Codelivery of equal amounts of antigen plasmid and helper plasmid did not enhance the immunogenicity of TCR-β cDNA. (A) TCR-β plasmid (1 μg/shot) was coprecipitated onto gold particles with the same amount of β-gal plasmid and delivered to mice by gene gun followed by subcutaneous MBL-2 tumor challenge. Tumor sizes (mean ± SEM of n = 6 mice/group) are shown for naive mice (○), mice immunized with the empty vector plus β-gal (△), and mice immunized with TCR-β plus β-gal plasmids (). Plasmid pcDNA-gag served as a positive control (n = 5 mice/group). Experiments were terminated when more than 50% of the mice in a group had been humanely killed. (B) Survival of mice after gene gun delivery of TCR-β (with or without an equal amount of β-gal plasmid) or gag-encoding plasmids and subcutaneous challenge with MBL-2 tumor.