Characterization of a feline infectious peritonitis virus isolate.

A virus isolated in cell culture from the spleen of a cat with feline infectious peritonitis was identified by physicochemical, morphological and antigenic criteria as a coronavirus. The feline infectious peritonitis virus was compared in vitro with canine coronavirus, a reported enteric pathogen of dogs. The feline isolate was characterized, by chloroform sensitivity and resistance to 5-iododeoxyuridine, respectively, as containing essential lipid and an RNA genome. Other traits of the isolate included resistance to acidic conditions, heat lability, and resistance to trypsin. Electron microscopy showed viral particles with a structure consistent with that of the prototype of the coronavirus group, infectious bronchitis virus. Indirect immunofluorescence with canine coronavirus monospecific antiserum showed the viral isolate to be antigenically related to canine coronavirus. Specific-pathogen-free cats inoculated by various routes with cell-culture-propagated virus had both clinical symptoms and lesions consistent with feline infectious peritonitis.