Interleukin-2 mutants with enhanced alpha-receptor subunit binding affinity.
Stimulation of T-cells by IL-2 has been exploited for treatment of metastatic renal carcinoma and melanoma. However, a narrow therapeutic window delimited by negligible stimulation of T-cells at low picomolar concentrations and undesirable stimulation of NK cells at nanomolar concentrations hampers IL-2-based therapies. We hypothesized that increasing the affinity of IL-2 for IL-2Ralpha may create a class of IL-2 mutants with increased biological potency as compared with wild-type IL-2. Towards this end, we have screened libraries of mutated IL-2 displayed on the surface of yeast and isolated mutants with a 15-30-fold improved affinity for the IL-2Ralpha subunit. These mutants do not exhibit appreciably altered bioactivity at 0.5-5 pM in steady-state bioassays, concentrations well below the IL-2Ralpha equilibrium binding constant for both the mutant and wild-type IL-2. A mutant was serendipitously identified that exhibited somewhat improved potency, perhaps via altered endocytic trafficking mechanisms described previously.
Rao
Balaji M
BM
Department of Chemical Engineering and Biological Engineering Division, Massachusetts Institute of Technology, MIT 66-552, Cambridge, MA 02139, USA.
Girvin
Andrew T
AT
Ciardelli
Thomas
T
Lauffenburger
Douglas A
DA
Wittrup
K Dane
KD
D002455:Cell Division / Q000235:genetics / Q000502:physiology; D003001:Cloning, Molecular; D007376:Interleukin-2 / Q000235:genetics* / Q000378:metabolism*; D053645:Interleukin-2 Receptor alpha Subunit; D009154:Mutation; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D018123:Receptors, Interleukin / Q000378:metabolism*; D012441:Saccharomyces cerevisiae
D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit; D018123:Receptors, Interleukin