Researchers at the National and Kapodistrian University of Athens have discovered that a retrovirus that infected our ancestors 100 million years ago became a human gene over time and may be behind health issues.
These viruses are found in embryos and cancers like ovarian cancer, and can also be detected in the blood of pregnant women. Their findings were featured in a paper titled, Roles of Endogenous Retroviruses in Early Life Events, published in the journal, Trends in Microbiology.
Regarding pregnant women, one of these strange retroviruses is called Hemo, is not actually made by the mother. Instead, it is created by her fetus and in the placenta.
It was discovered by French biologist Odile Heidmann and her team five years ago, but they still aren’t entirely sure what its purpose is.
“It’s very, very old, so it has to do something,” she said to the New York Times. “It’s possible that Hemo proteins are a message from fetus to mother, dampening the mother’s immune system so that it doesn’t attack the fetus."
Hemo isn’t the only protein with such a background, human DNA contains nearly 100,000 pieces of viral DNA, making up 8 percent of the human genome. Though we currently have no idea what they do.
“What do these efficient genomic colonizers do?” the paper’s authors mused. “Are they merely fossils that, like mosquitos in amber, were stuck and preserved in large host genomes while their functions decayed?”
These genomes are known as human endogenous retroviruses, or HERVs, though they no longer behave like viruses, because their genetic material, called RNA, a relative to DNA has been melded within our genome. Such a combination will be passed down to offspring.
These ancient viruses infect their host cells by inserting a DNA replica of their RNA into the genome. Over generations, this viral DNA replicates, and the HERVs lose their ability to infect other cells.
HERVs and Cancer
Some may be protecting us from disease while others could be increasing our risks for cancer,
“Research in this area started when retroviruses were accidentally discovered in the early 1900s as unseen transmissible agents of cancer.
The strong links of retroviruses with animal cancers created one great promise: if researchers identified infectious agents causing human cancer, they could design prevention strategies (e.g., vaccines) or drug treatments for cancer,” reads an excerpt from the study.
“It’s not an either-or — are these things good or bad? It’s a lot more complicated than that,” lead author and virologist at the University of Oxford Dr. Katzourakis said in an interview with the New York Times. “We’re barely at the beginning of this research.”
While a number of these HERVs are unique to humans, others are found in an array of species, including fish like cod or tuna. Something Dr. Katzourakis explored in another study which found that these retroviruses were invading our marine ancestors 450 million years ago.
This could imply that HERV is involved in the “manipulation of stem cells and early life events, which could have very important effects on adult diseases.”
The future of this research is still unknown, but the hope is that by discovering exactly how these ancient retroviruses affect our bodies, we may be closer to battling debilitating illnesses such as cancer at their source.