Unraveling the Impact of Epstein-Barr virus on Behavior and Circadian Rhythm: Insights from Drosophila melanogaster as a Model Organism

Abstract

Introduction: The Epstein-Barr virus (EBV) has been extensively studied for its association with autoimmune diseases and various malignancies. Research has demonstrated that EBV is capable of infecting neurons directly or indirectly through infected B-lymphocytes, leading to neuro-inflammation, demyelination, degeneration and necrosis of glial cells. Furthermore; EBV has been implicated in the pathogenesis of several nervous system diseases such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and brain tumors. Despite these associations, the specific molecular mechanisms underlying EBV-related neurological pathologies remain to be fully elucidated. Additionally, other research has suggested the association between EBV and diseases such as infectious mononucleosis (IM) and chronic fatigue syndrome (CFS) characterized by behavioral manifestations. Upon primary infection, EBV established a latency, undergoes reactivation and sheds DNA resulting in the activation of the immune system. A previous study from our labs demonstrated the activation of the IMD pathway in Drosophila melanogaster following injection with 70 EBV DNA copies.

Aim: A comprehensive project by our team is investigating the association of EBV with auto-immune diseases. As part of this project, we investigated the behavioral, activity, sleep, locomotor and circadian rhythm changes in EBV injected Drosophila melanogaster.

Methods: Behavioral changes in Drosophila melanogaster were assessed using the Drosophila Activity Monitor (DAM). Furthermore; circadian cycle analysis was conducted using the DAM under alternating conditions of 5 days of darkness and 5 days of light to evaluate any variations in behavioral patterns. Additionally, climbing assays have been performed to comprehensively evaluate any locomotor alterations resulting from the viral injections. These methods were performed on wild-type male adult flies (W1118) and comparison was done between uninjected and injected flies with phosphate-buffered saline (PBS), sterile water, 70 copies of EBV DNA, 35 and 70 EBV viral particles.

Results: Flies injected with EBV displayed a reduced lifespan, alongside decreased activity levels observed across all of EBV-injected flies, corresponding to altered sleep pattern. Upon closer examination under various conditions during both morning and evening phases, it was evident that activity levels decreased while sleep increased in EBV-injected flies. Furthermore, similar trends were observed during both day and night periods. Notably, a significant difference was only observed in older generation flies (14 days old and up). Analysis under light-dark and dark-dark conditions revealed no discernible behavioral disparities but did indicate an extended free-running period and a reduced proportion of rhythmic flies. Climbing assay results demonstrated an enhanced climbing ability among the tested flies.

Conclusion: Behavioral changes were detected in EBV-injected flies but whether these changes were the result of an altered circadian rhythm or the result of an immune response are to be elucidated. Further experiments and assays should be done to further understand the exact pathways and mechanisms in which this virus works.