Myriad organisms share this planet, and there is an ongoing evolutionary arms race between competing traits or species. Viruses are constantly improving ways to infect host cells, for example, and evade the host immune system, which can do some adapting of its own to mount a defense against these invaders. Many viruses are not serious enough to cause more than a mild illness like a cold, so if we can't fight them off immediately, they don't pose much of a threat. But the COVID-19 pandemic has illustrated the significant challenges posed by a virus that we don't know much about and have no treatment or vaccine for.
Researchers have now learned more about how viruses fight the immune system. In this work, reported in the Journal of Experimental Medicine, the scientists studied the tactics used by the herpes simplex virus to get around the immune system and infect the brain. The findings may help us develop new antiviral drugs.
It's thought that as many as 90 percent of adults will be infected by the herpes simplex virus 1 in their lifetime. The virus infects cells in the throat, enabling it to eventually move to nerve cells called trigeminal ganglia, where it stays for life. The virus can reactivate at any time and cause mild symptoms. Herpes infections have recently been linked to Alzheimer's disease as well. If the virus enters the brain it can cause a type of encephalitis (described in the video below), and the swelling and inflammation that results can cause severe damage.
It seems that the herpes virus can interfere with the immune response. "In the study, we found that the herpes simplex virus is capable of inhibiting a protein in the cells, known as STING, which is activated when there is a threat. When STING is inhibited, the body's immune system is also inhibited - the virus thereby puts the brakes on the body's brake, which is supposed to prevent us from becoming ill. Other viruses also make use of the same principle," explained virologist and professor Søren Riis Paludan of the Department of Biomedicine at Aarhus University, Denmark.
The STING (Stimulator of interferon genes) protein is able to sense DNA from bacteria and viruses. Once it does, it can activate the immune system.
While this work investigated herpes virus, it has parallels to the pandemic virus SARS-CoV-2, noted Søren Riis Paludan; other viruses inhibit the same protein.
"This suggests that we have found an Achilles heel in the virus and the way it establishes infections in the body. Our results lead us to hope that if we can prevent viruses from blocking STING, then we can prevent the virus from replicating. That could pave the way for new principles for [the] treatment of herpes, influenza and also the coronavirus," said Søren Riis Paludan.
"Previous studies have also shown that the coronavirus inhibits STING in the same way as the herpes virus. This suggests that we have found a common denominator for several types of virus, and that this is probably an important element in the development of treatment," he added.
Sources: AAAS/Eurekalert! via Aarhus University, Journal of Experimental Medicine