In the face of the emerging variants of SARS-CoV-2, there is an urgent need to develop a vaccine that can induce fast, effective, long-lasting and broad protective immunity against SARS-CoV-2. Here, we developed a trimeric SARS-CoV-2 S protein vaccine candidate adjuvanted by PIKA, which can induce robust cellular and humoral immune responses. The results showed a high level of neutralizing antibodies induced by the vaccine was maintained for at least 400 days. In the study of non-human primates, PIKA adjuvanted S-trimer induced high SARS-CoV-2 neutralization titers and protected from virus replication in the lung following SARS-CoV-2 challenge. In addition, the long-term neutralizing antibody response induced by S-trimer vaccine adjuvanted by PIKA could neutralize multiple SARS-CoV-2 variants and there is no obvious different among the SARS- CoV-2 variants of interest or concern, including B.1.351, B.1.1.7, P.1, B.1.617.1 and B.1.617.2 variants. These data support the utility of S-trimer protein adjuvanted by PIKA as a potential vaccine candidate against SARS-CoV-2 infection.

Here, authors studied the immunogenicity and protective efficacy of S-trimer protein adjuvanted by PIKA in rabbits, mice and nonhuman primates. Rabbit studies showed that the S-trimer protein adjuvanted with PIKA induced fast, high, and long-lasting neutralizing antibody against SARS-CoV-2 virus. Adjuvanting the S-trimer with PIKA induced potent cellular immune response and showed complete protection from SARS-CoV-2 infection in mice. Furthermore, studies in nonhuman primates demonstrated that S-trimer adjuvanted by PIKA induced high neutralization titer and protected from virus replication in the lung following SARS-CoV-2 virus challenge. In addition, the long-term neutralizing antibody response induced by S-trimer vaccine adjuvanted by PIKA could neutralize multiple SARS-CoV-2 variants and there is no obvious difference among the SARS- CoV-2 variants of interest (VOI) or concern (VOC), including B.1.351, B.1.1.7, P.1, B.1.617.1 and B.1.617.2 lineage viruses. These results support the S-trimer protein adjuvanted by PIKA as a potential COVID-19 vaccine candidate.

Schematic design of the S-trimer

Article Access: https://doi.org/10.1186/s43556-021-00054-z

Website for Molecular Biomedicine: https://www.springer.com/journal/43556

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