Structure of the thrombin complex with triabin, a lipocalin-like exosite-binding inhibitor derived from a triatomine bug

Triabin, a 142-residue protein from the saliva of the blood-sucking triatomine bug Triatoma pallidipennis, is a potent and selective thrombin inhibitor. Its stoichiometric complex with bovine α-thrombin was crystallized, and its crystal structure was solved by Patterson search methods and refined at 2.6-Å resolution to an R value of 0.184. The analysis revealed that triabin is a compact one-domain molecule essentially consisting of an eight-stranded β-barrel. The eight strands A to H are arranged in the order A-C-B-D-E-F-G-H, with the first four strands exhibiting a hitherto unobserved up-up-down-down topology. Except for the B-C inversion, the triabin fold exhibits the regular up-and-down topology of lipocalins. In contrast to the typical ligand-binding lipocalins, however, the triabin barrel encloses a hydrophobic core intersected by a unique salt-bridge cluster. Triabin interacts with thrombin exclusively via its fibrinogen-recognition exosite. Surprisingly, most of the interface interactions are hydrophobic. A prominent exception represents thrombin’s Arg-77A side chain, which extends into a hydrophobic triabin pocket forming partially buried salt bridges with Glu-128 and Asp-135 of the inhibitor. The fully accessible active site of thrombin in this complex is in agreement with its retained hydrolytic activity toward small chromogenic substrates. Impairment of thrombin’s fibrinogen converting activity or of its thrombomodulin-mediated protein C activation capacity upon triabin binding is explained by usage of overlapping interaction sites of fibrinogen, thrombomodulin, and triabin on thrombin. These data demonstrate that triabin inhibits thrombin via a novel and unique mechanism that might be of interest in the context of potential therapeutic applications.

Vivir con Chagas en Madrid: estructuras temporales de la vivencia de un grupo de pacientes bolivianos con el diagnóstico y la atención médica a la enfermedad de Chagas en un hospital metropolitano español

How can a chronic disease determine the life of a group of people diagnosed as seropositive away from their home country? And how do we account for that lived experience. Some diseases contemplated a few decades ago as strictly rural or of poor countries, are an urban reality now and are part of the epidemiological setting in wealthy developed countries. That is the case of Chagas disease in Spain. A disease linked for a long time to rural poverty, until migratory movements occurred nationwide from the country side to the city, and recently with international migration have turned pathology into a global public health issue. Chagas disease is a chronic parasitic infection, endemic in all Latin America and can be transmitted by triatomine or “kissing bug” (Triatoma Infestans), which lives and reproduces in straw houses of rural regions. According to the Pan American Health Organization (PAHO, 2006), the disease affects approximately eight million people. It is recognized by the WHO as a “neglected tropical disease”...

Distribuição da fauna triatomínica e infecção natural pelo Trypanosoma cruzi em diferentes municípios do semiárido do Rio Grande do Norte

The triatomine fauna distribution and the natural infection by Trypanosoma cruzi was evaluated aiming the comprehension of the transmission dynamics of this parasite in the countryside of the State of Rio Grande do Norte. Additionally, the research for Trypanosoma rangeli was also investigated. The captures of triatomines were performed at sylvatic, peridomicile and domicile environments at different municipalities of the central and western mesoregions of this state. The insects were identified and examined by direct method, xenoculture and PCR to detect T. cruzi. The detection of T. rangeli was performed by direct examination of the hemolymph and multiplex PCR of 151 positive specimens for T. cruzi. Of 824 captured insects, the species were distributed in Triatoma brasiliensis (66.4%), Triatoma pseudomaculata (18.2%), Panstrongylus lutzi (12.7%) and Rhodnius nasutus (2.7%), and T. brasiliensis was found in most of the evaluated municipalities. The species were captured at nymph and adult stages, except P. lutzi, exclusively in adult stage. In the sylvatic environment were captured T. brasiliensis (57%), P. lutzi (28%) and T. pseudomaculata (15%) species. At the peridomicile environment were identified T. brasiliensis (74%), T. pseudomaculata (21%) and R. nasutus (5.0%), while in the intradomicile was found only T. brasiliensis. The infection rate of triatomines by T. cruzi was 30.4%, P. lutzi showed highest rate (78%), followed by T. brasiliensis (24.4%), T. pseudomaculata (22.6%) and R. nasutus (4.5%). Infected triatomines indexes at silvatic, peridomicile and domicile environments were of 41.8%, 20.1% and 50.0%, respectively. T. rangeli was only detected by multiplex PCR in 2.6% (4/151) of examined insects, of these 4.4% (3/67) were T. brasiliensis and 1.5% (1/63) P. lutzi species. The data showed that the positivity of P. lutzi allied to its ability to invade domicile attracted by light, suggests a likely participation of this insect between epidemiological transmission cycles of T. cruzi. T. brasiliensis was the only specie present in all environments, what reinforces its importance related to the capacity for adapting to the domestic environment, potential as a vector, and maintenance of sylvatic and domestic transmissions cycles in the semiarid, indicating the necessity of continuous epidemiological surveillance. The presence of T. rangeli in T. brasiliensis and P. lutzi was first recorded in rural zone of this State, broadening the area of occurrence of this protozoan in northeastern Brazil.

