Researchers at INIA-CISA led by Javier Ortego and Alejandro Brun have developed a dual vaccine that simultaneously induces a protective immune response against the bluetongue virus (BTV) and the Rift Valley Fever Virus (RVFV).
These two arthropod-borne viruses are two important pathogens that seriously affect ruminants, causing great losses in livestock. BTV and RVFV share several epidemiological aspects, which makes the development of a bivalent vaccine very favorable to protect against both viruses.
In Europe, periodic vaccination campaigns are carried out to control the spread of BTV, which has become endemic to southern Europe. However, current BTV vaccines are serotype specific. On the other hand, the vector competition of European mosquitoes indicates that RVFV outbreaks in Europe would be possible.
In recent decades, various recombinant vaccine candidates have been explored to prevent BTV or RVFV separately. However, immunization with multivalent vaccines has potential advantages in reducing costs. The vaccine developed at the CISA is based on a recombinant modified Vaccinia Ankara virus that expresses the VP2, NS1 or a truncated form of NS1 (NS1-Nt) of BTV and the Gn and Gc glycoproteins of RVFV.
The efficacy of these experimental vaccines has first been tested in a mouse model. Two doses of the vaccine candidates MVA-GnGc-NS1 or MVA-GnGc-NS1-Nt induced high levels of RVFV-specific neutralizing antibodies and activated a potent BTV-specific cytotoxic CD8 + T cellular immune response.
The efficacy of in the mouse model demonstrated, sheep were vaccinated following the same strategy of two immunizations with MVA-GnGc-NS1. After vaccination, the animals were infected with RVFV or BTV and in both cases it was observed that both the clinical signs and viremia were absent or greatly reduced in the vaccinated ewes, confirming that the vaccines generated induce protection against two important ruminant infections as are BTV and RVFV.