Jorge Freitas

Ancestral Genomes, Sex, and the Population Structure of Trypanosoma cruzi

Acquisition of detailed knowledge of the structure and evolution of Trypanosoma cruzi populations is essential for control of Chagas disease. We profiled 75 strains of the parasite with five nuclear microsatellite loci, 24Sα RNA genes, and sequence polymorphisms in the mitochondrial cytochrome oxidase subunit II gene. We also used sequences available in GenBank for the mitochondrial genes cytochrome B and NADH dehydrogenase subunit 1. A multidimensional scaling plot (MDS) based in microsatellite data divided the parasites into four clusters corresponding to T. cruzi I (MDS-cluster A), T. cruzi II (MDS-cluster C), a third group of T. cruzi strains (MDS-cluster B), and hybrid strains (MDS-cluster BH). The first two clusters matched respectively mitochondrial clades A and C, while the other two belonged to mitochondrial clade B. The 24Sα rDNA and microsatellite profiling data were combined into multilocus genotypes that were analyzed by the haplotype reconstruction program PHASE. We identified 141 haplotypes that were clearly distributed into three haplogroups (X, Y, and Z). All strains belonging to T. cruzi I (MDS-cluster A) were Z/Z, the T. cruzi II strains (MDS-cluster C) were Y/Y, and those belonging to MDS-cluster B (unclassified T. cruzi) had X/X haplogroup genotypes. The strains grouped in the MDS-cluster BH were X/Y, confirming their hybrid character. Based on these results we propose the following minimal scenario for T. cruzi evolution. In a distant past there were at a minimum three ancestral lineages that we may call, respectively, T. cruzi I, T. cruzi II, and T. cruzi III. At least two hybridization events involving T. cruzi II and T. cruzi III produced evolutionarily viable progeny. In both events, the mitochondrial recipient (as identified by the mitochondrial clade of the hybrid strains) was T. cruzi II and the mitochondrial donor was T. cruzi III.

The MHC Gene Region of Murine Hosts Influences the Differential Tissue Tropism of Infecting Trypanosoma cruzi Strains

We have previously demonstrated that both parasite genetic variability and host genetic background were important in determining the differential tissue distribution of the Col1.7G2 and JG T. cruzi monoclonal strains after artificial infections in mice. We observed that the JG strain was most prevalent in hearts of mouse lineages with the MHC haplotype H-2 d (BALB/c and DBA2), while Col1.7G2 was predominant in hearts from C57BL/6 mice, which have the H-2 b haplotype. To assess whether the MHC gene region indeed influenced tissue tropism of T. cruzi, we used the same two parasite strains to infect C57BL/6 (H-2 b) and C57BLKS/J (H-2 d) mice; the latter strain results from the introgression of DBA2 MHC region into the C57BL/6 background. We also performed ex vivo infections of cardiac explants from four congenic mice lineages with the H-2 b and H-2 d haplotypes arranged in two different genetic backgrounds: C57BLKS/J (H-2 d) versus C57BL/6 (H-2 b) and BALB/c (H-2 d) versus BALB/B10-H2b (H-2 b). In agreement with our former observations, Col1.7G2 was predominant in hearts from C57BL/6 mice (H-2 b), but we observed a clear predominance of the JG strain in hearts from C57BLKS/J animals (H-2 d). In the ex vivo experiments Col1.7G2 also prevailed in explants from H-2 b animals while no predominance of any of the strains was observed in H-2 d mice explants, regardless of the genetic background. These observations clearly demonstrate that the MHC region influences the differential tissue distribution pattern of infecting T. cruzi strains, which by its turn may be in a human infection the determinant for the clinical forms of the Chagas disease.

