Immunity to infections of the respiratory system in man and animals.

Itis probable that RS virus is an important etiological agent in the bovine respiratory disease syndrome. This is the conclusion of groups of workers in Europe and Japan. In this country, significant levels of neutralizing antibody have been detected in 81 percent of cattle tested, while paired sera groups showed seroconversions of between 17 and 29 percent. RS virus has also been isolated from diseased calves and such isolates produce pyrexia and rhinitis in experimentally infected calves. The virus is localised in the respiratory tract. Serum antibody responses have not been consistent but it is likely that moderate serum antibody levels indicate that the animal is protected. These antibody levels can be achieved by injection of a formalin inactivated antigen. Calves vaccinated in this way showed no definite evidence of exacerbation of disease when challenged with infectious virus.