Vaccines made up of DNA sequences that code for the antigenic protein of pathogens. When these DNA vaccines are injected into the body cells they are transcribed and translated to produce antigenic proteins. These elicit the immune response against the pathogen.
DNA vaccine prepared by using only the part of pathogenic genome that elicit immune response but not the whole killed or attenuated form of pathogen.
Technique Used to Produce DNA Vaccine:
1. Viral gene responsible to elicit immune response is extracted from the genome of the pathogen (Bacteria, Virus )
2. Expression plasmid is taken and with the help of genetic engineering techniques the viral gene is inserted into the vector.
3. These vectors are then transformed into the host bacterial cell.
4. In the host bacterial cell these plasmid along with pathogen gene gets amplified into many times.
5. Plasmid DNA is purified using down processing.
6. This purified plasmid DNA is ready to use as DNA vaccine.
DNA vaccine can be delivered via syringes either by intramuscular or interdermal route, or can be delivered using gene gun method where plasmid DNA are absorbed into the small gold particles then ballastically accelerated into the body cell. DNA vaccines can also be delivered into the body by other methods like liposome, nanoparticles.
How DNA Vaccine Works?
DNA vaccine produces immune response in the body mainly by two methods. They are Endogenous pathway or exogenous pathway.
DNA vaccine is delivered into the muscle cell by any of the delivery methods. This plasmid DNA are absorbed into the nucleus of the cell and pathogenic genes are transcribed to form mRNA then these mRNA are translocated into the cytoplasm of the cell to produce proteins with the help of ribosome along with many translational proteins and enzymes. These produced antigenic peptides are then expressed in the MHC-1 receptor molecules. T-Helper cells identify these antigenic peptides presented by antigen presenting cells like MHC-1 and then elicit immunological response in the body. T-Helper cells multiply themselves and also produce Memory T-cells.
After producing viral peptides in the cell these viral peptides come outside of the cell and are phagocytosed by antigen presenting cell these activated T-Helper cells and then they produce different types of cytokines against the pathogen. T-Helper cells in turn activate the B-cells, activated plasma B-cell produces the antibody against the pathogen and also produces the memory B-cells.
When actually pathogen attacks the body memory T-cells and the antibodies produced from the memory B-cell help the body to fight against these pathogens.
1. DNA vaccine elicits both the humoral and cell mediated immunity in the body.
2. DNA vaccine induces long term immunity.
3. DNA vaccines are stable for storage, refrigeration is not needed.
1. Extended immunostimulation induced by DNA vaccine may some time lead to the chronic inflammation.
2. Post translational modifications required by some pathogenic peptides sometimes do not occur in the body.
3. Integration of DNA vaccine into the host genome may lead to genetic toxicity.
4. Over expression of DNA vaccine may lead to the destruction of normal tissue.
Single plasmid with many pathogenic genes may be used to provide vaccination against many diseases.
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