Marker vaccine
A marker vaccine or a marker vaccine (also: DIVA vaccine or -Vakzine ) is an animal vaccine , which allows to distinguish vaccinated from infected animals.
functionality
When a viral infection triggers an immune response, antibodies are formed to fight off the virus. In order to determine whether an animal is infected with certain viruses, a serological test can be used to check whether the corresponding antibodies are present. The desired reaction to a vaccination, however, is also the formation of antibodies against the pathogens, so that in conventionally vaccinated animals, an infection can no longer be concluded from the serological examination.
In a marker vaccine, for example, by deleting certain genes , selected strongly immunogenic features are suppressed, so that the antibodies required for protection are still formed, but none against the removed features. This makes it possible to distinguish whether an animal is carrying the antibodies because of an infection or because of a vaccination, because some antibodies that would be detected in infected animals are missing in non-infected but vaccinated animals. The name of these vaccines comes from the term marker used in biology (such as “marker”, see marker (genetics) , biomarker ), the abbreviation “DIVA” from English. di fferentiation of i nfected and v accinated a nimals (“differentiation between infected and vaccinated animals”).
application
Marker vaccines are especially important in livestock farming and in attempts to eradicate an animal disease nationwide. A common strategy to control animal diseases is to find infected animals through serological tests and to cull affected herds . Because a conventionally vaccinated animal appears infected by these tests, vaccinations against rare diseases are banned in many countries, vaccinated animals or meat from vaccinated animals may not be imported, and the sperm of a vaccinated animal cannot be used for artificial insemination . Marker vaccines and corresponding serological tests can make these restrictions and thus many slaughterings unnecessary.
In practice, marker vaccines are used, among other things, to eradicate Infectious Bovine Rhinotracheitis (IBR), a bovine disease, and Aujeszky's disease or pseudorabies, whose host animals are pigs, in certain countries. In the case of Aujeszky's disease, the marker vaccine arose naturally, with a specific glycoprotein (gE) disappearing from the vaccine virus; its usefulness as a marker vaccine was only later recognized. Various marker vaccines are now available, for example against foot-and-mouth disease , but these are not yet accepted worldwide by authorities and industry.
Manufacturing
Positive marker vaccines are made by genetic engineering of a marker antigen into the vaccine strain, which creates additional antibodies in the animal. However, such vaccines can be used to distinguish animals that have not been vaccinated but are still infected. In the case of negative marker vaccines, the vaccine strain lacks parts of the genome. They can be genetically engineered, but they can also arise naturally. The absence of this modifies the humoral defense , so that a distinction can be made between only infected, only vaccinated and vaccinated plus infected animals.
swell
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