Protein A ELISA Kits

Protein A ELISA Kits

Use Protein A ELISA kits in a therapeutic antibody manufacturing workflow

Protein A affinity chromatography is commonly used in monoclonal antibody (mAb) manufacturing workflows because of its high binding affinity and the purity of the product obtained with it (1). There are occasions where Protein A or its fragments leach from a purification column and remain bound to the Fc region of a therapeutic antibody. This must be avoided, particularly in instances where antibodies are manufactured for clinical uses, in order to preclude any adverse effects of residual protein A on the patient. 

R&D Systems has developed two ELISA kits for reliable supply and accurate detection of Protein A residuals in the manufacturing of therapeutic monoclonal antibodies. Both kits are designed for easy transfer to automated platforms with ready-to-use buffers, single-step sample pretreatment, and minimal assay incubations. The Protein A ELISA kit is for the detection of natural and recombinant Protein A constructs while the Protein A Engineered Variant ELISA kit detects unnatural recombinant Protein A constructs.

  Protein A Elisa Kit (Cat# BPPA00) Protein A Engineered Variant ELISA Kit (Cat# BPPAEV0)
Specificity  Natural Recombinant Protein A  Engineered Protein A Variants
Calibration E. coli expressed recombinant Protein A  MabSelect SuReTM


ELISA Protocol

Protein A ELISA ProtocolProtein A ELISA Protocol - Pretreatment releases Protein A from the therapeutic antibody sample followed by Protein A quantification via indirect ELISA. Click on image to view larger.

What is Protein A?

Protein A, also known as staphylococcus aureus protein A (SpA) is a 40-60 kDa surface protein originally found in the cell wall of the bacterium Staphylococcus aureus (2). The carboxyl terminal end of Protein A is anchored to the staphylococcus cell wall by the transpeptidase enzyme sortase.  It is encoded by the spa gene and consists of five homologous 6.7 kDA immunoglobulin domains (E, D, A, B, and C) joined by conserved linkers of six to nine residues (3). Protein A has been shown to stimulate inflammatory responses by interacting with several proteins including tumor necrosis factor alpha receptors, Willebrand factor and C1qR.

Protein A is most known for interacting with the Fc region of the antibody heavy chain. Although it binds all mouse immunoglobulin (IgG) subtypes (IgG1, IgG2a, IgG2b and IgG3), in humans, it binds to IgG1, IgG2 and IgG4 but not IgG3 (3). Protein A fails to bind IgG3 because of a single histidine to arginine change at amino acid 435 (3). Protein A reacts with Ig from a variety of other species including rhesus monkey, guinea pig, pig, cow and goat.



  1. Ramos-de-la-Pena, A.M. et al. (2019) Journal of Separation Science. 42: 1816
  2. Rigi, G. et al (2019) Biotechnology and Applied Biochemistry. 66:454
  3. Mazigi, O. et al (2019) Protein Engineering and Selection. 32: 359

    MabSelect SuRe™ is a trademark of GE Healthcare.