AUTHOR=Alcolea Pedro J. , Larraga Jaime , Rodríguez-Martín Daniel , Alonso Ana , Loayza Francisco J. , Rojas José M. , Ruiz-García Silvia , Louloudes-Lázaro Andrés , Carlón Ana B. , Sánchez-Cordón Pedro J. , Nogales-Altozano Pablo , Redondo Natalia , Manzano Miguel , Lozano Daniel , Palomero Jesús , Montoya María , Vallet-Regí María , Martín Verónica , Sevilla Noemí , Larraga Vicente TITLE=Non-replicative antibiotic resistance-free DNA vaccine encoding S and N proteins induces full protection in mice against SARS-CoV-2 JOURNAL=Frontiers in Immunology VOLUME=13 YEAR=2022 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.1023255 DOI=10.3389/fimmu.2022.1023255 ISSN=1664-3224 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.