2023-06-08 20:05:30
It concerns a protein that ensures that certain viruses, including the corona virus, are not detected in some people.
In many cases, when pathogens enter our bodies, alarm bells ring in immune cells. Those ‘alarm bells’ are the so-called inflammasomes; a type of warning system consisting of molecular sensors that our body uses to sound the alarm when an infection occurs. However, exactly how these sensors work, for example how they initiate responses to threats such as invading pathogens, is still a mystery. But in a new study, biologists describe a previously unknown way the immune system detects certain viruses.
More about inflammasomes
Inflammasomes are actually the warning systems in inflammatory cells that mobilize the chemicals needed to protect against infection. Once these inflammasomes are activated, this can lead, among other things, to the release of chemicals known as cytokines. These cytokines promote an immune and inflammatory response that can help protect us from viruses or bacteria.
This story stars the inflammasome immune protein known as CARD8. What the researchers discovered is that this protein can act as a kind of ‘tripwire’ in our immune system. Specifically, CARD8 prevents certain viruses, including SARS-Cov-2 that causes COVID-19, from being detected in some people. In short, they have lost the genetic ability to detect corona infections using this newly identified CARD8 sensor.
Viruses
Based on a single genetic difference, these individuals are therefore unable to detect corona infections. But that does not mean that they have no chance with every virus. “In fact, these people have acquired the ability to detect viruses from another family, namely the enteroviruses,” says researcher Matt Daugherty. Enteroviruses are a group of ssRNA viruses known to cause various diseases. One of the best-known enteroviruses is the poliovirus (which causes polio) and the rhinovirus (which causes the common cold).
Different
This discovery indicates that the CARD8 protein functions differently between people. “It’s apparently an evolutionary trade-off,” says Daugherty. “CARD8, in a way, determines which viruses are detected and which are not. It’s amazing to see this evolutionary trade-off between perceptive and non-perceptive of one virus over another. It’s amazing.”
Bats
In addition, the researchers discovered that CARD8 also varies between different animal species. For example, it appears that the bat version of the protein cannot detect coronaviruses. And that’s interesting. This could explain why coronaviruses so easily infect bats and thus form a virus reservoir.
Evolution
The findings, which are the result of a series of experiments on human cell lines and an analysis of the genetic variation of CARD8 among mammals, provide evidence that the CARD8 protein has evolved significantly between different mammal species and individual humans. “We hypothesize that CARD8 is a rapidly evolving, polymorphic, innate immune sensor of RNA viruses,” the researchers conclude.
Still a long way to go
Despite this new understanding, there is still a long way to go before scientists fully understand the way our immune system works. “We’ve just hit the tip of the iceberg,” says Daugherty. He says there is still a lot to learn about how immune sensors sound the alarm when pathogens enter our bodies.
In addition, more studies are needed to determine the role of CARD8 in the severity and duration of a corona infection. “It is tempting to speculate that CARD8 is a contributing factor to how sick a person becomes from COVID-19,” the researchers write in the journal PLOS Biology. Whether this is really the case remains to be seen in further research.
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