A team of scientists from India has found that the plasmid DNA-based vaccine candidate ZyCoV-D administered via Needle Free Injection System (NFIS) can significantly induce the production of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein-specific IgG and neutralizing antibodies for a prolonged period. They observed that 1 mg and 2 mg doses of the vaccine candidate administered via NFIS and syringe needle, respectively, could induce immune responses in only a limited number of monkeys, whereas 2 mg dose administered via NFIS could significantly induce the production of spike S1-specific IgGs and neutralizing antibodies during the immunization and viral challenge phases.
A robust antibody response induced by the 2 mg via NFIS regimen of the vaccine candidate was observed up until 14 weeks, further increasing in response to viral challenge and continued to 15 days post-infection. With the same regimen of the vaccine candidate, the robust neutralizing antibody response was observed from 6 weeks, which continued to increase throughout the immunization phase. A reduction in viral load was observed by day 7 post-infection in the throat and nasal samples collected from immunized monkeys. Complete viral clearance was observed by day 14 post-infection. The study findings reveal that a 2 mg dose of the DNA-based vaccine candidate ZyCoV-D administered via NFIS is highly efficient in inducing both binding and neutralizing antibody titers in monkeys, indicating the immunogenic efficacy of the vaccine candidate.
Ref link: https://www.biorxiv.org/content/10.1101/2021.02.02.429480v1