Scientists have a found a possible link between the herpes simplex virus and neurodegenerative diseases, according to a recent study.
The researchers also identified a protein that may restrict the spread of the herpes simplex virus type 1, which gives some indication as to why the virus is suppressed in most people but not in all.
The herpes virus is widespread and there are many types. Herpes simplex, a common type, is split into two categories: Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2).
In this study, the scientists focussed on HSV-1, which is mainly transmitted orally between people and can result in cold sores and genital herpes in infected people, according to the World Health Organization (WHO).
It’s thought that around 67 percent of the world’s population under the age of 50—around 3.7 billion people—have an HSV-1 infection. Once someone gets it, it is lifelong, and HSV-1 tends to lie dormant in the body’s nerve cells.
Most oral and genital herpes infections are asymptomatic.
However, in people with compromised immune systems, HSV-1 can cause more severe complications including encephalitis (inflammation of the brain) or keratitis (inflammation of the eye’s cornea).
Knowing this, scientists set out to discover why HSV-1 can be fatal in people with compromised immune systems.
Their research suggested that HSV-1 is suppressed in most people due to a protein called optineurin, or OPTN, which is able to stop the virus in its tracks due to a process called autophagy in which the virus particles are essentially engulfed, said Dr Deepak Shukla, study lead, eye expert, and vice chair for research at the University of Illinois Chicago (UIC) in a university news release.
This discovery was based on animal testing, in which mice were infected with an eye-targeting HSV-1 virus. The scientists found that the virus was more able to infect (and eventually kill) animals that did not have OPTN.
“The study also shows there is an impairment of immune response when there is a deficiency in OPTN,” said study co-author and UIC visual scientist Chandrashekhar Patil in a press release. “OPTN is needed to signal an influx of proper immune cells at the site of infection.”
In addition, the research also suggested that the herpes virus can cause neurodegenerative diseases. This may be because the virus lives inside nerve cells, which end up becoming damaged if the body continuously has to fire up an immune response to target them, proposed research collaborator and UIC neuropathologist Dr. Tibor Valyi-Nagy in a press release.
The study found that mice infected with HSV-1 which were deficient in OPTN showed “significant cognitive decline” and were more likely to die from a central nervous system infection.
OPTN dysfunction had been previously linked to neurodegenerative diseases such as ALS, the study states.
The research was published in the journal Nature Communications on September 13, 2021.