The pandemic coronavirus has caused a wide range of different symptoms, and as time goes on, we may find that it can have lasting effects for some people, which can be quite serious. This virus may be asymptomatic in the vast majority of people who are infected with it, but it can also do some weird things that are not like what we've seen from other viruses.
For example, scientists have now learned that when a cell is infected by SARS-CoV-2, it may grow long extensions called dendrites or filopodia that are studded with virus particles like a tentacle. These filopodia will then search for other cells and can reach through their walls, in what appears to be a second way of spreading infection through the body. This study, which will soon be reported in Cell, indicated that uninfected cells sometimes exhibit filopodia too, but their appearance is less frequent, and they are much shorter.
Typically, a virus infects host cells, and to put it simply, turns them into factories that churn out new virus particles. These viruses then attach to new cells in the same way the original infection entered cells, and the cycle continues. It was thought that SARS-CoV-2 was spreading through the body in this same way.
Led by systems biologist Nevan Krogan, UCSF researchers have also begun looking for ways to treat COVID-19 by targeting the human proteins used by the virus. Their work, which has been reported in Nature, may lead to COVID-19 therapeutics that halt filopodia growth to stop the secondary way the virus spreads in the body.
"It’s just so sinister that the virus uses other mechanisms to infect other cells before it kills the cell,” Krogan told the LA Times.
There are other viruses that use filopodia, Krogan noted, including the family of viruses that cause smallpox. But SARS-CoV-2 starts producing their tentacles unusually quickly. They also have a unique shape, with branches like trees that are not seen in other viruses that generate filopodia.
There are several existing cancer drugs that could be useful in fighting this aspect of COVID-19, including Xospata (used to treat acute myeloid leukemia), and ralimetinib, which is used to treat several types of cancer. All of them are known to be kinase inhibitors like remdesivir, a COVID-19 drug by Gilead.
"We've tested a number of these kinase inhibitors and some are better than remdesivir," Krogan told the Milwaukee Journal-Sentinel.