A generic cell-based biosensor converts bacterial infection signals into chemoattractants for immune cells.

Abstract

Bacterial infections are a major challenge to human health. Although various potent antibiotics have emerged in the last decades, current challenges arise from an increasing number of multi-drug-resistant species. Infections associated with implants represent a particular challenge since they are usually diagnosed at an advanced state, and are difficult to treat with antibiotics due to the formation of protecting biofilms. In this study, we designed and explored a synthetic biology-inspired, cell-based bio-sensor/actor for the detection and counteraction of bacterial infections. The system is generic as it senses diverse types of infections and acts by enhancement of the endogenous immune system. The strategy is based on genetically engineered sensor/actor cells that can sense type I interferons (IFNs), which are released by immune cells at the early stages of infections. IFN signalling activates a synthetic circuit to induce reporter genes with a sensitivity of only 5 pg/ml of IFN and leads to a therapeutic protein output of 100ng/ml, resulting in theranostic cells that visualize and fight infections. Robustness and resilience were achieved by the implementation of a positive feedback loop. We show that diverse gram-positive and gram-negative implant-associated pathogenic bacteria activate the cascade in co-culture systems in a dose-dependent manner. Finally, we show that this system can be used to secrete chemoattractants facilitating the infiltration of immune cells in response to bacterial triggers. Together, the system is not only universal to bacterial infections but at the same time hypersensitive allowing the sensing of infections at initial stages.