• Vaccine Name: ARCoV
• Target Pathogen: SARS-CoV-2
• Target Disease: COVID-19
• Manufacturer: Academy of Military Science (AMS), Walvax Biotechnology, Suzhou Abogen Biosciences
• Vaccine Ontology ID: VO_0005161
• Type: mRNA vaccine
• Status: Clinical trial
• Host Species for Licensed Use: Human
• Host Species as Laboratory Animal Model: mouse, cynomolgus monkeys
• Antigen: RBD domain of S protein (Zha, et al., 2020)
• Immunization Route: Intramuscular injection (i.m.)
• Storage: After treament can store
• Description: A SARS-CoV-2 mRNA vaccine made of lipid nanoparticle-encapsulated mRNA (mRNA-LNP) encoding the receptor binding domain (RBD) of SARS-CoV-2
  (Zha, et al., 2020)

Macaque Response

• Vaccination Protocol: Two groups of macaques (n = 10/group) were immunized with 100 or 1,000 μg of ARCoV mRNA-LNP via i.m. administration and boosted with the same dose 14 days after initial immunization. The same number of monkeys (n = 10) was vaccinated with PBS as a placebo. (Zhang et al., 2020)
• Immune Response: specific IgG antibodies were readily induced on day 14 after initial immunization, and the booster immunization resulted in a notable increase in IgG titers to ∼1/5,210 and ∼1/22,085 on day 28 after initial immunization. Fifty percent of animals that received high-dose ARCoV immunization developed low-level neutralizing antibodies on day 14 after initial immunization, whereas the booster immunization resulted in a notable increase in NT50 to ∼1/699 and ∼1/6,482 in monkeys vaccinated with low- or high-dose ARCoV, respectively. SARS-CoV-2 RBD-specific T cell responses were stimulated in peripheral blood monocytes (PBMCs) from monkeys vaccinated with a low or high dose of ARCoV on day 5 after booster immunization but not from animals receiving a placebo. There was no significant difference in IL-4+/CD4+ cell response to the SARS-CoV-2 RBD between ARCoV- and placebo-treated animals, suggesting induction of a Th1-biased cellular immune response by ARCoV immunization. (Zhang et al., 2020)

Mouse Response

• Vaccination Protocol: Female BALB/c mice were immunized i.m. with 2 μg (n = 8) or 10 μg (n = 8) of ARCoV or a placebo (n = 5) and boosted with an equivalent dose 14 days later. Serum was collected 7, 14, 21, and 28 days after initial vaccination. (Zhang et al., 2020)
• Immune Response: Remarkably, a second immunization with 2 or 10 μg of ARCoV mRNA-LNP resulted in rapid elevation of immunoglobulin G (IgG) and neutralizing antibodies in mice, whereas no SARS-CoV-2-specific IgG and neutralizing antibodies were detected in sera from mice vaccinated with empty LNPs. 28 days after initial immunization, the NT50 titers in mice immunized with 2 or 10 μg of ARCoV mRNA-LNP approached ∼1/2,540 and ∼1/7,079, respectively, and the PRNT50 reached ∼1/2,194 and ∼1/5,704, respectively. (Zhang et al., 2020)
  There was a significant increase in virus-specific CD4+ and CD8+ effector memory T (Tem) cells in splenocytes from ARCoV-vaccinated mice in comparison with placebo LNPs (Figure 4 A) upon stimulation with peptide pools covering the SARS-CoV-2 RBD. Secretion of interferon γ (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin-2 (IL-2) in splenocytes from mRNA-LNP-immunized mice was significantly higher than in those that received the placebo vaccination. There was no significant difference in IL-4 and IL-6 secretion between ARCoV-immunized animals and placebo-immunized ones, demonstrating that the mRNA-LNP vaccine successfully induces a Th1-biased, SARS-CoV-specific cellular immune response. (Zhang et al., 2020)
• Challenge Protocol: Mice that received two doses of immunization of ARCoV mRNA-LNP at 2 or 10 μg were challenged i.n. with 6,000 plaque-forming units (PFUs) of SARS-CoV-2 MASCp6 40 days after initial vaccination. (Zhang et al., 2020)
• Efficacy: All mice immunized with 2 or 10 μg of ARCoV mRNA-LNP showed full protection against SARS-CoV-2 infection, and no measurable viral RNA was detected in the lungs and trachea , whereas high levels of viral RNA were detected in the lungs and trachea (∼109 and 107 RNA copy equivalents per gram, respectively) of mice in the placebo group. (Zhang et al., 2020)