Intraphagosomally induced gene products of pathogenic mycobacteria with inhibitory effect on phagolysosome formation in eukaryotic cells

• Applicant: Privatdozent Dr. Georg Plum
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2002 to 2005
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5374086

Virulent mycobacteria reside inside their host cells in specialized phagosomes. The pathogens actively modify this vacuole according to their obvious needs, i.e. they prevent fusion of the phagosome with lysosomes and they inhibit acidification. In contrast to non-virulent or inactivated microorganisms the phagosomes containing live virulent mycobacteria continue to exhibit characteristics of a very early endosome. The maintenance of this specialized vacuole requires a bacterium which is metabolically active. The aim of this project is to identify and characterize the relevant mycobacterial genes for this adaptation. Using a novel promoter trap we found gene sequences with specifically induced transcriptional activity inside the phagosomes in several virulent mycobacteria for. We will analyze their activity quantitatively and compare them to known intraphagosomally induced promoters of M. tuberculosis, M. bovis, and M. avium. A mycobacterial reporter plasmid with a constitutive second reporter gene as internal control will be used in reporter gene assays in macrophage infection models. Genes with a clear cut in traphagosomal induction will be examined for their potential of interacting with the host cell. Furthermore, we will express the gene products as recombinant proteins and test them for the ability to confer the inhibition of phagolysosome formation in an avirulent organism. The identification and analysis of the function of genes responsible for the evasion of the phagolysosomal fusion will potentially lead to the development of effective therapeutics for prophylaxis or treatment of mycobacterial infection.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1131: Life Inside Cells