessment of treatment efficacy using whole-mouse bioluminescence imaging without the need to wait several weeks for spleen infections to be detectable by this non-invasive method. In conclusion, we propose the use of this model in an initial approach to evaluate the treatment efficacy of promising chemical entities without having to sacrifice large numbers of animals or to wait several days for a readout.We thank Carla Oliveira from i3S for the support with the statistical analysis. Part of the content of this manuscript has been released as a pre-print in BioRxiv (https://doi.org/10.1101/326355). This work was financed by FEDER - Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 - Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT - Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior in the framework of the project POCI-01-0145-FEDER-031013 (PTDC/SAU-PAR/31013/2017). This work also received funds from: Norte-01-0145-FEDER-000012 “Structured program on bioengineered therapies for infectious diseases and tissue regeneration” of Norte Portugal Regional Operational Programme (NORTE 2020) under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (FEDER) and through the Research Unit No. 4293; Individual funding from FCT through SFRH/BD/123734/2016 (to DC), SFRH/BD/121252/2016 (to PC) and CEECIND/02362/2017 (to JT)

Author Correction: Challenges in the serological evaluation of dogs clinically suspect for canine leishmaniasis

In Figure 1C, D, and E the positive and negative controls are missing. The correct Figure 1 appears below

Ribose 5-Phosphate Isomerase B Knockdown Compromises Trypanosoma brucei Bloodstream Form Infectivity

Ribose 5-phosphate isomerase is an enzyme involved in the non-oxidative branch of the pentose phosphate pathway, and catalyzes the inter-conversion of D-ribose 5-phosphate and D-ribulose 5-phosphate. Trypanosomatids, including the agent of African sleeping sickness namely Trypanosoma brucei, have a type B ribose-5-phosphate isomerase. This enzyme is absent from humans, which have a structurally unrelated ribose 5-phosphate isomerase type A, and therefore has been proposed as an attractive drug target waiting further characterization. In this study, Trypanosoma brucei ribose 5-phosphate isomerase B showed in vitro isomerase activity. RNAi against this enzyme reduced parasites' in vitro growth, and more importantly, bloodstream forms infectivity. Mice infected with induced RNAi clones exhibited lower parasitaemia and a prolonged survival compared to control mice. Phenotypic reversion was achieved by complementing induced RNAi clones with an ectopic copy of Trypanosoma cruzi gene. Our results present the first functional characterization of Trypanosoma brucei ribose 5-phosphate isomerase B, and show the relevance of an enzyme belonging to the non-oxidative branch of the pentose phosphate pathway in the context of Trypanosoma brucei infection.This work was funded by the European Community’s Seventh Framework Programme under grant agreement No. 602773 (Project KINDRED). The COST Action CM1307 ‘Targeted chemotherapy towards diseases caused by endoparasites’ and FEDER funds through the Operational Competitiveness Program – COMPETE and by National Funds through FCT – Fundação para a Ciência e a Tecnologia under the project PEstC/SAU/LA0002/2011 have also contributed for this work. IL and JF were supported by fellowships from FCT reference SFRH/BD/64528/2009 and SFRH/BD/79712/2011, respectively. NS is supported by a fellowship from the European Community’s Seventh Framework Programme under grant agreement No. 602773 (Project KINDRED). JT is an Investigator FCT funded by National funds through FCT and co-funded through European Social Fund within the Human Potential Operating Programme. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Visceral dissemination of mucocutaneous leishmaniasis in a kidney transplant recipient

Intracellular protozoan of the genus Leishmania, endemic in the Mediterranean basin, are the cause of cutaneous (CL), mucocutaneous (MCL), and visceral leishmaniasis (VL). A 75-year-old woman was admitted nine years after a second kidney transplant (KT), due to persistent pancytopenia and fever. She presented edema and erythema of the nose in the last two years and an exophytic nodular lesion located on the left arm, with areas of peripheral necrosis and central ulceration in the last 18 months. A bone marrow biopsy revealed features compatible with Leishmania amastigotes, and polymerase chain reaction test (PCR) for Leishmania infantum was positive. Moreover, biopsy and PCR for L. infantum of the cutaneous lesion on the patient’s left arm and nose and PCR from peripheral blood were positive. Thus, a diagnosis of CL, MCL, and VL was made, and liposomal amphotericin B was initiated, but the patient had an unfavorable outcome and died. This is the first report of a KT recipient presenting with the entire spectrum of leishmaniasis. In Portugal, this infection is rare—so a high degree of clinical suspicion is required for its diagnosis, especially in endemic regions, as visceral leishmaniasis is a potentially life-threatening infection

The use of Escherichia coli total antigens as a complementary approach to address seropositivity to Leishmania antigens in canine leishmaniosis

