Trypanosoma cruzi amastigotes have a reduced replication rate during chronic stage infections

Abstract

Chronic Trypanosoma cruzi infections are typically life-long, with small numbers of parasites surviving in restricted tissue sites, which include the gastro-intestinal tract. There is considerable debate about the replicative status of these persistent parasites. Here, we investigated T. cruzi proliferation in the colon of chronically infected mice using 5-ethynyl-2deoxyuridine incorporation into DNA to provide "snapshots" of parasite replication. Highly sensitive imaging of infection foci at single cell resolution revealed that parasites are three times more likely to be in S-phase during the acute stage than during the chronic stage. By implication, chronic infections are associated with a reduced rate of parasite replication. Despite this, very few host cells survive infection for >14 days, suggesting that T. cruzi persistence continues to involve regular cycles of replication, host cell lysis and re-infection. Therefore, long-term persistence in the colon is more likely to be associated with reduced proliferation than with dormancy.