Pathogenesis of oral type I feline infectious peritonitis virus (FIPV) infection: Antibodydependent enhancement infection of cats with type I FIPV via the oral route

Abstract

Feline infectious peritonitis virus (FIPV) causes a severe, immune-mediated diseasecalled FIP in domestic and wild cats. It is unclear whether FIP transmits from cat to cat throughthe oral route of FIPV infection, and the reason for this includes that FIP is caused by oralinoculation with some FIPV strains (e.g., type II FIPV WSU 79-1146), but is not caused by other FIPV(e.g., type I FIPV KU-2 strain: FIPV-I KU-2). In this study, when cats passively immunized with anti-FIPV-I KU-2 antibodies were orally inoculated with FIPV-I KU-2, FIP was caused at a 50% probability,i.e., FIPV not causing FIP through oral infection caused FIP by inducing antibody-dependentenhancement. Many strains of type I FIPV do not cause FIP by inoculation through the oral routein cats. Based on the findings of this study, type I FIPV which orally infected cats may cause FIPdepending on the condition.