At a population level, the humoral response to SARS-CoV-2 is heterogeneous. In the course of our development of EpitoGen SARS-CoV-2 assays, it was observed that significant number of cases (5%) react only to the spike or nucleocapsid antigens, but not both. Also, genomic variability of SARS-CoV-2 as a result of mutations in the spike and nucleocapsid proteins will further reduce sensitivity of the diagnostic tests. Therefore, traditional antibody assays using either the spike or nucleocapsid as antigens are less sensitive.
A novel approach is required to overcome inherent technical problems in existing assays to enhance specificity and sensitivity.
Principles of Universal EpitoGen® COVID-19 test
- Appreciation of the B-cell immunodominance phenomenon. This will enrich for the positive signal and improve sensitivity. Another advantage is that cross-reactive epitopes, especially those with homology with seasonal coronaviruses, can be eliminated, subsequently improving specificity.
- A platform to overcome population heterogeneity (i.e. HLA genetic variation, co-morbidities, age, ethnicity, etc).
- Universal EpitoGen is Differential EpitoGen amenable to combining multiple SARS-CoV-2 proteins (5 antigens) in one test, subsequently improving sensitivity of the assay.
- Universal EpitoGen overcomes SARS-CoV-2 genetic variability (i.e. mutations) by inclusion of prevalent mutations.
Using EpitoGen Technology, a set of 15 immunodominant epitopes, along with their corresponding major circulating mutants (45 prevalent mutations), from five (N, S, M, ORF3a and ORF7a) SARS-CoV-2 proteins were complexed to create a universal antigen. The mutations are present in the UK, South African, Brazilian and Indian variants.