At present, serological diagnostics for COVID-19 are only offered based on proteins. In addition, to unexpected false positives, clinical diagnostics specifically report problems with previous infections with related Corona viruses. This is because the recognition sites of the patients’ antibodies (epitopes) are only partly specific to SARS-CoV-2, while others are found in many related Corona viruses.
Therefore, in future, serological tests will also have to be developed on the basis of defined epitopes of SARS-CoV-2 or other Corona viruses which permit both simple and highly individualised diagnostics with the help of different specific and ubiquitous epitopes. The Ligand Development working group at Fraunhofer IZI has comprehensive experience in identifying epitopes directly from serums. It is already evident that SARS-CoV-2 infections lead to a strongly personalised immune response which is shaped by previous Corona infections as in the case of epitope diagnostics of food allergies (low allergen, food allergen) for various foods.
However, in all diagnostic activities, the serums obtained from infected patients are pre-treated to inactivate the virus before the serums can be used in testing. In the context of CoV-tot, it was demonstrated that different methods for virus inactivation have a very different influence on different antibodies in the sera. This can lead to very different results in serological tests in individual cases. Furthermore, the studies have shown that a slight denaturation of the sample seems to remove the blocking of individual antibodies by unknown serum components. Thus, better results can be obtained. Two methods of viral inactivation have been identified as suitable, firstly heating to 56 degrees Celsius for ten minutes for liquid samples and secondly treatment with 70% ethanol when antibodies are immobilized on protein A.
Based on these project results, a specific diagnostic that will distinguish different corona viruses will be further developed with industrial partners. The knowledge gained in CoV-tot is also a starting point to explore differences in disease progression also in the context of clinical trials for drug treatment of COVID-19.