In order to monitor further stages of infection in detail if APN-null pigs really infected with TGEV during viral challenge and if TGEV resistance is APN indel pattern-dependent, in Experiment 2, APN-null piglets (n = 4) with three distinct APN modifications (Table S3) and WT piglets (n = 5) were challenged with TGEV and sacrificed for pathological examination at 2 stages of infection: acute and mid stages (<48 h, and >48 h, respectively). This evidence concerns the gene ANPEP and infection.