Distribuição da fauna triatomínica e infecção natural pelo Trypanosoma cruzi em diferentes municípios do semiárido do Rio Grande do Norte

The triatomine fauna distribution and the natural infection by Trypanosoma cruzi was evaluated aiming the comprehension of the transmission dynamics of this parasite in the countryside of the State of Rio Grande do Norte. Additionally, the research for Trypanosoma rangeli was also investigated. The captures of triatomines were performed at sylvatic, peridomicile and domicile environments at different municipalities of the central and western mesoregions of this state. The insects were identified and examined by direct method, xenoculture and PCR to detect T. cruzi. The detection of T. rangeli was performed by direct examination of the hemolymph and multiplex PCR of 151 positive specimens for T. cruzi. Of 824 captured insects, the species were distributed in Triatoma brasiliensis (66.4%), Triatoma pseudomaculata (18.2%), Panstrongylus lutzi (12.7%) and Rhodnius nasutus (2.7%), and T. brasiliensis was found in most of the evaluated municipalities. The species were captured at nymph and adult stages, except P. lutzi, exclusively in adult stage. In the sylvatic environment were captured T. brasiliensis (57%), P. lutzi (28%) and T. pseudomaculata (15%) species. At the peridomicile environment were identified T. brasiliensis (74%), T. pseudomaculata (21%) and R. nasutus (5.0%), while in the intradomicile was found only T. brasiliensis. The infection rate of triatomines by T. cruzi was 30.4%, P. lutzi showed highest rate (78%), followed by T. brasiliensis (24.4%), T. pseudomaculata (22.6%) and R. nasutus (4.5%). Infected triatomines indexes at silvatic, peridomicile and domicile environments were of 41.8%, 20.1% and 50.0%, respectively. T. rangeli was only detected by multiplex PCR in 2.6% (4/151) of examined insects, of these 4.4% (3/67) were T. brasiliensis and 1.5% (1/63) P. lutzi species. The data showed that the positivity of P. lutzi allied to its ability to invade domicile attracted by light, suggests a likely participation of this insect between epidemiological transmission cycles of T. cruzi. T. brasiliensis was the only specie present in all environments, what reinforces its importance related to the capacity for adapting to the domestic environment, potential as a vector, and maintenance of sylvatic and domestic transmissions cycles in the semiarid, indicating the necessity of continuous epidemiological surveillance. The presence of T. rangeli in T. brasiliensis and P. lutzi was first recorded in rural zone of this State, broadening the area of occurrence of this protozoan in northeastern Brazil.

Búsqueda de triatóminos en el entorno familiar y presencia de la enfermedad de chagas en la población de 5 a 15 años, caserío San Rafael, cantón Guanacaste, municipio de Ciudad Barrios, departamento de San Miguel en el período de mayo a julio de 2014

