C. Garrison Fathman

Publication Details

  • Exploiting a natural conformational switch to engineer an interleukin-2 'superkine' NATURE Levin, A. M., Bates, D. L., Ring, A. M., Krieg, C., Lin, J. T., Su, L., Moraga, I., Raeber, M. E., Bowman, G. R., Novick, P., Pande, V. S., Fathman, C. G., Boyman, O., Garcia, K. C. 2012; 484 (7395): 529-U159

    Abstract:

    The immunostimulatory cytokine interleukin-2 (IL-2) is a growth factor for a wide range of leukocytes, including T cells and natural killer (NK) cells. Considerable effort has been invested in using IL-2 as a therapeutic agent for a variety of immune disorders ranging from AIDS to cancer. However, adverse effects have limited its use in the clinic. On activated T cells, IL-2 signals through a quaternary 'high affinity' receptor complex consisting of IL-2, IL-2R? (termed CD25), IL-2R? and IL-2R?. Naive T cells express only a low density of IL-2R? and IL-2R?, and are therefore relatively insensitive to IL-2, but acquire sensitivity after CD25 expression, which captures the cytokine and presents it to IL-2R? and IL-2R?. Here, using in vitro evolution, we eliminated the functional requirement of IL-2 for CD25 expression by engineering an IL-2 'superkine' (also called super-2) with increased binding affinity for IL-2R?. Crystal structures of the IL-2 superkine in free and receptor-bound forms showed that the evolved mutations are principally in the core of the cytokine, and molecular dynamics simulations indicated that the evolved mutations stabilized IL-2, reducing the flexibility of a helix in the IL-2R? binding site, into an optimized receptor-binding conformation resembling that when bound to CD25. The evolved mutations in the IL-2 superkine recapitulated the functional role of CD25 by eliciting potent phosphorylation of STAT5 and vigorous proliferation of T cells irrespective of CD25 expression. Compared to IL-2, the IL-2 superkine induced superior expansion of cytotoxic T cells, leading to improved antitumour responses in vivo, and elicited proportionally less expansion of T regulatory cells and reduced pulmonary oedema. Collectively, we show that in vitro evolution has mimicked the functional role of CD25 in enhancing IL-2 potency and regulating target cell specificity, which has implications for immunotherapy.

    View details for DOI 10.1038/nature10975

    View details for Web of Science ID 000303200400054

    View details for PubMedID 22446627

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