FIG 6.

Exogenous trypsin rescues replication of HKU5-CoV. Vero cells were infected with full-length HKU5-CoV in the presence or absence of trypsin. (A) Expression (reverse transcription-quantitative PCR [qRT-PCR]) of HKU5-CoV viral genome in the presence or absence of trypsin (n = 3). (B) Immunoblotting of HKU5 spike protein and cellular actin 24 and 48 hours postinfection with various concentrations of trypsin in the media. (C) Immunoblotting for MERS N protein and cellular actin following infection in the presence or absence of trypsin and human DPP4 antibody. (D) Alignment of amino acid sequence from the S1/S2, endosomal cysteine protease (ECP), and the S2 cleavage sites. Green boxes represent key residues conserved, and red boxes outline amino acid changes that potentially impact cleavage.