Figure 1.

Schematic representation of the mutants used in this study. (A) Three NDV strains were used as model viruses in this study, including the vaccine strain rMukteswar, the vaccine variant strain rJS/7/05/Ch, and the dual-site mutant strain rMukHN494 + 495^JS. rMukHN494 + 495^JS was the rMukteswar derivative bearing the 494 and 495 aa of rJS/7/05/Ch. The aa mutations in the HN protein of NDV are marked with yellow triangles, including P438S in NP, and N19S, S29T, M145T, V266I, A494D, and E495K in HN. (B) Schematic representation of the aa mutations ranging from position 490 to 500 of different HN expression plasmids. Residues in blue and yellow indicate amino acids from Mukteswar and JS/7/05/Ch, respectively. (C) Constructed clones were identified by Sanger sequencing. The sequences of key mutation sites were displayed in red frames using the SnapGene 3.2.1 software.