Attempts to recreate all the developmental stages of
Trypanosoma cruzi
in vitro have thus far been met with partial success. It is possible, for instance,
to produce trypomastigotes in tissue culture and to obtain metacyclic trypomastigotes
in axenic conditions. Even though
T. cruzi amastigotes are known to differentiate
from trypomastigotes and metacyclic trypomastigotes, it has only been possible
to generate amastigotes in vitro from the tissue-culture-derived trypomastigotes.
The factors and culture conditions required to trigger the transformation of metacyclic
trypomastigotes into amastigotes are as yet undetermined. We show here that pre-incubation
of metacyclic trypomastigotes in culture (MEMTAU) medium at 37°C for 48 h
is sufficient to commit the parasites to the transformation process. After 72
h of incubation in fresh MEMTAU medium, < 90% of the metacyclic parasites differentiate
into forms that are morphologically indistinguishable from normal amastigotes.
SDS-PAGE, Western blot and PAABS analyses indicate that the transformation of
axenic metacyclic trypomastigotes to amastigotes is associated with protein, glycoprotein
and antigenic modifications. These data suggest that (a)
T. cruzi amastigotes
can be obtained axenically in large amounts from metacyclic trypomastigotes, and
(b) the amastigotes thus obtained are morphological, biological and antigenically
similar to intracellular amastigotes. Consequently, this experimental system may
facilitate a direct, in vitro assessment of the mechanisms that enable
T. cruzi
metacyclic trypomastigotes to transform into amastigotes in the cells of mammalian
hosts.
