Thanks to progress made in biotechnology, the so-called second generation vaccines are now more effective, safer and less costly. A European partnership set up in the context of the BRIDGE programme has made it possible to develop vaccines produced through this new technology, the purpose of which is to combat a disease which affects several animal species, namely the parvoviruses affecting dogs, pigs and minks
Although they can also affect humans (for
example, parvovirus B19 is responsible for a childhood disease with
symptoms similar to those of German measles), parvoviruses pose
above all serious veterinary problems, particularly where pig farming
is concerned, which is an agricultural sector of prime economic
importance. Parvoviruses also affect domestic animals, such as cats
and dogs, and species such as minks, which are farmed in the Nordic
In this area, the value of traditional vaccination techniques based on inactivated viruses is questionable in terms of their reliability, production difficulties, and cost. That is why three teams of European researchers - Spanish, Dutch and Danish - got together in 1991, as part of the Community BRIDGE programme, to devise "second generation" veterinary vaccines, specifically for infections from parvoviruses, which could be used without risk on a large scale.
"This new generation of vaccines, a direct result of recent progress in genetic engineering, is characterised by the fact that it consists uniquely of antigens belonging to the virus capsid, i.e. all the proteins which form the viral coat, and yet provokes an immune response which is identical to that of traditional vaccines," explains Ignacio Casal, project coordinator. "Unlike the latter, the new vaccines are safer because the capsids do not contain any DNA - the basis for the virus's reproductive system - which eliminates the certainly minimal, but nevertheless real, risk of an unwanted multiplication of the virus. This technique also has another significant advantage: we can produce considerable quantities of antigens from in vitro cultures of insect cells in a very economical manner."
Proteins rather than DNA
"When the project started, however, the development of such vaccines was still beset with major difficulties as regards production techniques," stresses Ignacio Casal. "In parallel with work carried out in this context in human medicine - several second generation vaccines against human viruses are now available - we successfully concentrated our work on the veterinary field. The project thus culminated in the creation of three specific vaccines to combat parvoviruses of pigs, minks and dogs."
The first synthetic vaccine
One other significant advance made during the project deserves to be mentioned. While the first two vaccines - for pigs and minks - are obtained from capsids extracted directly from insect cell cultures, the third, for dogs, is produced from small synthetic elements of these proteins. "Major research groups have been trying to develop this technique without much success for more than two years," continues the project coordinator. "This synthetic vaccine, which is capable of giving total protection to an animal, is thus a first in its field".
The economic results of the project ase also quite significant: a patent has been filed for each type of vaccine and their commercial launch is now being negotiated.