VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

TYPES OF VACCINES

Live vaccines 

• These vaccines contain living organisms. The advantage of these vaccines is that it gives effective, prolonged and strong immunity. The disadvantages are they are difficult and expensive to produce, likely to cause disease due to residual virulence (not fully attenuated) or due to reversion to a more virulent form.

Killed or inactivated vaccine

• These vaccines contain killed or inactivated living oraginsms. Inactivation is done either by chemical or thermal treatment.

Recombinant vaccine

• Recombinant DNA techniques are employed to isolate genetic material coding for an antigen of interest. This DNA can then be placed in a bacterium, yeast or other cell and permitted to code for that protein. An alternative method is to clone the genes of interest into an attenuated living carrier organism. Genes coding for specific protein antigens may be cloned directly into a variety of organisms. The organism that has been most widely employed for this purpose is vaccinia virus. It has a large genome that makes it relatively easy to insert a new gene as it can express high levels of the new antigens and it can be easily administered by dermal scratching.

Synthetic peptides

• If the structure of a protective epitope is known, the epitope may be chemically synthesised and used as vaccine.

Anti-idiotype vaccine

• Antigens injected into any animal provokes the appearance of immunoglobulin molecules whose binding site (idiotype) has a complementary structure to that of the inducing isotopes. The binding site on an anti-idiotype antibody has the same shape as the antigen that induced the idiotype. Anti-idiotype antibodies can be made by making a monoclonal antibody against the epitope in question and using it to immunize an animal.

DNA vaccination

• DNA of the pathogens are used as vaccines which can be delivered by a gun or by injection. Such vaccines are not commercially available and not economically viable.