Fish Diseases and Management

7.4.4. Synthetic peptide and Anti-idiotype vaccines

Synthetic peptide vaccines

These have been engineered with distinct advantages in handling properties and safety, and they are relatively inexpensive to produce. Synthetic peptide may not induce full immunogenicity, including polymorphism of class II MHC (major histocompatibility complex) molecules, inadequate antigen presentation of peptides, and the high variability of RNA viruses. In order to address this problem, researchers have recently engineered parvovirus-like particles that express foreign polypeptides in certain positions, which in turn results in large-scale production of the foreign peptides and an enhanced cell-mediated immunity. Other virus-like particle vaccines that involve self-assembling proteins that can be used to carry foreign antigens have been made from particles produced from the TYA gene of the yeast retrotransposon Ty.

Anti-idiotype vaccines

These are antibodies, the antigen-binding site of which mimics the structure of a protective antigen. They are produced by first raising antibodies to the appropriate antigen in a suitable animal. The specific antibodies produced (idiotypes) are then used to raise further antibodies which react with the antigen-binding site of the first (anti-idiotypic antibodies). The antigen-binding site of the anti-idiotype can be used as a vaccine since it resembles stoichiometrically the original antigen and will induce formation of antibodies which cross-react with it. Such vaccines have advantages when the protective antigen is difficult to obtain in large amount or possesses undesirable side effects.

Processes involved in developing, licensing and marketing a new vaccine is a long, laborious, complex, and very expensive task. It needs extensive knowledge of all aspects of the pathogen including the structure, epidemiology, pathology, and immunobiology and concerted collaborative efforts between scientists, regulatory authorities and industrial entrepreneurs.