Full Name: SARS-CoV-2 S1RBD IgA ELISA Kit
Reactivity: Human
Sample Type: Plasma, Serum
Sensitivity: Qualitative


SARS-CoV-2 spike protein can be described as a glycoprotein envelope that is vital for many different processes that are occurring for example entry in host cells, viral attachment and fusion. This is initially synthesised as a precursor protein which is then cleaved into either the S1 sub-unit (N-terminal, approx. 700 amino acids long) or the S2 sub-unit (C-terminal, 600 amino acids long). Both sub-units play an essential role the attachment (S1) and the membrane fusion process (S2) of the virus. The S1 sub-unit contains three periplasmic regions, I, II and III. In addition to these regions, there are also two transmembrane helices that ensure stability as well as indicate potential attachment sites for viral glycoproteins on host cells. This region also contains a nucleocytoplasmic export signal (NES)-like sequence which is involved in mRNA translation and virion production during infection of cells. NES sequences are present on most members of the coronavirus family including those which belong to either the SARS-CoV-2.

The S2 and S3 sub-units contain a transmembrane area and the RNA polymerase core region. The RNA polymerase is responsible for transcription of SARS-CoV genomes as well as replication of the viral genome by assembling single-stranded negative-sense RNA molecules from genomic DNA. It is believed that coronavirus replicate their genomes during infection of cells via an intermediate process involving a positive stranded (dsRNA) intermediate. This dsRNA may be derived from viral mRNA or genomic DNA, but cannot be sensed by innate immune responses which are activated only against viral proteins. The S1 sub-unit is responsible for secretion of the viral RNA into the outside of the cell and contacting with other virions to form a new infectious particle.


Human SARS-CoV-2 S1RBD IgA ELISA kit is ideal for measuring anti-SARS-CoV-2 spike protein S1 receptor-domain (S1RBD)(IgA class antibodies) using human serum and plasma.


Each kit contains the following components and is sufficient for 96 tests.

  • One Aluminium Pouch: Containing microwell plate bound with SARS-CoV-2 S1RBD protein.
  • 10x Standard.
  • 100x Detection Antibody Solution: HRP coated anti IgA monoclonal antibody.
  • 10x Wash Buffer.
  • 5x Assay Buffer.
  • Substrate Solution.
  • Stop Solution.


Serum From COVID-19 Patients: 1.085, 0.203, 6.207, 1.557, 1.453, 0.509, 1.011, 0.254, 3.111, 0.496, 4.913, 4.902, 0.153, 1.856, 2.834 (OD450).
Serum From Healthy Subjects: 0.246, 0.234, 0.239, 0.239, 0.26, 0.311, 0.209, 0.287, 0.322, 0.293, 0.129, 0.147, 0.145, 0.18, 0.225, 0.204 (OD450).

It is advised that each laboratory establishes its own normal and pathological refence range for detection of anti-S1RBD IgA antibodies.


– Sensitivity: > 96%.
– Specificity: > 95%.
– Inter Assay Precision: CV = Less than 10%
– Intra Assay Precision: CV = Less than 8%.


  1. Evaluation of spike protein antigens for SARS-CoV-2 serology. J Virol Methods. (2021) 296: 114222. Jagtap S., et al.
  2. Dynamic Characteristic Analysis of Antibodies in Patients With COVID-19: A 13-Month Study. Front Immunol. (2021) 12: 708184. Shi D., et al.
  3. SARS-CoV-2 S1 is superior to the RBD as a COVID-19 subunit vaccine antigen. J Med Virol. (2021) 93 (2): 892-898. Wang Y., et al.
  4. Characterization of a Pan-Immunoglobulin Assay Quantifying Antibodies Directed against the Receptor Binding Domain of the SARS-CoV-2 S1-Subunit of the Spike Protein: A Population-Based Study. J Clin Med. (2020) 9 (12): 3989. Schaffner A., et al.


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