Fig 1.

Sequences and schematic diagram of constructs. The M2e sequence shown is the consensus of the human influenza A virus M2e sequence. In 4.M2e, four repetitive M2e regions (underlined) are located in a tandem. Sequences in italics are flexible linkers. A 6-histidine tag-encoding DNA was fused in frame. In the membrane-anchored 4.M2e-tFliC, the central immunogenic region of FliC (domain 3 [D3], aa 177 to 401) was replaced by the 4.M2e sequence. The melittin signal peptide (SP) was fused to the N terminus of 4.M2e-tFliC (N-terminal domains 1 and 2 [ND1-2] in FliC) to enable its ectodomain to reach the exocytic pathway and is removed in the mature protein by insect cell signal peptidase (44). The transmembrane and cytoplasmic domains (TM/CT) of A/PR8 virus HA were attached to the C terminus of the 4.M2e-tFliC (C-terminal domains 2 and 1 [CD2-1] in FliC).