Using a modified version of a standard serology test, BUSM researchers have found SARS-CoV-2 reactive antibodies in samples collected before the start of the pandemic, revealing antibody immunity to the virus that causes COVID-19 in unexposed people.
“Pre-existing T cell immunity to SARS-CoV-2 has been reported, but to our knowledge it was previously unclear if SARS-CoV-2 cross-reactive antibodies are present in unexposed people as well,” explained corresponding author Jennifer Snyder-Cappione, PhD, assistant professor of microbiology.
The researchers changed some steps of the Enzyme-Linked Immunosorbent Assay (ELISA) method to make this test more sensitive, most notably to the plate washing procedure. During the ‘BU ELISA’, plates are not washed in a machine; alternatively, an operator washes the plates and performs specific steps to be sure each well of the plate is washed thoroughly and there is no cross-contamination of liquid between wells. Once the modified procedure was complete, they tested 40 samples banked before the pandemic as well as samples from confirmed SARS-CoV-2 infected individuals.
ELISAs are plate-based assays used for detecting and quantifying a specific protein in a sample. In their study, the detection and quantification of SARS-CoV-2 binding antibodies was accomplished by coating the plates with two different SARS-CoV-2 proteins, adding blood samples (plasma or serum), then using highly specific enzyme-labeled antibodies to detect the virus-reactive antibodies bound to the proteins.
It is believed that the “BU ELISA” can measure much lower levels of SARS-CoV-2 reactive antibodies than other current tests. The researchers hope that the use of this new serology test will help determine an individual’s history of SARS-CoV-2 exposure and also help clarify if an individual is immunologically protected from SARS-CoV-2 infection.
According to the researchers, their changes to the ELISA method should improve detection of all proteins measured by the technique, including antibodies that impact other infectious and autoimmune diseases and molecules such as cytokines. In the short term, the BU researchers hope this low cost, easy to perform assay will be of use to many research labs to gain new knowledge about SARS-CoV-2 transmission and immunity to help combat COVID-19.
These findings currently appear online in preprint form.
Funding for this study was provided by the Boston University National Emerging Infectious Diseases Laboratories (NEIDL) Director’s Fund.