stable at room temperature allowing for low-cost storage and
transportation, can be rapidly produced, and are versatile, allowing
for easy changes in coding sequence design and synthesis.
However, success of DNA vaccines in veterinary vaccines has
not translated into successful human DNA vaccines. After more
than 100 clinical trials, no DNA vaccine has yet been approved for
humans, primarily due to their suboptimal immunogenicity in
humans. To date, many strategies have been tried to improve
their immunogenicity, including codon optimization, promoter
selection, adjuvant inclusion, and optimization of delivery route
but with electroporation (EP) remaining the most prominent
method use [1]. The downside to electroporation remains that it
requires bulky and expensive administration devices and is highly
uncomfortable if not downright painful to the recipient.
In this protocol, we will describe examples of our design of
several flavivirus DNA vaccines and the vaccination procedures we
used, including optimization of coadministered adjuvants. Flaviviruses are a genus of viruses that include Dengue (DENV), West
Nile virus (WNV), Japanese encephalitis virus (JEV), Murray Valley
encephalitis virus (MVEV), and Kunjin virus (KUNV) as well as
Zika virus and tickborne encephalitis virus. They are positive-sense,
single stranded RNA viruses with similar sized genomes
(10.5–11 kb) that consist of three structural and seven nonstructural proteins. The structural prM/E proteins have shown to
induce strong protection through neutralizing antibody responses.
Within the genus, the JE serocomplex is a monophyletic group
which includes WNV, JEV, MVEV and KUNV that are transmitted
by the Culex genus of mosquitoes. MVEV is a clinically important
virus which circulates in Australia and causes infrequent epidemics,
the last being in 2012. Although symptomatic infections are rare,
the mortality rate is ~20%. JEV has the highest incidence in the
serocomplex, causing ~50,000 infections and ~10,000 deaths in
Asia annually, with 30–50% of survivors suffering from irreversible
neurological damage. JEV has been identified in Northern
Australia and the presence of suitable vectors and hosts increases
the risk that it will spread further, although stable transmission
cycles have not yet established. KUNV is a strain of WNV which
was the cause of a recent equine encephalitis outbreak in Australia,
although reports of human infection have been rare. While outbreaks of Australian flaviviruses are relatively rare, changing climates favorable to transmitting mosquitos along with proposed
plans for increasing the population in Northern Australia may
lead to a higher incidence in the future.
Currently, there are no human vaccines for MVEV, KUNV, or
WNV. For JEV, there are several available vaccines including an
inactivated JEV vaccine formulated with alum adjuvant and a liveattenuated vaccine. MVEV and KUN infect a small number of
people yearly, and so development of a traditional vaccine is unlikely
406
Lei Li et al.
transportation, can be rapidly produced, and are versatile, allowing
for easy changes in coding sequence design and synthesis.
However, success of DNA vaccines in veterinary vaccines has
not translated into successful human DNA vaccines. After more
than 100 clinical trials, no DNA vaccine has yet been approved for
humans, primarily due to their suboptimal immunogenicity in
humans. To date, many strategies have been tried to improve
their immunogenicity, including codon optimization, promoter
selection, adjuvant inclusion, and optimization of delivery route
but with electroporation (EP) remaining the most prominent
method use [1]. The downside to electroporation remains that it
requires bulky and expensive administration devices and is highly
uncomfortable if not downright painful to the recipient.
In this protocol, we will describe examples of our design of
several flavivirus DNA vaccines and the vaccination procedures we
used, including optimization of coadministered adjuvants. Flaviviruses are a genus of viruses that include Dengue (DENV), West
Nile virus (WNV), Japanese encephalitis virus (JEV), Murray Valley
encephalitis virus (MVEV), and Kunjin virus (KUNV) as well as
Zika virus and tickborne encephalitis virus. They are positive-sense,
single stranded RNA viruses with similar sized genomes
(10.5–11 kb) that consist of three structural and seven nonstructural proteins. The structural prM/E proteins have shown to
induce strong protection through neutralizing antibody responses.
Within the genus, the JE serocomplex is a monophyletic group
which includes WNV, JEV, MVEV and KUNV that are transmitted
by the Culex genus of mosquitoes. MVEV is a clinically important
virus which circulates in Australia and causes infrequent epidemics,
the last being in 2012. Although symptomatic infections are rare,
the mortality rate is ~20%. JEV has the highest incidence in the
serocomplex, causing ~50,000 infections and ~10,000 deaths in
Asia annually, with 30–50% of survivors suffering from irreversible
neurological damage. JEV has been identified in Northern
Australia and the presence of suitable vectors and hosts increases
the risk that it will spread further, although stable transmission
cycles have not yet established. KUNV is a strain of WNV which
was the cause of a recent equine encephalitis outbreak in Australia,
although reports of human infection have been rare. While outbreaks of Australian flaviviruses are relatively rare, changing climates favorable to transmitting mosquitos along with proposed
plans for increasing the population in Northern Australia may
lead to a higher incidence in the future.
Currently, there are no human vaccines for MVEV, KUNV, or
WNV. For JEV, there are several available vaccines including an
inactivated JEV vaccine formulated with alum adjuvant and a liveattenuated vaccine. MVEV and KUN infect a small number of
people yearly, and so development of a traditional vaccine is unlikely
406
Lei Li et al.