title: Host cell invasion and oral infection by Trypanosoma cruzi strains of genetic groups TcI and TcIV from chagasic patients.
abstract: BACKGROUND
  Outbreaks of acute Chagas disease by oral infection have been reported frequently over the last ten years, with higher incidence in northern South America, where Trypanosoma cruzi lineage TcI predominates, being responsible for the major cause of resurgent human disease, and a small percentage is identified as TcIV. Mechanisms of oral infection and host-cell invasion by these parasites are poorly understood. To address that question, we analyzed T. cruzi strains isolated from chagasic patients in Venezuela, Guatemala and Brazil.
  
  
  METHODS
  Trypanosoma cruzi metacyclic trypomastigotes were orally inoculated into mice. The mouse stomach collected four days later, as well as the stomach and the heart collected 30 days post-infection, were processed for histological analysis. Assays to mimic parasite migration through the gastric mucus layer were performed by counting the parasites that traversed gastric mucin-coated transwell filters. For cell invasion assays, human epithelial HeLa cells were incubated with metacyclic forms and the number of internalized parasites was counted.
  
  
  RESULTS
  All TcI and TcIV T. cruzi strains were poorly infective by the oral route. Parasites were either undetectable or were detected in small numbers in the mouse stomach four days post oral administration. Replicating parasites were found in the stomach and/or in the heart 30 days post-infection. As compared to TcI lineage, the migration capacity of TcIV parasites through the gastric mucin-coated filter was higher but lower than that exhibited by TcVI metacyclic forms previously shown to be highly infective by the oral route. Expression of pepsin-resistant gp90, the surface molecule that downregulates cell invasion, was higher in TcI than in TcIV parasites and, accordingly, the invasion capacity of TcIV metacyclic forms was higher. Gp90 molecules spontaneously released by TcI metacyclic forms inhibited the parasite entry into host cells. TcI parasites exhibited low intracellular replication rate.
  
  
  CONCLUSIONS
  Our findings indicate that the poor capacity of TcI lineage, and to a lesser degree of TcIV parasites, in invading gastric epithelium after oral infection of mice may be associated with the inefficiency of metacyclic forms, in particular of TcI parasites, to migrate through the gastric mucus layer, to invade target epithelial cells and to replicate intracellularly.
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Fernando Yukio
authors.initials: FY
authors.lastname: Maeda
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Tatiana Mordente
authors.initials: TM
authors.lastname: Clemente
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Silene
authors.initials: S
authors.lastname: Macedo
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Cristian
authors.initials: C
authors.lastname: Cortez
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brazil. nyoshida@unifesp.br.
authors.forename: Nobuko
authors.initials: N
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D002465:Cell Movement; D014355:Chagas Disease / Q000469:parasitology*; D004195:Disease Models, Animal; D004705:Endocytosis; D005838:Genotype; D006367:HeLa Cells; D006651:Histocytochemistry; D006801:Humans; D051379:Mice; D009206:Myocardium / Q000473:pathology; D013270:Stomach / Q000469:parasitology / Q000473:pathology; D014349:Trypanosoma cruzi / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity*
keywords: Host cell invasion; Metacyclic trypomastigotes; Oral infection; TcI and TcIV lineages; Trypanosoma cruzi