Tag: virus

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The DNA of Infection-Fighting

Viral DNA in human genomes, embedded there from ancient infections, serve as antivirals that protect human cells against certain present-day viruses, according to new research.

The paper, “Evolution and Antiviral Activity of a Human Protein of Retroviral Origin,” published Oct. 28 in Science, provides proof of principle of this effect.

Previous studies have shown that fragments of ancient viral DNA – called endogenous retroviruses – in the genomes of mice, chickens, cats and sheep provide immunity against modern viruses that originate outside the body by blocking them from entering host cells. Though this study was conducted with human cells in culture in the lab, it shows that the antiviral effect of endogenous retroviruses likely also exists for humans.

The research is important because further inquiry could uncover a pool of natural antiviral proteins that lead to treatments without autoimmune side effects. The work reveals the possibility of a genome defense system that has not been characterized, but could be quite extensive.

Endogenous retroviruses account for about 8% of the human genome – at least four times the amount of DNA that make up the genes that code for proteins. Retroviruses introduce their RNA into a host cell, which is converted to DNA and integrated into the host’s genome. The cell then follows the genetic instructions and makes more virus.
In this way, the virus hijacks the cell’s transcriptional machinery to replicate itself. Typically, retroviruses infect cells that don’t pass from one generation to the next, but some infect germ cells, such as an egg or sperm, which opens the door for retroviral DNA to pass from parent to offspring and eventually become permanent fixtures in the host genome.

In order for retroviruses to enter a cell, a viral envelope protein binds to a receptor on the cell’s surface, much like a key into a lock. The envelope is also known as a spike protein for certain viruses, such as SARS-CoV-2.

The study shows how one human protein of retroviral origin blocks a cell receptor that allows viral entry and infection by a broad range of retroviruses circulating in many non-human species. In this way, Feschotte said, ancient retroviruses integrated into the human genome provide a mechanism for protecting the developing embryo against infection by related viruses.

Future work will explore the antiviral activity of other envelope-derived proteins encoded in the human genome, he said.

AR Issue #57

Sound & Genetic Healing

By Sol Luckman

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15,000-Year-Old Viruses Found in Chinese Glacier

Even though viruses from China are getting plenty of attention these days, most may be surprised to learn that still-living, 15,000-year-old, viruses have been discovered frozen in glacier ice from China’s Tibetan Plateau.

In 2015, ice cores gathered from the Guliya ice cap in western China, 22,000 feet above sea level, were studied by an international team of microbiologists, including scientists from Ohio State University. Not to worry though. For their study, the scientists claim to have created a “new, ultra-clean method of analyzing microbes and viruses in ice without contaminating it”. Apparently, at that altitude, no one needs to worry about bats. In all, 33 viruses were discovered, and at least 28 of those are previously unknown to science. The findings, were published in the journal Microbiome (https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-021-01106-w).

Life found in conditions which one might think would preclude it, has, in recent years, come to be labeled as ‘extremophile,’ and includes not only that found in extremely cold conditions, like on the Tibetan glacier, but in hot spots like volcanic vents deep in the ocean. The existence of such life forms has encouraged those who speculate about the possibility of life on other celestial bodies, such as the moons of Jupiter, both within, and beyond, the solar system.

The new discovery has reminded some observers of the announcement published in Nature in March 2002 of 20,000-year-old hand prints and footprints found in an area of Tibet, where at a time, it was believed, everything was covered by a giant glacier (https://www.nature.com/articles/news020325-5). A primitive stove found nearby suggested the area might  have been a camp or settlement. Mainstream archaeology had previously insisted that there were no human settlements on the Tibetan plateau before 2,000 BC. The news was taken by alternative scholars, as corroboration for more traditional indigenous accounts claiming a far greater antiquity for life in Tibet…viral and otherwise.