The entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into human cells is an essential step for virus transmission and development of COVID 19. Although the lung epithelial cells are its initial target, SARS-CoV-2 also can infect endothelial cells. Endothelial cells are the major constituents of the vascular system and cardiovascular complication is a hallmark of severe COVID-19. Angiotensin-converting enzyme 2 (ACE2) is the entry receptor for SARS-CoV-2. However, the possible involvement of other cellular components in the viral entry is not fully understood.

A team of BUSM researchers has identified extracellular vimentin as an attachment factor that facilitates SARS-CoV-2 entry into human cells. Vimentin is a structural protein that is widely expressed in the cells of mesenchymal origin such as endothelial cells and a potential novel target against SARS-CoV-2, which could block the infection of the SARS-CoV-2.

“Severe endothelial injury, vascular thrombosis, and obstruction of alveolar capillaries (tiny air sacs scattered throughout the lungs) are common features of severe COVID-19. Identification of vimentin as a host attachment factor for SARS-CoV-2 can provide new insight into the mechanism of SARS-CoV-2 infection of the vascular system and can lead to the development of novel treatment strategies,” said co-corresponding author Nader Rahimi, PhD, associate professor of pathology & laboratory medicine.

The researchers used liquid chromatography–tandem mass spectrometry (LC-MS/MS) and identified vimentin as a protein that binds to the SARS-CoV-2 spike (S) protein and facilitates SARS-CoV-2 infection. They also found that depletion of vimentin significantly reduces SARS-CoV-2 infection of human endothelial cells. In contrast, over-expression of vimentin with ACE2 significantly increased the infection rate. “More importantly, we saw that the CR3022 antibody inhibited the binding of vimentin with CoV-2-S-protein, and neutralized SARS-CoV-2 entry into human cells,” explained Rahimi.

“The course of infection with SARS-Cov-2 is dependent on multiple factors that affect the attachment and entry of the virus into host cells, so casting a wide net and using multiple approaches to define and validate the critical components is an important strategy that can lead to the identification of protective or therapeutic targets. We show here that, in the vascular system, vimentin plays a key role in attachment of the virus to its best-known receptor, ACE2; we determined in an earlier paper in the journal ACS Central Science that CD209 and CD209L are alternative receptors that may expedite infection of tissues where ACE2 has low abundance,” said co-corresponding author Catherine E. Costello, PhD, William Fairfield Warren Distinguished Professor, Biochemistry and director of the Center for Biomedical Mass Spectrometry at BUSM.

Other collaborators from BUSM include Elke Mühlberger, PhD, and Vipul Chitalia, MD, PhD.

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These findings appear online in the Proceedings of the National Academy of Sciences.