Coronaviruses are enveloped, single-strand RNA viruses known to cause respiratory illness in humans. In December 2019 a new coronavirus was identified in Wuhan, Hubei Province of China and named SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2), with the resulting illness known as coronavirus disease 2019 (COVID-19). The virus spread rapidly and on March 11 2020, SARS-CoV-2 was declared a global pandemic.

Antigen	Description
Nucleocapsid protein (N)	Immunodominant coronavirus antigen containing diagnostically important epitopes for the diagnosis of SARS-Cov-2 and sensitive detection of specific IgG antibodies.
Spike Protein	A trimer made up of S1 and S2 proteins. Spike antigens trigger the host’s cellular immune system resulting in B cells producing antibodies.
S1-RBD	Receptor binding domain of the S1 subunit of the Spike protein of SARS-Cov-2. Binds to the ACE2 receptor in the cell membrane to gain access to the host cell. Anti-RBD SARS-Cov-2 antibodies are highly subtype specific and protective. Most SARS-CoV-2 neutralising antibodies are directed against S1-RBD.
Envelope protein (E)	The smallest major structural protein. Plays an important role in the life cycle of the virus and is important for the different stages of viral infection and replication.
Angiotensin Converting enzyme (ACE2)	ACE2 is a transmembrane glycoprotein. It is a key component of the renin-angiotensin system, involved in the regulation of cardiovascular and renal function. SARS-Cov-2 uses the ACE2 receptor for entry into the host cell.

A variety of laboratory and point of care tests are now available to detect the virus in human samples and to measure the antibody response to the individual viral proteins.

The information these tests provide is essential to monitor and control the infection, for the development and monitoring of effective therapeutic treatment and vaccines, and for essential seroprevalence and surveillance studies.

SARS-CoV-2 Antibody Detection and Quantification

Antibody response to SARS-CoV-2 is usually detectable 2-3 weeks after infection, although in some cases it may take longer. Antigen-specific IgA and IgM levels start to decline after a few weeks but IgG titres have been shown to decrease at a much slower rate. Combining the measurement of multiple antibody isotypes has been shown to improve the predictive accuracy of serological tests. Anti-RBD IgG concentrations have been shown to correlate with neutralising antibody titres.

Serological testing is a useful tool with a variety of potential applications:

• Retrospective contact tracing
• Identification of patients that have had asymptomatic infections
• Seroprevalence surveillance
• Assessment of herd immunity & longevity of protective immunity
• Assessment of vaccine efficacy
• Monitoring nAb titers in vaccinees after mass vaccination

Oxford Biosystems has several kits available for antibody detection.

Contact us for more information regarding our range of products detailed below for COVID-19 antibody detection, including sensitivity and specificity.

SD Biosensor Standard Q COVID-19 IgM/IgG PLUS is a lateral flow device that can be read by eye.

• Rapid results in 10-15 minutes
• Differentiation of IgG and IgM antibodies
• Whole blood (finger prick), serum or plasma samples
• CE marked
• Ready-to-use and room temperature storage
• No additional equipment or reagents necessary

SD Biosensor Standard F COVID-19 IgM/IgG Combo FIA is a rapid fluorescent immunoassay for use with the Standard F analysers.

• Rapid results in 15 minutes
• Differentiation of IgG and IgM antibodies
• Whole blood (finger prick), serum or plasma samples
• CE marked
• Ready-to-use and room temperature storage
• Automatic reading and analysis of results
• F2400 analyser provides random access testing for up to 60 samples per hour
• Data management via LIS/HIS connectivity

SD Biosensor Standard F SARS-CoV-2 nAb FIA is a rapid fluorescent immunoassay and a surrogate VNT (virus neutralisation test) for the detection of total immuno-dominant neutralising antibodies (nAb) targeting the spike protein RBD in serum and plasma.

A neutralising antibody is one that defends a cell from a virus by neutralising the biological effect. It prevents the virus from interacting with host cells by binding to the virus surface Ag.

• Rapid results in 35 minutes
• Serum or plasma samples
• Recombinant ACE2 & RBD proteins mimic the virus-host interaction
• Differentiates antibodies to SARS-Cov-2 variants
• Differentiates antibodies to SARS-Cov-2 variants
• Ready-to-use and room temperature storage
• Automatic reading and analysis of results on F200 or F2400 instruments

TestLine Clinical Diagnostics, a Czech company and part of the BioVendor Group, has developed a range of ELISA kits for the determination of specific IgG, IgM and IgA antibodies against SARS-CoV-2 (COVID-19) in human serum or plasma.

• ELISA kits optimized and validated for detection of IgA, IgG and IgM antibodies against recombinant SARS-CoV-2 Nucleocapsid protein (NP) or S1 Receptor-binding domain (RBD)
• ELISA kits for manual use and automated on a variety of ELISA processing platforms
• SmartEIA kits, specifically designed for automated analysis using the Dynex Agility ELISA instrument
• Microblot Array for the simultaneous detection of antibodies to multiple proteins and efficient multiplex diagnostics

For more information on the Testline product range for COVID-19 visit their website