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.

Leishmania and HIV co-infection: first naturally Leishmania strain presenting decreased susceptibility to miltefosine, recovered from a patient in Portugal.

BACKGROUND: In Europe, up to 70% of visceral leishmaniasis (VL) cases occurring in adults living with HIV. People living with HIV with VL co-infection often display persistent parasitemia, requiring chronic intermittent anti-Leishmania therapies. Consequently, frequent VL relapses and higher mortality rates are common in these individuals. As such, it is of paramount importance to understand the reasons for parasite persistence to improve infection management. METHODS: To outline possible causes for treatment failure in the context of HIV-VL, we followed a person living with HIV-VL co-infection for nine years in a 12-month period. We characterized: HIV-related clinicopathological alterations (CD4+ T counts and viremia) and Leishmania-specific seroreactivity, parasitemia, quantification of pro-inflammatory cytokines upon stimulation and studied a Leishmania clinical isolate recovered during this period. RESULTS: The subject presented controlled viremia and low CD4+ counts. The subject remained PCR positive for Leishmania and also seropositive. The cellular response to parasite antigens was erratic. The isolate was identified as the first Leishmania infantum case with evidence of decreased miltefosine susceptibility in Portugal. CONCLUSION: Treatment failure is a multifactorial process driven by host and parasite determinants. Still, the real-time determination of drug susceptibility profiles in clinical isolates is an unexplored resource in the monitoring of VL.

Synthesis and anti-parasitic activity of a novel quinolinone-chalcone series.

A series of novel quinolinone-chalcone hybrids and analogues were designed, synthesized and their biological activity against the mammalian stages of Trypanosoma brucei and Leishmania infantum evaluated. Promising molecular scaffolds with significant microbicidal activity and low cytotoxicity were identified. Quinolinone-chalcone 10 exhibited anti-parasitic properties against both organisms, being the most potent anti-L. infantum agent of the entire series (IC50 value of 1.3±0.1 µM). Compounds 4 and 11 showed potency toward the intracellular, amastigote stage of L. infantum (IC50 values of 2.1±0.6 and 3.1±1.05 µM, respectively). Promising trypanocidal compounds include 5 and 10 (IC50 values of 2.6±0.1 and 3.3±0.1 µM, respectively) as well as 6 and 9 (both having IC50 values of <5 µM). Chemical modifications on the quinolinone-chalcone scaffold were performed on selected compounds in order to investigate the influence of these structural features on antiparasitic activity.

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

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

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

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Challenges in the serological evaluation of dogs clinically suspect for canine leishmaniasis.

Canine leishmaniasis is a major veterinary issue and also a public health challenge due to its zoonotic potential. In this context, serological evaluation is essential for Canine leishmaniasis management. Several serological alternatives, such as rapid diagnostic tests, enzyme-linked immunosorbent assay (ELISA) and immunofluorescence antibody test (IFAT), are well established. In fact, the capacity of distinct tests and antigens, evaluated by their sensitivity and specificity, to detect disease is normally considered sufficient for diagnosing Canine leishmaniasis. In this context, we evaluated the seropositivity using 8 different serological tests (ELISA with Leishmania recombinant proteins (rK39, LicTXNPx); soluble promastigote Leishmania antigens (SPLA); commercial ELISA test) in 82 clinically suspect animals from Northern Portugal. The obtained serological data originated 50% of inconclusive serological information with a mixture of seropositive and seronegative results for individual animals. Cut-off independent risk groups were then generated from the serological data to evaluate the clustering of the samples. This analysis originated risk groups that correlated with the most seropositive samples, suggesting that this method might be used, in a cut-off independent manner, to improve conventional serological evaluation. Ultimately, given that no test prioritization exists, the use of any single serological test increases the potential for misdiagnosis, along with all associated risks for the dog as well as public health. The use of a cut-off independent analysis has the potential to improve the predictive values of these tests, enabling a more accurate evaluation of the dog's condition.

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.

Proof of interaction between Leishmania SIR2RP1 deacetylase and chaperone HSP83.

The cytoplasmic Leishmania silent information regulator 2 (SIR2)RP1 protein is essential for parasite growth and survival and constitutes an attractive therapeutic target. Little information is available on putative substrate(s) and/or partner(s) that could shed light on the pathways in which this enzyme plays a role. We carried out co-immunoprecipitation experiments on the soluble fractions of wild-type and parasites overexpressing LmSIR2RP1 and found that the essential chaperone heat shock protein (HSP) 83, the Leishmania ortholog of the mammalian HSP90, constantly co-immunoprecipitated with LmSIR2RP1. We found that Leishmania HSP83 is among the lysine acetylated protein, but the intracellular level of SIR2RP1 does not influence the acetylation status of HSP83. Finally, the modified Geldanamycin susceptibility (an inhibitor of HSP83) exhibited by SIR2RP1 mutant parasites support an in vivo relationship between the chaperone activity of HSP83 and LmSIR2RP1. An insight on the nature of the interaction in Leishmania is required to understand its role in the cell fate control during cytodifferentiation.

Peptide-based analysis of the amino acid sequence important to the immunoregulatory function of Trypanosoma cruzi Tc52 virulence factor.

The intracellular protozoan parasite Trypanosoma cruzi is the aetiological agent of Chagas' disease. We have previously identified a T. cruzi-released protein called Tc52, which is crucial for parasite survival and virulence. In the present study, we attempted to define the Tc52 epitope(s) responsible for its immunoregulatory function. A naturally occurring major peptide fragment of molecular mass 28 kDa (Tc28k) was identified, which was localized in the C-terminal portion of Tc52 and was inhibitory for T-cell activation. Synthetic peptides corresponding to amino acid sequences in Tc52 were evaluated for their ability to modulate T-cell proliferation and cytokine production. Results obtained using five peptides spanning the N-terminal or C-terminal domain of the Tc52 protein indicated that the activity mapped to Tc52 residues 432-445. Moreover, it was found that the peptide, when coupled to a carrier protein (ovalbumin), exhibited increased inhibitory activity on T-lymphocyte activation. Incubation with 8 nm ovalbumin-coupled peptide 432-445 resulted in approximately the same levels (>75%) of inhibition of T-cell proliferation as 5 micro g/ml Tc28k. Furthermore, we showed that the coupled peptide significantly down-regulated the secretion of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2). Likewise, in immunized mice, the coupled peptide 432-445 was a very poor B- and T-cell antigen compared with the other Tc52-derived peptides. These results suggest that the immunomodulatory portion of the T. cruzi Tc52 virulent factor may reside, at least in part, in a conserved sequence within its C-terminal domain, which could minimize its antigenicity.