Pyrazinamide is a first line drug used for the treatment of tuberculosis, a pathology that caused the death of more than 1.3 million people in the world during 2022, according to WHO, being a drug of current interest due to its relevance in pharmaceutical and medical sciences. In this context, solubility is one of the most important physicochemical parameters in the development and/or optimization of new pharmaceutical forms, so the present work aims to present a thermodynamic study of the solubility of pyrazinamide in nine organic solvents of pharmaceutical interest. Using the shake-flask method and UV/Vis spectrophotometry, the solubility of this drug was determined at 9 temperatures; the maximum solubility was obtained in dimethyl sulfoxide at 318.15 K ($x_2=0.0816\pm 0.004$) and the minimum in cyclohexane at 283.15 K ($1.73\pm 0.05\times {10}^{-5}$). From the apparent solubility data, the thermodynamic functions of solution and mixing were calculated, indicating an endothermic process. In addition, the solubility parameter of pyrazinamide was calculated using the Hoftyzer-van Krevelen (32.90 MPa^1/2) and Bustamante (28.14 MPa^1/2) methods. The maximum solubility was reached in dimethyl sulfoxide and the minimum in cyclohexane. As for the thermodynamic functions, the entropy drives the solution process in all cases. In relation to the solubility parameter, it can be analyzed that the mathematical models offer approximations; however, the experimental data are still primordial at the time of inferring any process.

The Tc964 protein was initially identified by its presence in the interactome associated with the LYT1 mRNAs, which code for a virulence factor of Trypanosoma cruzi. Tc964 is annotated in the T. cruzi genome as a hypothetical protein. According to phylogenetic analysis, the protein is conserved in the different genera of the Trypanosomatidae family; however, recognizable orthologues were not identified in other groups of organisms. Therefore, as a first step, an in-depth molecular characterization of the Tc946 protein was carried out. Based on structural predictions and molecular dynamics studies, the Tc964 protein would belong to a particular class of GTPases. Subcellular fractionation analysis indicated that Tc964 is a nucleocytoplasmic protein. Additionally, the protein was expressed as a recombinant protein in order to analyze its antigenicity with sera from Chagas disease (CD) patients. Tc964 was found to be antigenic, and B-cell epitopes were mapped by the use of synthetic peptides. In parallel, the Leishmania major homologue (Lm964) was also expressed as recombinant protein and used for a preliminary evaluation of antigen cross-reactivity in CD patients. Interestingly, Tc964 was recognized by sera from Chronic CD (CCD) patients at different stages of disease severity, but no reactivity against this protein was observed when sera from Colombian patients with cutaneous leishmaniasis were analyzed. Therefore, Tc964 would be adequate for CD diagnosis in areas where both infections (CD and leishmaniasis) coexist, even though additional assays using larger collections of sera are needed in order to confirm its usefulness for differential serodiagnosis.

Leishmaniasis causes skin ulcers to complex visceral involvement, and available treatment options for humans are highly toxic and have prolonged application schemes. So far, there are no licensed vaccines for humans, so it is necessary to develop a strategy that can prevent the development of the disease. A cellular immune response of a CD4⁺ Th1 profile is essential to eliminate intracellular Leishmania amastigotes; therefore, the identification of sequences that bind to HLA class II pockets could induce a protective immune response. This study aimed to identify CD4⁺ T epitopes from immunogenic Leishmania proteins. First, three prediction tools were used to compare 15-mer sequences throughout the complete protein sequence against 25 HLA-DR alleles using NH, SMT, CPA, CPB, and CPC proteins. Six peptides were identified as strong HLA-DR binders using the three bioinformatic prediction tools. After alignment, molecular docking analysis, and molecular dynamics, the stability and affinity of the peptide–DR4 complex were confirmed for three sequences. This bioinformatics strategy allowed a sequential screening from 1857 to three promising candidates, namely, SMT_133-148, CPA_39-54, and CPA_301-316, which increases the probability of being natural Leishmania spp. CD4⁺ T cell epitopes in humans.

Introducción. El parásito Leishmania es fagocitado por los macrófagos y se aloja en el fagolisosoma; por consiguiente, se necesita la activación por los linfocitos CD4-Th1 para controlar la infección. La presentación antigénica es crítica para dicha activación al presentar secuencias cortas del parásito en el bolsillo de las moléculas del complejo mayor de histocompatibilidad (CMH) de clase II.Objetivo. Identificar las secuencias lineales de proteínas inmunogénicas de Leishmania (Viannia) spp., mediante herramientas bioinformáticas frente a moléculas humanas del CMH de clase II.Materiales y métodos. Se tomaron secuencias lineales de las proteínas GP63, HSP70 y PEPCK de Leishmania panamensis y se predijo la unión de secuencias de 15 aminoácidos frente a diversos HLA-DRβ*04 por medio de herramientas de predicción. Se confirmó que las regiones están muy conservadas entre las especies del parásito, con nula o poca analogía con las proteínas humanas. Finalmente, se analizaron las interacciones de los péptidos con mejores resultados por acoplamiento molecular frente al HLA-DRβ*04:01. Resultados. En la primera fase del estudio, se identificaron seis secuencias con gran potencial de ser epítopos T naturales de Leishmania spp. Las secuencias GP63267-282, GP63282-297 y PEPCK535-550 presentaron múltiples interacciones y bajas energías de interacción frente al bolsillo del HLA-DRβ*04:01 y orientación de N-terminal a C-terminal. Conclusiones. Se identificaron tres secuencias como posibles epítopos Th1 de Leishmania spp.; sin embargo, es necesaria la validación in vitro para confirmar estos hallazgos.

Leishmaniasis is a disease that causes a cutaneous lesion where the vector insect bites. In Colombia this disease is a big public health problem. The intracellular parasite invades macrophages parasitophorous vacuole, therefore parasite elimination needs TH1 lymphocyte activation with INFγ production and Nitric Oxide synthesis inside macrophages, so antigen presentation by binding short parasite sequences to MHC class II pocket is critical. Such interactions may be predicted with bioinformatic tools. The aim of this work was to identify linear sequences from immunogenic proteins of Leishmania (Viannia) spp. through bioinformatic tools against MHC class II human molecules. Methodology: linear sequences of GP63, HSP70 y PEPCK were taken from L. panamensis and binding of 15mer peptides to different HLA-DR*04s were predicted. Highly conserved sequences were selected among the parasite species and null or low identity among human proteins. Finally molecular docking was performed against HLA-DR*04:01 pocket. Results: 3 sequences were identified as potential Leishmanial T epitopes. Conclusion: GP63267-282, GP63282-297; and PEPCK535-550 peptides could induce a Th1 response in humans and therefore they can be evaluated as prophylactic or therapeutic candidates against leishmaniasis.