While the world waits eagerly for a safe and effective vaccine to prevent infections from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing the COVID-19 pandemic, researchers also are focusing on better understanding how SARS-CoV-2 attacks the body in the search for other means of stopping its devastating impact. The key to one possibility--blocking a protein that enables the virus to turn the immune system against healthy cells--has been identified in a recent study by a team of Johns Hopkins Medicine researchers. Based on their findings, the researchers believe that inhibiting the protein, known as factor D (image), also will curtail the potentially deadly inflammatory reactions that many patients have to the virus. Making the discovery even more exciting is the fact that there may already be drugs in development and testing for other diseases that can do the required blocking. The study was published online on September 2, 2020, in Blood. The open-access article is titled “Direct Activation of the Alternative Complement Pathway by SARS-CoV-2 Spike Proteins Is Blocked by Factor D Inhibition.” Scientists already know that spike proteins on the surface of the SARS-CoV-2 virus are the means by which it attaches to cells targeted for infection. To do this, the spikes first grab hold of heparan sulfate, a large, complex sugar molecule found on the surfaces of cells in the lungs, blood vessels, and smooth muscle making up most organs. Facilitated by its initial binding with heparan sulfate, SARS-CoV-2 then uses another cell-surface component, the protein known as angiotensin-converting enzyme 2 (ACE2), as its doorway into the attacked cell. The Johns Hopkins Medicine team discovered that when SARS-CoV-2 ties up heparan sulfate, it prevents factor H from using the sugar molecule to bind with cells.
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