La enfermedad de Chagas, también conocida como tripanosomiasis americana o Mal de Chagas-Mazza, es una enfermedad parasitaria tropical, generalmente crónica, causada por el protozoo flagelado Trypanosoma cruzi. Esta enfermedad afecta mayormente a las zonas con un gran índice de pobreza, siendo un problema en El Salvador, por lo cual se realizó el estudio de búsqueda de triatóminos en el entorno familiar y presencia de la enfermedad de Chagas en la población de 5 a 15 años, caserío San Rafael, cantón Guanaste, municipio de Ciudad Barrios, departamento de San Miguel en el período de mayo a julio de 2014. Se plantearon como Objetivos Aplicar los indicadores entomológicos en los vectores capturados y las viviendas inspeccionadas donde habita la población de 5 a 15 años de edad del caserío San Rafael y determinar la presencia de la enfermedad de Chagas en la población de 5 a 15 años de edad. La Metodología empleada en el estudio es de tipo prospectivo de corte transversal, descriptivo, de campo y de laboratorio. La población estuvo formada por 63 menores de edad y 37 viviendas. Resultados de esta investigación son: respecto a las viviendas se estudiaron 37 casas donde residen menores de 5 a 15 años de edad, encontrándose en viviendas un total de 22 vectores transmisores de la enfermedad, de las cuales en 3 (13.6%) de estas se encontraron positivas al parásito Trypanosoma cruzi; favorece a la proliferación de este vector en la comunidad el tipo de construcción de las viviendas, en las cuales predominó las casas de pared, piso y tierra con adobe, tierra y teja y bahareque, tierra y teja, respectivamente En la población se examinaron a 63 menores entre 5 a 15 años, de estos se detectaron 9 casos sospechosos y confirmaron 6 casos positivos, lo que equivale al 9% a la presencia de la enfermedad de Chagas. Conclusiones Se estudiaron 37 viviendas dado que en ellas habitan menores de 5 a 15 años, 10 de estas se encuentran infectadas con el vector. Encontrando un total de 22 chinches con un porcentaje de 27.02% de infestación de vivienda por Triatoma dimidiata. Se realizó una búsqueda dentro de las viviendas, con un índice de infestación intradomiciliar de 27.02%. A pesar de la búsqueda exhaustiva realizada en el área peridomiciliar de las viviendas no se logró encontrar el vector por lo tanto el índice de infestación peridomiciliar es de 0.0%. Al realizar la compresión abdominal de los 22 triatóminos capturados 3 resultaron positivos a la presencia del parásito, obteniéndose el índice de infestación natural de T. cruzi de 13.6%. De las chinches positivas, 2 de ellas fueron encontradas en viviendas de menores que salieron negativos a las pruebas parasitológicas directas e indirectas. Un factor importante para la detección de la enfermedad es que la comunidad esté informada completamente sobre los signos y síntomas de esta, y así evitar que la enfermedad pase desapercibida.

Enfermedad de Chagas en la población de 5 a 15 años de edad y búsqueda del vector en el ámbito familiar, caserío Los Orellana, cantón San Matías del municipio de Ciudad Barrios, departamento de San Miguel en el periodo de mayo a julio de 2014

La Enfermedad de Chagas es una enfermedad causada por un parásito llamado Trypanosoma cruzi, que puede vivir en la sangre y en los tejidos de personas y animales y en el tubo digestivo de unos insectos conocidos como triatóminos o chinches. El OBJETIVO de esta investigación fue detectar casos de la Enfermedad de Chagas en la población de 5 a 15 años de edad en el caserío Los Orellana y determinar la presencia de Triatoma dimidiata en el ámbito familiar de la población en estudio. METODOLOGÍA: El estudio fue prospectivo, transversal, descriptivo, de campo y de laboratorio. La población estuvo constituida por 66 menores en edades de 5 a 15 años que cumplieron con los criterios de inclusión. Así como también la búsqueda de Triatoma dimidiata que se llevó a cabo en las viviendas donde se buscó el vector. Se llenó una cédula de entrevista con respuestas de los representantes de cada hogar inspeccionado la cual constaba de 8 preguntas referentes a la investigación. A los vectores capturados se les realizó la técnica de compresión abdominal en busca del parásito Trypanosoma cruzi en la deyecciones de estos. Posteriormente se procedió a tomar una muestra de sangre a los menores que participaron en el estudio para realizar las pruebas parasitológicas que fueron el frotis de sangre periférica, gota gruesa y concentrado de Strout en busca del parásito en la sangre y las pruebas serológicas de ELISA Tercera y Cuarta generación e Inmunofluorescencia Indirecta para confirmar los casos que resultaron reactivos. RESULTADOS OBTENIDOS: El porcentaje de casas infestadas con Triatoma dimidiata fue de 9 (21.43 %) habiendo capturado 28 triatóminos los cuales 3 presentaron el parásito que corresponde al 10.71 %. En los métodos parasitológicos directos (Frotis de sangre periférica, Gota gruesa y Concentrado de Strout) no se observó la presencia del parásito; El método serológico indirecto ELISA de Tercera generación dio como resultado 3 casos reactivos (4.5%) procediéndose a realizar su respectiva confirmación a través de ELISA de Cuarta generación e Inmunofluorescencia Indirecta, detectándose anticuerpos anti - Trypanosoma cruzi tipo IgG en las tres muestras. CONCLUSIÓN: Se encontró en un 21.43 % (9) de las casas la presencia del vector transmisor de la Enfermedad de Chagas los cuales se analizaron encontrándose en el 10.71 % (3) la presencia del parásito. Finalmente se encontró el 4.5 % (3) de los menores con la enfermedad en su fase crónica.

