The Role of microRNAs in the Infection by T. gondii in Humans.

MicroRNAs are molecules belonging to an evolutionarily conserved family of small non-coding RNAs, which act on post-transcriptional gene regulation, causing messenger RNA (mRNA) degradation or inhibiting mRNA translation into proteins. These molecules represent potential biomarkers for diagnosis, non-invasive prognosis, and monitoring the development of the disease. Moreover, they may provide additional information on the pathophysiology of parasitic infections and guide strategies for treatment. The Apicomplexan parasite Toxoplasma gondii modifies the levels of microRNAs and mRNAs in infected host cells by modulating the innate and adaptive immune responses, facilitating its survival within the host. Some studies have shown that microRNAs are promising molecular markers for developing diagnostic tools for human toxoplasmosis. MicroRNAs can be detected in human specimens collected using non-invasive procedures. changes in the circulating host microRNAs have been associated with T. gondii infection in mice and ocular toxoplasmosis in humans. Besides, microRNAs can be amplified from samples using sensitive and molecular-specific approaches such as real-time PCR. This review presents recent findings of the role that microRNAs play during T. gondii infection and discuss their potential use of these small nuclei acid molecules to different approaches such as laboratory diagnosis, modulation of cell and tissue infected as other potential applications in human toxoplasmosis.

Integration of expression vectors into the ribosomal locus of Trypanosoma cruzi.

The expression vectors of the protozoan parasite Trypanosoma cruzi pRIBOTEX and pTREX harbor a ribosomal promoter that improves gene expression and clone selection. Interestingly, the solely presence of this 810 bp long sequence leads to the integration of these vectors into the ribosomal locus, even though circular plasmids are poorly recombinogenic. Initially, it was suggested that a 174 bp long ribosomal-specific repeat element present in the ribosomal promoter region could be responsible for the genetic exchange. On the contrary, we demonstrate that recombination of pTREX occurs within a 86 bp long region located 120 bp downstream the transcription start point (tsp1) of the ribosomal promoter, and it does not depend on the presence of the ribosomal repeat. We also determined that a 291 bp segment encompassing the tsp1 and the 86 bp long recombination region contains all necessary signals to drive transcription and complete recombination into the rRNA locus. Finally, we demonstrate that the integration of pTREX derived plasmids into the nuclear genome occurs within the first 5 h post-transfection, and that non-integrated copies are rapidly degraded.