Local and systemic response after simultaneous intranasal inoculation of temperature-sensitive mutants of parainfluenza 3, IBR and bovine adenovirus 3.

Triple seronegative calves were exposed by the nasal route to three (ts) mutants of bovine respiratory viruses (PI3, IBR, Adeno3). After a single exposure, they responded with significant levels of serum antibodies to the three viruses. Nasal antibodies were demonstrated for PI3 and adenovirus antigens. The failure to demonstrate nasal antibodies to IBR may be due to lack of sensitivity of the procedure used. When reexposed six weeks later, calves had sharp increases in levels of serum antibodies and developed a secondary type response at the local level for all three viruses. The persistence of the local antibodies was much longer after reexposure than after primary inoculation. This study indicates that the simultaneous application of these three (ts) viruses by the respiratory route is perfectly safe and affords a long lasting immunity towards homologous respiratory infections.