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Measuring the immune response to Covid vaccines
A powerful trio of CE-marked tests from EUROIMMUN enables comprehensive investigation of immune responses to SARS-CoV-2 following vaccination or infection. The analysis encompasses quantitative measurement of anti-S1/RBD IgG antibodies, determination of the neutralising effect of these antibodies and analysis of SARS-CoV-2-reactive T cells.
V
accination plays a pivotal role in strategies to fight the pandemic. The majority of Covid-19 vaccines are
based on the SARS-CoV-2 spike protein. The receptor binding domain (RBD) of the spike protein S1 subunit is responsible for binding to the human receptor angiotensin- converting enzyme 2 (ACE2) and enabling the virus to invade the host cells. Antibodies directed against the S1/RBD and long-lived specific T cells appear to play the most important roles in virus neutralisation and development of immunity.
Antibody detection
Quantitative determination of antibodies against S1/RBD is an important tool for assessing the individual immune response to SARS-CoV-2 after infection and measuring the immune reaction following vaccination with spike protein-based vaccines. The CE-marked and fully automatable Anti- SARS-CoV-2 QuantiVac ELISA (IgG) from EUROIMMUN enables quantitative detection of IgG antibodies against S1/RBD using a six-point calibration curve.
The antibody concentration is measured in standardised binding antibody units (BAU/ml) based on the international reference material (NIBSC code: 20/136). In a first study using the Anti-SARS-
CoV-2 QuantiVac ELISA (IgG) the immune response was analysed in 57 people over a time frame of three weeks after first and second immunisation with vaccines from Moderna, Pfizer-BioNTech or AstraZeneca. The results showed that the longer the time interval following vaccination, the higher the antibody concentration. Furthermore, different antibody concentrations were determined depending on the vaccine used. All samples taken after second vaccination showed very high antibody concentrations.
Practical Patient Care /
www.practical-patient-care.com EUROIMMUN’s tests provide an all-round analysis of immune reactions to SARS-CoV-2.
The samples were also analysed using a surrogate virus neutralisation test. The CE-marked, automatable SARS-CoV-2 NeutraLISA enables fast and economical determination of anti-SARS-CoV-2 antibodies that are capable of inhibiting binding of the RBD to ACE2 and therefore hindering invasion of the host cell by the virus. The assay shows a very good (98.6%) agreement with the gold standard plaque reduction neutralisation test. It is, moreover, much easier to perform, as it takes just two hours and does not require the use of biosafety level 3 laboratory conditions. The study results confirmed that the antibodies detected in the samples of the vaccinated study participants were for the most part neutralising antibodies. These antibodies provide the greatest protection.
T-cell analysis T-cell immunity, especially against the spike protein, is associated with strong protection against Covid-19 and plays an important role in patients who do not exhibit measurable concentrations of specific antibodies. The T-cell-mediated cellular immune response to SARS-CoV-2 can be determined using the interferon gamma release assay (IGRA).
The new CE-marked Quan-T-Cell ELISA used in combination with the Quan-T-Cell SARS-CoV-2 enables fast, automatable and quantitative determination of the IFN- released by SARS-CoV-2-specific T cells. The T cells in the samples are stimulated using spike protein-based antigens in special tubes and the released IFN- is measured using a fully automated quantitative ELISA. The test is performed on heparinised whole blood samples, circumventing the need to prepare purified peripheral mononuclear cells. The EUROIMMUN assay is already well established in the research field and can now also be used for in vitro diagnostics. It supports detection of past contact with SARS-CoV-2 or detection of an immune reaction following vaccination. In a study, samples from 46 healthy blood donors with a concordant positive or negative antibody test result for IgG and IgA were investigated using the EUROIMMUN IGRA. There was a 93.8% agreement for positive samples and a 96.7% agreement for negative samples, showing the concurrent presence of humoral and cellular responses in the majority of tested persons. ●
www.euroimmun.com 29
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