New Product Launch: Protein L ELISA Kit
1. Background
Advances in Novel Antibody Applications
In recent years, antibody derivatives such as Fab (antigen-binding fragments), scFv (single-chain variable fragments), and nanobodies (e.g., VHH) have demonstrated significant advantages in both therapeutic and diagnostic fields. Compared to conventional IgG antibodies, these novel antibody formats offer smaller molecular weights, better tissue penetration, lower immunogenicity, flexible multivalent construction, and the ability to target hidden epitopes. These features have enabled breakthroughs in tumor-targeted therapies, immunotherapies, and molecular imaging.
In oncology, scFvs and nanobodies (15–30 kDa, approximately 3.5 × 2.5 nm) are increasingly used in CAR-T/NK cell therapies, bispecific/multispecific antibody treatments, and immune checkpoint blockade therapies due to their compact size, which reduces CAR aggregation and tonic signaling while enhancing T cell persistence. For example, anti-CD3/CD38 scFv fusion antibodies have shown potent anti-tumor efficacy in AML therapy.
In diagnostics, Fab/scFv formats help reduce nonspecific binding and enhance detection sensitivity and signal-to-noise ratio. In molecular imaging, scFvs combined with charged nanozyme probes allow for high-sensitivity and precision imaging.
However, these novel antibody fragments pose unique challenges in downstream purification. Traditional Protein A/G resins are inadequate for these molecules (see Table 1 for comparison), which has led to the development and application of Protein L resins derived from Peptostreptococcus magnus.
2. Product Overview
1) Protein L Summary
Protein L is a 95 kDa cell wall protein (pI 4.0) secreted by the anaerobic bacterium Peptostreptococcus magnus. Its structure includes an 18-amino acid signal peptide, a 79-amino acid N-terminal domain (A), five β-folded domains (B, each 72–76 amino acids), two 52-amino acid C-terminal repeats, a hydrophilic wall-spanning region (W), and a hydrophobic membrane-anchoring domain (M). The B domains mediate specific binding to antibody light chains.
Unlike Protein A/G, Protein L selectively binds κ light chains of human Ig (VκI/III/IV subtypes) and mouse Ig (VκII), without interacting with the heavy chain. Its binding capacity to λ light chains remains unclear. Protein L can bind a wide range of antibody classes, including IgG, IgM, IgA, IgD, and IgE. This binding versatility makes it particularly suitable for purifying and detecting novel antibody formats such as scFv, single-domain antibodies, Fab fragments, and CAR constructs.
2) Technical Challenges
Protein L may co-elute with κ light chain antibodies, which can interfere with immunoassays and structural analyses such as X-ray crystallography and cryo-electron microscopy. Furthermore, its interaction with B-cell receptors (BCRs) may affect downstream signaling pathways. Additionally, its immunogenicity could potentially induce anti-drug antibody (ADA) responses in therapeutic applications.
Current strategies for Protein L removal include ion exchange chromatography (IEX) and size exclusion chromatography (SEC), while quantification is typically performed using mass spectrometry (high sensitivity) or ELISA (high throughput).
3) Our Solution
We have developed a two-step sandwich ELISA kit for the specific quantification of residual Protein L in κ light chain-containing antibody drugs. This kit includes proprietary buffer systems and offers excellent resistance to interference, ensuring reliable, high-throughput detection of Protein L contamination.
3.Application
Sample Description:
IgG products containing κ light chains were purified using Protein L affinity columns. After adsorption, the antibodies were eluted with low pH buffer, followed by neutralization. The resulting solution was used as the test sample. Samples were diluted at 10×, 100×, 1,000×, and 10,000× using the kit’s proprietary buffer (CG-P0200), yielding consistent recovery rates and stable detection results, as shown below.
Note: This ELISA kit is currently validated for IgG products containing κ light chains. For antibodies with special structural features, please contact us for customized optimization.
4. Reference Standards and Literature
1) ICH Q6B: Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products.
2) ICH Q7: Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients.
3) ICH S6 (R1)
4) EMA: Guideline on Immunogenicity assessment of therapeutic proteins (2017).
5) FDA: Points to Consider in the Manufacture and Testing of Monoclonal Antibody Products (1997).
