The first object of this project is to identify the key antigenic sites in the porcine parvovirus and to test peptides representing these sites for their ability to induce immunity.
The second object of this project is to produce the designed new proteins in bulk to scale up the bacterial or eukaryotic fermentation process, to select the proper downstream purification methods, to formulate the vaccines, to test the vaccines on a laboratory scale followed by field trials to assess the protection in target animals.
Porcine parvovirus (PPV) is one of the major causes of reproductive failure in pigs with control of the disease usually carried out with conventional vaccines made of inactivated viruses. In order to develop a more cost effective subunit vaccine, the current project was undertaken. Objectives set were production of PPV antigens; production and maintenance of specific monoclonal antibodies;
recombinant polypeptide expression;
optimization of the recombinant protein purification;
fine mapping of PPV.
The major achievement has been the production of porcine parvo-like capsids, similar to the original virus. These particles have shown a high immunogenic activity, eliciting an immune response in pigs indistinguishable from that obtained with a commercial inactivated vaccine. This is a promising feature for the commercial application of these particles as a vaccine. The baculovirus/insect cell line system is already capable of producing attractive amounts of antigen at a low price. Another interesting point is the efficacy of the putative subunit vaccine when combined with standard adjuvants.
The rather simple structure of the parvoviruses constitute a good model for the preparation of recombinant subunit vaccines. Procaryotic (E coli) expression has failed to give useful products. It is therefore of major importance that the eucaryotic baculovirus insect cell expression system has been able to produce parvovirus VP2 protein in a conformation which seems to be indistinguishable from native capsids and carrying all immunodominant epitopes. This will facilitate the development of large scale fermentor techniques leading to a more cost effective and nucleic acid-free second generation parvovirus vaccines in a foreseable future. These vaccines will be extremely safe, innocuous for the animal and devoid of any residual infectivity. They should constitute the technologically improved alternative to the classical vaccines.
In the modern pig industry of the EC the control of porcine parvovirus (PPV) is mandatory. Vaccination against this disease is a prerequisite for a profitable production of pig meat. Currently available vaccines are produced by conventional techniques. However, PPV is difficult to grow in cell culture, which makes the vaccine production technically demanding, laborious and expensive. It is doubtful whether the current, first generation vaccine production based on fast growing cells will be able to cope with the increasing demand, caused by the increasing industrialization of pig farming.
Thus, we propose to develop a second generation vaccine using recombinant DNA technology, gene expression, epitope scanning by multiple overlapping peptides (PEPSCAN technique, mimotopes), monoclonal antibodies (MAbs) and modern adjuvants (ie ISCOMS). The object is to define the key antigenic sites necessary for protection and to construct expression systems able to produce proteins exposing these sites in the best possible way. Finally, the new proteins will be incorporated into vaccines. The vaccines will be tested in the target animal (field trials). On the basis of the experience obtained with PPV it is envisaged that second generation vaccines against closely related viruses of large economic and social importance (mink enteritis virus, canine parvovirus and feline panleukopenia virus) can be produced along the same lines. These parvoviruses are similar to PPV and of great economical and social importance.
Funding SchemeCSC - Cost-sharing contracts
8219 PH Lelystad