SARS-CoV-2 Virus Can Find Alternate Route to Infect Cells

COVID-19 drugs, vaccines that are still effective against mutating virus.

Early in the COVID-19 pandemic, scientists determined how SARS-CoV-2, the virus that causes COVID-19, gets into cells to cause infection. All current COVID-19 vaccines and antibody-based therapies are designed to disrupt this pathway to cells, requiring a receptor called ACE2.

Now, researchers at Washington University School of Medicine in St. Louis have found that a single mutation gives SARS-CoV-2 the ability to enter cells through a different pathway — one that doesn’t require ACE2. The possibility of using an alternative entry route opens up the possibility of evading COVID-19 antibodies or vaccines, but the researchers found no evidence of such evasion. However, the discovery shows that the virus can change in unexpected ways and find new ways to cause infection. The study was published June 23 in Cell Reports.

“This mutation occurred in one of the spots that changes a lot as the virus circulates in the human population,” said co-senior author Sebla Kutluay, PhD, an assistant professor of molecular microbiology. “Usually, alternative receptors and attachment factors simply enhance ACE2-dependent access. But in this case, we discovered an alternative way to infect a key cell type — a human lung cell — and that the virus acquired this ability through a mutation that we know of. that it occurs in the population, which is something we definitely need to know more about.”

The find was accidental. Last year, Kutluay and co-senior author M. Ben Major, PhD, the Alan A. and Edith L. Wolff Distinguished Professor of Cell Biology & Physiology, set out to study the molecular changes that occur in cells infected with SARS. -CoV-2 . Most researchers study SARS-CoV-2 in primate kidney cells because the virus grows well in them, but Kutluay and Major felt it was important to conduct the study in lung or other cells similar to those naturally infected. to be. To find more relevant cells capable of growing SARS-CoV-2, Kutluay and Major screened a panel of 10 lung and head and neck cell lines.

“The only one that could get infected was the one I added as a negative control,” Major said. “It was a human lung cancer cell line with no detectable ACE2. So that was a crazy surprise.”

Kutluay, Major and colleagues — including co-first authors and postdoctoral researchers Maritza Puray-Chavez, PhD, and Kyle LaPak, PhD, as well as co-authors Dennis Goldfarb, PhD, an assistant professor of cell biology and physiology and medicine, and Steven L. Brody, MD, the Dorothy R. and Hubert C. Moog professor of lung diseases in medicine and a professor of radiology — found that the virus they used for experiments had picked up a mutation. The virus was originally obtained from a person in Washington State with COVID-19, but as it had grown over time in the lab, it had acquired a mutation that led to a change of a single amino acid at position 484 in the peak of the virus protein. SARS-CoV-2 uses spike to attach to ACE2, and position 484 is a hotspot for mutations. Several mutations at the same position have been found in viral variants from humans and mice, and in lab-grown virus. Some of the mutations found in virus samples from humans are identical to the mutations Kutluay and Major found in their variant. The Alpha and Beta variants of concern have mutations at position 484, although those mutations are different.

“This position evolves over time within the human population and in the laboratory,” Major said. “Given our data and that of others, it is possible that the virus is under selective pressure to enter cells without using ACE2. In so many ways, it is terrifying to think of the world’s population battling a virus that is diversifying the mechanisms by which it can infect cells.”

To determine whether the ability to use an alternate entry route allowed the virus to escape from COVID-19 antibodies or vaccines, the researchers screened panels of antibodies and blood serum containing antibodies from people vaccinated against COVID-19. or have recovered from COVID-19 infection. There was some variation, but overall the antibodies and blood sera were effective against the virus with the mutation.

It is not yet clear whether the alternative route will play a role under real conditions when people are infected with SARS-CoV-2. Before the researchers can answer that question, they must find the alternative receptor that the virus uses to get into cells.

“It’s possible that the virus uses ACE2 until it runs out of cells with ACE2, and then switches to using this alternate pathway,” Kutluay said. “This may be relevant in the body, but without knowing the receptor, we can’t say what the relevance will be.”

Major added, “That’s where we’re going now. What is the receptor? If it’s not ACE2, what is it?”

Reference: “Systematic analysis of SARS-CoV-2 infection of an ACE2-negative human airway cell” by Maritza Puray-Chavez, Kyle M. LaPak, Travis P. Schrank, Jennifer L. Elliott, Dhaval P. Bhatt, Megan J. Agajanian, Ria Jasuja, Dana Q. Lawson, Keanu Davis, Paul W. Rothlauf, Zhuoming Liu, Heejoon Jo, Nakyung Lee, Kasyap Tenneti, Jenna E. Eschbach, Christian Shema Mugisha, Emily M. Cousins, Erica W. Cloer, Hung R. Vuong, Laura A. VanBlargan, Adam L. Bailey, Pavlo Gilchuk, James E. Crowe, Jr., Michael S. Diamond, D. Neil Hayes, Sean PJ Whelan, Amjad Horani, Steven L. Brody, Dennis Goldfarb, M. Ben Major and Sebla B. Kutluay, accepted, cell reports.
DOI: 10.116/j.celrep.2021.109364

This work was supported in part by the Washington University School of Medicine; V Foundation, grant number T2014-009; the National Institutes of Health (NIH), grant numbers T32CA009547-34, 5T32HL007106-39, K08HL150223, AI059371, AI157155, and 75N93019C00074; and the Defense Advanced Research Projects Agency, grant number HR001117S0019. This study used samples obtained from the COVID-19 Biorepository of Washington University School of Medicine, supported by the NIH/National Center for Advancing Translational Sciences, grant number UL1 TR002345.