Invasion von Mycoplasma gallisepticum in Epithelzellen

The aim of this project was to better understand the interaction between the avian pathogen Mycoplasma gallisepticum and non-phagocytic host cells. The results have demonstrated that M. gallisepticum, previously described as strictly extracellular, can act as a facultative intracellular organism and can survive in the host cell for extended period of time. This capacity can be lost upon passaging the organism in artificial media: a high passage of the strain R, Rhigh, was found not to invade eukaryotic cells, while a low passage, Rlow, was shown to enter and survive within the cells. Entry of the mycoplasma occurs within 10 min following contact with the eukaryotic cell, and intracellular, viable mycoplasmas can again leave the intracellular space. Detailed investigations revealed that passaging of the non-invasive population Rhigh in HeLa cell culture resulted in an enrichment of invasive mycoplasmas in the new population RhighP10. Examination of RhighP10 revealed that this population contained a high proportion of cells expressing two proteins with cytadhesin properties, namely GapA and CrmA, which were not expressed in the parental Rhigh population. These products are encoded by two distinct single-copy genes that are part of the same transcription unit and were shown in Rlow to undergo concomitant ON-OFF switching in expression. Further results showed that both products are not involved in the invasion process itself, but are required to cross tight cell monolayers. Infection via aerosol of birds with Rlow and Rhigh showed that after 9 days of infection, Rlow and Rhigh colonize the respiratory tract, but only Rlow was recovered from inner organs. Further experiments showed that only invasive clones expressing GapA and CrmA generated a systemic infection. These data support the in-vitro findings, although the role of GapA and CrmA in the disease process yet needs to be assessed with stable mutants lacking both products.

Zentrum für Pathobiologie

University of Connecticut, Center of Excellence for Vaccine Research, Department of Pathobiology
Funktion: Partner
Ungarische Akademie der Wissenschaften - Magyar Tudományos Akadémia
Funktion: Partner
Abteilung: Veterinary Medical Research Institute