Relationship Among Blastocystis, the Firmicutes/Bacteroidetes Ratio and Chronic Stress in Mexican University Students.

The role played by Blastocystis in humans has been a subject of discussion due to its intestinal effects and modifications in the intestinal microbiota. We aimed to analyze the relationship between Blastocystis subtypes ST1-4 and 7, the Firmicutes to Bacteroidetes ratio (F/B ratio) of fecal microbiota, and chronic stress in university students. This study had a cross-sectional design with a sample of 202 students. We analyzed fecal and hair samples, and stress inventories were applied to the students. The results showed a frequency of Blastocystis-colonized students of 52.97%. Regarding fecal microbiota, a median RAU of 0.801 for Firmicutes and 0.82 of Bacteroidetes were obtained, with an F/B ratio of 0.83. A low F/B ratio (66.04%) was more frequent in Blastocystis-colonized students, whereas a high F/B ratio (68.09%) (p = < 0.0001) was found in the Blastocystis-non-colonized. Only Blastocystis ST3 did not significantly correlate with a low F/B ratio (p = 0.290). The ST4 was associated with lower values of cortisol (p = 0.030), psychological stress (p = 0.040), and lower frequency of constipation (p = 0.010). Only two students with the ST1 had abdominal pain (p = 0.007). Our results suggest that colonization by Blastocystis subtypes can modify the intestinal microbiota due to a decreased ratio between the two most representative phyla (F/B). Also, the results of this study show that ST4 colonization is related to a lower level of chronic stress.

Characterization of human astrovirus cell entry.

Human astroviruses (HAstV) are a frequent cause of gastroenteritis in young children and immunocompromised patients. To understand the early steps of HAstV infection in the highly permissive Caco-2 cell line, the binding and entry processes of the virus were characterized. The half-time of virus binding to the cell surface was about 10 min, while virus decapsidation took around 130 min. Drugs affecting clathrin-mediated endocytosis, endosome acidification, and actin filament polymerization, as well as those that reduce the presence of cholesterol in the cell membrane, decreased the infectivity of the virus. The infection was also reduced by silencing the expression of the clathrin heavy chain (CHC) by RNA interference or by overexpression of dominant-negative mutants of dynamin 2 and Eps15. Furthermore, the entry of HAstV apparently depends on the maturation of endosomes, since the infection was reduced by silencing the expression of Rab7, a small GTPase involved in the early- to late-endosome maturation. Altogether, our results suggest that HAstV enters Caco-2 cells using a clathrin-dependent pathway and reaches late endosomes to enter cells. Here, we have characterized the mechanism used by human astroviruses, important agents of gastroenteritis in children, to gain entry into their host cells. Using a combination of biochemical and genetic tools, we found that these viruses enter Caco-2 cells using a clathrin-dependent endocytic pathway, where they most likely need to travel to late endosomes to reach the cytoplasm and begin their replication cycle.