Diagnostic markers selected by immunoproteomics and phage display applied for the serodiagnosis of canine leishmaniosis

Immunoproteomics and phage display in the context of leishmaniasis complexity

Leishmaniasis is defined as a complex of diseases caused by protozoan parasites of the genus Leishmania, which comprises 20 parasite species pathogenic to mammalians, such as humans and dogs. From a clinical point of view, and considering the diversity and biological complexity of the parasites, vectors, and vertebrate hosts, leishmaniasis is classified according to the distinct clinical manifestations, such as tegumentary (involving the cutaneous, mucosal, and cutaneous-diffuse forms) and visceral leishmaniasis. Many issues and challenges remain unaddressed, which could be attributed to the complexity and diversity of the disease. The current demand for the identification of new Leishmania antigenic targets for the development of multicomponent-based vaccines, as well as for the production of specific diagnostic tests, is evident. In recent years, biotechnological tools have allowed the identification of several Leishmania biomarkers that might potentially be used for diagnosis and have an application in vaccine development. In this Mini Review, we discuss the different aspects of this complex disease that have been addressed by technologies such as immunoproteomics and phage display. It is extremely important to be aware of the potential applications of antigens selected in different screening context, so that they can be used appropriately, so understanding their performance, characteristics, and self-limitations.

Validation of an immunochromatographic assay kit based on colored latex particles for the identification of the canine visceral leishmaniasis

Visceral leishmaniasis is a zoonotic infectious disease with a severe impact on humans and animals. Infection is transmitted by phlebotomine sand flies. The dogs are main reservoir for human infection. A rapid and accurate diagnosis of canine visceral leishmaniasis is essential for an efficient surveillance program. The aim of this study was to assess the performance of a rapid immunochromatographic strip test based on functionalized colored particles and a new recombinant antigenic protein, as a visual "in situ" method for the diagnosis of canine visceral leishmaniasis. The results were evaluated using an in-house ELISA assay with the same antigen. Both tests produced concordant results and the immunochromatographic strip test showed good diagnostic sensitivity (98%) and specificity (95%). Finally, meta-analysis was used to compare the sensitivity and specificity of the here developed test with the results of commercial immunochromatographic strip tests obtained from literature.

The Screen of a Phage Display Library Identifies a Peptide That Binds to the Surface of Trypanosoma cruzi Trypomastigotes and Impairs Their Infection of Mammalian Cells

Background

Chagas is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. On the order of seven million people are infected worldwide and current therapies are limited, highlighting the urgent need for new interventions. T. cruzi trypomastigotes can infect a variety of mammalian cells, recognition and adhesion to the host cell being critical for parasite entry. This study focuses on trypomastigote surface ligands involved in cell invasion.

Methods

Three selection rounds of a phage peptide display library for isolation of phages that bind to trypomastigotes, resulted in the identification of the N3 dodecapeptide. N3 peptide binding to T. cruzi developmental forms (trypomastigotes, amastigotes and epimastigotes) was evaluated by flow cytometry and immunofluorescence assays. Parasite invasion of Vero cells was assessed by flow cytometry and immunofluorescence assays.

Results

Phage display screening identified the N3 peptide that binds preferentially to the surface of the trypomastigote and amastigote infective forms as opposed to non-infective epimastigotes. Importantly, the N3 peptide, but not a control scrambled peptide, inhibits trypomastigote invasion of Vero cells by 50%.

Conclusion

The N3 peptide specifically binds to T. cruzi, and by doing so, inhibits Vero cell infection. Follow-up studies will identify the molecule on the parasite surface to which the N3 peptide binds. This putative T. cruzi ligand may advance chemotherapy design and vaccine development.

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.

Biotechnological applications from a Leishmania amastigote-specific hypothetical protein in the canine and human visceral leishmaniasis

The treatment against visceral leishmaniasis (VL) presents problems, mainly related to the toxicity and/or high cost of the drugs. In this context, a rapid and precise diagnosis of the disease should be performed, mainly to treat patients as soon as possible, aiming to reduce the treatment time and the toxicity of the therapeutics. In the present study, the diagnostic role of an amastigote-specific Leishmania protein was evaluated in the canine and human VL. Results showed that the recombinant protein (called rLiHyJ) and one specific B cell epitope (called PeptJ) predicted from protein sequence presented high sensitivity and specificity values to diagnose canine and human disease, showing also a low reactivity against cross-reactive samples. The rA2 protein and a parasite antigenic extract showed variable sensitivity and/or specificity values in the ELISA experiments. A prognostic evaluation of protein and peptide in the human VL indicated that specific IgG antibodies significantly decreased after treatment, when compared to be values obtained before therapy. The in vitro immunogenicity using rLiHyJ in peripheral blood mononuclear cell (PBMC) cultures collected of such patients and healthy subjects suggested that the protein induced lymphoproliferation and high IFN-γ production in the stimulated cells. In conclusion, although preliminary, results suggest that rLiHyJ and PeptJ could present distinct biotechnological applications in the canine and human VL.

Novel multi-epitope protein containing conserved epitopes from different Leishmania species as potential vaccine candidate: Integrated immunoinformatics and molecular dynamics approach

Leishmaniosis, caused by intracellular parasites of the genus Leishmania, has become a serious public health problem around the world, and for which there are currently extensive limitations. In this work, a theoretical model was proposed for the development of a multi-epitope vaccine. The protein GP63 of the parasite was selected for epitopes prediction, due to its important biological role for the infection process and abundance. IEDB tools were used to determine epitopes B and T in Leishmania braziliensis; besides, other conserved epitopes in three species were selected. To improve immunogenicity, 50S ribosomal protein L7 / L12 (ID: P9WHE3) was used as a domain of adjuvant in the assembly process. The folding arrangement of the vaccine was obtained through homologous modeling multi-template with MODELLER v9.21, and a Ramachandran plot analysis was done. Furthermore, physicochemical properties were described with the ProtParam tool and secondary structure prediction combining GOR-IV and SOPMA tools. Finally, a molecular dynamics simulation (50 ns) was performed to establish flexibility and conformational changes. The analysis of the results indicates high conservancy in the epitopes predicted among the four species. Moreover, Ramachandran plot, physicochemical parameters, and secondary structure prediction suggest a stable conformation of the vaccine, after a minimum conformational change that was evaluated with the free energy landscape. The conformational change does not drive any substantial change for epitope exposition on the surface. The vaccine proposed could be tested experimentally to guide new approaches in the development of pan-vaccines; vaccines with regions conserved in multiple species.