Immunity to influenza in ferrets. II. Influence of adjuvants on immunization

Abstract

Immunization of ferrets with a single intramuscular inoculation of killed A2/Hong Kong virus did not induce serum or nasal antibody, and these animals were found to be completely susceptible to subsequent infection with virulent influenza virus A2/Hong Kong/3/68. A similar result was found for ferrets immunized with 2 inoculations of killed virus vaccine given 2 weeks apart. Ferrets immunized with killed A2/Hong Kong virus in conjunction with Bordetella pertussis produced relatively low levels of serum HI antibody to A2/Hong Kong virus; when infected with virulent influenza virus, these ferrets showed a modified reaction, with a less marked febrile reaction than was observed for non-immunized animals.

Immunization of ferrets with killed A2/Hong Kong virus in Freund's complete adjuvant resulted in the production of relatively high levels of serum HI antibody, but no detectable nasal antibody. These animals were shown to be partially immune to subsequent infection with virulent influenza virus. However, although the serum antibody levels of these animals following immunization was comparable to that found following infection with live virus, the degree of immunity to infection with virulent influenza virus was measurably less.