Canine leishmaniosis (CanL) is a major veterinary concern and a public health issue. Serological data are essential for disease management. Several antigens used in serological assays have specificity related problems preventing relevant seropositivity values establishment. Herein we report significant seropositivity level disparity in a study cohort with 384 dogs from eight countries, for antigens traditionally used in CanL - soluble promastigote Leishmania antigens (SPLA) and K39 recombinant protein (rK39): 43·8 and 2·9% for SPLA and rK39, respectively. To better understand the reasons for this disparity, CanL-associated serological response was characterized using, for complement serological evaluation, a ubiquitous antigen - soluble Escherichia coli antigens (SECAs). Using cohorts of CanL dogs and dogs without clinical evidences of CanL from non-endemic regions of Portugal, the serological response of CanL animals followed specific trend of seropositivity rK39 > SPLA > SECA absent in non-diseased animals. Using receiver operating characteristic curve analysis, these characteristic trends were converted in ratios, SPLA/SECA, rK39/SECA and rK39/SPLA, that presented high predictive for discriminating the CanL cohort that was potentiated when applied in a scoring system involving positivity to four out of five predictors (rK39, SPLA, SPLA/SECA, rK39/SECA and rK39/SPLA). In fact, this approach discriminated CanL with similar sensitivity/specificity as reference antigens, diminishing seropositivity in European cohort to 1·8%. Ultimately, non-related antigens like SECA and seropositivity ratios between antigens enable different perspectives into serological data focusing on the search of characteristic serological signatures and not simple absolute serology values contributing to comprehensive serological status characterization.This work was financed by FEDER–Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020–Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior in the framework of the project‘Institute for Research and Innovation in Health Sciences’(POCI-01-0145-FEDER-007274) and from the European Community’s Seventh Framework Programme under grant agreement No. 603181 [Clinical Studies on a Multivalent Vaccine for Human Visceral Leishmaniasis (MuLeVaClin)]. ‘This article is a result of the project NORTE-01-0145-FEDER-000012, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF)’. C.L. and N.S. were supported by BD SFRH/BD/89183/2012 and European Community’s Seventh Framework Programme under grant agreement No. 602773 (Project KINDRED), respectively

Improved Canine and Human Visceral Leishmaniasis Immunodiagnosis Using Combinations of Synthetic Peptides in Enzyme-Linked Immunosorbent Assay

Visceral leishmaniasis is endemic in many areas of tropical and subtropical America where it constitutes a significant public health problem. It is usually diagnosed by enzyme-linked immunosorbent assays (ELISA) using crude Leishmania antigens, but a variety of other immunological methods may also be applied. Although these approaches are useful, historically their sensitivity and specificity have often been compromised by the use of complex mixtures of antigens. In this context, the use of combinations of purified, well-characterized antigens appears preferable and may yield better results. In the present study, combinations of peptides derived from the previously described Leishmania diagnostic antigens A2, NH, LACK and K39 were used in ELISA against sera from 106 dogs and 44 human patients. Improved sensitivities and specificities, close to 100%, for both sera of patients and dogs was observed for ELISA using some combinations of the peptides, including the detection of VL in dogs with low anti-Leishmania antibody titers and asymptomatic infection. So, the use of combinations of B cell predicted synthetic peptides derived from antigens A2, NH, LACK and K39 may provide an alternative for improved sensitivities and specificities for immunodiagnostic assays of VL

Human toxocariasis: contribution by Brazilian researchers

In the present paper the main aspects of the natural history of human infection by Toxocara larvae that occasionally result in the occurrence of visceral and/or ocular larva migrans syndrome were reviewed. The contribution by Brazilian researchers was emphasized, especially the staff of the Tropical Medicine Institute of São Paulo (IMT)

Leishmania infantum Asparagine Synthetase A Is Dispensable for Parasites Survival and Infectivity

A growing interest in asparagine (Asn) metabolism has currently been observed in cancer and infection fields. Asparagine synthetase (AS) is responsible for the conversion of aspartate into Asn in an ATP-dependent manner, using ammonia or glutamine as a nitrogen source. There are two structurally distinct AS: the strictly ammonia dependent, type A, and the type B, which preferably uses glutamine. Absent in humans and present in trypanosomatids, AS-A was worthy of exploring as a potential drug target candidate. Appealingly, it was reported that AS-A was essential in Leishmania donovani, making it a promising drug target. In the work herein we demonstrate that Leishmania infantum AS-A, similarly to Trypanosoma spp. and L. donovani, is able to use both ammonia and glutamine as nitrogen donors. Moreover, we have successfully generated LiASA null mutants by targeted gene replacement in L. infantum, and these parasites do not display any significant growth or infectivity defect. Indeed, a severe impairment of in vitro growth was only observed when null mutants were cultured in asparagine limiting conditions. Altogether our results demonstrate that despite being important under asparagine limitation, LiAS-A is not essential for parasite survival, growth or infectivity in normal in vitro and in vivo conditions. Therefore we exclude AS-A as a suitable drug target against L. infantum parasites