Threonine 143 in HA enhances H7 pseudovirus infectivity.

(A) Comparison of WT and mutation on residue 143. (B) Comparison of WT and mutations on residues 183, 195 and 198. The infectivity of pseudoviruses bearing wild type (WT) HA and its mutants is compared (Top panels in A and B). Data are shown as mean and standard deviation of three independent experiments. P<0.001 of T-test were shown. The levels of mature HA (HA1) and p24 in HA-pseudoviruses shown by Western blotting were detected with goat antisera against A/Netherlands/219/2003 HA and mouse mAb (183-H12-5C) against HIV-1 p24 Gag, respectively (Bottom panels in A and B). NL: A/Netherlands/219/2003 HA-pseudoviruses; SH: A/Shanghai/02/2013 HA-pseudoviruses.