The Unsolved Jigsaw Puzzle of the Immune Response in Chagas Disease

Trypanosoma cruzi interacts with the different arms of the innate and adaptive host's immune response in a very complex and flowery manner. The history of host-parasite co-evolution has provided this protozoan with means of resisting, escaping or subverting the mechanisms of immunity and establishing a chronic infection. Despite many decades of research on the subject, the infection remains incurable, and the factors that steer chronic Chagas disease from an asymptomatic state to clinical onset are still unclear. As the relationship between T. cruzi and the host immune system is intricate, so is the amount and diversity of scientific knowledge on the matter. Many of the mechanisms of immunity are fairly well understood, but unveiling the factors that lead each of these to success or failure, within the coordinated response as a whole, requires further research. The intention behind this Review is to compile the available information on the different aspects of the immune response, with an emphasis on those phenomena that have been studied and confirmed in the human host. For ease of comprehension, it has been subdivided in sections that cover the main humoral and cell-mediated components involved therein. However, we also intend to underline that these elements are not independent, but function intimately and concertedly. Here, we summarize years of investigation carried out to unravel the puzzling interplay between the host and the parasite

Local dispersal pathways during the invasion of the cactus moth, Cactoblastis cactorum, within North America and the Caribbean

Cactoblastis cactorum, a species of moth native to Argentina, feeds on several prickly pear cactus species (Opuntia) and has been successfully used as a biological control of invading Opuntia species in Australia, South Africa and native ruderal Opuntia species in some Caribbean islands. Since its introduction to the Caribbean its spread was uncontrolled, invading successfully Florida, Texas and Louisiana. Despite this long history of invasion, we are still far from understanding the factors determining the patterns of invasion of Cactoblastis in North America. Here, we explored three non-mutually exclusive explanations: a) a stepping stone model of colonization, b) long distance colonization due to hurricanes, and/or c) hitchhiking through previously reported commercial routes. Genetic diversity, genetic structure and the patterns of migration among populations were obtained by analyzing 10 nuclear microsatellite loci. Results revealed the presence of genetic structure among populations of C. cactorum in the invaded region and suggest that both marine commercial trade between the Caribbean islands and continental USA, as well as recurrent transport by hurricanes, explain the observed patterns of colonization. Provided that sanitary regulations avoiding humanmediated dispersal are enforced, hurricanes probably represent the most important agent of dispersal and future invasion to continental areas.Fil: Andraca Gómez, Guadalupe. Universidad Nacional Autónoma de México. Instituto de Ecología; MéxicoFil: Lombaert, Eric. Université Côte d'Azur; Francia. Centre National de la Recherche Scientifique; FranciaFil: Ordano, Mariano Andrés. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Pérez Ishiwara, Rubén. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; MéxicoFil: Boege, Karina. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; MéxicoFil: Domínguez, César A.. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; MéxicoFil: Fornoni, Juan. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; Méxic

Crystal Structure of the Complex mAb 17.2 and the C-Terminal Region of Trypanosoma cruzi P2β Protein: Implications in Cross-Reactivity

Patients with Chronic Chagas' Heart Disease possess high levels of antibodies against the carboxyl-terminal end of the ribosomal P2ß protein of Trypanosoma cruzi (TcP2ß). These antibodies, as well as the murine monoclonal antibody (mAb) 17.2, recognize the last 13 amino acids of TcP2ß (called the R13 epitope: EEEDDDMGFGLFD) and are able to cross-react with, and stimulate, the ß1 adrenergic receptor (ß1-AR). Indeed, the mAb 17.2 was able to specifically detect human β1-AR, stably transfected into HEK cells, by flow cytometry and to induce repolarisation abnormalities and first degree atrioventricular conduction block after passive transfer to naïve mice. To study the structural basis of this cross-reactivity, we determined the crystal structure of the Fab region of the mAb 17.2 alone at 2.31 Å resolution and in complex with the R13 peptide at 1.89 Å resolution. We identified as key contact residues on R13 peptide Glu3, Asp6 and Phe9 as was previously shown by alanine scanning. Additionally, we generated a model of human β1-AR to elucidate the interaction with anti-R13 antibodies. These data provide an understanding of the molecular basis of cross-reactive antibodies induced by chronic infection with Trypanosoma cruzi

Selective Blockade of Trypanosomatid Protein Synthesis by a Recombinant Antibody Anti-Trypanosoma cruzi P2β Protein

The ribosomal P proteins are located on the stalk of the ribosomal large subunit and play a critical role during the elongation step of protein synthesis. The single chain recombinant antibody C5 (scFv C5) directed against the C-terminal region of the Trypanosoma cruzi P2β protein (TcP2β) recognizes the conserved C-terminal end of all T. cruzi ribosomal P proteins. Although this region is highly conserved among different species, surface plasmon resonance analysis showed that the scFv C5 possesses very low affinity for the corresponding mammalian epitope, despite having only one single amino-acid change. Crystallographic analysis, in silico modelization and NMR assays support the analysis, increasing our understanding on the structural basis of epitope specificity. In vitro protein synthesis experiments showed that scFv C5 was able to specifically block translation by T. cruzi and Crithidia fasciculata ribosomes, but virtually had no effect on Rattus norvegicus ribosomes. Therefore, we used the scFv C5 coding sequence to make inducible intrabodies in Trypanosoma brucei. Transgenic parasites showed a strong decrease in their growth rate after induction. These results strengthen the importance of the P protein C terminal regions for ribosomal translation activity and suggest that trypanosomatid ribosomal P proteins could be a possible target for selective therapeutic agents that could be derived from structural analysis of the scFv C5 antibody paratope

