PSMD1 and infection: ELISA reactivity towards non-feline CoV S1 proteins might be explained by infection with the respective or related CoVs or by the presence of cross-reacting antibodies, although there was low sequence identity (< 32.8%) between S1 proteins of FCoV type 1 and related non-feline coronaviruses (for the complete comparison of S1 sequence identities, see Table 2).