Humoral Immunity to Canine Distemper After Immunization of Dogs with Inactivated and Live Measles Virus

Pairs of dogs were immunized with 2 injections of a) measles virus material containing hemagglutinin but no hemolysin [Tween 80 and ether (TE) treated] b) material containing both hemagglutinin and hemolysin (freeze-dried and heated at 95 degrees C for 30 minutes), and c) live measles virus. Two unimmunized dogs were used as controls. All 8 dogs were challenged with virulent canine distemper virus (CDV). The two unimmunized dogs contracted a lethal infection, whereas immunized animals only showed mild signs of infection. Preimmunization with TE treated antigen gave the weakest protection. The animals displayed fever between day 4 and 10 after challenge. All titers of preexisting antibodies were boosted and antibodies against the measles hemolysin and CDV neutralizing antibodies increased from undetectable to moderate levels. Non-infectious intact virus (b) gave a more pronounced antibody response than TE antigen but antibodies against the hemolysin could not be detected. There was a good protection against disease (limited fever response). Replication of CDV caused a raise of antibody titers to levels normally seen only under conditions of hyperimmunization. Live measles virus stimulated the production of antibodies against both envelope components, but in spite of this virulent CDV could multiply and boost the titers of all antibodies.