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To adapt to different environments, Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, expresses a different set of proteins during development. To begin to understand the mechanism that controls this differential gene expression, we have analyzed the levels of amastin and trans-sialidase mRNAs and the mRNAs encoding members of the 85-kDa glycoprotein gene family, which are differentially expressed in the T. cruzi stages found in the mammalian host. Amastin mRNA is expressed predominantly in intracellular and proliferative amastigotes. trans-Sialidase mRNAs are found mostly in forms undergoing transformation from amastigotes to trypomastigotes inside infected cells, whereas mRNAs encoding the 85-kDa glycoproteins appear only in the infective trypomastigotes released from the cells. The genes coding for these mRNA species are constitutively transcribed in all stages of T. cruzi cells, suggesting that expression is controlled post-transcriptionally during differentiation. Inhibition of transcription by actinomycin D revealed that each mRNA species has a relatively long half-life in stages where it accumulates. In the case of the transsialidase and 85-kDa glycoprotein genes, mRNA accumulation was induced by treatment with the protein synthesis inhibitor cycloheximide at the stages that preceded the normal accumulation. Therefore, mRNA stabilization may account for mRNA accumulation. mRNA degradation could be promoted by proteins with high turnover, or stabilization could be promoted by forming a complex with the translational machinery at defined times in development. Identification of the factors that induce mRNA degradation or stabilization is essential to the understanding of control of gene expression in these organisms.Gene expression in Trypanosoma cruzi as well as in other trypanosomes is largely controlled at the post-transcriptional level (1-6), although there are a few exceptions where promoters and transcriptional activation have been described (7). Well defined RNA polymerase II initiation sites have not been found, and most genes are transcribed as part of polycistronic units and are processed by trans-splicing (8, 9). During processing, capped spliced leader sequence is added to the 5Ј-end, and a polyadenosine tail is added to the 3Ј-end of mRNA (10), probably ensuring mRNA stability and transport to the cytoplasm (11). In particular, correct splicing and polyadenylation, as well as the existence of specific 3Ј-untranslated portions of the transcribed genes, have been shown to promote either mRNA stability (12) or an increase in the translational efficiency (13). However, the nature of controlling factors and how environmental modifications induce differential expression remain obscure.T. cruzi provides an attractive model to study how modifications in the environment induce differential gene expression. In the insect host, the epimastigote form of the parasite proliferates in the gut. In the posterior gut, where the nutrients become scarce, the parasite transforms into metacyclic ...

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A monoclonal antibody (B2/5) raised against Trypanosoma cruzi was able to immunoprecipitate a major 100 kDa polypeptide in 84% of the urines collected from chronic chagasic patients. Other polypeptides were also detected. The antibody recognized polypeptides on the surface of epimastigotes (150-25 kDa) and metacyclic trypomastigotes (150-50 kDa), suggesting that the antigens share a common epitope.