Clearance of infection in cats naturally infected with feline coronaviruses is associated with an anti-S glycoprotein antibody response

We have investigated by Western blotting the antibody responses against the three major structural proteins in cats naturally infected with feline cor onaviruses that cleared virus infection (group I), established chronic asym ptomatic infection (group II) or were sick (group III). The cats of group I developed an anti-S glycoprotein response that was, relative to the anti-M glycoprotein response, at least 30-fold higher than that of chronically in fected cats from groups II and III. These results suggest that the anti-S g lycoprotein response against antigenic domains revealed by Western blot is associated with clearance of the virus after natural infection, and is not a risk factor for the establishment of a chronic infection.