amastigotes that persist in the colon during chronic stage murine infections have a reduced replication rate.

Abstract

Chronicinfections are typically lifelong, with small numbers of parasites surviving in restricted tissue sites, which include the gastrointestinal tract. There is considerable debate about the replicative status of these persistent parasites and whether there is a role for dormancy in long-term infection. Here, we investigatedproliferation in the colon of chronically infected mice using 5-ethynyl-2'deoxyuridine incorporation into DNA to provide 'snapshots' of parasite replication status. Highly sensitive imaging of the extremely rare 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 of the colon are associated with a reduced rate of parasite replication. Despite this, very few host cells survived infection for more than 14 days, suggesting thatpersistence continues to involve regular cycles of replication, host cell lysis and re-infection. We could find no evidence for wide-spread dormancy in parasites that persist in this tissue reservoir.