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In evolving to infect mink, SARS-CoV-2's risk for humans changes

Added 04-20-21 03:10:08pm EST - “It's less infective, but it has a lower immune profile.” - Arstechnica.com

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Posted By TheNewsCommenter: From Arstechnica.com: “In evolving to infect mink, SARS-CoV-2’s risk for humans changes”. Below is an excerpt from the article.

We've always needed to limit the total SARS-CoV-2 infections for reasons beyond the immediate risk they pose to the infected. Each new infected individual is a chance for the virus to evolve in a way that makes it more dangerous—more infective or more lethal. This is true even when an individual has a completely symptom-free infection. The more the virus replicates, the more mutations it will experience and the greater chance that something threatening will evolve.

One of the disturbing discoveries of the past year has been that it's not just the human population we have to worry about. SARS-CoV-2 has been found in a number of species, notably cats and mink, that we spend a lot of time around. It has even spread from there to the wild mink population, and the virus has jumped back and forth between humans and farmed mink. These animal reservoirs provide added opportunities for COVID to evolve in ways that make it more dangerous to us—perhaps via mutations that allow it to adapt to the new species.

A group of German researchers has now tested some of the mutations that have appeared in viruses circulating in mink populations, and the news is mixed. One specific mutation makes the virus somewhat less infectious to humans but reduces the probability that antibodies raised against the virus will recognize it.

When we first reported on the virus appearing in mink, all we really knew was that it picked up mutations while infecting the animals; we were still too early to even put together a list of mutations commonly seen in mink. That has now changed, and the research team has a list to work with; there's now a catalog of mutations found in European mink farms but not circulating in humans. The researchers focused on mutations in the Spike protein, which the virus uses to latch on to human cells and infect them. Spike is important both because it determines which cells the virus can infect, and it's often the target of antibodies that can block the virus from entering cells.

To look into these mutations, the researchers engineered different versions of the Spike protein into a harmless virus and tested whether the engineered virus could infect cells. They found that certain mutations made it harder for Spike to get the virus into some human cells. There were still some types of human cells it could infect—notably intestine and lung cells, two major sites of SARS-CoV-2 infection. But the virus had a harder time infecting others.

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