During the peak of the flu season, while many of my classmates are sick at home, I have always found myself able to make it to class. I have often considered my body in particular to be a very strong fortress. But now, I have come to realize that in order to have become such strong a fortress, it had to have been invaded many times, sometimes even destroyed. The remnants of those battles are from the endogenous retroviruses (RNA viruses), that have infected our DNA and embedded their own. The sections where they are found are considered “junk DNA.” However, one’s man trash is another one’s treasure.
After the successful revival of several ancient viruses, many clues about our ancestry cane to light. For example, endogenous viruses may have caused mammals to develop a placenta which allow for live birth and the capacity develop large brains adding to the complexity of mammals. Endogenous viruses also allow scientists to look back millions of years ago because the earliest retroviruses found in humans are only four thousand years old, too short of a time for evolution to be observed. However, because there are retroviruses that do not affect the germ line, they cannot be inherited. Despite this, ten percent of our DNA is comprised of old retroviruses suggesting that viruses have colonized the human population several times. Only through severe impacts on the human population could we have evolved defenses against those viruses.
There is so much potential with retrovirology. The battle continues as viruses continue to evolve while the host adapts, promoting the virus to evade our changing proteins. HIV has evolved to block the protein, because of its gene “vif,” that would stop it from replicating. I was surprised to learn that despite being nearly identical to chimpanzees, humans are vulnerable to HIV while chimpanzees are not. This is due to the presence of a virus in the chimp genome called PtERV. The article suggests that it is likely we were able to prevent the infection of the virus. In this case, I was surprised to learn that because evolution protected us from PtERV, now we are let with little defense against HIV.
I was most surprised and intrigued by how endogenous viruses can enter our genome. The article states that it is because of genetic mutations produce many errors the faster a virus reproduces. As the errors accumulate, the virus itself is less likely to be dangerous. The article also states that perhaps that solution to HIV is not preventing its reproduction but speeding up its reproduction so it produces so many errors it no longer is a danger. That is amazing. My view of viruses as the enemy is no longer as extreme after learning how they have shaped by defenses that have protected me.