A four-week study on the toxicity of repeated intramuscular administration of plant-based BA-CoV2-0301 vaccine against SARS-CoV-2 in Sprague-Dawley rats

In December 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified in Wuhan, China, leading to the global Coronavirus Disease pandemic. The rapid spread of SARS-CoV-2 highlighted the urgent need for effective vaccines. However, the high cost, cold storage requirements, and scalability challenges associated with mRNA vaccines have necessitated alternative vaccine technologies. In the study, the safety of a plant-based vaccine was evaluated. The vaccine, an emulsion of the SARS-CoV-2 S1 antigen and a synthetic TLR4 agonist produced and purified from <i>Nicotiana benthamiana</i>, was administered to Sprague-Dawley rats three times over 4 wk. Mortality, clinical signs, body weight, food consumption, vision, urinalysis, gross findings, organ weight, hematology, serum biochemistry, histopathology, and immunogenicity were evaluated. The results showed that antibodies were efficiently produced and maintained for one month following vaccination with the plant-derived receptor-binding domain (RBD) antigen of COVID-19. Furthermore, the rats showed no toxicological symptoms, with reversible changes at the injection site and minor histological alterations in the spinal cord and bone marrow, typical of vaccine responses. The plant-derived SARS-CoV-2 vaccine appears safe following repeated administration over 4 wk and represents a promising alternative for potential use in human clinical trials and clinical applications.