Is it possible that some common diseases are due to latent viral infections? It’s been hypothesized before, and new work has looked at whether human herpesvirus 6 (HHV-6) is to blame for cases of chronic fatigue or multiple sclerosis, and what might be causing that to happen. Most people on the planet are thought to carry the HHV-6 virus, which doesn’t cause symptoms in the majority of cases. Antibodies to the virus can be found in anywhere from 95 to 100 percent of healthy individuals, showing that most adults have become infected at some point. It’s thought to be harmless, but in people that have undergone organ transplant, take immunosuppressants, or get a chlamydia infection, the virus can become active.
Two types of the virus exist; HHV-6B tends to infect infants and HHV-6A is usually asymptomatic. It does, however, integrate into cellular DNA, where it can remain for a lifetime. It has recently been suggested that the virus can reactivate and may play a role in a variety of diseases including depression, bipolar disorder, schizophrenia, or Alzheimer's.
Led by Dr. Bhupesh Prusty of the Department of Microbiology at the University of Würzburg, scientists found a way to detect reactivated human herpesvirus at an early stage.
"Betaherpesviruses like human herpesvirus 6A, 6B and 7 integrate into subtelomeric ends of human chromosomes and acquire latency. This makes it difficult to recognize the early phase of viral activation based on an analysis of the viral DNA," Prusty explained. A method to detect a biomarker was engineered.
While DNA contains the information for running an organism, it’s RNA that acts as the messenger for active portions of that DNA, and microRNAs are an important part of this system. With microRNAs, proteins can be made, or that process can be prevented. Those microRNAs can, therefore, act as biomarkers for an active virus.
"We have identified several viral microRNA molecules which are produced both during active infection and viral activation," Prusty said.
With a condition called drug-induced hypersensitivity syndrome (DRESS) as a model, the scientists were able to confirm their work. It’s been hypothesized that HHV-6 caused the disease. Prusty’s team found traces of HHV-6 DNA in a patient that died from DRESS. Virus levels were very low, but viral microRNAs were comparatively high.
"All biopsy samples showed a positive signal for this special type of RNA," Bhupesh Prusty said. This indicates the potential effectiveness of RNA as a viral biomarker for the detection of active viral infection in the body.
This work indicates that some prescriptions drugs might be able to reactivate HHV-6, leading to life-threatening danger for the patient. It may be very useful to identify these cases early.