Clever though the herpesvirus may be, the researchers from the University of Liege found a weak point: making it easy to manipulate, genetically speaking! By perfecting and then using the BAC cloning technique (bacterial artificial chromosome), the team from Liege succeeded in tweaking the genetic apparatus of the virus by removing the infamous ORF73 from it. Theoretically, AlHV-1 then becomes incapable of remaining in a latent state.

The theory was then confirmed in practice. After re-infecting rabbits (that exhibit disease symptoms comparable to those of cattle) with this so-called “deleted” virus, the researchers noticed that the disease had disappeared. “We no longer detected a viral genome in their blood or organs”. We can say goodbye to malignant catarrhal fever!

Even better: Benjamin Dewals noticed that the infectious microorganism that was genetically modified in this way was capable of inducing an immune response. “Different experiments carried out showed that this virus was still capable of replicating itself in the nasal mucous membranes during the first few days of the infection, exactly like a virulent virus. It is only after this that the virus can no longer be detected which signifies that it has the capacity to induce an effective viral response.”

It was time for one final experiment, to ensure that this immunity was truly protective and not just superficial. Rabbits were infected with the virus that had ORF73 removed to induce an anti-viral response. One month later, these rabbits were subjected to a second infection which was virulent this time. What was the outcome? All of them survived!

Without really doing so intentionally, Benjamin Dewals had succeeded in finding a vaccine. The next stage will be to repeat these tests, on cattle this time, in order to completely verify the results. “In any event, it already looks promising”!