Human serum albumin promotes interactions between HSA-IL-2 fusion protein and CD122 for enhancing immunotherapy

Interleukin 2 (IL-2) is a multifunctional cytokine that is crucial for T-lymphocytes proliferation and differentiation. However, IL-2 binds to IL-2Rα (CD25) subunit preferentially and tends to stimulate regulatory T cells (Tregs), which express high-affinity trimeric receptors (IL-2Rαβγ), resulting in immunosuppressive effects. Therefore, development of methods that enhance IL-2/CD122 interactions and activate immune responses without affecting therapeutic efficacy of IL-2 may be desirable. In this work, we constructed a recombinant IL-2 fusion protein (HSA-IL-2), comprising human serum albumin (HSA) and IL-2, there was a new interaction interface between HSA domain and CD122 in HSA-IL-2 fusion protein predicted by AlphaFold2, and followed by determining binding affinity between HSA-IL-2 and CD122 through ForteBio's Bio-Layer Interferometry technology. Strikingly, HSA did promoted interactions between HSA-IL-2 fusion protein and CD122 compared with wild-type IL-2. In vivo experiments, HSA-IL-2 fusion protein had capacity to promote CD8⁺ T cells infiltration while reducing Treg cells infiltration for boosting immunotherapeutic efficacy. Furthermore, it facilitated synergistic therapeutic effect with α-PD-L1 to inhibit tumor growth. Overall, our research unveiled an enhanced binding affinity method underlying interactions between IL-2 and CD122 via fusing albumin, and propose a promising therapeutic strategy to facilitate IL-2 administration and broaden its clinical use.