BACKGROUND Fatigue is a common complication of stroke that has a significant impact on quality of life. The biological mechanisms that underly post-stroke fatigue are currently unclear, however, reactivation of latent viruses and their impact on systemic immune function have been increasingly reported in other conditions where fatigue is a predominant symptom. Epstein-Barr virus (EBV) in particular has been associated with fatigue, including in long-COVID and myalgic encephalomyelitis/chronic fatigue syndrome, but has not yet been explored within the context of stroke. AIMS We performed an exploratory analysis to determine if there is evidence of a relationship between EBV reactivation and post-stroke fatigue. METHODS In a chronic ischemic stroke cohort (>6 months post-stroke), we assayed circulating EBV by qPCR and measured the titres of anti-EBV antibodies by ELISA in patients with high fatigue (FACIT-F <40) and low fatigue (FACIT-F >41). Statistical analysis between two-groups were performed by t-test when normally distributed according to the Shapiro-Wilk test, by Mann-Whitney test when the data was not normally distributed, and by Fishers exact test for categorical data. RESULTS We observed a similar incidence of viral reactivation between people with low versus high levels of post-stroke fatigue (5 of 22 participants (24%) versus 6 of 22 participants (27%)). Although the amount of circulating EBV was similar between the groups, we observed an altered antibody response against EBV antigens in participants with high fatigue, with reduced IgM against the Viral Capsid Antigen (VCA; 2.244 +/- 0.926 vs 3.334 +/- 2.68; P = 0.031). Total IgM levels were not different between groups indicating this effect was specific to EBV (3.23 x 10^5 +/- 4.44 x 10^4 high fatigue versus 4.60 x 10^5 +/- 9.28 x 10^4 low fatigue; P= 0.288). CONCLUSIONS These findings indicate that EBV is not more prone to reactivation during chronic stroke recovery in those with post-stroke fatigue. However, the dysregulated antibody response to EBV may be suggestive of viral reactivation at an earlier stage after stroke and warrants further investigation.

The authors have declared no competing interest.

This research was funded by the Leducq Stroke-IMPaCT Transatlantic Network of Excellence (19CVD01; MSB/ICM/BM/SA/CS), an American Heart Institute / Allen Frontiers Group Brain Health Award (19PABHI34580007; MSB), the Wu Tsai Neurosciences Institute (MSB), and a Wellcome Sir Henry Dale Fellowship (220755/Z/20/Z; LM).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Institutional Review Board of Stanford University gave ethical approval for this work.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present study are available upon reasonable request to the authors