Earlier this month, a review by Jente Van Campenhout – who is currently working on PhD level research funded by ME Research UK, was published which highlights the potential role of immune exhaustion – a process thought to be driven by prolonged immune activation, such as during chronic viral infections, in ME/CFS.
Based on the idea that prolonged exposure to viral infections could be linked to immune exhaustion in people with ME/CFS, a study in Sweden looked to investigate whether higher numbers of cells from several different viruses could be identified in people with ME/CFS compared to those without the disease.
The researchers collected samples of the thick type of mucus that is made in your lungs (sputum) from:
- 13 people with ME/CFS.
- 10 healthy people.
- 4 healthy elderly people (65-77 years old).
- 2 people whose immune systems were not working as well as it normally would (immuno-supressed).
These samples were then looked at in detail to assess the number of cells that were present from specific viruses:
- Epstein–Barr virus (EBV) – the virus that causes glandular fever (infectious mononucleosis).
- Human adenovirus (HAdV) – a common group of viruses that usually cause mild respiratory illnesses, like cold.
- Human cytomegalovirus (HCMV) – a virus that’s usually harmless, in fact most people who have it do not experience any symptoms at all. However, sometimes it causes problems in babies and people with a weakened immune system.
- Human herpesvirus 6 (HHV6) – a virus that causes a rash called ‘roseola’ in infants, and a more threatening infection for those with weakened immune systems. It is also thought to play a role in several neurological diseases including multiple sclerosis.
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the virus that causes Coronavirus disease (COVID-19).
Results showed that people with ME/CFS had a significantly higher amounts of EBV cells in their sputum samples compared with the control groups. Although there were some slight differences between participant groups in the amounts of other viruses considered, none were found to be of scientific importance in this study.
Notably, EBV infection is commonly reported by people with ME/CFS at – or preceding – the onset of their disease. Additionally, previous research has linked antibodies – protective proteins produced by the immune system in response to foreign substances such as viruses, to EBV with ME/CFS.
There are several theories as to how EBV could be involved in ME/CFS disease mechanisms, for example; an EBV infection could lead to chronic immune activation or autoimmune responses contributing to the symptoms associated with ME/CFS. It is also possible that EBV cells may lay inactive in cells of the body, then under conditions where the immune system is dysregulated – such as another infection, during a stressful life event, or due to an injury, the dormant cells activate – known as pathogen reactivation, leading to ME/CFS.
Findings from the study in Sweden support existing observations linking EBV to ME/CFS. However, the other viruses that were considered – such as HHV-6, which have also been associated with the ME/CFS previously, were not here. The inconsistency in findings between this study and others may be due to the small sample size of only 29 participants in the current study. More research is needed in studies with larger sample sizes to assess viral activity in people with ME/CFS – such as ME Research UK funded work currently being carried out by Dr Amy Proal and her team at the PolyBio Research Foundation.
