Protocol: PK Bridging ELISA for Use with Anti-Abatacept Antibodies

Reagents

BSA
​HISPEC Assay Diluent (BUF049)
Human Serum (Sigma-Aldrich, H4522)
LYNX Rapid HRP Antibody Conjugation Kit (LNK001P-LNK006P)

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, e.g. 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) e.g. 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 the detection Anti-Abatacept Antibody: conjugate HCA335 (AbD37058ia) using a LYNX Rapid HRP Antibody Conjugation Kit.
2. Prepare the capture Anti-CTLA-4 Antibody MCA1724 at 1 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 antibody, and incubate overnight at 4°C.
3. Wash the microtiter plate five times (5x) with PBST.
4. Block the microtiter plate by adding 100 µl 5% BSA in PBST to each well, and then incubate for 1 hr at RT.
5. Wash the microtiter plate 5x with PBST.
6. For the standard curve, prepare a dilution series of abatacept in 10% human serum in PBST in triplicate. Final concentration of abatacept should cover the range from 0.01 ng/ml to 4,000 ng/ml. Include a zero abatacept concentration as the background value.
7. Add 20 μl of abatacept 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.
8. Wash the microtiter plate 5x with PBST.
9. To each well, add 20 µl HRP conjugated detection Anti-Abatacept Antibody, HCA335 (AbD37058ia), at 2 µg/ml in HISPEC Assay Diluent. Incubate for 1 hr at RT.
10. Wash the microtiter plate 10x with PBST.
11. Add 20 µl QuantaBlu Fluorogenic Peroxidase Substrate to each well and measure the fluorescence after 30 min.