SARS-CoV-2 S1RBD IgG ELISA Kit

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

INTRODUCTION

Spike protein is an envelope glycoprotein that has important roles in viral attachment, entry into the host cell and the fusion process. The S-protein is produced in the precursor form, this is then cleaved to from two smaller sub-units S1 and S2. The S1 is around 700 amino acids in length and represent the amino terminal, whereas the S2 is about 600 amino acids longs and represents the carboxyl terminal. Both the S1 and S2 sub-units are vital for viral attachment and the membrane fusion process. S2 is further cleaved into two smaller sub-units, S3 and S4. The S3 consists of about 350 amino acids longs and it associates with a coiled coil region to form the spike protein fusogenic domain.

The spike protein is important for viral entry, although it can also anchor itself to the cell membrane via its fusogenic domain. The S2 gene is on the long arm of chromosome 5 and consists of 10 exons. It is arranged in two clusters, one on the left and one on the right. The first cluster contains exons 1-3; these encode the amino terminal portion of S2 (S1), whereas exons 4-7 encode the carboxyl terminal part (S4). The second cluster contains exons 8-10, coding for an N-terminal extension of S2 that interacts with cell membrane via its fusogenic domain.

The S1 sub-unit contains the receptor binding domain (RBD), this is instrumental in attachment of extracellular peptidase domain of SARS-CoV-2 to the cell membrane. The S2 sub-unit is known to interact with the receptor binding domain on a complex that also contains S3 and S4 subunits. The purpose of this interaction is unknown but it may facilitate assembly of the virus particle or help maintain genome stability during infection. The S2 sub-unit is a single polypeptide of 437 amino acids in length. The S2 sub-unit is inserted into the membrane and acts as a receptor for membrane fusion to create new virions. It also functions as one of the structural proteins that helps maintain genome stability during infection.

The gene encoding this protein resides on the minus strand of the genome and its expression is induced by cellular signals during viremia, which causes both increases in cell membrane permeability and ion changes within cells. This leads to entry into cells, release of viral RNA molecules, synthesis of viral proteins and formation of virions.

INTENDED USE

Human SARS-CoV-2 S1RBD IgG ELISA kit is designed to detect IgG class antibodies in human anti-SARS-CoV-2 spike protein S1 receptor-domain (S1RBD) using plasma or serum.

CONTENT

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

SARS-Co-V-2 S1RBD Coated ELISA Plate.
5x Assay Buffer.
10x Wash Buffer.
100x Detection Antibody Buffer.
Substrate Solution.
Stop Solution.
Positive Control.
Blank Control.

TYPICAL RESULTS

Blank Control: 0.063, 0.052 (OD450).
Positive Control: 0.661, 0.658 (OD450).
Serum From Healthy Subjects: 0.144, 0.158, 0.174 (OD450).
Serum From COVID-19 Patients: 0.511, 0.656, 0.361 (OD450).

Suggested Cut-Off Values:
Blank: < 0.170 (450nm).
Positive: ≥ 0.500 (450nm).

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

ASSAY CHARACTERISTICS

– Inter Assay Precision: CV% 7.66, 6.68, 5.13.
– Intra Assay Precision: CV% 5.78, 6.31, 4.55.

REFERENCES

Seroconversion and Abundance of IgG Antibodies against S1-RBD of SARS-CoV-2 and Neutralizing Activity in the Chilean Population. J Immunol Res. (2021) 2021: 6680337. González-Stegmaier R, et al.
Prospective serological evaluation of anti SARS-CoV-2 IgG and anti S1-RBD antibodies in a community outbreak. Clin Chem Lab Med. (2021) 59 (8): e322-e325. Carta M., et al.
Anti-spike S1 receptor-binding domain antibodies against SARS-CoV-2 persist several months after infection regardless of disease severity. J Med Virol. (2021) 93 (5): 3158-3164. Bavaro D.F., et al.
Equipment-free, gold nanoparticle based semiquantitative assay of SARS-CoV-2-S1RBD IgG from fingertip blood: A practical strategy for on-site measurement of COVID-19 antibodies. Talanta. (2022) 246: 123498. Zhu Z., et al.

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