Non-replicative antibiotic resistance-free DNA vaccine encoding S and N proteins induces full protection in mice against SARS-CoV-2

Abstract

SARS-CoV-2 vaccines currently in use have contributed to controlling the COVID-19 pandemic. Notwithstanding, the high mutation rate, fundamentally in the spike glycoprotein (S), is causing the emergence of new variants. Solely utilizing this antigen is a drawback that may reduce the efficacy of these vaccines. Herein we present a DNA vaccine candidate that contains the genes encoding the S and the nucleocapsid (N) proteins implemented into the non-replicative mammalian expression plasmid vector, pPAL. This plasmid lacks antibiotic resistance genes and contains an alternative selectable marker for production. The S gene sequence was modified to avoid furin cleavage (Sfs). Potent humoral and cellular immune responses were observed in C57BL/6J mice vaccinated with pPAL-Sfs + pPAL-N following a prime/boost regimen by the intramuscular route applying in vivo electroporation. The immunogen fully protected K18-hACE2 mice against a lethal dose (105 PFU) of SARS-CoV-2. Viral replication was completely controlled in the lungs, brain, and heart of vaccinated mice. Therefore, pPAL-Sfs + pPAL-N is a promising DNA vaccine candidate for protection from COVID-19.

Intranasal inoculation of female BALB/c mice with replication-deficient human adenovirus type 5 expressing SARS-CoV‐2 nucleocapsid protein aggravates lung pathology upon re-encountering the antigen

“…Along with other viral protein(s), SARS-CoV-2 N-based vaccines confer protection in various animal models against infection by SARS-CoV-2 ancestral virus and variants of concern ( Dangi et al., 2021 ; Jia et al., 2021 ; Jiang et al., 2021 ; Afkhami et al., 2022 ; Castro et al., 2022 ; Wussow et al., 2023 ; Alcolea et al., 2022 ; Deschambault et al., 2022; Ishii et al., 2022 ; Wang et al., 2022 ; Chiuppesi et al., 2022 ; Hajnik et al., 2022 ; Hasanpourghadi et al., 2023 ). However, it remained unclear whether immunization with an N-based COVID-19 vaccine alone could induce immune-mediated control of SARS-CoV-2 infection.…”

“…1 G) indicate that these SARS-CoV-2 N-specific CD8 + T cells in Ad5‐N vaccination group could not efficiently kill target cells. Based on the protective roles conferred by immunization with SARS-CoV-2 N protein along with other viral proteins ( Dangi et al., 2021 ; Jia et al., 2021 ; Jiang et al., 2021 ; Afkhami et al., 2022 ; Castro et al., 2022 ; Wussow et al., 2023 ; Alcolea et al., 2022 ; Deschambault et al., 2022; Ishii et al., 2022 ; Wang et al., 2022 ; Chiuppesi et al., 2022 ; Hajnik et al., 2022 ; Hasanpourghadi et al., 2023 ), these SARS-CoV-2 N-specific CD8 + T cells might need the collaboration of T cells against other viral proteins to efficiently kill target cells. Without efficient killing, these accumulated CD8 + T cells in Ad5‐N vaccination group might keep expressing IFN‐γ ( Fig.…”

“…Since most putative T cell epitopes in SARS-CoV-2 N protein are conserved among variants of concern, it has become a target for vaccine development. Preclinical studies indicate that N-based vaccines conferred protection in various animal models against infection by SARS-CoV-2 ancestral virus ( Dangi et al., 2021 ; Jia et al., 2021 ; Jiang et al., 2021 ; Matchett et al., 2021 ; Alcolea et al., 2022 ; Ishii et al., 2022 ; Wang et al., 2022 ) or variants of concern ( Afkhami et al., 2022 ; Castro et al., 2022 ; Chiuppesi et al., 2022 ; Hajnik et al., 2022 ; Hasanpourghadi et al., 2023 ; Wussow et al., 2023 ). In particular, intranasal immunization with SARS-CoV-2 N protein along with other viral proteins induces robust mucosal and systemic N-protein-specific T cells with equivalent cross-reactivity against SARS CoV-2 ancestral virus and variants of concern ( Jiang et al., 2021 ; Afkhami et al., 2022 ; Ishii et al., 2022 ).…”

DNA Vaccines: Their Formulations, Engineering and Delivery

“…Repeat data may be harder to generate because the FDA has proposed that DNA vaccines prepared using a plasmid DNA previously documented to have an acceptable DNA biodistribution/integration profile could waive biodistribution/persistence studies. Additionally, newer bacterial-plasmid systems without antibiotic resistance genes are under investigation [ 208 ]. One bacterial-free DNA amplification system, the doggybone, has demonstrated an equivalent immune response from an entirely enzymatically constructed linear DNA vaccine [ 209 ].…”

A non-replicative antibiotic resistance-free DNA vaccine delivered by the intranasal route protects against canine leishmaniasis

“…DNA vaccines have been used in veterinary and human medicine against pathogens to a limited extent, even though they induce specific protective responses. At present, only a vaccine against hemorrhagic fever in salmonids ( 24 ) and a vaccine against SARS-CoV-2 infection in humans ( 25 ) are available, and preclinical studies with a pPAL-based vaccine have been performed in the mouse model ( 26 ). It has been shown that they induce a robust cellular and humoral immune response.…”