Detection of SARS-CoV-2 virus structural proteins as an aid to diagnosis and monitoring of COVID-19
It has recently become clear that COVID‑19 is not just a respiratory disease but also an illness that can affect multiple organs since there are receptors for the causative virus throughout the human body. There is a need for tools to study the presence of the causative virus and its effects on various physiological and immunological systems of the human host to enable better strategies for COVID‑19 control. Herein we focus on development of highly sensitive and accurate tests for detecting and quantitating the main structural proteins of the SARS-CoV-2 virus and selected human proteins to allow measurement of host biomarker responses. The foundation of our approach is Stable Isotope Standards and Capture by Anti-Peptide Antibodies (SISCAPA), a technology that offers sensitive measurement of biomarkers indicative of disease; in this case the virus proteins themselves and host proteins that change in response to viral infection of different cells and organs. This technology allows inexpensive, multiplexed biomarker measurement in complex biological fluids such as whole blood, plasma, serum and saliva. SISCAPA technology will allow direct measurement of the SARS-CoV-2 virus proteins and thus determination of active infections, the gold standard for diagnosis of infectious diseases. Current diagnostic tests using the standard polymerase chain reaction (PCR) only detect genetic material from the virus, not the assembled viruses themselves. Although PCR tests are excellent for population screening, they are prone to false negative and false positive results, thus a separate test that measures structural components of the virus will complement diagnosis by PCR, allowing a better understanding of the disease state. Since SISCAPA technology uses enzyme-digested blood and saliva samples, virus-specific host antibodies that interfere with standard immunoassays are destroyed, allowing accurate detection of virus proteins. In addition to measurement of the SARS-CoV-2 virus, multiplexed SISCAPA measurement of host proteins produced in response to virus infection will yield information about the infection process, thus offering strategies for treatment and control of COVID-19.