Coronavirus produces ‘sinister’ tentacles in infected cells

Scientists have discovered that the virus behind Covid-19 causes the infected cells to grow stringy protruding branches — a highly unusual structure that allows the virus to attack several cells at once. 

Researchers led by the University of California San Francisco have released the first ever close-up images of the spaghetti-like tentacles that were taken using an ultra-powerful electron microscope.

“There are long strings that poke holes in other cells and the virus passes through the tube from cell to cell,” said Professor Nevan Krogan, director of the Quantitative Biosciences Institute at UCSF who led the project. “Our hypothesis is that these speed up infection,” Prof Krogan said of the “nasty and sinister” branches.

The images taken by scientists at the National Institutes of Health (NIH) laboratory in the US and University of Freiburg in Germany will be published in the medical journal Cell on Saturday.

Most viruses do not cause infected cells to grow these tentacles. Even those that do, such as smallpox, do not have as many or the same type of branching as Sars-Cov-2, the virus behind Covid-19.

The discovery has highlighted a number of drugs that could be deployed against the disease, most of which were previously being developed to treat cancer. Prof Krogan said cancers, HIV, or Sars-Cov-2 were all searching for the “Achilles heel of the cell”. 

“It totally makes sense there’s an overlap in anticancer drugs and an antiviral effect,” he said. 

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The initial experiments were done in African green monkey kidney cells, which have previously been shown to become easily infected by the virus. But the potential drugs were then tested in human lung cells.

The potential Covid-19 drugs include silmitasertib, made by Taiwan-based Senhwa Biosciences, which directly inhibits the CK2 enzyme used to build the tubes. Senhwa is already working with the NIH to run trials in the US. 

The researchers compared these cancer treatments to remdesivir, a Gilead Sciences drug that has shown it can cut recovery times in a large trial. They found five drugs that were more potent against the virus, including Xospata, also known as gilteritinib, made by Japan’s Astellas Pharma and already approved by the US Food and Drug Administration for leukaemia patients. 

Other possible treatments include abemaciclib, an FDA-approved drug sold as Verzenio by Eli Lilly, and ralimetinib, also developed by Indianapolis-based Lilly, as well as dasatinib, an approved drug from Bristol-Myers Squibb.

The Quantitative Biosciences Institute’s coronavirus research group — which includes researchers from New York to Paris — specialises in searching for drugs that target the human proteins the virus needs to reproduce, rather than tackling the virus directly. 

In a previous paper published in the journal Nature, they discovered potential drugs that could be repurposed including over-the-counter medicines for coughs and allergies. 

So far, their work has been focused in the laboratory but they are looking to start clinical trials in humans. The scientists also suggest trying these new drugs in combination with remdesivir