Trypanosoma cruzi-triatomine associations and the presence of mixed infections in single triatomine bugs in Paraná state, Brazil

Eighteen strains of Trypanosoma cruzi isolated from two species of triatomines in the state of Paraná, Brazil, were characterized molecularly using three strategies: RAPD (randomly amplified polymorphic DNA) with four primers, analysis of the D7 polymorphic region of the 24Sα rDNA, and RFLP (restriction fragment length polymorphism) of region 5′ of the mitochondrial gene COII (cytochrome oxidase subunit 2). The phenogram constructed with the RAPD data showed that only three strains isolated from Panstrongylus megistus collected in the Municipality of Arapongas were grouped together in a sub-branch. None of the other 15 strains could be clustered according to triatomine species or geographical origin. The strains were grouped with the T. cruzi I reference sample, indicating closer association with the sylvatic transmission cycle of T. cruzi in the state of Paraná. However, analyses of the rDNA and COII gene polymorphisms revealed the presence of populations from both T. cruzi I and II major lineages. In half of the analyzed triatomines, we found parasites from both lineages coinfecting the same bugs. Of these, most (6/9) were isolated from Triatoma sordida, and 3/9 from Panstrongylus megistus. These results contribute to a better comprehension of the ecoepidemiology of Chagas’ disease in Paraná, and raise questions about the role of studies of polyclonal population dynamics for controlling the transmission of T. cruzi to humans in this region.

Ingestion of saliva during carbohydrate feeding by Lutzomyia longipalpis (Diptera; Psychodidae)

The aim of this study was to obtain experimental evidence that phlebotomine saliva is actually ingested during the carbohydrate ingestion phase (before and after blood digestion). The ingestion of carbohydrate was simulated as it occurs in the field by offering the insects balls of cotton soaked in sucrose, sucrose crystals or orange juice cells. The results obtained here showed that ingestion occurred under each condition investigated, as indicated by the presence of apyrase, an enzyme used as a marker to detect saliva in the insect gut and/or carbohydrate sources. Saliva ingestion by phlebotomine during the carbohydrate ingestion phase is important to explain how it could promote starch digestion and to trigger Leishmania promastigotes to follow a differentiation pathway as proposed previously by some authors.

De Hans-Georg Gadamer para Walter Benjamin, no meio Paul Celan e o “Acúmulo de palavras” [Wortaufschütung]

A partir da leitura de Hans-Georg Gadamer do poema “Acumulo de palavras” [ Wortaufschutung ], de Paul Celan, publicado no ciclo de poemas Hausto-cristal [ Atemkristall ], de 1965, este artigo analisa algumas hipoteses que sugerem um redirecionamento da interpretacao proposta por Gadamer em direcao a um vies de teoria historiografica cuja matriz residiria em Walter Benjamin, iluminando, desse modo, uma outra possibilidade de leitura do poema de Celan.

Sobre as coleções e colecionadores em Ver: Amor, de David Grossman

Este artigo define-se como a analise do conceito de colecao no romance do escritor israelense David Grossman (2007), Ver: Amor . Nesse sentido, pretendemos elaborar um percurso pelas caracteristicas principais do romance de Grossman que giram em torno de uma escrita enciclopedica, labirintica, metalinguistica, rizomatica e fragmentaria. Caracteristicas, convem ressaltar, tipicas de um romance pos-moderno, sobretudo, de um romance que pretende se confrontar com questoes durissimas sobre o exterminio, a morte, a catastrofe, mas que tambem, aponta para temas como a vida, a memoria, o amor e a sobrevivencia.

Anotações sobre a teoria da alegoria barroca de Walter Benjamin

A primeira reabilitacao do conceito de alegoria realizada pelo filosofo Walter Benjamin encontra-se em sua teoria sobre as pecas do drama tragico alemao, na obra Origem do Drama Tragico Alemao . Buscaremos, no desenvolvimento deste artigo, apresentar uma breve introducao sobre a obra de Benjamin, cuja prioridade sera a explanacao da teoria benjaminiana da alegoria relacionada com a producao da arte do Barroco do seculo XVII. Procuraremos, ainda, discutir as peculiaridades filosoficas, historicas e teologicas dessa teoria, atentando, sobretudo, para sua constituicao como expressao de uma epoca