Development of an mRNA-LNP Vaccine against SARS-CoV-2: Evaluation of Immune Response in Mouse and Rhesus Macaque
Alireza Naderi Sohi, Jafar Kiani, Ehsan Arefian, Arezou Khosrojerdi, Zahra Fekrirad, Shokoofeh Ghaemi, Mohammad Kazem Zim, Arsalan Jalili, Nazila Bostanshirin, Masoud Soleimani
Abstract
Among the vaccines have been developed thus far against SARS-CoV-2, the mRNA-based ones have demonstrated more promising results regarding both safety and efficacy. Two remarkable features of the mRNA vaccines introduced by the Pfizer/BioNTech and Moderna companies are the use of (N1-methyl-pseudouridine-) modified mRNA and the microfluidics-based production of lipid nanoparticles (LNPs) as the carrier. In the present study, except Anti-Reverse Cap Analog (ARCA), no other nucleoside analogs were employed to synthesize Spike-encoding mRNA using the in vitro transcription (IVT) method. Furthermore, LNPs were prepared via the ethanol injection method commonly used for liposome formation as an alternative for microfluidics-based approaches. The produced mRNA-LNP vaccine was evaluated for nanoparticles characteristics, encapsulation and transfection efficiencies, in vitro cytotoxicity as well as stability and storability. The safety of vaccine was assessed in Balb/c mice injected with mRNA-LNPs containing 10 µg of spike-encoding mRNA. Eventually, the vaccine efficacy in inducing an immune response against SARS-CoV-2 was studied in Balb/c and C57BL/6 mice (received either 1 or 10 µg of mRNA) as well as in rhesus macaque monkeys (infused with mRNA-LNPs containing 100 µg of mRNA). The ELISA and virus neutralizing test (VNT) results showed a significant augmentation in the level of neutralizing antibodies against SARS-CoV-2. Moreover, the ELISA assay showed virus-specific IFN-γ secretion in immunized mice as a marker of TH1 cell-based immune response, whereas favorably no change in the production of IL-4 was detected.