Friday, 20 October 2017 10:26

Study of asymptomatic EBV patients suggests immune response drives disease symptoms

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Published in mBiosphere

Those who don’t contract Epstein-Barr virus (EBV) in early childhood remain susceptible later in life, when infection is associated with infectious mononucleosis (IM), sometimes simply called mono. Young adults who become infected with EBV can be asymptomatic, or they may display mono-associated symptoms such as fever and lethargy. Why are some young adult infections symptomatic and others asymptomatic? That question is addressed in a recent

2017.10.20 EBV 1No difference of average EBV genome number in asymptomatic (AS) + mono (IM) patients. Source.

Journal of Virology study, led by first author Rachel Abbott and senior scientist Andrew Bell

 

JVirology: Asymptomatic Primary Infection with Epstein-Barr Virus: Observations on Young Adult Cases 

 

The researchers monitored the serologic status of 450 young adults for a number of viruses, including EBV. Six individuals were identified as infected with EBV based on their antibody responses, despite showing no symptoms of disease. Viral DNA was measured in these patients and shown to be well within the range of those infected and displaying symptoms of IM (see scatter plot, right). This suggests that the onset of symptoms is not due to differences in viral load between individuals.

 

The immune responses of infected individuals revealed a different story. Patients experiencing IM had increased lymphocyte numbers and an expanded population of activated CD8+ T cells, whereas this expansion wasn’t observed in the asymptomatic subjects (see graphs, right). Similar immune response differences were observed in activated natural killer cells, which were elevated in IM patients compared with asymptomatic patients, and in circulating dendritic cells, which were depleted in IM patients compared with asymptomatic patients. These differences in cellular immune responses may account for the disease symptom differences, speculate the research team. 

2017.10.20 EBV 2Asymptomatic patients (right five graphs) showed lower T cell activation than patients with mono (left-most graph). Source.

 

This study involved a large population of students, some of whom hadn’t experienced EBV infection; association with the medical school (the subjects were students there) made testing convenient. However, even students can be difficult to enroll in long-term studies, and measuring serum responses every six months, as done here, can cause researchers to miss early infection data points or miss some asymptomatic cases altogether. More intensive studies may help refine the results by increasing the number of described cases in various populations and environments.

 

Most of what scientists understand about EBV comes from studying IM patients. To fully understand the course of infection and EBV virus-host interactions, researchers must also look at asymptomatically infected populations. The results reported here may help clinicians learn how to modulate the immune response to decrease the 6-8 weeks of symptoms that accompany IM.

Photo credit EBV micrograph

Last modified on Friday, 20 October 2017 10:50
Julie Wolf

Julie Wolf is the ASM Science Communications Specialist. She contributes to the ASM social media and blog network and hosts the Meet the Microbiologist podcast. She also runs workshops at ASM conferences to help scientists improve their own communication skills. Follow Julie on Twitter for more ASM and microbiology highlights at @JulieMarieWolf.

Julie earned her Ph.D. from the University of Minnesota, focusing on medical mycology and infectious disease. Outside of her work at ASM, she maintains a strong commitment to scientific education and teaches molecular biology at the community biolab, Genspace. She lives in beautiful New York City.

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