IL-15:IL-15 receptor alpha superagonist complex: high-level co-expression in recombinant mammalian cells, purification and characterization

Cytokine. 2011 Dec;56(3):804-10. doi: 10.1016/j.cyto.2011.09.028. Epub 2011 Oct 22.


IL-15, a promising cytokine for treating cancer and viral diseases, is presented in trans by the IL-15 receptor (IL-15R) alpha-chain to the IL-15Rβγc complex displayed on the surface of T cells and natural killer (NK) cells. We previously reported that an asparagine to aspartic acid substitution at amino acid 72 (N72D) of IL-15 provides a 4-5-fold increase in biological activity compared to the native molecule. In this report, we describe Chinese hamster ovary (CHO) cell expression of a soluble complex (IL-15 N72D:IL-15RαSu/Fc) consisting of the IL-15 N72D superagonist and a dimeric IL-15Rα sushi domain-IgG1 Fc fusion protein. A simple but readily scalable affinity and ion exchange chromatography method was developed to highly purify the complex having both IL-15 binding sites fully occupied. The immunostimulatory effects of this complex were confirmed using cell proliferation assays. Treatment of mice with a single intravenous dose of IL-15N72D:IL-15RαSu/Fc resulted in a significant increase in CD8+ T cells and NK cells that was not observed following IL-15 treatment. Pharmacokinetic analysis indicated that the complex has a 25-h half-life in mice which is considerably longer than <40-min half-life of IL-15. Thus, the enhanced activity of the IL-15N72D:IL-15RαSu/Fc complex is likely the result of the increased binding activity of IL-15N72D to IL-15Rβγc, optimized cytokine trans-presentation by the IL-15RαSu domain, the dimeric nature of the cytokine domain and its increased in vivo half-life compared to IL-15. These findings indicate that this IL-15 superagonist complex could serve as a superior immunostimulatory therapeutic agent.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Body Weight / drug effects
  • CHO Cells
  • Cell Separation
  • Chromatography, Gel
  • Cricetinae
  • Cricetulus
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Interleukin-15 / agonists*
  • Interleukin-15 / isolation & purification*
  • Interleukin-15 Receptor alpha Subunit / agonists*
  • Interleukin-15 Receptor alpha Subunit / isolation & purification*
  • Lymphocytes / drug effects
  • Lymphocytes / metabolism
  • Male
  • Mammals / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mutant Proteins / metabolism
  • Organ Size / drug effects
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Recombinant Fusion Proteins / pharmacokinetics
  • Recombinant Fusion Proteins / pharmacology
  • Recombination, Genetic / genetics*


  • Interleukin-15
  • Interleukin-15 Receptor alpha Subunit
  • Mutant Proteins
  • Recombinant Fusion Proteins