A new animal model, which allows scientists to study human cells in the living brain, has shed new light on progressive multifocal leukoencephalopathy (PML), a deadly brain infection found in people with compromised immune systems.
PML is triggered by the JC virus; an infection so ubiquitous that we are essentially all exposed to it and probably carry the virus in a dormant form. While in most people the virus stays locked away in our kidneys or other organs, in individuals with compromised immune systems – either from a disease or because they are taking immunosuppressive drugs – the virus can become infective and eventually make its way to the brain.
Once in the brain, the virus ultimately destroys the cells responsible for producing myelin – the fatty tissue that insulates nerve connections in the brain, causing PML. This condition is almost uniformly fatal.
Because the JC virus only targets human brain cells (specifically, the support cells called glia), scientists have be unable to understand how the infection progresses. The virus does not infect the brain cells in animals such as mice and rats, where are traditionally used by scientists to study diseases in the lab.
The new research, led by neurologist Steve Goldman, M.D., Ph.D., with the University of Rochester Center for Translational Neuromedicine, uses a new animal model which enables researchers to study human glia cells in the brains of mice.
The study – which appears in the Journal of Clinical Investigation – showed that the JC virus initially targets cells called astrocytes, which act as hosts for the virus, enabling it to replicate and mutate and ultimately spread through the brain.
You can read more about the study here.