6) Bo Akerstrom et al. Protein L: An Immunoglobulin Light Chain-binding Bacterial Protein[J]. Biological Chemistry. 1989. 264(33) :19740-19746.
7) Nilson BH et al. Purification of antibodies using protein L-binding framework structures in the light chain variable domain[J]. J. Immunol. Methods. 1993.164 (1): 33-40.
8) Myhre, E. B., et al. Protein L from Peptostreptococcus magnus binds to the kappa light chain variable domain[J]. Mol. Immunol. 1985. 22(8): 879-885.
9) Bjorck, L. Protein L: An immunoglobulin light chain-binding bacterial protein[J]. J. Immunol. 1988. 140(4), 1194-1197.
10) Zhili Zheng et al. Protein L: a novel reagent for the detection of Chimeric Antigen Receptor (CAR) expression by flow cytometry[J]. Translational Medicine. 2012. 10:29.
Cellgene Bioscience has specialized in the field of biopharmaceutical process testing for 15 years. We offer a full range of solutions including HCP residual detection kits, HCP-specific antibody development, and coverage analysis services.
| Cellgene Bioscience-Drug Residue Products | |
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| CH-K0018-2 | CHO Host Cell Protein (CHO HCP) ELISA kit, G2 |
| CH-K0018-3 | CHO Host Cell Protein (CHO HCP) ELISA kit, G3 |
| HH-H0019-2 | HEK293 Host Cell Protein (HEK293 HCP) ELISA kit, G2 |
| EH-E0020-3 | E. coli Host Cell Protein (E. coli HCP) ELISA kit, G3 |
| PH-E0021-3 | Pichia Pastoris Host Cell Protein (PP HCP) ELISA kit, G3 |
| HP-H0023-3 | Hansenula Polymorpha Host Cell Protein ELISA kit, G3 |
| SC-H0024-3 | Saccharomyces Cerevisiae Host Cell Protein ELISA kit, G3 |
| SF-H0025-3 | Spodoptera Frugiperda 9 Host Cell Protein ELISA kit, G3 |
| Medium Residues Detection kits | |
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| NEGEP0890 | Protein A ELISA Kit |
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| NE11I0431 | Bovine Immunoglobulin G ELISA Kit |
| NE01I0431 | Human Immunoglobulin G ELISA Kit |
| NE06I0431 | Goat Immunoglobulin G ELISA Kit |
| NEGEK0006 | Kanamycin ELISA Kit |
| NEGEP1270 | Protein L ELISA Kit |
| NEGEP1271 | Protein G ELISA Kit |
| NEGES0014 | Bovine Serum Albumin ELISA Kit |
| NEGES0015 | Human Serum Albumin ELISA Kit |
| NEGED0018 | Dextran Sulfate Salt Detection kit |
| Host Cell DNA Detection kits (HCD) | |
| NS-D050T/NS-D100T | NS0 Host Cell DNA (NS0 HCD) Residue Detection kit |
| EC-D050T/EC-D100T | E.coli Host Cell DNA (E.coli HCD) Residue Detection kit |
| VE-D050T/VE-D100T | Vero Host Cell DNA (Vero HCD) Residue Detection kit |
| HK-D050T/HK-D100T | HEK293 Host Cell DNA (HEK293 HCD) Residue Detection kit |
| CH-D050T/CH-D100T | CHO Host Cell DNA (CHO HCD) Residue Detection Kit |
| PP-D050T/PP-D100T | Pichia Pastoris Host Cell DNA (PP HCD) Residue Detection Kit |
| CG-DP050/CG-DP100 | Magnetic Residual DNA Sample Preparation Kit |
| Host Cell Protein Antibodies | |
| CH-K0018-3-Ab | CHO Host Cell Protein G3 Antibody |
| CH-K0018-2-Ab | CHO Host Cell Protein G2 Antibody |
| EH-E0020-3-Ab | E.coli Host Cell Protein G3 Antibody |
| PH-E0021-3-Ab | Pichia Yeast Host Cell Protein G3 Antibody |
| HH-H0019-2-Ab | HEK293 Host Cell Protein G2 Antibody |
| Buffer Products | |
| CG-H0100 | HCP ELISA buffer |
| CG-P0200 | Protein L ELISA buffer |
