Figure 2.

Antibody Responses Induced by DPDL1E Vaccination in C57BL/6 and BALB/c Mice

(A) Mice (n = 8) were immunized with DPDL1E three times at 2-week intervals. One week after the third immunization, the antibody titers were measured by ELISA using His-tagged PDL1 recombinant protein as a coating antigen. DTT-immunized serum was used as a negative control. (B) The levels of PD-L1- and DTT-specific antibody subclasses induced by DPDL1E vaccination. Sera were isolated from C57BL/6 and BALB/C mice immunized with the DPDL1E vaccine. The levels of the indicated antibody subclasses were measured by ELISA. (C) The sera from DPDL1E-immunized mice inhibited binding of PD-L1 to PD-1. PD-L1 mAb at 20 μg/mL was used as a positive control, and sera from DTT-immunized mice and PBS were used as a negative control and blank control, respectively. (D) The inhibition efficiency of sera at different concentrations was tested and compared with the control group. (E) A standard curve was created (relative inhibition versus concentration of PD-L1 mAb) to calculate the effective anti-PD-L1 concentration in vitro. ****p < 0.0001.