Fig. 5.

Coculture of mammalian cells and bacteria: a pilot study for paracrine-based antibody selection. In this ecosystem, E. coli produce multiple copies of phages that act on mammalian cells in the same community. The mammalian cells were engineered to have a reporter system by infecting CellSensor NFAT-bla CHO-K1 cells with lentivirus expressing TrkB as described previously (9). If the phage displays an agonist antibody, the mammalian cell would be turned on and show fluorescence (Pacific blue) on flow cytometry. (A) Mammalian cells cultured together with E. coli that produce a whole phage library are not activated. (B) Mammalian cells cultured together with E. coli that produce a random phage are not activated. (C) Mammalian cells cultured together with E. coli that produce TrkB agonist scFv-bearing phage are activated and show fluorescence (Pacific blue).