Though a recent entrant into our daily vocabulary, the word ‘coronavirus’ was first coined in 1968 to describe a family of viruses, so named because the viruses were surrounded by a ‘crown’ of spiky protein projections.
As it turns out, these spikes give coronaviruses more than just their crown-like shape and name: they are also the key to their infectious ability. Each coronavirus spike contains a receptor-binding domain which binds to a specific target protein on host cells so that the virus can enter and infect them.
Interestingly, the spike of SARS-CoV-1, the virus responsible for the severe acute respiratory syndrome (SARS) epidemic in 2003, has some similarity to the spike of SARS-CoV-2, the virus responsible for the current COVID-19 pandemic. They both also share the same target: a protein on host cells called angiotensin-converting enzyme 2.
With this knowledge, a team of researchers led by Yee-Joo Tan, a Principal Investigator at A*STAR’s Institute of Molecular and Cell Biology (IMCB), decided to see if SARS-CoV-1 monoclonal antibodies (mAbs) could cross-react with SARS-CoV-2, in the hope that the same antibodies may be applied in COVID-19 research.
Using a range of immunological and bioinformatics analyses, they discovered that four monoclonal antibodies they previously generated and reported in a 2006 study to react to a section of the SARS-CoV-1 spike protein are able to recognize and cross-react with SARS-CoV-2 as well.
“SARS-CoV-1 and SARS-CoV-2 have a similar protein known as viral surface spike glycoprotein (S protein), which is responsible for binding to the host cell. 77.8 percent of the amino acid sequences in the S protein of these two viruses are identical,” Tan explained. “These antibodies bind to a part of the spike that is the same in both viruses.”
One of the antibodies, mAb 1A9, was shown to be able to detect purified S protein in a sandwich ELISA assay, as well as SARS-CoV-2-infected cells 24 hours after infection. The findings are an encouraging testament to the antibodies’ potential as a diagnostic tool, but the team noted that there is still a need to determine if the antibodies are sensitive enough to detect SARS-CoV-2 in clinical settings.
“We are working with industry partners to see if mAb 1A9 can be incorporated into COVID-19 diagnostic kits,” said Tan, adding that an antibody-based approach would complement existing PCR-based detection methods.