Efeito das frações do veneno de Bothrops jararaca na interação bactéria-hospedeiro in vitro entre Escherichia coli enteropatogênica e células epiteliais.

YANG, M. J. Effect of fractions of Bothrops jararaca venom in bacteria-host interaction in vitro between enteropathogenic Escherichia coli and epithelial cells. 2015. 64 p. Masters thesis (Microbiology) – Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, 2015. Enteropathogenic Escherichia coli (EPEC) is a microorganism of great importance in public health, being one of the main causes of diarrhea in children in developing countries. EPEC causes a histopathologic lesion named attaching and effacing (A/E), characterized by destruction of intestine microvilli and formation of a pedestal, due to the intimate adherence of the bacterium to the epithelial cell and rearranging of cytoskeleton. The genes responsible for this lesion are encoded in a pathogenicity island named LEE, which is, among other factors, subject to regulation by quorum sensing, a cell density dependent mechanism that involves low mass signaling molecules known as autoinducers. Bothrops jararaca venom is a complex mixture of different components such as metalloprotease, serine protease, phospholipase A2, L-amino acid oxidase, bradykinin potentiating peptides, among others, with different biological effects in both bacteria and eukaryotic cells. To this day, there has not been references describing their effects on bacteria-host interactions, and the major part of the works with snake venom have been focused on components with a high molecular weight. The goal of this work was to analyze the effect of fractions of Bothrops jararaca venom with different molecular weights, including that ones containing components with low molecular weight. For this purpose, venom of Bothrops jararaca was fractionated by ultrafiltration, using membranes with molecular weight cut-off of 10 kDa and 3 kDa. According to colorimetric assay using resazurin, none of the fractions had bactericidal effect against EPEC. Adherence assay in HEp-2 cells with different concentrations of the different fractions of venom showed that, independent of the fraction tested, a concentration of 100 ng caused an increase of bacterial adherence when compared to the control test, however the adherence decreased when the concentration of the fraction was increased, suggesting the possibility that there is a component in the venom that potentiates the EPEC adherence to the epithelial cells up to a certain concentration. The phenotype observed with samples treated with a higher concentration were similar to that observed in the control test, except for the one with 1000 ng of fraction lower than 3 kDa, in which the bacterial adherence decreased in comparison to the control test, indicating the presence of a component with low molecular weight that is able to negatively affect the EPEC adherence as its concentration is increased. These results show how the fractions of venom of serpents with different molecular weight can affect the bacteria-host cell interaction, and present a biological potential of components of low molecular weight present in the venom, which tend to be neglected in favor of those with a higher molecular weight.