Engineered endosymbionts that alter mammalian cell surface marker, cytokine and chemokine expression

Abstract

AbstractDeveloping modular tools that direct mammalian cell function and activity through controlled delivery of essential regulators would improve methods of guiding tissue regeneration, enhancing cellular-based therapeutics and modulating immune responses. To address this challenge,Bacillus subtiliswas developed as a chassis organism for engineered endosymbionts (EES) that escape phagosome destruction, reside in the cytoplasm of mammalian cells, and secrete proteins that are transported to the nucleus to impact host cell response and function. Two synthetic operons encoding either the mammalian transcription factorsStat-1andKlf6orKlf4andGata-3were recombined into the genome ofB. subtilisexpressing listeriolysin O (LLO) fromListeria monocytogenesand expressed from regulated promoters. Controlled expression of the mammalian proteins fromB. subtilisLLO in the cytoplasm of J774A.1 macrophage/monocyte cells altered surface marker, cytokine and chemokine expression. Modulation of host cell fates displayed some expected patterns towards anti- or pro-inflammatory phenotypes by each of the distinct transcription factor pairs with further demonstration of complex regulation caused by a combination of the EES interaction and transcription factors. Expressing mammalian transcription factors from engineered intracellularB. subtilisas engineered endosymbionts comprises a new tool for directing host cell gene expression for therapeutic and research purposes.