Protocol: PK Antigen Capture ELISA for Use with Anti-Tremelimumab (Imjudo) Antibodies

Reagents

BSA (Sigma-Aldrich, A7906)

HISPEC Assay Diluent  (BUF049)

Human Serum (Sigma-Aldrich, H4522)

Phosphate buffer saline (PBS)

136 mM NaCl
2.68 mM KCl
8.1 mM Na₂HPO₄
1.46 mM KH₂PO₄

PBST

PBS with 0.05% Tween 20

QuantaBlu Fluorogenic Peroxidase Substrate (Thermo Fisher Scientific, 15169)

Materials

384-well microtiter plate, black, square flat-bottom wells, for example, Black 384-Well Immuno Plates (Thermo Fisher Scientific, 460518)

Fluorescence plate reader
96-well plates can be used instead of 384-well plates (black, flat-bottom wells), for example, Black 96-Well Immuno Plates (Thermo Fisher Scientific, 437111). For the 96-well format, use 100 μL (instead of 20 μL) of antigen, antibodies, or substrate and 300 μL for the blocking step.

Method

1. Prepare human CTLA-4 (capture antigen) at 5 µg/mL in PBS. Coat the required number of wells of a 384-well microtiter plate with 20 µL per well of the prepared capture antigen, and incubate overnight at 4°C.
2. Wash the microtiter plate five times (5x) with PBST.
3. Block the microtiter plate by adding 100 µL 5% BSA in PBST to each well, and then incubate for 1 hr at RT.
4. Wash the microtiter plate 5x with PBST.
5. For the standard curve, prepare a dilution series of tremelimumab in 10% human serum in PBST in triplicate. Final concentration of tremelimumab should cover the range from 0.1 ng/mL to 10,000 ng/mL. Include a zero tremelimumab concentration as the background value.
6. Add 20 µL of tremelimumab dilution per well (in triplicate for each standard recommended). Add 20 µL of each test sample to the other wells (in triplicate for each sample recommended). Incubate for 1 hr at RT.
7. Wash the microtiter plate 5x with PBST.
8. To each well, add 20 µL detection HRP-conjugated Anti-Tremelimumab Antibody, TZA0128P (AbD64586pap), at 0.5 µg/mL in HISPEC Assay Diluent. Incubate for 1 hr at RT.
9. Wash the microtiter plate 5x with PBST.
10. Add 20 µL QuantaBlu Fluorogenic Peroxidase Substrate to each well and measure the fluorescence after 30 min.