CU researchers identify how shingles causes lasting pain, opening new treatment paths

A person recovers from shingles—the painful viral infection that strikes without warning—and expects relief. The rash fades. The acute symptoms subside. But the pain lingers. Weeks turn into months. Months stretch into years. For many patients, this aftermath, called postherpetic neuralgia, becomes more disabling than the infection itself, a phantom ache that resists standard painkillers and fundamentally alters how someone moves through the world.

Researchers at the University of Colorado Anschutz Medical Campus have identified a mechanism that explains why this happens. The culprit is not the virus itself—by the time chronic pain sets in, the varicella-zoster virus that causes shingles has already been cleared from the body. Instead, the damage is done by exosomes, microscopic particles released by cells in response to viral infection. These exosomes circulate through nerve tissue and alter the structure and function of neurons in ways that keep pain signals firing long after the infection has resolved.

The discovery matters because it points toward a new target for treatment. If exosomes are the mechanism perpetuating pain, then blocking or modifying their activity could interrupt the cycle that traps patients in chronic suffering. This is not a minor clinical problem. Shingles strikes roughly one in three Americans at some point in their lifetime, and a significant fraction of those who contract it will develop postherpetic neuralgia—a condition that can last for months or years and severely limit quality of life.

The research team's work focused on understanding how exosomes, which are released by infected and damaged cells, interact with nerve cells to change their pain-signaling behavior. Exosomes are essentially cellular messengers, carrying proteins and other molecules from one cell to another. In the context of shingles, these particles appear to reprogram neurons in a way that makes them hypersensitive to stimuli and more likely to transmit pain signals continuously. The team identified specific molecular changes in neurons exposed to shingles-related exosomes, revealing a pathway that could be interrupted with targeted intervention.

This understanding opens several avenues for treatment development. Researchers could work to prevent exosomes from being released in the first place, or to block their interaction with nerve cells. Alternatively, therapies could be designed to reverse the changes exosomes cause in neurons, essentially resetting the pain-signaling system to normal. Each approach has potential, and the identification of this mechanism gives pharmaceutical and biotech researchers a concrete target to pursue rather than working in the dark.

For patients currently suffering from postherpetic neuralgia, the timeline for new treatments remains uncertain. Basic research discoveries like this one typically require years of additional work before they translate into clinical therapies. But the pathway is now visible. The mystery of why shingles pain persists has been partially solved, and that knowledge is the foundation upon which new treatments will be built. The next phase will be determining which of these potential interventions actually works in human patients and can be safely deployed at scale.