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Virulence plasmid-associated HeLa cell induced cytotoxicity of Yersinia pseudotuberculosis
1Division of Experimental Medicine, National Defence Research Institute, Umeå, Sweden.
Abstract:
A virulent plasmid-containing strain and an isogenic plasmid-free avirulent derivative strain of Y. pseudotuberculosis were compared with respect to the interaction with cultured HeLa cells. No difference in the ability to adhere to HeLa cells was observed. Both strains invaded the HeLa cells to the same degree. The internalized bacteria did not multiply over a 24-h period. When incubated at 37 degrees C HeLa cells infected with the virulent plasmid-containing strain YPIII(pIB1) showed morphological changes in contrast to the avirulent plasmid-free strain YPIII which showed no such effect. This cytotoxic effect was recorded after about 2 hours of incubation at 37 degrees C. This event could be prevented by addition of gentamicin 1 hour before the predicted time of the morphological changes of the HeLa cells. A number of transposon Tn5 derived plasmid mutants were analyzed and a correlation was found between virulence and ability to induce cytotoxicity. The cytotoxic effect was not absolutely linked to Ca2+-dependence because one Ca2+-independent mutant was found to be cytotoxic. This mutant was able to express the temperature-inducible plasmid-coded outer membrane proteins (YOPs) as well as the V-antigen. On the molecular level a strong correlation was found between expression of some of the YOPs, the V-antigen and the cytotoxic effect. However, one of these YOPs, YOP1, could be eliminated as being an important determinant of cytotoxicity because an insertion mutant of the corresponding structural gene was still able to induce cytotoxicity.
Insights
The Yersinia pseudotuberculosis plasmid is crucial for virulence, inducing cytotoxic effects on HeLa cells. This cytotoxicity is linked to the expression of specific Yersinia outer proteins (YOPs) and V-antigen, independent of Ca2+-dependence.
Area of Science:
- Microbiology
- Cell Biology
- Pathogenesis
Background:
- Yersinia pseudotuberculosis virulence is often associated with plasmid-encoded factors.
- The interaction of Y. pseudotuberculosis with host cells is critical for disease development.
Purpose of the Study:
- To investigate the role of the Y. pseudotuberculosis plasmid in host cell interactions and cytotoxicity.
- To identify specific virulence factors responsible for cytotoxic effects on cultured HeLa cells.
Main Methods:
- Comparative analysis of a virulent plasmid-containing strain (YPIII(pIB1)) and an isogenic avirulent plasmid-free strain of Y. pseudotuberculosis using cultured HeLa cells.
- Assessment of bacterial adherence, invasion, intracellular multiplication, and induction of host cell morphological changes.
- Analysis of transposon Tn5-derived plasmid mutants to correlate virulence and cytotoxicity, including investigation of Ca2+-dependence and expression of Yersinia outer proteins (YOPs) and V-antigen.
Main Results:
- No significant differences in adherence or invasion of HeLa cells were observed between virulent and avirulent strains.
- The virulent strain induced significant morphological changes (cytotoxicity) in HeLa cells at 37°C, which could be prevented by gentamicin treatment.
- A strong correlation was found between virulence, cytotoxicity, and the expression of certain YOPs and V-antigen, although YOP1 was not essential for cytotoxicity.
Conclusions:
- The plasmid of Y. pseudotuberculosis encodes factors essential for inducing cytotoxicity in HeLa cells.
- Cytotoxicity is closely linked to the expression of specific YOPs and V-antigen, contributing to the virulence of Y. pseudotuberculosis.
- The cytotoxic mechanism is not solely dependent on Ca2+ regulation and involves specific plasmid-associated virulence factors.