Protooncogene C-myc in buccal mucosa overexpression

The superfamily c-myc would be associated with different neoplasms. C-myc is amplified when the cell proliferation index is high. For some epithelial tumors, aggressiveness and risk of metastasis would increase when there is overexpression of c-myc. The objective of this work was to study the amplification and/or overexpression of the protooncogene c-myc in benign proliferative lesions and cancer located in buccal mucosa. Consequently, we analyzed 15 footage samples corresponding to the former and 10 carcinomas corresponding to squamous cells, all HPV, and 10 control samples.Facultad de Odontologí

Molecular annotation of ketol-acid reductoisomerases fromStreptomycesreveals a novel amino acid biosynthesis interlock mediated by enzyme promiscuity

The 6-phosphogluconate dehydrogenase superfamily oxidize and reduce a wide range of substrates, making their functional annotation challenging. Ketolacid reductoisomerase (KARI), encoded by the ilvC gene in branched-chain amino acids biosynthesis, is a promiscuous reductase enzyme within this superfamily. Here, we obtain steady-state enzyme kinetic parameters for 10 IlvC homologues from the genera Streptomyces and Corynebacterium, upon eight selected chemically diverse substrates, including some not normally recognized by enzymes of this superfamily. This biochemical data suggested a Streptomyces biosynthetic interlock between proline and the branched-chain amino acids, mediated by enzyme substrate promiscuity, which was confirmed via mutagenesis and complementation analyses of the proC, ilvC1 and ilvC2 genes in Streptomyces coelicolor. Moreover, both ilvC orthologues and paralogues were analysed, such that the relationship between gene duplication and functional diversification could be explored. The KARI paralogues present in S. coelicolor and Streptomyces lividans, despite their conserved high sequence identity (97%), were shown to be more promiscuous, suggesting a recent functional diversification. In contrast, the KARI paralogue from Streptomyces viridifaciens showed selectivity towards the synthesis of valine precursors, explaining its recruitment within the biosynthetic gene cluster of valanimycin. These results allowed us to assess substrate promiscuity indices as a tool to annotate new molecular functions with metabolic implications

Ameloblastoma, HPV and p53

Ameloblastomas are odontogenic tumors with an aggressive local behavior. While Human Papilloma Virus (HPV) is often identified in various oral pathologies of the soft tissue, there are studies that associate it with ameloblastomas, having detected it in 30 to 60% of cases. It has been postulated that the gene p53 (phosphoprotein) in one of its polymorphic forms would increase the risk of malignant transformation in neoplasms in which HPV is identified.Facultad de Odontologí

Reacción en cadena de la polimerasa para la detección del VPH en mucosa bucal

Varias patologías de la mucosa bucal y de los huesos maxilares han sido relacionadas con el Virus Papiloma Humano (VPH). Aquellas conforman un amplio espectro: benignas, potencialmente malignas y malignas. Las más llamativas son las lesiones de estirpe odontogénica. El ameloblastoma es un tumor epitelial odontogénico localmente agresivo de frecuencia relativa de localización maxilar con la posibilidad de ser periférico. El carcinoma a células escamosas es la neoplasia más frecuente de la mucosa bucal. Como el VPH es un virus epiteliotrópico, sus funciones y la síntesis viral de su ADN se realiza a nivel de las células del estrato espinoso. Si bien la vía de contacto con el virus es la transmisión sexual, no puede dejarse de lado la transmisión vertical. Por este motivo existen lesiones pediátricas que se asociaron al virus tanto de bajo como de alto riesgo para la transformación a la malignidad. La técnica de reacción en cadena de la polimerasa (PCR) sigue demostrando su alta especificidad y sensibilidad para la identificación y sobre todo la genotipificación viral.Facultad de Odontologí

Reacción en cadena de la polimerasa para la detección del VPH en mucosa bucal

Varias patologías de la mucosa bucal y de los huesos maxilares han sido relacionadas con el Virus Papiloma Humano (VPH). Aquellas conforman un amplio espectro: benignas, potencialmente malignas y malignas. Las más llamativas son las lesiones de estirpe odontogénica. El ameloblastoma es un tumor epitelial odontogénico localmente agresivo de frecuencia relativa de localización maxilar con la posibilidad de ser periférico. El carcinoma a células escamosas es la neoplasia más frecuente de la mucosa bucal. Como el VPH es un virus epiteliotrópico, sus funciones y la síntesis viral de su ADN se realiza a nivel de las células del estrato espinoso. Si bien la vía de contacto con el virus es la transmisión sexual, no puede dejarse de lado la transmisión vertical. Por este motivo existen lesiones pediátricas que se asociaron al virus tanto de bajo como de alto riesgo para la transformación a la malignidad. La técnica de reacción en cadena de la polimerasa (PCR) sigue demostrando su alta especificidad y sensibilidad para la identificación y sobre todo la genotipificación viral.Facultad de Odontologí