Abstract
In view of addressing the global necessity of an effective vaccine in the SARS-CoV-2 pandemic, a plasmid DNA vaccine, expressing for the spike (S) protein and formulated in lipoplexes, was manufactured and tested for in vitro transfection and in vivo immunogenicity. Blank cationic liposomes of 130.9 ± 5.8 nm in size and with a zeta potential of +48 ± 12 mV were formulated using the thin-film layer rehydration method. Liposomes were complexed with pCMVkan-S at different N/P ratios. Ratios of 0.25:1 and 1:1 were selected according to their complex stability and controlled size compared to other ratios and tested in vitro for transfection studies and in vivo for immunogenicity. Both selected formulations showed enhanced neutralizing antibody responses compared to pCMVkan-S injected alone, as well as an increased T cell response. The titers observed were similar to those of intramuscular electroporation (IM-EP), which was set as an efficacy goal.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a positive-sense single-stranded RNA virus from the coronavirus family that causes a respiratory disease called COVID-19 in humans [1]
We previously reported a SARS-CoV-2 DNA vaccine candidate expressing spike (S) protein delivered by intramuscular electroporation (IM-EP) and showing excellent immune response in mice [21]
We aimed to investigate the immunogenicity in mice of a SARS-CoV-2 DNA vaccine candidate expressing S protein formulated for intramuscular (i.m.) injection using DOTAP-based cationic liposomes (DOTAP4)
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a positive-sense single-stranded RNA virus from the coronavirus family that causes a respiratory disease called COVID-19 in humans [1]. The rapid spread of the disease and the gravity of the symptoms caused in some patients, resulting in strain on healthcare systems worldwide, led the World Health Organization (WHO) to declare COVID-19 a pandemic on 11 March 2020 [2]. The COVID-19 pathogen is suggested to be a bat-borne virus that was probably amplified in an intermediate host before transitioning to humans. Since early 2020, huge efforts have been made in vaccine research. According to WHO, there are currently more than 100 COVID-19 vaccine candidates under clinical evaluation [4]. Around 10 vaccines were approved by emergency use authorization (EUA) or by standard procedure in several countries [5]
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