An induced population of Trypanosoma cruzi epimastigotes more resistant to complement lysis promotes a phenotype with greater differentiation, invasiveness, and release of extracellular vesicles.

Introduction: Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi, which uses blood-feeding triatomine bugs as a vector to finally infect mammalian hosts. Upon entering the host, the parasite needs to effectively evade the attack of the complement system and quickly invade cells to guarantee an infection. In order to accomplish this, T. cruzi expresses different molecules on its surface and releases extracellular vesicles (EVs). Methods: Here, we have selected a population of epimastigotes (a replicative form) from T. cruzi through two rounds of exposure to normal human serum (NHS), to reach 30% survival (2R population). This 2R population was characterized in several aspects and compared to Wild type population. Results: The 2R population had a favored metacyclogenesis compared with wild-type (WT) parasites. 2R metacyclic trypomastigotes had a two-fold increase in resistance to complementmediated lysis and were at least three times more infective to eukaryotic cells, probably due to a higher GP82 expression in the resistant population. Moreover, we have shown that EVs from resistant parasites can transfer the invasive phenotype to the WT population. In addition, we showed that the virulence phenotype of the selected population remains in the trypomastigote form derived from cell culture, which is more infective and also has a higher rate of release of trypomastigotes from infected cells. Conclusions: Altogether, these data indicate that it is possible to select parasites after exposure to a particular stress factor and that the phenotype of epimastigotes remained in the infective stage. Importantly, EVs seem to be an important virulence fator increasing mechanism in this context of survival and persistence in the host.

Active learning tools improve the learning outcomes, scientific attitude, and critical thinking in higher education: Experiences in an online course during the COVID-19 pandemic.

Active teaching methodologies have been placed as a hope for changing education at different levels, transiting from passive lecture-centered to student-centered learning. With the health measures of social distance, the COVID-19 pandemic forced a strong shift to remote education. With the challenge of delivering quality education through a computer screen, we validated and applied an online course model using active teaching tools for higher education. We incorporated published active-learning strategies into an online construct, with problem-based inquiry and design of inquiry research projects to serve as our core active learning tool. The gains related to students' science learning experiences and their attitudes toward science were assessed by applying questionnaires before, during, and after the course. The course counted on the participation of 83 students, most of them (60.8%) from postgraduate students. Our results show that engagement provided by active learning methods can improve performance both in hard and soft skills. Students' participation seems to be more relevant when activities require the interaction of information, prediction, and reasoning, such as open-ended questions and design of research projects. Therefore, our data show that, in pandemic, active learning tools benefit students and improve their critical thinking and their motivation and positive positioning in science.