Serologic classification of feline caliciviruses by plaque-reduction neutralization and immunodiffusion.

Serologic classification of 14 isolated of feline caliciviruses was carried out, using plaque-reduction neutralization tests. Sixty to 200 plaque-forming units of virus were employed against 20 antibody units of hyperimmune goat antiserums prepared to individual isolates. The results established that these viruses were related in various degrees, but no 2 were identical. Arrangements in order of the greatest intergroup reactions yielded essentially 1 serotype with the exception of 1 virus showing 1-way neutralization reactions with heterologous isolates. The geographic origin, the site of viral isolation, or the plaque size had no relationship with the neutralization pattern. The F-9 isolate that showed the greatest intergroup reactions was proposed as the possible reference virus. The viruses were indistinguishable by using gel-diffusion analysis against cat antiserums.