Ultrastructural characterization of the AAF fimbriae encoded by the hybrid agg/agg5 operon of enteroaggregative Escherichia coli and its role in interaction with host cells

• Grant number: 22/09435-9
• Support Opportunities: Scholarships in Brazil - Master
• Start date: November 01, 2022
• End date: May 31, 2024
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal Investigator: Waldir Pereira Elias Junior
• Grantee: Ester Castro Araujo
• Host Institution: Instituto Butantan. Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

Enteroaggregative Escherichia coli (EAEC) is an intestinal pathogen associated with acute and persistent childhood/adult diarrhea in developed and low-income countries, corresponding to the most prevalent diarrheagenic E. coli pathotype in our country. Asymptomatic colonization by EAEC may leads to malnutrition and impairment of physical and cognitive development in children living in a vulnerable economic situation. EAEC is characterized by the production of the aggregative adherence pattern (AA) in cultured epithelial cells, and its infection and colonization success is associated with high ability to adhere to the intestinal mucosa due to the aggregative adherence fimbriae (AAF). The five AAF variants are encoded by genes organized in an operon harboring four genetic determinants related to fimbria biogenesis: major pilin, minor pilin, usher and chaperone. The aggregative adherence plasmid (pAA), present in the most of EAEC strains, harbors the genes associated to only one of the already described AAF variants. However, a recent study identified EAEC isolates harboring the genes of two AAF variants: agg3A e agg5A, which encode the major pilin subunits of AAF/III and AAF/V, respectively. Genetic analysis identified a region that encode the complete AAF/III operon, followed by a truncated variant of the operon encoding AAF/V. Although, the assembly of the fimbria on the bacterial surface and its ultrastructural characterization were not verified. Thus, the aim of this study is to evaluate the ultrastructure of the fimbria encoded by the hybrid operon agg3A-agg5A and its role in interacting with host cells in order to understand how these fimbriae are arranged: as a unique quimeric fimbria composed by Agg3A and Agg5A, or as two separate fimbria (AAF/III e AAF/V) separately assembled. Studies characterizing the fimbrial repertoire of EAEC strains will contribute to the choice of potential specific targets for diagnosis and prophylactic immunization against EAEC.