The relationship between herpesviruses and Parkinson’s disease: prevalence, viral load, and clinical implications

Parkinson’s disease (PD) is a complex neurodegenerative disorder characterized by dopaminergic neuronal loss, motor dysfunction, and a range of non-motor symptoms. While the etiology of PD remains elusive, emerging evidence suggests a significant role for latent herpesvirus infections in its pathogenesis. This study investigates the prevalence and viral loads of herpes simplex virus type 1 (HSV-1), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), and cytomegalovirus (CMV) in PD patients compared to age- and sex-matched healthy controls. Using multiplex PCR and quantitative PCR, we demonstrate a higher prevalence of HSV-1 and VZV in PD patients, with their viral loads correlating significantly with disease severity and elevated levels of interleukin-6 (IL-6), a marker of systemic inflammation. Our findings reveal that active herpesvirus infections exacerbate neuroinflammation, potentially accelerating dopaminergic neurodegeneration. While CMV and HSV-2 showed no significant differences, the co-infection of HSV-1 and VZV was associated with more severe non-motor symptoms, such as cognitive decline and depression. These results underscore the potential of targeting herpesvirus reactivation and associated inflammation as a novel therapeutic approach for managing PD. Antiviral therapies and vaccination strategies, particularly for HSV-1 and VZV, warrant further investigation to mitigate PD progression.