Molecular mechanisms of Trypanosoma cruzi infection by oral route

Frequent reports on outbreaks of acute Chagas' disease by ingestion of food contaminated with parasites from triatomine insects illustrate the importance of this mode of transmission. Studies on oral Trypanosoma cruzi infection in mice have indicated that metacyclic trypomastigotes invade the gastric mucosal epithelium. A key molecule in this process is gp82, a stage-specific surface glycoprotein that binds to both gastric mucin and to target epithelial cells. By triggering Ca2+ signalling, gp82 promotes parasite internalisation. Gp82 is relatively resistant to peptic digestion at acidic pH, thus preserving the properties critical for oral infection. The infection process is also influenced by gp90, a metacyclic stage-specific molecule that negatively regulates the invasion process. T. cruzi strains expressing high gp90 levels invade cells poorly in vitro. However, their infectivity by oral route varies considerably due to varying susceptibilities of different gp90 isoforms to peptic digestion. Parasites expressing pepsin-susceptible gp90 become highly invasive against target cells upon contact with gastric juice. Such is the case of a T. cruzi isolate from an acute case of orally acquired Chagas' disease; the gp90 from this strain is extensively degraded upon short period of parasite permanence in the gastric milieu. If such an exacerbation of infectivity occurs in humans, it may be responsible for the severity of Chagas' disease reported in outbreaks of oral infection.

Proviral Genomic Variation of EIAV Envelop gp 90 Gene Observed in Experimentally Infected Horse / 中国兽医学报

The present experiment was designed to observe the genetic variation of equine infectious anemia virus (EIAV) envelop gp 90 gene in infected horse. One horse was infected experimentally with P337-V70 strain and showed no clinical signs after being infected at twice with the same virus strain. Seventeen proviral sequences covering principal neutralizing domain (PND) of EIAV gp 90 gene were obtained from the buffy coat and liver of the horse through PCR amplification and cloning. Comparative analysis of the sequences revealed that some sequences contained the nucleotide insertions in the PND region. The insertions might be generated by direct repeat and strand displacement of sequence segment in their PND gene, showing different lenghts.