Expression, purification and characterization of recombinant human interleukin-2-serum albumin (rhIL-2-HSA) fusion protein in Pichia pastoris

Interleukin-2 (IL-2) plays important roles in variety of immune functions. Recombinant IL-2 has become an important therapeutic protein for therapy of melanoma and renal cell carcinoma. Previously, it was proved that the therapeutic efficacy of rIL-2 expressed in Saccharomyces cerevisiae was improved by prolonging its in vivo half-life through genetic fusion with albumin. In this study, a fusion protein composed of hIL-2 genetically fused to HSA was expressed as a secretory protein under AOX1 (alcohol oxidase 1) promoter in Pichia pastoris. An effective strategy was established to express rhIL-2-HSA fusion protein in 5 L scale and the optimal purification procedure was investigated. The purity of rhIL-2-HSA in final product was about 95%. The purified rhIL-2-HSA fusion protein could be recognized by both anti-hIL-2 and anti-human serum albumin monoclonal antibody. Bioactivity analysis showed that the purified rhIL-2-HSA fusion protein displayed high level activity on proliferation in IL-2 dependent manner in CTLL2-cells. rhIL-2-HSA fusion protein also showed a extended half-life in plasma compared with IL-2 when tested in a BALB/c mouse model. This study provides an alternative strategy for large-scale production of bioactive rhIL-2-HSA fusion protein using P. pastoris as an expression host.

► rhIL-2-HSA gene was cloned under the control of the AOX1 promoter and expressed in pichia GS115.
► Efficient fermentation strategy and purification procedures of rhIL-2-HSA protein were established.
► Purified rhIL-2-HSA stimulates proliferation of CTLL-2 cells with a dose-dependent manner similarly to the standard hIL-2.
► Elimination half-life of IL2-HSA in plasma after a single subcutaneous dose prolonged to about 13.24 h in mice.