Comparison of Wild Type DNA Sequence of Spike Protein from SARS-CoV-2 with Optimized Sequence on The Induction of Protective Responses Against SARS-Cov-2 Challenge in Mouse Model

Abstract

Genetic optimization of Nucleic Acid immunogens is important for potentially improving their immune potency. A COVID-19 DNA vaccine is in phase III clinical trial which is based on a promising highly developable technology platform. Here, we show optimization in mice generating a pGX-9501 DNA vaccine encoding full-length spike protein, which results in induction of potent humoral and cellular immune responses, including neutralizing antibodies, that block hACE2-RBD binding of live CoV2 virus in vitro. Optimization resulted in improved induction of cellular immunity by pGX-9501 as demonstrated by increased IFN-γ expression in both CD8+ and CD4 + T cells and this was associated with more robust antiviral CTL responses compared to unoptimized constructs. Vaccination with pGX-9501 induced subsequent protection against virus challenge in a rigorous hACE2 transgenic mouse model. Overall, pGX-9501 is a promising optimized COVID-19 DNA vaccine candidate inducing humoral and cellular immunity contributing to the vaccine’s protective effects.

A DNA Vaccine Encoding the Full-Length Spike Protein of Beta Variant (B.1.351) Elicited Broader Cross-Reactive Immune Responses against Other SARS-CoV-2 Variants

“…pWT was constructed by inserting a full-length spike-coding gene of SARS-CoV-2 into the pVAX1 vector, which was named the pGX9501 described in the previous publication [ 38 ]. pWT (pGX9501) was proven to induce potent humoral, cellular immunity, and a protective effect after a wild-type SARS-CoV-2 challenge in hACE2 transgenic mice [ 39 ]. DNA vaccines against the SARS-CoV-2 P.1 (Gamma) variant and B.1.351 (Beta) variant were constructed using the same strategy.…”

“…Sera were three-fold serially diluted starting at 1:200, using PBST containing 3% BSA. The antibody titer was defined as the reciprocal of the largest serum dilution for which the OD 450nm value was greater than 2.1-fold of the negative sera, according to the previous method [ 39 ].…”

“…Experiments were performed as described previously [ 39 ]. In brief, target cells were an equal mixture of 5 nM of eflour 450-labeled SARS-CoV-2 WT spike peptide pool-pulsed splenocytes and 0.5 nM of eflour 450-labeled un-pulsed splenocytes from naïve C57BL/6 mice.…”

Factors That Affect the COVID-19 Pandemic in Summer 2022 Compared to Summer 2021

“…SARS-CoV-2, the virus that is responsible for COVID-19, is a single-strand positivesense RNA virus [4]. Thanks to the genomic sequence monitoring of SARS-CoV-2, the evolution of this virus can be observed.…”