Engineered human cells: say no to sepsis

Abstract

Mammalian systems can be a subject of cellular engineering in a similar way to bacterial cells. Our team decided to modify the existing mammalian cell signalling network of the innate immune response to bacterial infection. Binding of bacterial components (pathogen associated molecular patterns, or PAMPs) to a family of Toll-like receptors (TLRs) activates the cells of the immune system but an exaggerated response may lead to systemic inflammation and sepsis which is often fatal. We designed a feedback loop, which inhibits the signalling cascade at the weak spot – protein MyD88 – which is the consensus adaptor protein of the surface-expressed TLRs. A mathematical model of cell activation with an engineered feedback loop predicts a decrease of cellular activation after repeated stimulation of TLR. We have prepared 26 BioBricks for mammalian systems and deposited them into the BioBrick Registry at MIT. Mammalian cells transfected with the feedback loop construct performed as designed with a decrease in the cellular response upon repeated stimulation with PAMPs. Cell activation decreased without completely abolishing the responsiveness to the bacterial stimulus, therefore our engineered system represents an artificial type of immunotolerance. The Slovenian team was composed of seven undergraduate students of microbiology and biochemistry and five mentors from the National Institute of Chemistry and University of Ljubljana Faculty of Chemistry and Chemical Technology.