Targeting of mCherry towards major histocompatibility complex (MHC) class II enhanced the level of mCherry-specific Abs. (A) The targeting unit of [scFvI-E-mCherry]2 binds specifically to MHC class II. Supernatants harvested from transfected HEK293 were used to stain EβdEαk- or Dd-transfected L cells. The bound vaccine proteins were detected by biotinylated anti-mCherry, streptavidin-PE and flow cytometry. (B) BALB/c were given DNA encoding [scFvI-E-mCherry]2, [MIP1α-mCherry]2 or mCherry i.m. before electroporation. Blood was harvested after 14 days, and the titres of mCherry-specific IgG was determined by ELISA (n = 5 mice/group). (C) Time line. BALB/c were immunized as described previously, and draining lymph nodes (LN) and spleen were harvested for generation of hybridomas. (D) ELISA measurements of mCherry-specific Abs following fusion of draining LN with OURI cells. DNA encoding [scFvI-E-mCherry]2 or mCherry was injected into quadriceps of BALB/c before electroporation (n = 3 mice/group). After 29 days, the draining LN were harvested, fused with OURI cells and cultivated in 96-well plates. The cell supernatants were analysed in ELISA containing mCherry as coat.