Towards a new vaccine solution for bovine respiratory syncytial virus

Bovine Respiratory Syncytial virus, or BRSV, is a major pathogenic agent that causes respiratory diseases in cattle, particularly when they are young. The vaccines available until now offered only partial protection. In the context of the European SAPHIR consortium, several candidate vaccines against BRSV were tested in calves whose specific immunological features linked to their young age represented an obstacle to the efficacy of conventional vaccines. One of the major problems is to be able to effectively vaccinate calves carrying interfering antibodies from their mothers. The results were the fruit of collaboration between INRA, the Pirbright Institute (UK), the Swedish University of Agricultural Sciences (Sweden), the PME Ingenasa (Spain) and the NIH (USA).

Better protection than vaccines currently on the market

Several vaccine strategies were tested during the SAPHIR project. Some achieved remarkable performances, better than those procured by any vaccines currently available on the market. Amongst these successful candidates, it was a solution using a recombinant protein from BRSV, called pre-F (for pre-fusion protein), which notably attracted the attention of the scientists. This candidate vaccine was effective in a single dose. It demonstrated the best clinical protection (fewer clinical signs and fewer pulmonary lesions observed after an experimental infection in animals vaccinated using pre-F) and virological protection (little or no virus detected in the upper or lower airways of animals vaccinated with pre-F following an experimental infection). The candidate vaccine also displayed excellent safety and could be administered simply via the intramuscular route using a standard veterinary adjuvant employed in bovine vaccines. The pre-F vaccine was able to induce more specific immunoglobulins (including neutralising antibodies) and interferon-producing cells (IFN γ) than the other strategies studied.

A single-dose vaccine associated with a DIVA test

Effective with a single injection, the pre-F candidate appears to be the optimum solution for the development of a commercial vaccine against BRSV. In addition, using just a specific protein fraction from the BRS virus, a companion DIVA test (Differentiating Infected from Vaccinated Animals) was also developed during this project. This test, based on an INRA patent, will facilitate control of the infection in livestock units.