Epstein Barr virus shedding in multiple sclerosis: similar frequencies of EBV in saliva across separate patient cohorts

Background: Epstein Barr Virus (EBV) infection is closely associated with multiple sclerosis (MS), but the relationship between viral load and disease activity is unclear. This study tested the observed levels of salivary EBV in MS, as a first step in investigating this relationship. Methods: Real-time quantitative PCR (qPCR) was used to measure EBV DNA levels in saliva samples from three separate Multiple Sclerosis (MS) patient cohorts. Results: The qPCR assay was used to delineate EBV shedding, defined here as a reliably detectable level of extracellular EBV DNA in saliva. Frequency of EBV shedding was found to be similar across the groups, with 20–25% of subjects releasing virus on any given sampling date. Diurnal variation in EBV count was tested in one of the cohorts, in which 26% of subjects showed more than a 10-fold difference between the highest and lowest EBV levels on a single day. In the same cohort, elevated viral levels at one time point did not predict elevated viral levels at a subsequent time point. Conclusions: These results indicate that EBV lytic activity in a subject cannot be inferred from a single measure of EBV in saliva. Also, subjects do not appear to be behave constantly as “EBV shedders” or “non-shedders”. The assay is useful in giving a clear indication of salivary gland EBV lytic activity across a patient cohort – for example, in testing anti-viral drugs in MS