Download DNA vaccination

DNA vaccination
advanced microbiology course
Prof: Rula darwish
Why did we choose it?

Because it’s represent the most recent approach to
produce vaccine against a variety of diseases , and it
shows a brilliant result in veterinary field, and many
studies focused on the possibility to improve DNA vaccine
for diseases that infect human and have no way to
prevent until now

Many people even in medical field are still doesn’t know
this technique
introduction

One of the most astonishing and important applications in the
field of immunology in the last century was the invention and
development of the vaccines. It was a significant leap forward
in the prevention of infectious diseases that saved the lives of
millions of people.
Definition

DNA vaccination is a third generation novel technique which includes
introducing genetically engineered DNA to produce immune reaction so as to
immunize the population against certain disease[10].

DNA vaccines contain the nucleotides encoding an antigenic portion of the
virus such as the viral core region or envelope region. The DNA is taken up
into the host cell, translated, and the protein product expressed
History

Experiments outlining the transfer of DNA into cells of living animals were
reported as early as 1950

In 1983, Paoletti and Panicali developed multi- vaccine by inserting gene from
namely Herpes simplex virus, hepatitis B and influenza into smallpox vaccine.

In 1992, scientists Tang and Johnson, demonstrated that the delivery of
human growth hormone into mice , resulted in developing antibodies against
the human growth hormone.

In 2016, there are many trial to develop a vaccine for Zika virus
Vector design

DNA vaccines elicit the best immune response when highly active expression
vectors are used

Expression plasmids contain two unites:
1.
the antigen expression unit composed of promoter sequences AND antigenencoding and polyadenylation sequences (termination signal)
2.
production unit composed of bacterial sequences necessary for plasmid
amplification and selection

a strong viral promoter to drive the in vivo transcription and translation of the
gene of interest such as SV40 promoter, Rous Sarcoma Virus (RSV) promoter
The most recent one is cytomegalovirus (CMV).

Intron A may sometimes be included to improve mRNA stability and hence
increase protein expression

transcription-stop sequence such as bovine growth hormone or rabbit betaglobulin [1],[4]

To construct a vector, they should treat vectors and copied genes with
“restriction enzymes” which are agents that cut DNA sequences at known
locations

After construction, plasmids transferred to bacteria and are allowed to
multiply

Then when the bacterial colony grow sufficiently, the plasmids purified and
used as vaccine
Mechanism of action

A plasmid vector that expresses the viral protein is injected into the
skin or muscle of the host. After plasmid is uptaken. Translation and
transcription is started then it processed into small antigenic peptides
by proteases. They enter the lumen of the endoplasmic reticulum
(E.R.) .

In the E.R., peptides bind to MHC class I molecules and they
presented on the cell surface . Subsequent CD8+ cytotoxic T
lymphocytes (CTL) are stimulated and they evoke cell-mediated
immunity. CTLs inhibit viruses through both cytolysis of infected cells
and non-cytolysis mechanisms such as cytokine production.

Also they can be presented by the MHC class II pathway by Antigen presenting
cells which will elicit helper T cells (CD4+) responses. These CD4+ cells are
able to recognize the peptides formed from exogenous proteins that were
endocytosed by APC.

Then they fragmented and uptaked by MHC class II molecules, B cells are
stimulates the antibodies start to form .
Delivery methods

the type of immune responses induced by plasmid immunisation is
significantly affected by

(i) the mode and site of gene delivery,

(ii) the dose of plasmid and

(iii) the administration of booster injections and the interval between
immunisations

Saline injection

most commonly used (IM) in skeletal muscle, or intradermally (ID), in
extracellular spaces.

assisted by electroporation; by temporarily damaging muscle fibres with
myotoxins

or by using hypertonic solutions of saline or sucrose. can be affected by
factors including needle type, needle alignment, speed of injection, volume
of injection, muscle type, and age, sex and physiological condition of the host

Advantages
I.
No special delivery mechanism
II.
Permanent or semi-permanent expression
III.
pDNA spreads rapidly throughout the body

Disadvantages
I.
Inefficient site for uptake due to morphology of muscle tissue
II.
Relatively large amounts of DNA used
III.
Th1 response may not be the response required

Gene gun delivery

plasmid DNA (pDNA) that has been adsorbed onto gold or tungsten
microparticles into the target cells, using compressed helium as an accelerant

ED (abdominal skin); vaginal mucosa; surgically exposed muscle

Advantages
I.
DNA bombarded directly into cells
II.
Small amounts DNA

Disadvantages
I.
Th2 response may not be the response required
II.
Requires inert particles as carrier

Liposome-mediated delivery

Advantages
I.
High levels of immune response can be generated
II.
Can increase transfection of intravenously delivered pDNA
III.
Intravenously delivered liposome-DNA complexes can potentially transfect all
tissues
IV.
Intranasally delivered liposome-DNA complexes can result in expression in
distal mucosa as well as nasal muscosa and the generation of IgA antibodies

Disadvantages :
I.
Toxicity
II.
Ineffectiveness in serum
III.
Risk of disease or immune reactions
Advantages of DNA vaccines

The ability to induce both cellular and humoral immune responses.

highly specific and the expressed immunizing antigen is subjected to the
same glycosylation and post-translational modifications as natural viral
infection

therapeutic potential for ongoing chronic viral infections.

Obviates need for peptide synthesis, expression and purification of
recombinant proteins and use of toxic adjuvants

Long-term persistence of immunogen

Rapid and large-scale production are available at costs considerably lower
than traditional vaccines, and they are also very temperature stable making
storage and transport much easier.
Disadvantages

May activation of oncogenes occure

eliciting anti-DNA antibodies

Possibility of tolerance to the antigen (protein) produced

Limited to protein immunogens (not useful for non-protein based antigens
such as bacterial polysaccharides)
Clinical use

Until now, no DNA vaccine is approved to use at human scale

Most of its use is in veterinary scale (to protect horses from West Nile virus)

June 2015 one human DNA vaccine had been approved for human use, the
single-dose Japanese encephalitis vaccine

It show a promising future
Applications and clinical
studies
DNA vaccination and Zika virus

What is Zika virus ?

Why it’s important for us to develop a vaccine against it ?

What are the latest results about the development of a
vaccine?
HPV VACCINE

What is HPV?

Is vaccine useful in treatment or prevention of
HPV &it’s complication ?
In Japan, Prevention of cervical cancer has been unsuccessful, because of
low rates of cancer screening and vaccination
this study indicates that HPV vaccination is associated with a reduction in the incidence of
cervical abnormalities.
Bacterial toxin's DNA vaccine serves as a
strategy for the treatment of cancer, infectious
and autoimmune diseases

1 . DNA toxin vaccine for cancer therapy
To produce this kind of vaccine the relevant tumor antigens
and their related MHC Class I and MHC Class II epitopes
must be determined.

2 . DNA toxin vaccine for autoimmune diseases
multiple sclerosis (MS).
autoimmune encephalomyelitis (EAE)

3.
Concluding remarks and future perspectives
In cancer therapy, bacterial DNA toxin vaccines proved to have less sideeffects and more effective compared to conventional cancer therapy
Done by:
Mokhlesa Rimawi , Mays Adnan , Marwa
Abdulla ,
Esraa Freijat , Amal AlJammal .