seminar about DNA vaccine

1. DNA VACCINES
IMMUNOGENETICS
Presented by
PhD - Ghazwan Faisal Hussein

2. Introduction
A vaccine is a biological preparation which enhances the immunity to a particular
disease. A vaccine typically contains an agent that resembles a disease-causing
microorganism and is often made from weakened or killed forms of the microbe,
its toxins or one of its surface proteins. This agent stimulates the body immune
system to recognize the agent as foreign, destroy it, and keep a record of it, so
that the immune system can more easily recognize and destroy any of these
microorganisms that it later encounters. Vaccines may be therapeutic (means
vaccines against cancer are also being investigated) or prophylactic (means to
prevent or ameliorate the effects of a future infection by any natural or "wild"
pathogen).

3. Types of Vaccines
Whole-Organism
◦ Attenuated Viral/Bacterial
◦ Inactivated Viral/Bacterial
Purified Macromolecules
◦ Polysaccharide
◦ Toxoid
◦ Recombinant Antigen
◦ Recombinant-Vector
DNA Vaccines
Synthetic Peptide
Multivalent Subunit

4. Several factors still limit the effectiveness of vaccination, which must be overcomed with the advances in the
biotechnology field and a deeper comprehension of the immune system. In this regard, an ideal vaccine should
include the following characteristics:
1) safe profile for the entire population
2) long-term immunity and efficacy
3) single dose administration
4) easy administration through mucosal routes
5) simple manufacturing
6) resistance to temperature changes
7) multivalency
8) disease control.
In this regard, a new generation of vaccines is being developed to overcome technological limitations and to
achieve safety and desirable requirements to prevent and/or treat diseases called DNA vaccines.

5. Cont……
DNA vaccines are the new breakthrough in the field of immunization and are quite
different from traditional vaccines. In DNA vaccines, the genes responsible for causing
the diseases, (the genes coding for the antigenic protein) are identified and isolated
from the pathogen and incorporated into a vector (plasmid) carrying the gene into the
living system. The plasmid carrying the gene is injected into the muscle cells and is
translated into antigenic protein that elicits the immune response normally triggered
by the pathogen. It is different from recombinant vaccine, where the gene coding for
the antigenic protein is expressed in a prokaryotic system as the carrier.

8. 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).
DNA vaccine—plasmids can be administered to the animals by one of the following delivery
methods.
i. Nasal spray
ii. Intramuscular injection
iii. Intravenous injection
iv. Intradermal injection
v. Gene gun or biolistic delivery (involves pressure delivery of DNA-coated gold beads).

9. Gene Gun
One of the most efficient routes of
administration of DNA vaccines is intradermal
vaccination via the gene gun, which
traditionally utilizes compressed helium to
deliver DNA-coated gold particles to
immature DCs (Langerhans cells) in the
epidermis. After transfection, the DCs
mature, travel to lymphoid organs, and prime
T cells for an adaptive immune response.

10. Pathways of DNA vaccines
Molecular pathways of DNA vaccine by presenting the antigen to the T cells through the MHC
class I and class II molecules. In endogenous pathway, the DNA plasmid enters the cell and
nucleus, where the gene is transcribed into messenger RNA (mRNA). Then, mRNA is translated
into protein by ribosomes in the rough endoplasmic reticulum (ER, not shown). In the cytosol
the protein is cleaved by proteasomes, and the short peptides (contaning 8 to 10 amino acids)
are transported into the ER with transport associated proteins (TAP1 and TAP2) and bind to
MHC class I molecules. After binding, the complex is transported through the Golgi apparatus
to the cell surface, where it can be recognized by cytotoxic T cells (CD8+) and stimulation of
cell-mediated immunity occurs.

12. Exogenous pathway
In exogenous pathway, antigen-presenting cells take up extracellular proteins by either
endocytosis or phagocytosis. MHC class II molecules in ER pass through the Golgi apparatus
and enter acidified endosomes in which the foreign protein has been fragmented into
peptides (Endolysosomal degradation pathway). The MHC–peptide complex is then brought to
the cell surface, where it can be recognized by helper T cells (CD4+). Specific helper T cells
recognize this antigen peptide/MHC class II molecule complex and are activated to produce
help in the form of cytokines. These cytokines have many activities, depending on their types,
helping B cell to produce antibody and helping cytolytic T lymphocyte (CTL) responses.

14. TRADITIONAL VACCINES
• Uses weakened or killed form of
infectious organism.
• Create possible risk of the vaccine
being fatal.
• Provide primarily Humoral
immunity
• Usually requires Refrigeration.
DNA VACCINES
• Uses only the DNA from infectious
organisms.
• Avoid the risk of using actual
infectious organism.
• Provide both Humoral & Cell
mediated immunity
• Refrigeration is not required

16. Applications of DNA vaccines
human trials are under way with several DNA vaccines, including those for malaria, AIDS, influenza, Ebola
and herpesvirus. There are many studies on DNA vaccines in a number of diseases :
1-DNA vaccines against cancer :including cervical carcinoma (CC). Persistent infection with human
papillomaviruses (HPV).
2-DNA vaccines against tuberculosis :DNA vaccine expression of IL-2 and the HSP65 fusion gene was
studied. It elevated the immunogenicity and protective as well as therapeutic effects of the HSP65-DNA
vaccine against TB in mice.
3-DNA vaccines against Edwardsiella tarda
4-DNA vaccines against anthrax.
5-DNA vaccine against dengue
6-DNA vaccine against typhoid.

17. Thank you