Immunity system complexity: cellular viral defenses (Introduction)

by David Turell , Wednesday, June 28, 2023, 19:59 (303 days ago) @ David Turell

These cells do gear up with defenses:

https://phys.org/news/2023-06-war-cells-survive-viral-invasion.html

"When a virus enters a cell, it can gain control of the protein production mechanisms, forcing them to make multiple copies of itself. But infection might not lead to all-out war. While an active infection entails the virus killing the cell as it spreads its copies to other cells, at times a virus fails to take over the production mechanisms of the host cell, remaining latent within it, sometimes for decades. Herpes viruses, for example, are notorious for their ability to hide inside the body in a dormant state. What determines whether an active infection occurs, or the virus remains latent?

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"'As expected, shortly after infection the cells still only produced their own proteins," says Schwartz. "However, a few hours later, the cells split into two groups. As some kept making their own proteins, others started assembling viral proteins, a step that initiates the multiplication of the viral genome and its spread throughout the body. We found this step to be irreversible: From the moment cells expressed just two initial viral proteins, we couldn't stop the viral takeover."

"Searching for an explanation as to why the virus took over some cells but not others, the team examined the differences in proteins produced by each group of cells before and during infection. They discovered that the virus failed to take over cells that had already produced more antiviral defenses prior to infection. While the virus stayed as a latent guest within these cells, those with a lower routine production of defense proteins were open to a viral takeover.

"This local protein "shield," produced not only by the attacked cell but throughout its environment, had long been recognized as the first line of defense against an ongoing viral infection. It was known to be generated in response to viral invasion, which prompts cells to secrete protein alerts called interferons. These warning signs, in turn, elicit antiviral protein production in nearby cells—a sort of code red to get ready for battle. Following the secretion of interferons, hundreds of genes for defense proteins are activated. The team's finding showed that these defense proteins play a significant role even before the infection occurs and the warning signs are flagged.

"The researchers believe that high levels of routine defense protein production might serve to immunize cells against a potential active infection. This idea suggests a possible solution to a previously unsolved mystery—why do cytomegaloviruses tend to accumulate in a latent state within bone marrow stem cells? Previous research by other scientists had found that stem cells routinely produce relatively high levels of defense proteins, compared to such mature immune cells as macrophages. These proteins' newly discovered immunizing effect against active infection could explain why the viruses remain latent within the stem cells.

"The scientists also discovered that mature macrophages, which had been thought to only play host to active infection, can harbor latent viral infection as well. This means that contrary to the prevailing view, cells don't fall into one of two categories—harboring either active or latent infection—but can be host to either, depending on their levels of defense protein production. In other words, various cell types in the body, formerly thought to be subject to active infection alone, might in fact form unknown reservoirs of latent, potentially harmful viruses. Discovering such reservoirs can lead to preventive treatments."

Comment: These defense mechanisms. I think were designed by an all-knowing God who knew that His designed viruses could cause trouble. That viruses exist means God created them for His positive purposes, just like bacteria, but God also knew both organisms entering the wrong places would cause illness and therefore provided immune mechanisms.