Evaluating the Neutralizing Ability of a CpG-Adjuvanted S-2P Subunit Vaccine Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Variants of Concern

• Published in: Clinical infectious diseases Vol. 74; no. 11; pp. 1899 - 1905
• Main Authors: Lien, Chia-En, Kuo, Tsun-Yung, Lin, Yi-Jiun, Lian, Wei-Cheng, Lin, Meei-Yun, Liu, Luke Tzu-Chi, Cheng, Jinyi, Chou, Yu-Chi, Chen, Charles
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 10.06.2022
• Subjects: Adjuvants, Immunologic; Animals; Antibodies, Neutralizing; Antibodies, Viral; COVID-19 - prevention & control; Humans; Major and Commentaries; Rats; SARS-CoV-2 - genetics; Spike Glycoprotein, Coronavirus; Vaccines, Subunit; Viral Envelope Proteins; COVID-19; subunit SARS-CoV-2 vaccine; variant of concern; SARS-CoV-2; immunogenicity
• ISSN: 1058-4838; 1537-6591; 1537-6591
• DOI: 10.1093/cid/ciab711

Abstract Background Variants of concern (VoCs) have the potential to diminish the neutralizing capacity of antibodies elicited by vaccines. MVC-COV1901 is a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine consisting of recombinant prefusion stabilized spike protein S-2P adjuvanted with CpG 1018 and aluminum hydroxide. We explored the effectiveness of MVC-COV1901 against the VoCs. Methods Serum samples were taken from rats and phase 1 clinical trial human subjects immunized with a low, medium, or high dose of MVC-COV1901. The neutralizing titers of serum antibodies were assayed with pseudoviruses coated with the SARS-CoV-2 spike protein of the wild-type (WT), D614G, Alpha, or Beta variants. Results Rats vaccinated twice with vaccine containing high doses of antigen retained high levels of neutralization activity against the Beta variant, albeit with a slight reduction compared to WT. After the third dose, neutralizing titers against the Beta variant were noticeably enhanced regardless of the amount of antigen used for immunization. In humans, vaccinated phase 1 subjects still showed appreciable neutralization abilities against the D614G, Alpha, and Beta variants, although neutralizing titers were significantly reduced against the Beta variant. Conclusions Two doses of MVC-COV1901 were able to elicit neutralizing antibodies against SARS-CoV-2 variants with an overall tendency of inducing higher immune response at a higher dose level. The neutralizing titers to the Beta variant in rats and humans were lower than those for WT and the Alpha variant. An additional third dose in rats was able to partially compensate for the reduction in neutralization against the Beta variant. We have demonstrated that immunization with MVC-COV1901 was effective against VoCs. CpG 1018–adjuvanted S-2P subunit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine administered to rats and humans induced neutralizing antibodies against circulating SARS-CoV-2 variants of concern, including the Beta variant.