Fig. 3

Mutations identified in the PEDV 8aa S gene and the effects of trypsin treatment on PEDV 8aa on virus binding or viral replication. a Amino acid changes in PEDV 8aa P70 or P105 from multiple sequence alignments with the parental PEDV 8aa P0 and >100 US PEDV strains. The S1/S2 junction (758/579), HR1 (aa 979–1088) and HR2 (aa 1239–1277) are indicated based on the literature [44, 45]. Fusion peptide (FP, aa 895–912) and transmembrane (TM) region are also shown in the schematic drawing. b and c Effects of trypsin treatment on PEDV 8aa or PEDV KD on virus binding. Unconcentrated or concentrated (10 ×) PEDV 8aa (P70) or PEDV KD (P70) was treated with trypsin (5 μg/ml) or mock-medium at 37 °C for 1 h and the treated virus was added to confluent Vero cells. The cells were then incubated in a cold room (4 °C) for 1 h and cell lysates were prepared for real time RT-qPCR (b) or Western blot analysis (c). The percentage of trypsin-treated viruses bound to the cells were compared to mock-medium treatment (No T, no treatment). d Effects of trypsin pre-treatment on PEDV 8aa on virus replication. Concentrated (10 ×) PEDV 8aa was pre-treated with trypsin (5 μg/ml) or mock-medium at 37 °C for 1 h, and added to confluent Vero cells. After incubation of the virus infected cells at 37 °C for 24 h, they were fixed for IFA staining for PEDV. Panels 1 and 2 show the cells incubated with trypsin or with mock-medium without virus infection, respectively. Panels 3 and 4 show PEDV 8aa grown in the cells with mock medium or trypsin respectively