Phoolcharoen W.Shanmugaraj B.Khorattanakulchai N.Sunyakumthorn P.Pichyangkul S.Taepavarapruk P.Praserthsee W.Malaivijitnond S.Manopwisedjaroen S.Thitithanyanont A.Srisutthisamphan K.Jongkaewwattana A.Tomai M.Fox C.B.Taychakhoonavudh S.Mahidol University2023-05-152023-05-152023-04-24Vaccine Vol.41 No.17 (2023) , 2781-27920264410Xhttps://repository.li.mahidol.ac.th/handle/20.500.14594/81361Cost-effective, and accessible vaccines are needed for mass immunization to control the ongoing coronavirus disease 2019 (COVID-19), especially in low- and middle-income countries (LMIC). A plant-based vaccine is an attractive technology platform since the recombinant proteins can be easily produced at large scale and low cost. For the recombinant subunit-based vaccines, effective adjuvants are crucial to enhance the magnitude and breadth of immune responses elicited by the vaccine. In this study, we report a preclinical evaluation of the immunogenicity, efficacy and safety of a recombinant plant-based SARS-CoV-2 RBD vaccine formulated with 3M-052 (TLR7/8 agonist)-Alum adjuvant. This vaccine formulation, named Baiya SARS-CoV-2 Vax 2, induced significant levels of RBD-specific IgG and neutralizing antibody responses in mice. A viral challenge study using humanized K18-hACE2 mice has shown that animals vaccinated with two doses of Baiya SARS-CoV-2 Vax 2 established immune protection against SARS-CoV-2. A study in nonhuman primates (cynomolgus monkeys) indicated that immunization with two doses of Baiya SARS-CoV-2 Vax 2 was safe, well tolerated, and induced neutralizing antibodies against the prototype virus and other viral variants (Alpha, Beta, Gamma, Delta, and Omicron subvariants). The toxicity of Baiya SARS-CoV-2 Vax 2 was further investigated in Jcl:SD rats, which demonstrated that a single dose and repeated doses of Baiya SARS-CoV-2 Vax 2 were well tolerated and no mortality or unanticipated findings were observed. Overall, these preclinical findings support further clinical development of Baiya SARS-CoV-2 Vax 2.VeterinaryArticleSCOPUS10.1016/j.vaccine.2023.03.0272-s2.0-851514195151873251836963999