New research from the University of Pennsylvania suggests that herpesviruses might play a role in brain disorders such as Alzheimer’s disease and multiple sclerosis (MS).
The cerebrospinal fluid of Alzheimer’s disease patients is filled with Epstein-Barr virus
(EBV), and those with a history of mononucleosis (caused by EBV) are more likely to develop MS. What’s more, the antiviral drug acyclovir has been investigated as a treatment for MS. Aside from these findings, no clear links between gammaherpesviruses
and brain disorders have been found.
To determine whether herpesviruses could even infect neurons, University of Pennsylvania researchers modified EBV and Kaposi’s sarcoma-associated herpesvirus
(KSHV) to produce green fluorescent protein (GFP). They observed GFP-labeled virus in both human neuroblastoma cells and primary human fetal neurons. According to study author Erle Robertson, "after 50 years of studying EBV, nobody had ever seen the virus in nerve cells. But maybe they just never looked". GFP-labeled virus was also found in the culture medium, indicating that the virus underwent a lytic infection in the neurons.
Gammaherpesviruses typically undergo lytic infection in fibroblasts and epithelial cells where they replicate until the host cell bursts, releasing virus particles. They can, however, establish a latent infection in B cells. During latent infection, the viruses incorporate their double-stranded DNA genomes into the host cell genome.
According to Robertson, this data indicates that “there’s likely to be association of this virus with neurons … but more studies will be necessary to know whether it is actually associated with disease pathology”.