Role of GP82 in the Selective Binding to Gastric Mucin during Oral Infection with Trypanosoma cruzi

Abstract

Oral infection by Trypanosoma cruzi has been the primary cause of recent outbreaks of acute Chagas' diseases. This route of infection may involve selective binding of the metacyclic trypomastigote surface molecule gp82 to gastric mucin as a first step towards invasion of the gastric mucosal epithelium and subsequent systemic infection. Here we addressed that question by performing in vitro and in vivo experiments. A recombinant protein containing the complete gp82 sequence (J18), a construct lacking the gp82 central domain (J18*), and 20-mer synthetic peptides based on the gp82 central domain, were used for gastric mucin binding and HeLa cell invasion assays, or for in vivo experiments. Metacyclic trypomastigotes and J18 bound to gastric mucin whereas J18* failed to bind. Parasite or J18 binding to submaxillary mucin was negligible. HeLa cell invasion by metacyclic forms was not affected by gastric mucin but was inhibited in the presence of submaxillary mucin. Of peptides tested for inhibition of J18 binding to gastric mucin, the inhibitory peptide p7 markedly reduced parasite invasion of HeLa cells in the presence of gastric mucin. Peptide p7*, with the same composition as p7 but with a scrambled sequence, had no effect. Mice fed with peptide p7 before oral infection with metacyclic forms developed lower parasitemias than mice fed with peptide p7*. Our results indicate that selective binding of gp82 to gastric mucin may direct T. cruzi metacyclic trypomastigotes to stomach mucosal epithelium in oral infection.

The gp82 Surface Molecule of Trypanosoma cruzi Metacyclic Forms

“…In vitro , MT traverse a gastric mucin-coated transwell fi lter ( c ) Schematic representation of gp82 recombinant proteins fused to GST, containing the full-length gp82 sequence or the C-terminal domain only, which display similar cell adhesion capacity, and the construct lacking P4 and P8 sites, which is unable to bind to host cells and to inhibit MT invasion as effi ciently as the empty fi lter, but are blocked by a submaxillary mucin-coated fi lter (Fig. 6.3a ), confi rming previous fi ndings (Staquicini et al 2010 ). Gp82 binds to gastric mucin mainly through the surface-exposed portion of sequence P7 (Fig.…”

“…cruzi infection, MT binding to gastric mucin is the fi rst step for migration toward the underlying target epithelial cells. MT, as well as the recombinant protein based on gp82, bind to gastric mucin but not to submaxillary mucin (Staquicini et al 2010 ). This binding property is associated with the parasite ability to migrate through the gastric mucus barrier.…”

“…cruzi lineage that infects bats (Marcili et al 2009 ). Gp82 contains in its C-terminal domain the cell adhesion sites P4 and P8 , as well as the gastric mucin-binding sequence P7 (Staquicini et al 2010 ), which are 100 % identical in G and CL strains (Fig. 6.1 ).…”

“…The relevance of gp82 sequence P7 in oral T . cruzi infection was demonstrated in experiments in which mice that received peptide P7, before oral MT administration, exhibited in the histological sections of the stomach much fewer amastigote nests at day four post-infection, and later on much fewer parasites circulating in the bloodstream, as compared to mice given the scrambled peptide P7* (Staquicini et al 2010 ).…”

Fibronectin-Degrading Activity of Trypanosoma cruzi Cysteine Proteinase Plays a Role in Host Cell Invasion

“…There is no information on whether FN is required for MT internalization. As different T. cruzi developmental forms may differentially interact with ECM components, we investigated the participation of FN in MT entry into human epithelial cells, as well as the FN-binding property of gp82, the metacyclic-stage surface molecule implicated in T. cruzi infection in vitro as well as in vivo (11)(12)(13). Gp82 is an adhesion molecule that binds to host cells in a receptor-mediated manner and promotes MT internalization (11).…”