During his doctoral research, Stephen Kaba made two vaccines based on a protein found on the surface of the parasite. In total, 72 percent of the animals that were injected with the new protein vaccines and subsequently infected with the parasite, were found to be protected. This protection was achieved with a low vaccine dosage and with just two injections. Previous protein vaccines could only protect half of the animals.
Up until now, veterinary surgeons have injected the entire parasite instead of one of its proteins. The cattle were also simultaneously treated with a cure of antibiotics. This method, which requires considerable skill and the culturing of large quantities of parasites, is a time-consuming and expensive process. An associated problem is that the parasites must be stored at a very low temperature, which is difficult in tropical areas. Furthermore, with this method there is always the chance that the animal could become ill as a result of the vaccination. The new vaccines do not have these problems.
The researchers developed two methods to make a stable form of the parasite protein, in large quantities in insect cells. They used modified baculovirusses for this. In one method the researchers linked the parasite protein to the carrier protein (Green Fluorescent Protein or GFP). In the other method the protein was attached to the outside of the baculovirus particles. Both products provided vaccines with a good level of effectiveness.
The protein used, p67, ensures that the parasite can penetrate white blood cells. The immune system of the cattle recognises this protein and makes antibodies against it
Contact: Lydie van der Meer
Netherlands Organization for Scientific Research