Ultrastructural damage of Trypanosoma cruzi epimastigotes exposed to decomplemented immune sera

Abstract

The susceptibility of Trypanosoma cruzi epimastigotes to lysis by normal or immune sera in a complement-dependent reaction has been reported, but the effects induced directly by immune serum depleted of complement remain unstudied. The aim of this work was to study the ultrastructural alterations induced in T. cruzi epimastigotes by immune mouse or rabbit sera with or without complement. A local isolate of T. cruzi (Queretaro) was used in all experiments. Immune sera were raised in both mouse and rabbit by immunization with T. cruzi epimastigote antigens. Light microscopy showed intense agglutination of epimastigotes when incubated with decomplemented mouse or rabbit immune sera. A distinctive ultrastructural feature of this agglutination pattern was the fusion of plasma membranes and a pattern of intercrossing between subpellicular microtubules. Agglutination was associated with fragmentation of nuclear membranes and swelling of cytoplasm, Golgi cisternae, endoplasmic reticulum, mitochondria and kinetoplast membranes. Agglutinated parasites also incorporated trypan blue stain. Results of [3H]-thymidine incorporation confirmed that epimastigotes exposed to specific antibodies in the absence of complement were incapable of proliferating. Ultrastructural changes observed in epimastigote micrographs incubated with decomplemented immune mouse sera were statistically significant (P<0.001) when compared with results obtained from images after incubation with decomplemented normal mouse sera.

Enveloped and non-enveloped viral-like particles in Trypanosoma cruzi epimastigotes

“…Thus, trypomastigotes or amastigotes infected with viral-like particles could possibly be eliminated by the cytotoxic immune response of the mammalian host, such as that enacted by NK cells, that recognize viral particles and eliminate the trypomastigotes or amastigotes containing VLPs. The fact that epimastigotes possibly harbor VLPs could have biological implications for the disease severity, because an epimastigote-like stage has been described in infected heart-smears of mice 41 - 46 . Yet, a more detailed investigation of VLPs in the trypomastigote and amastigote stages will be fundamental to better understand their biological implications on the severity of T. cruzi infection/ disease.…”