Project Details
Projekt
Analysis of Acinetobacter trimeric adhesin (Ata) in multi-drug resistant clinical isolates and its contribution to the pathogenic potential of Acinetobacter baumannii
Applicants
Dr. Stephan Göttig; Professor Dr. Volkhard A. J. Kempf
Subject Area
Metabolism, Biochemistry and Genetics of Microorganisms
Term
from 2014 to 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 258351992
The outer membrane protein Acinetobacter trimeric autotransporter adhesin (Ata) is a new member of the family of bacterial trimeric autotransporter adhesins and represents an important pathogenicity factor of Acinetobacter baumannii. We have generated Ata-deficient mutants of A. baumannii (Δata) and analysed the role of Ata in adherence to extracellular matrix components and endothelial and epithelial cells, respectively. We established a novel human organ infection model (human umbilical cord veins) mimicking the bacteria-host interactions close to the physiological situation in humans (peristaltic blood flow conditions) and, furthermore, determined the role of Ata using the Galleria mellonella infection model. Ata expression mediates adhesion to the host and correlates with the induction of a proinflammatory phenotype of infected endothelial cells and the induction of apoptosis. Ata and the newly discovered plasminogen-binding and complement-inhibitory protein CipA proved to be two key determinants of complement resistance of A. baumannii which inhibit activation of the alternative complement cascade pathway. Our data suggest that Ata plays a crucial role in the pathogenicity in vitro, ex vivo and in vivo and influences the outcome of infections with A. baumannii. In the proposed work programme, we will address the following questions: (i) Identification of host cell receptors involved in Ata-dependent adhesion of A. baumannii to human endothelial cells. For this purpose, a siRNA library-based approach to systemically silence adhesion-molecule expression will be employed, followed by specific validation of identified target genes in vitro (endothelial cells) and ex vivo (dynamic human organ infection model). Next (ii), we will analyse the host cell response with a special emphasis on inflammation (e.g., functional assays of leukocyte chemotaxis and transmigration); moreover, Ata-mediated activation of apoptosis will be analysed. (iii) By using systematic transcriptome analysis ("dual RNA-seq") we will identify signalling pathways in host cells and in A. baumannii to determine how Ata affects the host cell response upon infection and to identify virulence traits of A. baumannii (in vitro, ex vivo and in vivo). (iv) Molecular mechanisms by which Ata facilitates complement evasion -in combination with CipA- will be elucidated by investigating their interactions with purified complement components and sera of infected patients. Our experiments will clarify the role of Ata in triggering the host response, help to understand the pathobiology underlying A. baumannii infections and the role of trimeric autotransporter adhesins in general. This might aid to develop novel therapeutic concepts to combat infections with MDR bacteria.
DFG Programme
Research Units
