- A research team from the
University of Pennsylvania have developed an mRNA based Zika vaccine that
was found to be effective.
- This vaccine was found to provide high level of antibodies against
the Zika virus.
- A single dose provided long-term immunity, thereby cost effective.
A potential Zika vaccine
has been developed by a research team from Perelman School of Medicine at the
University of Pennsylvania with the ability to offer protection against the
virus after administration of a single dose. This new discovery was published
as a study in the Journal Nature
after initial studies showed effectiveness in both monkeys as well as in mice.
Dr. Drew Weissman, who
is the senior author of the study said that the research team observed a rapid
as well as a durable protective immunity that did not show any signs of an
adverse effect, raising hopes for use as a vaccine that could be used in the
fight against Zika virus
clinical trials will be started in 12 to 18 months,
according to the scientist.
‘mRNA based Zika vaccine could provide the necessary shield against the viral infection.’
The study was a
collaborative effort between Weissman's laboratory and several other
laboratories including laboratories at National Institute of Allergy and
Infectious Diseases (NIAID) which was part of the National Institutes of Health
(NIH) and Duke University.
The Zika epidemic had
generated a race to develop an effective vaccine that will aid in curbing the
spread of this disease. There are several candidate vaccines which are already
being tested on animals but this current vaccine is the first one to show such
potent and a long-lasting protection but which did not use live virus.
Features and Mechanism of the New Potential Zika
- The earlier
traditional vaccines for viral infections are usually composed of killed
viruses or weakened viruses. However, the new Zika vaccine contains
only small strands of the viral RNA.
- This viral RNA
contains the genetic information for synthesizing viral proteins.
- The RNA strands
that are used in the vaccine are modified versions of messenger RNAs
which are involved in the transfer of information from genes and act as
blueprints for the synthesis of proteins.
- These mRNAs are
manufactured in the laboratory and then incorporated into the vaccine and
administered into the patient as an injection.
- Under normal
circumstances mRNA that is injected into an individual are removed from
the body via the host's immune system. However, these modified mRNAs
bypass the immune system and enter cells.
- Once these mRNAs
are taken up by individual cells, they begin to synthesize the viral
proteins that they code for.
The viral proteins that
are produced by the cells imitate a live virus vaccine, inducing a powerful
immune protection. Live vaccines have always been considered to be more potent
than killed virus vaccine as they trigger an immune response that is more
effective. The main drawback about live
vaccines is that they could result in a potentially serious infection,
especially among immune compromised individuals.
Certain latest versions
of vaccines include viruses, which are modified adenoviruses, and considered
harmless to deliver genes that aid in the synthesis of viral proteins. This
type of vaccine, which includes an adenovirus, has been the only type of
vaccine that has been found to offer maximum protection in monkeys after a
single dose. The main disadvantage associated with such adenovirus based
vaccine is that the immune system could attack these adenoviruses and prevent
the delivery of the necessary genes into the cell.
mRNA based Vaccine
The new potential mRNA
vaccine does not have any of the drawbacks of the earlier versions of the Zika
vaccine and it contains the mRNA for two important proteins of a Zika strain
which was isolated during the outbreak in 2013.
In the study, mice were injected with 30
millionths of a gram of the mRNA to elicit an immune response. When the Zika
virus was introduced into the mice nearly 2 weeks after the vaccine
administration, it was found that
- There was no
detectable virus in the blood of the mice a few days after exposure to the
- The mice remained
protected even when the virus was re-introduced 5 months later
Studies conducted on
macaque monkeys showed that 50 micrograms of the mRNA provided strong
protection against the Zika virus even when the virus was introduced 5 weeks
after the administration of the vaccine.
The animal trials that
were conducted showed that
- High levels of
antibodies were induced by the vaccine which aided in preventing a Zika
- The antibody
levels peaked after a few weeks and they stayed high even after several
- There was 25
times greater viral neutralization than standard vaccines, according to
- There is a strong
stimulation of CD4 helper T cells, found to be important for long-term immunity
This vaccine is based on
mRNA and was found to offer good protection after a single dose, which makes it
cheaper to carry out large scale administration. The production costs of this
vaccine is also lower than vaccines that are based on live or viral protein
based vaccines. The success of this mRNA vaccine has encouraged the scientists
to develop similar vaccines for other diseases.
The main mode of
Zika virus is via the Aedes mosquitoes. The symptoms
associated with the infection are characterized by skin rash, muscle pain,
, mild fever and conjunctivitis
. However, Zika virus epidemic
rose to significance when it was associated with the development of
microcephaly in newborns.
There have been many
travel advisories that have been issued, warning people against traveling to
Zika prone areas and pregnant women have been the most affected, as the virus
affects the fetuses. An effective Zika vaccine
will aid in
protecting against the infection and will safeguard the health of people
traveling to or living in Zika prone areas.
- Zika virus - (http://www.who.int/mediacentre/factsheets/zika/en/)