Characterization of rNP purified from E. coli transformed with pET30a-NP or expressed from BHK cells infected with RVJ1175NP. (A) Schematic representation of the expression plasmid (pET30a-NP) used to express the NP of influenza A/Jingke/30/95(H3N2) in E. coli BL21(DE3). (B) SDS-PAGE of purified rNP. Purified rNP was fractionated by 10% SDS-PAGE and stained with Coomassie blue. BL21(DE3) transformed with pET-30a was used as a negative control. (C) Western blot analysis of purified rNP with mouse polyclonal antibodies specific for NP. (D) Schematic representation of RVJ1175NP encoding the influenza NP gene. ITR, inverted terminal repeat; P7.5 K, P7.5 later promoter; P11K, P11 later promoter; TKR, right thymidine kinase; TKL, left thymidine kinase. (E) Western blot analysis of influenza NP expressed in BHK cells infected with RVJ1175NP using mouse polyclonal antibodies specific for NP. BHK cells infected with RVJ1175 were used as a negative control. The expression bands for NP and their molecular weights are indicated.