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Synergistic toxicity of IFN-gamma-producing Escherichia coli K12 cells
R Dijkmans1, F Cornette, S Kreps
1Laboratory Genetics and Biotechnology, Vlaamse Instelling voor Technologisch Onderzoek (VITO), Mol, Belgium.
Abstract:
Genetically modified microorganisms (GMMs) are frequently used as producers of mammalian immunomodulatory proteins, e.g. interferons and interleukins. Here we have examined the question of whether such GMMs interact in a way different from that of their non-modified parent micro-organisms with mammalian antimicrobial defence systems. As a typical GMM host micro-organism we used Escherichia coli K12, and as a typical immunomodulatory protein produced by a GMM we used mouse interferon-gamma (MuIFN-gamma). Two experimental systems are described in which synergistic "toxic" biological effects are induced by a combined treatment with E. coli and MuIFN-gamma but not, or less so, by the parental strain and the recombinant protein separately. First, it is shown that the IFN-gamma-producing GMM, or mixtures of E. coli cells and IFN-gamma, are cytolytic for mouse embryo fibroblastoid cells (MEF), whereas no cell killing occurs in MEF cultures treated with control E. coli cells or in those treated with bacteria-free recombinant IFN-gamma. Second, it is demonstrated that intraperitoneal injection in mice of high but not low numbers of control E. coli K12 cells induces a shock-like mortality, whereas co-injection with IFN-gamma induces killing at low numbers. IFN-gamma-producing E. coli cells cause a mortality rate that does not differ from that of control E. coli cells, probably because in these experimental conditions the level of recombinant MuIFN-gamma per cell is insufficiently high. Taken together, these data indicate that synergistic toxic effects induced by bacteria and their recombinant products can occur and may in certain situations enhance the intrinsic toxic capacity of the GMM. Synergistic toxic effects may thus be of relevance for identifying the safety level that should be employed when working with GMMs.
Insights
Genetically modified microorganisms (GMMs) producing proteins like mouse interferon-gamma (MuIFN-gamma) can exhibit synergistic toxicity. This combined effect with bacteria enhances cellular damage and mortality in experimental models.
Area of Science:
- Microbiology
- Immunology
- Biotechnology
Background:
- Genetically modified microorganisms (GMMs) are widely used for producing mammalian immunomodulatory proteins, such as interferons and interleukins.
- The interaction of GMMs with mammalian antimicrobial defense systems may differ from their non-modified counterparts.
- Understanding these interactions is crucial for assessing the safety of GMMs.
Purpose of the Study:
- To investigate whether genetically modified microorganisms (GMMs) interact differently with mammalian antimicrobial defense systems compared to their parent strains.
- To determine if synergistic toxic effects occur when GMMs producing immunomodulatory proteins are combined with the proteins themselves.
- To evaluate the implications of these synergistic effects for GMM safety assessments.
Main Methods:
- Utilized Escherichia coli K12 as a model GMM host and mouse interferon-gamma (MuIFN-gamma) as the model immunomodulatory protein.
- Assessed cytotoxicity using mouse embryo fibroblastoid cells (MEF) treated with GMMs, control bacteria, and/or recombinant MuIFN-gamma.
- Evaluated in vivo toxicity by intraperitoneal injection of control E. coli K12 and/or MuIFN-gamma into mice.
Main Results:
- Combined treatment of E. coli and MuIFN-gamma showed synergistic cytotoxicity towards MEF cells, unlike individual treatments.
- In vivo studies revealed that co-injection of E. coli and MuIFN-gamma induced mortality at lower bacterial doses compared to E. coli alone.
- IFN-gamma-producing E. coli did not show increased mortality compared to control E. coli, likely due to insufficient recombinant protein levels per cell.
Conclusions:
- Synergistic toxic effects can arise from the combined action of bacteria and their recombinant products.
- These synergistic effects can enhance the intrinsic toxicity of GMMs.
- The findings highlight the importance of considering synergistic toxicity for establishing appropriate safety levels when working with GMMs.