Cell receptor specific targeted toxins: genetic construction and characterization of an interleukin 2 diphtheria toxin-related fusion protein.

We have genetically replaced the diphtheria toxin receptor binding domain with a DNA insert encoding the T-cell growth factor interleukin-2 (IL-2). The toxin-related IL-2 fusion gene encodes a 70,586 dalton protein, pro-IL-2-toxin. The mature form of IL-2-toxin is exported to the periplasmic space of recombinant Escherichia coli and has a molecular weight of 68,086. IL-2-toxin has been partially purified from periplasmic extracts of recombinant E. coli, and it is shown to contain immunologic determinants intrinsic to both its diphtheria toxin and IL-2 components. The chimeric toxin is targeted toward IL-2 receptor bearing T-cells in vitro.