O papel do receptor NLRP6 na manutenção da homeostase intestinal frente à infecção por via oral pela Brucella abortus

Abstract

Brucella abortus is a gram-negative, facultative intracellular bacterium that causes Brucellosis acquired through ingestion of meat, milk and its contaminated derivatives. In addition, it one of the most widespread bacterial zoonosis, leading to abortion in domestic and farmed animals. Recent studies suggest that the NLRP6, a member of NOD-like receptor family, plays an important role in the regulation of immune response, epithelial cell turnover and in the composition of the gut microbiota. In this context, the objective of this work was to study the mechanisms involved in the invasion and establishment of oral Brucella abortus infection, exploring the role of NLRP6 in the intestinal homeostasis during infection. Wild-type (WT) and NLRP6 (Nlrp6-/-) deficient animals were inoculated intragastrically with B. abortus virulent strain S2308 and samples from different tissues were collected at different times. As results, it was observed that Nlrp6-/- mice were more resistant to oral infection, presenting reduction of bacterial load in the liver when compared to WT animals. However, this phenotype was not observed when the infection occurred intraperitoneally, suggesting that NLRP6 is important in the phase of B. abortus invasion through the intestinal mucosa. In addition, oral infection induced an increase in intestinal permeability in infected WT mice, but not in Nlrp6-/-. Significant changes in the composition of the intestinal microbiota during infection in both groups of animals were also observed, suggesting dysbiosis. Therefore, our findings suggest the participation of the gut microbiota in the context of B. abortus infection. Additionally, fecal transplantation of the microbiota from the infected WT and Nlrp6-/- to germ-free mice resulted in similar donor permeability phenotype. However, depletion of the microbiota by broad-spectrum antibiotics in WT animals prevent leaky gut and reduced systemic bacterial load. On the other hand, depletion of the microbiota in Nlrp6-/- favored the invasion of B. abortus, even without intestinal permeability change. In summary, these results indicate that oral infection by Brucella abortus alters intestinal homeostasis in favor of its invasion and establishment of systemic infection in a mechanism dependent of NLRP6. NLRP6 is important in the control of bacteria survival, in the maintenance of the intestinal epithelial barrier and in the negative regulation of the immune response against oral infection caused by Brucella abortus, in which the gut microbiota seems to play a critical role