An Anti-Programmed Death-1 Antibody (alpha PD-1) Fusion Protein That Self-Assembles into a Multivalent and Functional alpha PD-1 Nanoparticle

Cancer immune checkpoint therapy has achieved remarkable clinical successes in various cancers. However, current immune checkpoint inhibitors block the checkpoint of not only the immune cells that are important to canter therapy but also the immune cells that are irrelevant to the therapy. Such an indiscriminate blockade limits the efficacy and causes the autoimmune toxicity of the therapy. It might be beneficial to use a carrier to target immune checkpoint inhibitors to cancer reactive immune cells. Here, we explore a method to load the inhibitors into carriers. We used the anti-programmed death-1 antibody (alpha PD-1) as a model immune checkpoint inhibitor. First, we generated a recombinant single-chain variable fragment (scFv) of aPD-1. Then, we designed and generated a fusion protein consisting of the scFv and an amphiphilic immune-tolerant elastin-like polypeptide (iTEP). Because of the amphiphilic iTEP, the fusion was able to self-assemble into a nanoparticle (NP). The NP was proved to block the PD-1 immune checkpoint in vitro and in vivo. Particularly, the NP exacerbated diabetes development in nonobese diabetic mice as effectively as natural, intact aPD-1. In summary, we successfully expressed aPD-1 as a recombinant protein and linked aPD-1 to a NP, which lays a foundation to develop a delivery system to target aPD-1 to a subpopulation of immune cells.