Line immunoassay with antigens produced by recombinant techniques for the detection of IgG antibodies against the coronavirus SARS-CoV-2 in human serum or plasma.

In December 2019, a pandemic spread of the disease caused by a new variant of the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) began in the city of Wuhan, capital of Hubei in China. The newly discovered variant is called SARS-CoV-2 and is closely related to SARS-CoV(-1). SARS coronaviruses spread primarily via droplets and airborne particles in exhaled air by transmission from person to person.

Symptoms range from fever, cough and dyspnoea to pneumonia and acute respiratory distress syndrome and ultimately death in persons with comorbidities. Optimal vaccination with mRNA- or vector-based vaccines allows to reduce or prevent asymptomatic infections with the original SARS-CoV-2 virus strain and its variants (including the Delta variant), the spread of these viruses, symptomatic infection, as well as more severe disease. Optimal vaccination even has a preventive effect towards symptomatic or more severe disease caused by the immune-escape variant Omicron.

Persons infected with SARS-CoV-2 usually develop detectable antibodies 2-21 days after the onset of symptoms. But vaccination against COVID-19 leads also to the production of IgG antibodies after few days. Thus, serological detection of antibodies is a clear indication of a past SARS-CoV-2 infection if the time frame to detect a possible current infection by a PCR or antigen test was passed, or of a vaccination status. Antibody testing can be used for public and occupational health purposes, as well as epidemiological studies and treatment of patients suffering from long-term consequences of COVID-19 disease.

In commercial screening tests for antibody detection, the nucleocapsid protein (NP) and/or the spike protein (S) or corresponding subunits are usually used as immunodominant antigens. The recomLine SARS-CoV-2 IgG [Avidität] immunoassay combines these diagnostic markers and allows the identification of specific antibodies against the individual antigens. In addition, reactivities against the seasonally occurring coronaviruses (HCoV) are detected. The test allows the assessment of the adaptive immune response induced by SARS-CoV-2 infection and/or vaccination. Additional benefit can be derived from this test system when the quality of the antibodies is determined through avidity measurement.

NEW: Current findings on avidity determination

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