Production of novel SARS‐CoV‐2 Spike truncations in Chinese hamster ovary cells leads to high expression and binding to antibodies. Issue 9 (10th June 2022) - Minami, Shiaki A.
Abstract: SARS‐CoV‐2 Spike is a key protein that mediates viral entry into cells and elicits antibody responses. Its importance in infection, diagnostics, and vaccinations has created a large demand for purified Spike for clinical and research applications. Spike is difficult to express, prompting modifications to the protein and expression platforms to improve yields. Alternatively, the Spike receptor‐binding domain (RBD) is commonly expressed with higher titers, though it has lower sensitivity in serological assays. Here, we improve transient Spike expression in Chinese hamster ovary (CHO) cells. We demonstrate that Spike titers increase significantly over the expression period, maximizing at 14 mg L −1 on day 7. In comparison, RBD titers peak at 54 mg L −1 on day 3. Next, we develop eight Spike truncations (T1–T8) in pursuit of truncation with high expression and antibody binding. The truncations T1 and T4 express at 130 and 73 mg L −1, respectively, which are higher than our RBD titers. Purified proteins were evaluated for binding to antibodies raised against full‐length Spike. T1 has similar sensitivity as Spike against a monoclonal antibody and even outperforms Spike for a polyclonal antibody. These results suggest that T1 is a promising Spike alternative for use in various applications. Graphical Abstract and Lay Summary: SARS‐CoV‐2 Spike protein is an important component of diagnostics and vaccines, but it is difficult to produce in large quantities. In this work, transient protein production or SARS‐CoV‐2 Spike and receptor‐binding domain (RBD) was optimized, and novel Spike truncations were tested for improved characteristics. One novel truncation with improved production and antibody binding qualities shows promise for serology applications and potentially in protein‐based vaccines.