Expressão gênica dos fatores de virulência da Shigella de amostras clínicas em modelo experimental murino

Abstract

A complex sequence of events is initiated during the Shigellose invasion process. Shigella spp is a bacillus belonging to the enterobacteria family whose virulence strategy is related to epithelial invasion and escape from the host defense system. At in vivo model, one of the methodologies used is murine pulmonary infection, which presents a good characterization to study the behavior of Shigella during epithelial cell colonization. Rationale: The knowledge of the behavior of wild Shigella clinical samples from the Amazon region carring different virulence profiles and the effect of these in vivo in a murine animal model is unprecedented. Objective: The evaluation of the virulence factors expressed during infection by strains of Shigella spp from the Fiocruz bacterial library in a murine model was performed. Material and Methods: Real-time PCR for gene expression of 18 virulence factors with seven Shigella spp samples from a study enrroling 1,500 children from 2007 to 2009 of the Public Hospitals of Manaus-Amazonas was carried out. Intranasal infection in Balb/c mice with the wild strains of Shigella occurred for in vivo evaluation. Statistical analysis was performed on Student's t-test to verify significance with p ˂ 0.05. Results: The study showed that the IpaA, IpaB, IpaC and IpaD effectors were positively expressed in the seven clinical samples of Shigella . The regulatory genes VirF and VirB were negatively expressed in the samples tested. Conclusion: The infection model based on intranasal inoculation in Balb/c mice is feasible. The pathogenic clinical picture in Balb/c evidenced the occurrence of the infectious process. Real-time PCR allowed to characterize the virulence strategies of Shigella strains. In the 48-h period of infection, there was positive expression in the clinical samples of SST3 genes IpaA, IpaB, IpaC and IpaD and regulator genes VirA; and negative of their regulators VirF and VirB, suggesting that this scenario reflects the virulence genes expressed during the second phase of the Shigella infection, maintained by cell-to-cell propagation, not its early stages.