A DNA vaccine is a type of vaccine that transfects a specific antigen-coding DNA sequence into the cells of an organism as a mechanism to induce an immune response. DNA vaccines work by injecting genetically engineered plasmid containing the DNA sequence encoding the antigen(s) against which an immune response is sought, so the cells directly produce the antigen, thus causing a protective immunological response.

1. Dr. Rachana Choudhary
Department of Microbiology
Shri Shankaracharya Mahavidyalya,Junwani Bhilai
DNA VACCINE

2. CONTENTS
•Introduction
•History
•Active & Passive Immunization
•Types of Vaccines
•DNA Vaccine
•Advantages & Disadvantages of DNA Vaccines
•Conclusion
•References

3. INTRODUCTION
Vaccination is the phenomenon of preventive immunization.
Term Vaccination ( Latin:vacca – cow) is so named because the
first vaccine was derived from a virus affecting cows relatively
begins cowpox virus which provides a degree of immunity to
smallpox, a contagious and deadly disease.
Traditional vaccines have relied on either live- replicating or
nonliving preparations of microorganisms. The injected material
functions as a vaccine by generating immunity against the
inoculum, and the resulting immune responses function to prevent
disease.

4. HISTORY
1. The history of vaccine use dates back to ancient times. In the 7th century, Indian
Buddhist drank snack venom to protect themselves from snake bite.
2. In 9th century China, the correct treatment of smallpox was written by Buddhist nun.
The manuscript recommended that a mixture of ground dried smallpox scabs and herbs
be blown into the nostrils of children.
3. It was on May 14, 1796, that Jenner extracted the contents of a pustule from the arm of
a cowpox-infected milkmaid, Sarah Nelmes, and injected it into the arm of eight-year-
old James Phipps.
4. A vaccine meeting held at the Cold Spring Harbor Laboratory in September 1992
described the use of DNA immunization to generate humoral and cellular immune
responses against a human pathogen as well as protection from both tumors and viral
challenges in animal system.

5. Active and Passive Immunization
 Immunity to infectious microorganisms can be achieved by
active or passive immunization. In each case, immunity can be
acquired either by natural processes or by artificial means such
as injection of antibodies or vaccines.
 Passive immunization, in which preformed antibodies are
transferred to a recipient, occurs naturally by transfer of
maternal antibodies across the placenta to the developing fetus.
 Active immunization can be achieved by natural infection with
a microorganism, or it can be acquired artificially by
administration of a vaccine

6. Acquisition of passive and active immunity
Type Acquired Through
Passive Immunity Natural maternal antibody
Immunoglobulin
Humanized monoclonal antibody
Antitoxin
Active Immunity Natural infection
Vaccines
Attenuated organisms
Inactivated organisms
Purified microbial macromolecules
Cloned microbial antigens
Expressed as recombinant protein
As cloned DNA alone or in virus
vectors
Multivalent complexes
Toxoid

7. Designing Vaccines for Active Immunization
The adaptive immune response provides a more flexible resistance
to pathogens. Vaccination educates the adaptive immune system,
preparing it to deal effectively and swiftly with pathogen not
readily eliminated by innate immunity.
Several factors must be kept in mind in developing a successful
vaccine.
First and foremost, vaccine must determine differences between
activation of the humoral and the cell mediated branches.
A second factor is the development of immunologic memory.

8. 1. Live attenuated Vaccine
2. Inactivated “killed” Vaccine
3. Subunit Vaccine
4. Toxoid Vaccine
5. DNA Vaccine
6. Recombinant Vector Vaccine

9. Classification of common vaccines for humans
Disease or Pathogen Type of Vaccine
Whole Organism
Bacterial cell Anthrax
Plague
Tuberculosis
Typhoid
Inactivated
Inactivated
Live attenuated BCG
Live attenuated
Viral Particle Hepatitis A
Influenza
Measles
Mumps
Inactivated
Inactivated
Live attenuated
Live attenuated
Purified Macromolecules
Toxoids Diphtheria
Tetanus
Capsular polysaccharides
Haemophilus influenzae type b
Streptococcus pneumoniae
Surface antigen
Hepatitis B
Inactivated exotoxin
Inactivated exotoxin
Polysaccharide protein carrier
23 distinct capsular polysaccharides
Recombinant surface antigen (HBsAg)

10. Characteristic Attenuated vaccine Inactivated
vaccine
DNA vaccine
Production Selection for avirulent organisms:
virulent pathogen is grown under
adverse culture conditions or
prolonged passage of a virulent human
pathogen through different hosts
Virulent pathogen
is inactivated by
chemicals or
irradiation with γ-
rays
Easily manufactured
and purified
Booster
requirement
Generally requires only a single
booster
Requires multiple
boosters
Single injection may
suffice
Relative stability Less stable More stable Highly stable
Type of immunity
induced
Humoral and cell-mediated Mainly humoral Humoral and cell-
mediated
Reversion
tendency
May revert to virulent form Cannot revert to
virulent form
Cannot revert

11. • DNA vaccines consist of plasmids that
contains genes for certain types of
antigens.
• Once administered, the plasmid is taken
up by the target cell and the genes are
expressed.
• The cell then either excretes the antigen or
displays it on an MHC-I molecule.
• DNA Vaccine constructs are produces as
small circular vehicles or plasmids . These
plasmids are constructed with a promoter
site, which starts the transcription process
DNA Vaccine construct consisting of a
mammalian expression vector. The plasmids
are constructed with a promoter, an
antigenic DNA sequence, and a mRNA stop
site containing the poly A tract.

