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Mammals Inherit Viral Fragments From Ancestors That Protect Them From Infections: Study

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Sep 14, 2021

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According to two new studies, mammals have a “graveyard of viruses” in their DNA, which work behind the scenes, offering protection against different infections.

Published in Microbiology Australia and Oxford’s Virus Evolution, the studies found non-coding genes in the bodies of mammals — that have been regarded as “junk DNA” for a long time — may be protecting us from ancient viruses.

The researchers explained that when a virus infects us, it leaves behind a piece of itself in our DNA. When the DNA in question is part of an egg or sperm cell, it is passed across generations. The researchers looked for these viral fragments in the genomes of 13 species of marsupials, including the tammar wallaby, koalas, opossums, fat-tailed dunnarts, and the Tasmanian devil.

“These viral fragments have been retained for a reason… Over millions of years of evolution, we would expect all DNA to change. However, these fossils are preserved and kept intact,” said Emma Harding, lead author of both studies and a paleovirologist at the School of Biotechnology and Biomolecular Sciences at the University of New South Wales. “The animal DNA has basically grabbed a viral sequence — which used to harm it — and ends up using it for its own benefit,” she added.

She explained that the viral fragments help protect the cells of animals whose bodies are contained against infections.


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“This could be a mechanism similar to vaccination but is inherited through generations. By keeping a viral fossil, the cell is immunized against future infection,” Harding noted. In fact, some of the viral fragments found in different American and Australian mammals are believed to have made their way into the animals’ DNA during the time of the dinosaurs — “when the South American and Australian landmasses were still joined together” — she notes.

Interestingly, “if we can show it was occurring in marsupials, it may also be occurring in other animals, including humans,” Harding said. So, is there a possible future generation of human beings who will have immunity against Covid19? There does seem to be the hope of that, but we would need to wait for researchers to confirm the possibility.

This May, a study found that future generations of the bubonic plague victims — a devastating global pandemic that ravaged parts of Europe and Asia in the 1300s — had better immunity against the pathogen. The findings indicated an evolutionary capacity in our genes to build resistance against disease-causing microorganisms. However, while a virus causes Covid19, the bubonic plague outbreak (also known as Black Death) was caused by a bacteria called Yersinia pestis — so its long-term impact on people’s immunity levels may not necessarily be the same as Covid19’s.

At present, irrespective of what studies on genetic immunity against diseases may indicate, when it comes to efficacy in fighting the novel coronavirus, vaccinations are still the best way. “I wouldn’t want to discourage anyone from taking a vaccine for the current pandemic — it’s a much safer bet than counting on your genes to save you,” Paul Norman, from the Department of Immunology and Microbiology at the University of Colorado School of Medicine in the U.S., who co-authored the plague study, said in a statement.

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Written By Devrupa Rakshit

Devrupa Rakshit is an associate editor with The Swaddle. She is a lawyer by education, a poet by accident, and a painter by shaukh. She has her own podcast called #DateNightsWithD on Spotify. You can find her on Instagram @devruparakshit.

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