Optimization of In Vivo Electroporation Conditions and Delivery of DNA Vaccine Encoding SARS-CoV-2 RBD Using the Determined Protocol

Abstract

Vaccination against SARS-CoV-2 and other viral infections requires safe, effective, and inexpensive vaccines that can be rapidly developed. DNA vaccines are candidates that meet these criteria, but one of their drawbacks is their relatively weak immunogenicity. Electroporation (EP) is an effective way to enhance the immunogenicity of DNA vaccines, but because of the different configurations of the devices that are used for EP, it is necessary to carefully select the conditions of the procedure, including characteristics such as voltage, current strength, number of pulses, etc. In this study, we determined the optimal parameters for delivery DNA vaccine by electroporation using the BEX CO device. BALB/c mice were used as a model. Plasmid DNA phMGFP was intramuscular (I/M) injected into the quadriceps muscle of the left hind leg of animals using insulin syringes, followed by EP. As a result of the experiments, the following EP parameters were determined: direct and reverse polarity rectangular DC current in three pulses, 12 V voltage for 30 ms and 950 ms intervals, with a current limit of 45 mA. The selected protocol induced a low level of injury and provided a high level of GFP expression. The chosen protocol was used to evaluate the immunogenicity of the DNA vaccine encoding the receptor-binding domain (RBD) of the SARS-CoV-2 protein (pVAXrbd) injected by EP. It was shown that the delivery of pVAXrbd via EP significantly enhanced both specific humoral and cellular immune responses compared to the intramuscular injection of the DNA vaccine.

Approaches to Improve the Immunogenicity of Plasmid DNA-Based Vaccines against COVID-19

“…Electroporation was performed using a CUY21 EDIT II electroporator and LF650P5 5-mm forceps electrode (BEX CO, Ltd.). The following electroporation protocol was used: rectangular direct and reverse polarity direct current with 3 pulses at 12 V for 30 and 950 ms interval with a current limit of 45 mA [37]. Ten to fourteen days after the second/third immunization, the mice were taken out from the experiment by cervical dislocation, sera were collected from the blood samples, and the spleens were isolated to study the immune response.…”

Dendrimer-Mediated Delivery of DNA and RNA Vaccines

“…A wide range of strategies have been tried for the delivery of DNA vaccines, including viral carriers, liposomal packaging, the use of adjuvant plasmids encoding cytokines, and delivery by gene gun, electroporation, or injection. These methods help to solve the problem of immunogenicity, but are sometimes associated with some safety problems, technological difficulties, and an increase in the cost of the developed vaccine [5,[15][16][17][18].…”

Immunogenic Effects and Clinical Applications of Electroporation-Based Treatments

“…All these procedures have demonstrated their capability to recruit different immune cells for innate and adaptive immune responses. However, many efforts are underway in in vitro and in vivo studies to optimize EP protocols to minimize tissue damage and improve gene transfection efficiency [ 9 , 10 , 11 , 12 ] or drug administration [ 13 , 14 ].…”