To further investigate the molecular basis of the ability of rHN/TAR6-VP0 and rHN/FJ9-VP1 to utilize the HS receptor for efficient infection in WT-CHO cells, single amino acid mutations Gln-2080 → Leu in VP2 of O/Tibet/CHA/6/99tc and Lys-1083 → Glu in VP1 of O/Fujian/CHA/9/99tc were introduced into pOFS/TAR6-VP0 and pOFS/FJ9-VP1, respectively, to construct two site-directed mutated cDNA clones (pOFS/TAR6-VP0Q2080L and pOFS/FJ9-VP1K1083E) (Figure 2). This evidence concerns the gene TAAR6 and infection.