Preclinical evaluation of manufacturable SARS-CoV-2 spike virus-like particles produced in Chinese Hamster Ovary cells

Abstract

Background As the COVID-19 pandemic continues to evolve, novel vaccines need to be developed that are readily manufacturable and provide clinical efficacy against emerging SARS-CoV-2 variants. Virus-like particles (VLPs) presenting the spike antigen at their surface offer remarkable benefits over other vaccine antigen formats; however, current SARS-CoV-2 VLP vaccines candidates in clinical development suffer from challenges including low volumetric productivity, poor spike antigen density, expression platform-driven divergent protein glycosylation and complex upstream/downstream processing requirements. Despite their extensive use for therapeutic protein manufacturing and proven ability to produce enveloped VLPs, Chinese Hamster Ovary (CHO) cells are rarely used for the commercial production of VLP-based vaccines. Methods Using CHO cells, we aimed to produce VLPs displaying the full-length SARS-CoV-2 spike. Affinity chromatography was used to capture VLPs released in the culture medium from engineered CHO cells expressing spike. The structure, protein content, and glycosylation of spikes in VLPs were characterized by several biochemical and biophysical methods. In vivo, the generation of neutralizing antibodies and protection against SARS-CoV-2 infection was tested in mouse and hamster models. Results We demonstrate that spike overexpression in CHO cells is sufficient by itself to generate high VLP titers. These VLPs are evocative of the native virus but with at least three-fold higher spike density. In vivo, purified VLPs elicit strong humoral and cellular immunity at nanogram dose levels which grant protection against SARS-CoV-2 infection. Conclusions Our results show that CHO cells are amenable to efficient manufacturing of high titers of a potently immunogenic spike protein-based VLP vaccine antigen.

Gag Virus-like Particles Functionalized with SARS-CoV-2 Variants: Generation, Characterization and Recognition by COVID-19 Convalescent Patients’ Sera

“…The current VLP-based SARS-CoV-2 vaccine candidates in clinical development face various obstacles, such as limited production efficiency, sub-optimal spike functionalization, differences in glycosylation depending on the selected expression platform, and complex upstream and downstream processing demands [53]. In this work, the expressions of three different rationally engineered VLP candidates were studied.…”

“…Finally, future research should focus on the ability of the presented candidates to elicit strong protective cellular and humoral immune responses in immunized mice, and compare the outcomes with those reported in the current literature, particularly for Spike VLPs based on MLV-Gag viral proteins [34] and Spike VLPs based on M and E SARS-CoV-2 proteins [53]. Such studies will help to determine if the high flexibility and strong immunogenicity of Gag-based VLPs [54] make them a better carrier platform for the presentation of the Spike protein to the vaccinated individuals.…”