Belgian scientists from the Center for Medical Biotechnology at Ghent University have discovered a way for one of the immune proteins to block and even destroy herpes simplex and human immunodeficiency viruses (HIV). The study is published in the scientific journal Cell Host and Microbe (CHM). The human body's innate immune system can sense and respond to viruses by producing interferons. These proteins act as a signaling system that is triggered when a cell is infected by a virus. They alert surrounding cells to the invasion and prompt them to activate their antiviral defenses. The defenses include so-called interferon-stimulated genes that produce specific proteins with antiviral properties. One example of this is the MX protein, which was discovered 60 years ago. It inhibits a wide range of viruses, including those that cause AIDS and herpes. Until now, researchers did not know exactly how MX's antiviral properties work. The herpes virus or HIV delivers its genome into the nucleus of a host cell through a complex of nuclear pores. This is necessary for the virus to start its genetic program, take over the cellular machinery, and spread. This results in the formation of new viruses that spread to surrounding cells. In the new study, the scientists found that the MX protein controls the assembly of bait structures that mimic nuclear pore complexes. “We observed that the MX protein organizes the assembly of nucleoporins into biomolecular condensates, membrane-free droplets inside the cell that act as a separate compartment. Viruses mistake these condensates for a real door to the cell nucleus and are trapped or destroyed by piercing,” the authors of the discovery specified. According to scientists, understanding the mechanism opens the possibility of creating new methods of antiviral therapy.