• Competitive ELISA for detection of neutralising antibodies
  • Independent of antibody isotype
  • Low sample volume
  • Highly sensitive and specific (in house evaluation)
  • Ready to use reagents

The Spike Protein Inhibition Assay (SPIA) is a competitive immunoenzymatic colorimetric method used for research purposes only to detect neutralising antibodies against SARS-CoV-2 in human serum.

  • Receptor-mediated endocytosis is the main process of virus entry to the host cells: S protein contains a receptor binding domain (RBD) involved in the binding of the angiotensin-converting enzyme 2 (ACE2)1. ACE2 is a cell-surface receptor that is present in the kidney, blood vessels, heart and importantly, in the lung alveolar type II (AT2) cells which are respiratory tract epithelial cells.
  • Once the virus gains access inside the target cell, the host immune system recognises the whole virus or its surface epitopes, eliciting an immune response, characterised by elevations in specific antibodies. Antibodies that are able to bind to the spike protein and prevent it from entering cells by inhibition of the RBD-ACE2 interaction are known as neutralising antibodies (nAb) and the presence of these have been shown to be associated with protection against infection in disease models2.  While nAb are believed to be important for protection, the level required is not defined.  As such a wide range of nAb titres have been reported following SARS-CoV-2 infection and these vary depending on the length of time from infection and the severity of the disease.  Neutralising antibodies also rapidly appear following administration of COVID-19 vaccinations3 and are maintained for several months4-5.
  1. Jiang S, Zhang X, Yang Y, Hotez PJ, Du L. Neutralizing antibodies for the treatment of COVID-19. Nat Biomed Eng. 2020 Dec;4(12):1134-1139.
  2. Rogers TF, Zhao F, Huang D, et al. Isolation of potent SARS-CoV-2 neutralizing antibodies and protection from disease in a small animal model. Science. 2020 Aug 21;369(6506):956-963.
  3. Jackson LA, Anderson EJ, Rouphael NG, et al; mRNA-1273 Study Group.  An mRNA vaccine against SARS-CoV-2.  N Engl J Med. 2020;383(20):1920-1931.
  4. Dan JM, Mateus J, Kato Y, et al.  Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.  Science. 2021;371(6529):eabf4063.
  5. Widge AT, Rouphael NG, Jackson LA, et al; mRNA-1273 Study Group.  Durability of responses after SARS-CoV-2 mRNA-1273 vaccination.  N Engl J Med. 2021;384(1):80-82.

– SARS-CoV-2 Antigen Rapid Test Kit
– Coronavirus Antigen Rapid Test Cassette (swab)