The Epstein-Barr virus (EBV) infects almost everyone by the time they’re 30, but not everyone necessarily shows symptoms of the illness, acute infectious mononucleosis, which many call the “kissing disease.” In a new study from the American Society for Microbiology, researchers uncover details about why some people develop the illness and others don’t.
The fatigue, fever, and sore throat that are characteristic of mono are also usually accompanied by enlarged lymph nodes, swollen spleen, and a swollen liver. Some people even develop a rash. EBV can hide undetected for years of the tonsils, so the person carrying the disease is completely unaware. Someone they exchange saliva with could then unknowingly be infected with the virus and develop the illness, hence the infection’s nickname. Although the connection is not very well understood, having mono is also associated with autoimmune disease, i.e. having infectious mono may raise the risk of developing multiple sclerosis.
In the present study, researchers aimed to understand the rationale behind the development of acute infectious mono. Most children and some adults rarely develop symptoms, while others are bedridden for weeks to months. Why? Researchers believe it’s because of cross-reactive memory T cells, potentially with a connection to the flu.
Researchers conducted their study with blood samples collected from college students; 32 were diagnosed with mono, 17 tested positive for EBV but did not develop the infection. Of those with a mono diagnosis, the most severe cases showed a whopping 25 times more T cells that reacted to both EBV and influenza A virus in the blood, compared to controls. People with mild cases of mono had 10 times as many cross-reactive T cells as healthy controls.
"If you have a lot of these flu memory T-cells in your tonsils and you get EBV, instead of silently hanging around, it activates those memory cells," explained study leader Liisa Selin.
The new study suggests that a previous flu infection paired with interaction with the EBV virus could trigger an infection or make the infection more severe, making a person’s history of disease exposure a predictive factor of their risk of developing mono. Flu vaccination could also potentially provide protection from mono, at least a severe form of the illness.
The findings from this study indicate an area of research that needs to be explored further, the identification of memory T cells with receptors that increase the risk of certain diseases and increase the likelihood that those diseases will be particularly severe.
The present study was published in the journal mBio.