It seems like nothing about herpes is particularly pleasant. The complex virus is transmitted orally or sexually, and at least one form of herpes infects over two-thirds of the global population under the age of 50. While many people won't show symptoms, those that do have painful sores and blisters. But on the molecular level, as Ryan F. Mandelbaum at Gizmodo reports, the virus is surprisingly pretty—as long as you don't overthink it.
In two papers released in the journal Science, American and Chinese researchers took the closest look yet at the molecular structure of both types of the herpes virus, HSV-1 and HSV-2. In particular, they examined the cages composed of protein that encapsulate their DNA, known as capsids.
Unlike bacteria, viruses cannot reproduce on their own. Instead, they hijack a host cell by inserting their own genetic material and using the host's cellular “machinery” to reproduce. Some viruses can chill in the host cells for a period, laying dormant. But once activated, the virus will reproduce and burst through the cell wall to infect surrounding cells.
The capsids of HSV-1 and HSV-2 are not just protective shells for the virus genome, according to a press release. They are also the mechanism the virus uses to insert its genetic material into a cell. Understanding the structure of the capsid could be the key to stopping a viral spread. “A clear understanding of the structure and function of the various proteins of herpesvirus could help guide development of anti-viral agents as well as increase its utility and efficiency as a therapeutic agent for treating tumors,” co-author Xiangxi Wang of the Chinese Academy of Sciences tells Mandelbaum.
The teams used a method called cryo-electron microscopy, an imaging technique that won its developers the Nobel prize last year. In essence, this method allows researchers to freeze a biomolecule in solution then fire electrons at it to study its structure up close. While researchers first developed the technique in the 1970s and 1980s, recent advances in computing power have transformed what was once 2D images into detailed 3D models of biomolecules, with increasingly fine resolution.
In the case of herpes, the researchers used this method to get the most detailed views of the virus yet, showing how around 3,000 proteins are arranged to form the soccer-ball-like capsid. In a commentary in Science, Ekaterina E. Heldwein, a virologist at Tufts University who was not involved in the study, explains that these capsids are one of nature’s great engineering marvels. They are strong enough to contain the massive viral genome packed inside, but bust open easily when its time to let the genome out.
While these studies go a long way showing just how the capsid is constructed, Heldwein writes, they don’t really show how DNA gets inside the capsule—something she hopes future researchers will be able to figure out. Still, she writes, these studies are a breakthrough, and the latest imaging techniques are a positive step toward getting a handle on herpes.