12.  Genetic immunization by
using DNA vaccines is a novel
approach that came into being
in 1990. A DNA vaccine
consists of a gene encoding an
antigen protein, inserted onto a
plasmid, and then incorporated
into the cells in a target
animal.
 The plasmid carrying DNA
vaccine normally contains a
promoter site, cloning site for
the DNA vaccine gene, origin
of replication, a selectable
marker sequence (e.g. a gene
for ampicillin resistance and a
terminator sequence a poly A
tail )

13. Mechanism of DNA Vaccines
In body’s immune system, cells need to
process and present antigenic peptides to
lymphocytes in order to stimulate antigen-
specific immune response. Thus, antigen must
be processed and presented to T lymphocyte
by antigen – presenting cells (APC’s).
Four primary components are critical in the
professional APC’s ability to present the
antigen to T- cells and activate them for
appropriate immune response.
These components are as following-
a) MHC – antigen complexes.
b) Costimulatory molecules (primarily CD80
& CD86).
c) Intracellular adhesion molecules.
d) Soluble cytokines.

14. DNA Vaccine for HIV – 1
• The HIV-1 is a retrovirus, which preferentially infects and kills CD4+
T-cells and macrophages, ultimately resulting in immune system
failure and multipathogen infections.
• Within the HIV genome, there are several potential immunological
targets for DNA vaccination. The HIV-1 genome is organized into 3
major structural and enzymatic genes, 2 regulatory genes and 4
accessory genes.
• The first major gene target is env, which codes for the outer viral
envelope proteins. HIV enters the CD4 receptor complex following
entry of HIV viral core, synthesis of a ds DNA version of the HIV
genome begins by the viral DNA polymerase reverse transcriptase.

15. DNA Vaccines for Cancer
Tumor-associated antigens (TAA) are proteins produced by tumor cells that can
be presented on the cell surface in the context of MHC complexes.
Immunological effects of 2 such TAAs: carcinoembryonic antigen(CEA) and
prostatespecific antigen(PSA).
1.DNA Vaccine Strategies using CEA- The immune response to nucleic acid
vaccination using a CEA insert was cloned into vector containing the
cytomegalovirus(CMV) early promoter /enhancer and injected intramuscularly.
These responses were detected in the immunized mice.
2.DNA Vaccine Strategies using PSA- The immune responses induced by a
DNA vaccine encoding for human PSA has been investigated in a murine
model. The vaccine construct was constructed by cloning a gene for PSA into
expression vectors under control of a CMV promoter.

16. Safety and Efficacy Studies in Humans
• The ultimate goal of vaccine development is to demonstrate safety and efficacy in
humans. The first vaccine studies to enter the clinic were DNA vaccines encoding for
HIV-1 envelope.
• 15 healthy HIV-1 seropositive volunteers with >500 CD4+ lymphocytes/ml were
enrolled in this study. Patients in the trial received 3 injections, each separated by 10
weeks, with escalating dosage (3 dosage groups of 5 subjects) of envelope vaccine.
• Preliminary results reveal no significant clinical or laboratory adverse effects
measured in any of the dosage groups (30,100,300µg).
• Low doses of a single immunogen DNA vaccine is capable of augmenting both
existing humoral and cellular immune responses in humans.

17. Advantages of DNA Vaccine
• Subunit vaccination with no risk for infection.
• Antigen presentation by both MHC class I and class II molecules.
• Able to polarize T-cell help toward type 1 or type 2.
• Immune response focused only on antigen of interest.
• Ease of development and production.
• Stability of vaccine for storage and shipping
• Cost-effectiveness
• Obviates need for peptide synthesis, expression and purification
of recombinant proteins and the use of toxic adjuvants.
• In vivo expression ensures protein more closely resembles normal
eukaryotic structure, with accompanying post-translational
modifications.

18. Disadvantages of DNA Vaccine
• Limited to protein immunogens (not useful for non-protein based
antigens such as bacterial polysaccharides).
• Risk of affecting genes controlling cell growth.
• Possibility of inducing antibody production against DNA.
• Possibility of tolerance to the antigen (protein) produced.
• Potential for atypical processing of bacterial and parasite proteins.

19. Conclusions
1. DNA immunization holds great promise for providing safe inexpensive
vaccines for many infectious pathogens, including HIV-1.
2. DNA vaccine constructs for cancer-targeting tumor-specific antigens have
also been studied in a variety of animal models.
3. DNA vaccines can be combined with other vaccines including recombinant
protein, poxvirus, adenovirus as well as others to further enhance initial
immune responses.
4. An important problem for developing DNA vaccine is the huge quantity of
DNA needed for inducing immune responses in large animals and human.
The production and purification of large quantity of plasmid DNA not only
would be a financial burden but would increase the risks of side effects of
DNA immunization, especially causing autoimmune responses or plasmid
DNA integration into host cells.

20. REFERENCE
Immunology Seventh Edition -(David Male ,
Jonathan Brostoff, David B. Roth, Ivan Roitt).
Immunology & Immunotechnology – Ashim K.
Chakravarty.
Immunology by Kuby
Cellular And Molecular Immunology- A.K Abbas
Prescott, Herley, Klein’s Microbiology

21. THANK YOU