Domestic Rhodnius ecuadoriensis (Hemiptera, Reduviidae) infestation in Northern Peru: a comparative trial of detection methods during a six-month follow-up

Two passive methods in the assessment of intradomiciliary infestation by Rhodnius ecuadoriensis were tested: (i) the Gomes Nuñez sensor box (GN), (ii) sheets of white typing paper and (iii) one active timed manual method. The study was carried out in the Alto Chicama River Valley, Province of Gran Chimú, Department of La Libertad. The study design consisted of an initial searching of triatomines inside of the domestic environment by the manual capture active procedure (man/hour) covering all the studied houses. Then, matched pairs of GN boxes and paper sheets were simultaneously installed in the bedrooms of 207 households distributed in 19 localities. A comparative prospective trial of these passive detection devices were monitored at 2, 4 and, finally 6 months follow-up. Parasitological Trypanosoma rangeli and/or T. cruzi infections were investigated in two houses with high level of infestation by R. ecuadoriensis.16.9% of the 207 households investigated by an initial active manual method were infested with R. ecuadoriensis. The proportion of infested houses fluctuated from 6.2 to 55.5% amongst the 19 localities investigated. T. rangeli natural infection was detected in R.ecuadoriensis specimens collected in two households. Parasite rates in the bugs ranged from 16.6 to 21.7% respectively. The most striking fact was an average rate of salivary gland infection ranging from 7.4 to 8.3%. At the end of the sixth month period, a cumulative incidence of 31.4% of positive GN boxes against 15.9% for paper sheets was recorded. All three methods combined detected domestic infestation in 129 (62.3%) of the 207 houses studied in the 19 localities. The range of houses infested varies from 6.7% to 92.9%. In areas with low bug density infestation rates, the methodology experienced in our studies, seems to be the best choice for investigations on domestic R. ecuadoriensis populations.

Detecção parasitológica e molecular de tripanossomatídeos em triatomíneos sinantrópicos e primatas neotropicais no Brasil central

Tese (doutorado)—Universidade de Brasília, Faculdade de Medicina, Programa de Pós-Graduação em Medicina Tropical, 2016.

Spatial distribution of triatomines in domiciles of an urban area of the Brazilian Southeast Region

Reports of triatomine infestation in urban areas have increased. We analysed the spatial distribution of infestation by triatomines in the urban area of Diamantina, in the state of Minas Gerais, Brazil. Triatomines were obtained by community-based entomological surveillance. Spatial patterns of infestation were analysed by Ripley’s K function and Kernel density estimator. Normalised difference vegetation index (NDVI) and land cover derived from satellite imagery were compared between infested and uninfested areas. A total of 140 adults of four species were captured (100 Triatoma vitticeps, 25 Panstrongylus geniculatus, 8 Panstrongylus megistus, and 7 Triatoma arthurneivai specimens). In total, 87.9% were captured within domiciles. Infection by trypanosomes was observed in 19.6% of 107 examined insects. The spatial distributions of T. vitticeps, P. geniculatus, T. arthurneivai, and trypanosome-positive triatomines were clustered, occurring mainly in peripheral areas. NDVI values were statistically higher in areas infested by T. vitticeps and P. geniculatus. Buildings infested by these species were located closer to open fields, whereas infestations of P. megistus and T. arthurneivai were closer to bare soil. Human occupation and modification of natural areas may be involved in triatomine invasion, exposing the population to these vectors.