Delivery of a DNA vaccine encoding SARS-CoV-2 receptor-binding domain (RBD) by electroporation

BACKGROUND: Nucleic acid-based prevention tools provide a promising platform for developing vaccines, including those against COVID-19. Previously, we developed the pVAXrbd DNA vaccine encoding the receptor-binding domain (RBD) of SARS-CoV-2, which, when administered intramuscularly to animals, induced a relatively weak immune response. The next stage of the study is to increase the immune response, in particular, using electroporation as one of the methods for increasing the immunogenicity of DNA vaccines.

AIM: The aim of this article is to evaluate the immune response using electroporation in mice after immunization with pVAXrbd.

MATERIALS AND METHODS: BALB/c mice were immunized with pVAXrbd using direct and reverse polarity square wave direct current electroporation with three pulses of 12 V for 30 ms and an interval of 950 ml with a current limit of 45 mA.

RESULTS: BALB/c mice were immunized twice with an interval of three weeks with a dose of 100 μg of DNA. Using ELISA, the titers of RBD-specific antibodies in the group of animals immunized with pVAXrbd using electroporation were 1:109350, which is 16 times higher than in the group of animals that received the DNA vaccine only intramuscularly (titers 1:6750). IFNγ ELISpot analysis showed that the largest number of cells (2434 spots/splenocytes, million) producing IFNγ in response to stimulation with peptides from the RBD protein was registered in the group of animals immunized with pVAXrbd using electroporation. For comparison, in the control group, the number of cells is 6.5 times lower: 380 spots / splenocytes, mln.

CONCLUSIONS: Administration of the pVAXrbd DNA vaccine to laboratory animals by electroporation significantly enhances both the humoral and cellular specific immune response compared to intramuscular administration of the naked DNA vaccine.