A Custom, Multiplex Human Coronavirus Serological Assay

In less than a year, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) swept globally, infecting over 30 million people. Of those infected, more than 1 million people have been killed by Coronavirus 2019 (COVID-19) disease. As such, assessing the prevalence of SARS-CoV-2, along with SARS-CoV-2 vaccine development have been top global priorities. COVID-19 screening assays can be broadly classified into diagnostic/ antigen tests¹ that detect viral RNA or viral protein in the host during an active infection, and serological assays that detect the antibody response to the virus. Screening for active infections has been challenging for two interrelated reasons. Although SARSCoV-2 has a lower mortality rate than the related SARS-CoV and middle east respiratory syndrome coronavirus (MERS-CoV), it has a higher transmission rate^2-4. Furthermore, it has been estimated that ~45% of those infected with the virus are asymptomatic5. In the absence of symptoms to inspire diagnostic testing, it is apparent that the percentage of COVID-19 infected people may be severely underestimated. Given the possibility of such a large percentage of asymptomatic carriers, serological assays play a crucial role in the Center for Disease Control (CDC) COVID-19 serology surveillance strategy⁶. SARS-CoV2 is a member of the coronaviridae family, specifically the coronavirinae subfamily that includes 4 genera: α-coronavirus, β-coronavirus, γ-coronavirus and δ-coronavirus². SARS-CoV-2, SARS-CoV and MERS-CoV are all RNA β coronaviruses. SARS-CoV-2 shares 80% sequence identity with SARS-CoV and 50% sequence identity with MERS-CoV^3,7. It has been estimated that members of the α-coronavirus and β-coronavirus family are also responsible for 10-30% of common colds^8,9. Given the promiscuous nature of coronavirus, the need to evaluate the immune response to coronavirus subtypes becomes apparent. To what degree does exposure to the common cold virus, SARS-CoV or MERS-CoV enhance or diminish immunity to SARS-CoV-2? To answer this question, investigators need to be able to evaluate the specificity and cross-reactivity of the immune response to coronaviruses. R&D Systems, a Bio-Techne brand, has developed a novel custom Luminex serological assay that distinguishes between coronavirus subtypes. Using our high-quality recombinant proteins, this antigen-down assay saves  time and precious sample by multiplexing many coronavirus subtypes simultaneously in each sample.