Fish Diseases and Management

7.4.3. DNA and Subunit vaccines

DNA vaccines

DNA vaccination is the direct introduction into host cells of a bacterial plasmid DNA that is able to cause expression of an antigenic protein. Several DNA vaccines for veterinary use are currently being developed. Such genetic immunisation is a very promising new approach to vaccination. For this, a plasmid DNA, carrying a gene of the immunising protein under the control of a eukaryotic promoter, is inoculated into the host animal. The foreign antigen is expressed within the host and will stimulate the host’s immune system. It has been demonstrated that such a vaccine can be produced at a low cost and can provoke strong humoral and cellular immunity. The immune response can be further improved by simultaneous inoculation of immunostimulators such as CpG motif sequences and plasmids expressing cytokines.

Subunit vaccines

These contain purified protein or glycoprotein components of a pathogen that have been identified as carrying critical epitopes involved in inducing a protective immune response. These vaccines have distinct advantages in the realm of safety, and recent improvements in their production using recombinant DNA technology may facilitate more widespread usage.