Schematic representation of the capsid coding regions of the chimeric and site-directed mutated full-length genomic cDNA clones. The parental plasmid pOFS of rHN was used as the genomic backbone to generate the chimeric and site-directed mutated full-length cDNAs (left) of each rescued virus (right). The VP1–VP4 coding regions of rHN, O/Tibet/CHA/6/99tc (TAR6) and O/Fujian/CHA/9/99tc (FJ9) are represented by solid grey boxes with black borders, and hollow boxes with purple and blue borders, respectively. One-letter amino acid codes are used and positions at which amino acid residues differ in the compared chimeric and site-directed mutated regions are labeled at the bottom (see Table 1). Single amino acid substitutions at residues 2080 of the VP2 coding region and 1083 of the VP1 coding region are marked in red. Procedures for the construction of chimeric and site-directed mutated full-length cDNA clones are described in Methods. *, The site-directed mutant rHN/FJ9-VP0L2080Q could not be rescued successfully from the original plasmid pOFS/FJ9-VP0L2080Q in BHK-21 cells (see Figure 1).