Immunization of Cats Against Feline Infectious Peritonitis with Anti-Idiotypic Antibodies

Anti-idiotypic antibodies (Ab2s) generated against neutralizing antibodies (Ab1s) specific for feline infectious peritonitis virus (FIPV) were shown to be specific for paratope-associated idiotopes of the Ab1s and not against isotypic determinants. In a study to determine the efficacy of an anti-idiotypic vaccine against feline infectious peritonitis (FIP), cats that were immunized with a pool of monoclonal Ab2s developed Ab3s that recognized the variable regions of the Ab2s as well as the natural antigen. In cats challenged with a lethal dose of virus the control group followed a predictable course of infection ultimately succumbing to FIP. Two immunized cats survived virus challenge and a third cat lived twice as long as the controls. The fourth immunized cat showed no evidence of protection. The ability to induce levels of protection against FIP lends support to the concept of using anti-idiotypic antibodies as a prophylactic vaccine.