Chapter 21
Flavivirus DNA Vaccine Design and Adjuvant Selection
Lei Li, Yoshikazu Honda-Okubo, and Nikolai Petrovsky
Abstract
A DNA vaccine is a plasmid encoding a vaccine antigen together with an efficient eukaryotic promoter to
drive protein expression. The chief problem of DNA vaccines has been their suboptimal immunogenicity in
humans. Many different flaviviruses infect and cause serious illness and even death in humans, but human
vaccines are not available against most of the relevant flaviviruses with the exception of Japanese encephalitis
virus. DNA vaccines are easy and fast to produce at relatively low cost, do not require handling of dangerous
pathogens, are stable at room temperature allowing for low-cost storage and transportation, and are highly
versatile, allowing for rapid changes in coding sequence design and synthesis. This makes a DNA vaccine
approach ideally suited for development as a broad-based flavivirus vaccine platform. However, to be useful
as a flavivirus prophylactic vaccine platform in humans, a method would need to be found to enhance DNA
vaccine immunogenicity without the need for the cumbersome and expensive equipment involved with
electroporation. We describe here a protocol used to test different adjuvants with flavivirus DNA vaccines to
determine an optimal formulation. An optimal regimen involving a DNA adjuvanted vaccine prime
followed by an adjuvanted protein vaccine boost is described and can be applied by readers to solve barriers
to the development of other DNA vaccines where immunogenicity is a problem.
Key words DNA vaccine, Flavivirus, Adjuvant, Codon optimization, Electroporation
1 Introduction
A DNA vaccine is usually a plasmid that encodes a vaccine antigen
together with an efficient eukaryotic promoter for protein expression. DNA vaccines are usually administered intramuscularly, intradermally, or mucosally with the aim that the plasmid will gain access
to the nuclei of cells and thereby induce expression of RNA encoding the relevant antigen, followed by protein translation and direct
or cross-presentation on major histocompatibility molecules within
the expressing cell. There is generally no risk of infection with DNA
vaccines, they have minimal side effects and can induce both
humoral and cellular responses. Hence DNA vaccines satisfy most
points of the “ideal” vaccine profile recommended by the World
Health Organization: they are easy and fast to produce at relatively
low cost, do not require handling of dangerous pathogens, are
Blaine A. Pfeifer and Andrew Hill (eds.), Vaccine Delivery Technology: Methods and Protocols, Methods in Molecular Biology,
vol. 2183, https://doi.org/10.1007/978-1-0716-0795-4_21, © Springer Science+Business Media, LLC, part of Springer Nature 2021
405
Flavivirus DNA Vaccine Design and Adjuvant Selection
Lei Li, Yoshikazu Honda-Okubo, and Nikolai Petrovsky
Abstract
A DNA vaccine is a plasmid encoding a vaccine antigen together with an efficient eukaryotic promoter to
drive protein expression. The chief problem of DNA vaccines has been their suboptimal immunogenicity in
humans. Many different flaviviruses infect and cause serious illness and even death in humans, but human
vaccines are not available against most of the relevant flaviviruses with the exception of Japanese encephalitis
virus. DNA vaccines are easy and fast to produce at relatively low cost, do not require handling of dangerous
pathogens, are stable at room temperature allowing for low-cost storage and transportation, and are highly
versatile, allowing for rapid changes in coding sequence design and synthesis. This makes a DNA vaccine
approach ideally suited for development as a broad-based flavivirus vaccine platform. However, to be useful
as a flavivirus prophylactic vaccine platform in humans, a method would need to be found to enhance DNA
vaccine immunogenicity without the need for the cumbersome and expensive equipment involved with
electroporation. We describe here a protocol used to test different adjuvants with flavivirus DNA vaccines to
determine an optimal formulation. An optimal regimen involving a DNA adjuvanted vaccine prime
followed by an adjuvanted protein vaccine boost is described and can be applied by readers to solve barriers
to the development of other DNA vaccines where immunogenicity is a problem.
Key words DNA vaccine, Flavivirus, Adjuvant, Codon optimization, Electroporation
1 Introduction
A DNA vaccine is usually a plasmid that encodes a vaccine antigen
together with an efficient eukaryotic promoter for protein expression. DNA vaccines are usually administered intramuscularly, intradermally, or mucosally with the aim that the plasmid will gain access
to the nuclei of cells and thereby induce expression of RNA encoding the relevant antigen, followed by protein translation and direct
or cross-presentation on major histocompatibility molecules within
the expressing cell. There is generally no risk of infection with DNA
vaccines, they have minimal side effects and can induce both
humoral and cellular responses. Hence DNA vaccines satisfy most
points of the “ideal” vaccine profile recommended by the World
Health Organization: they are easy and fast to produce at relatively
low cost, do not require handling of dangerous pathogens, are
Blaine A. Pfeifer and Andrew Hill (eds.), Vaccine Delivery Technology: Methods and Protocols, Methods in Molecular Biology,
vol. 2183, https://doi.org/10.1007/978-1-0716-0795-4_21, © Springer Science+Business Media, LLC, part of Springer Nature 2021
405