Response of ferrets to infection with a live attenuated influenza virus and to subsequent heterologous challenge.

Groups of three ferrets were inoculated with a live influenza vaccine ("Alice" strain) and the degree of protection afforded against a challenge inoculation was measured by several parameters. After vaccination, virus excretion was studied and the genetic characteristics of the virus isolates were investigated. After 5-8 weeks, the challenge inoculations were performed with antigenic drifts of the H3N2 virus: A/Dunedin/4/73 (Port-Chalmers-like), A/England/635/74 and A/Scotland/840/74. The following parameters of infection were evaluated: temperature rises, clinical symptoms, viral excretion, serological responses and increases in the nasal protein contents (Potter et. al(1972). Immunity to influenza in ferrets. I. Response to live and killed virus. Brit. J. Exp. Path., 53, 153-167.) A very high degree of protection was observed in the immunized animals.