Biological behavior of Trypanosoma cruzi stocks obtained from the state of Amazonas, Western Brazilian Amazon, in mice

Abstract

Introduction:The biological diversity of circulating Trypanosoma cruzi stocks in the Amazon region most likely plays an important role in the peculiar clinic-epidemiological features of Chagas disease in this area. Methods: Seven stocks of T. cruzi were recently isolated in the State of Amazonas, Brazil, from humans, wild mammals, and triatomines. They belonged to the TcI and Z3 genotypes and were biologically characterized in Swiss mice. Parasitological and histopathological parameters were determined. Results: Four stocks did not promote patent parasitemia in mice. Three stocks produced low parasitemia, long pre-patent periods, and a patent period of 1 day or oscillating parasitemia. Maximum parasitemia ranged from 1,400 to 2,800 trypomastigotes/0.1mL blood. Mice inoculated with the T. cruzi stocks studied showed low positivity during fresh blood examinations, ranging from 0% to 28.6%. In hemoculture, positivity ranged from 0% to 100%. Heart tissue parasitism was observed in mice inoculated with stocks AM49 and AM61. Stock AM49 triggered a moderate inflammatory process in heart tissue. A mild inflammatory process was observed in heart tissue for stocks AM28, AM38, AM61, and AM69. An inflammatory process was frequently observed in skeletal muscle. Examinations of brain tissue revealed inflammatory foci and gliosis in mice inoculated with stock AM49. Conclusions: Biological and histopathological characterization allowed us to demonstrate the low infectivity and virulence of T. cruzi stocks isolated from the State of Amazonas. Keywords: Chagas disease. Trypanosoma cruzi. Virulence. Pathogenicity. Swiss mice. Amazon. RESUMO Introdução:A diversidade biológica dos estoques Trypanosoma cruzi circulantes na Região Amazônica pode desempenhar importante papel nas características clínico-epidemiológicas peculiares da doença de Chagas nesta área. Métodos: Sete isolados de T. cruzi do Estado do Amazonas provenientes de humanos, mamíferos silvestres e triatomíneos, pertencentes aos genótipos TcI e Z3, foram biologicamente caracterizados em camundongos Swiss. Foram avaliados parâmetros parasitológicos e histopatológicos. Resultados: Quatro isolados não produziram parasitemia patente em camundongos. Três isolados promoveram baixa parasitemia com longos períodos pré-patentes, período patente de um dia ou parasitemia oscilante. A parasitemia máxima variou de 1.400 a 2.800 tripomastigotas/0,1mL de sangue. Os camundongos inoculados com os isolados estudados mostraram baixa positividade no exame a fresco, variando de 0 a 28,6%. Para a hemocultura, a positividade variou de 0 a 100%. Parasitismo cardíaco foi observado em camundongos inoculados com os isolados AM49 e AM61. O isolado AM49 produziu inflamação moderada no tecido cardíaco. Processo inflamatório discreto foi observado no tecido cardíaco de camundongos inoculados com os isolados AM28, AM38, AM61 e AM69. Processo inflamatório em músculo esquelético foi muito frequente. O exame do tecido cerebral revelou focos inflamatórios e gliose em camundongos inoculados com o i...

Trypanosoma cruzi IV Causing Outbreaks of Acute Chagas Disease and Infections by Different Haplotypes in the Western Brazilian Amazonia

“…Acquiring knowledge about the biological properties of the TcIV lineage, which certainly plays an important role in the Chagas disease pathogenesis and response to the specific chemotherapy in the Amazon region, represents a challenge for future research. Our preliminary results indicate that Amazonian T. cruzi isolates promote scarce parasitemia and low virulence and pathogenicity in mice in comparison to TcII strains [54], [55]. At least in Brazil, TcII and rarely TcI, appear to be exclusively responsible for the tissue lesions in chronic Chagas disease [19], [23], [56], [57].…”

Chagas disease in the State of Amazonas: history, epidemiological evolution, risks of endemicity and future perspectives

“…TcIV predominates among orally transmitted acute human cases (34) , and TcI predominates among the isolated and chronic cases (35) (38) , suggesting their association with different transmission profiles. The T. cruzi isolates showed variable behavior in experimental infections in mice, promoting low parasitemia, virulence and pathogenicity, which is compatible with the low parasitemia and morbidity profi le of CD in humans and with the poor performance of diagnostic methods in the region (43) . In mice, the frequency of resistance to benznidazole among the TcIV isolates was signifi cantly higher than in the TcI isolates (35) .…”

Piassaba palm extractivism as an associated factor with Chagas disease: seroprevalence and immunological profile in native inhabitants of the Central Amazonia, Brazil

“…Despite the high prevalence, several clinical studies have reported that the acute phase is marked with high morbidity, including some fatal cases of dilated cardiomyopathy 6,19 . It has been reported that Chagas disease in the Middle Negro river has a clinical profile of low morbidity and mortality in the chronic phase 12 . The biological diversity of circulating T. cruzi has an important role in the clinical, immunological and epidemiological features of Chagas disease in the Amazon basin 12,13,18 .…”

“…It has been reported that Chagas disease in the Middle Negro river has a clinical profile of low morbidity and mortality in the chronic phase 12 . The biological diversity of circulating T. cruzi has an important role in the clinical, immunological and epidemiological features of Chagas disease in the Amazon basin 12,13,18 . It has been suggested that the low parasite load and low levels of serum IgG anti-T. cruzi might reflect the discrete typing units of T. cruzi in this case TcI prevalent in the Brazilian Amazon, instead of the TcII, TcV and TcVI genotypes predominant in the domestic transmission cycle of the South Cone in the South America, where chagasic patients are characterised by higher parasitaemia, virulence and pathogenicity 12 .…”