Differential modulation of mouse heart gene expression by infection with twoTrypanosoma cruzistrains: a transcriptome analysis
Authors: Castro TBR , Canesso MCC , Boroni M , Chame DF , de Laet Souza D , Toledo NE , Tahara EB , Pena SD , Machado CR , Chiari E , Macedo AM , Franco GR 
Published: March 2019

The protozoanTrypanosoma cruzi(T. cruzi) is a well-adapted parasite to mammalian hosts and the pathogen of Chagas disease in humans. As both host andT. cruziare highly genetically diverse, many variables come into play during infection, making disease outcomes difficult to predict. One important challenge in the field of Chagas disease research is determining the main factors leading to parasite establishment in the chronic stage in some organs, mainly the heart and/or digestive system. Our group previously showed that distinct strains ofT. cruzi(JG and Col1.7G2) acquired differential tissue distribution in the chronic stage in dually-infected BALB/c mice. To investigate changes in the host triggered by the two distinctT. cruzistrains, we assessed the gene expression profile of BALB/c mouse hearts infected with either JG, Col1.7G2 or an equivalent mixture of both parasites during the initial phase of infection. This study demonstrates a clear distinction in host gene expression modulation by both parasites. Col1.7G2 strongly activated Th1-polarized immune signature genes, whereas JG showed only minor activation of the host immune response. Moreover, JG strongly reduced the expression of genes for ribosomal proteins and mitochondrial proteins related to the electron transport chain. Interestingly, evaluation of gene expression in mice inoculated with the mixture of parasites showed expression profiles for both up- and down-regulated genes, indicating the coexistence of both parasite strains in the heart during the acute phase. This study suggests that different strains ofT. cruzimay be distinguished by their efficiency in activating the immune system, modulating host energy and reactive oxygen species production and decreasing protein synthesis during early infection, which may be crucial in defining parasite persistence in specific organs.

Author Summary

The causative agent of Chagas disease,Trypanosoma cruzi, retains high genetic diversity, and its populations vary greatly across geographic locations. TheT. cruzimammalian hosts, including humans, also have high genetic variation, making it difficult to predict the disease outcome. Accordingly, this variability must be taken into account in several studies aiming to interrogate the effect of polyparasitism in drug trials, vaccines, diagnosis or basic research. Therefore, there is a growing need to consider the interaction between the pathogen and the host immune system in mixed infections. In the present work, we present an in-depth analysis of the gene expression of hearts from BALB/c mice infected with Col1.7G2 and JG alone or a mixture of both strains. Col1.7G2 induced a higher Th1 inflammatory response, while JG exhibited a weaker activation of immune response genes. Furthermore, JG-infected mice showed a notable reduction in the expression of genes responsible for mitochondrial oxidative phosphorylation and protein synthesis. Interestingly, the mixture-infected group displayed changes in gene expression as caused by both strains. Overall, we provided new insights into the host-pathogen interaction in the context of single and dual infection, showing remarkable differences in host gene expression modulation by twoT. cruzistrains.