These factors, combined with a) low virus inoculation dose (1-mL/cat of 1 TCID50), b) oral/nasal inoculation route, and/or c) low S1/RBD immunogenicity of the infection, may have contributed to the lack of SCoV2 RBD cross-reactivity, similar to the lack/loss of cross-reactivity of UGAQ1 and UGAQ3 sera to SCoV2 RBD (Figure 3A). This evidence concerns the gene PSMD1 and infection.