Comparison of DNA application methods to reduce BRSV shedding in cattle.

We compared the protection afforded by three different DNA application methods against bovine respiratory syncytial virus (BRSV) infection in cattle. A synthetic gene that codes for the G protein of BRSV was inserted into a eukaryotic vector and was used in the vaccine. Intradermal (i.d.) application with a needleless injector (NI), the Pigjet, reduced BRSV excretion significantly better after BRSV challenge than intramuscular (i.m.) or i.d. vaccination with a needle. Serum antibodies against the G protein were consistently the highest and showed less variation in Calves vaccinated with the NI compared with those in i.m. and i.d. vaccinated calves. After BRSV challenge, secondary serum and mucosal antibody responses were also the highest in NI vaccinated calves. We conclude that DNA application with the needleless injector is substantially better than i.m. or i.d. application, and is capable to prime the immune response at the respiratory mucosa.