Using antibodies generated against the latent membrane protein 1 of Epstein-Barr virus, intense immunoreactivity of Lewy bodies (in PD and dementia with Lewy bodies) and glial cytoplasmic inclusions (in multiple system atrophy) was demonstrated. ELISA and Western blotting techniques confirmed that this immunolabeling was due to cross-reactivity of the antiviral antibody with alpha-synuclein, a neuronal protein implicated in the pathogenesis of PD. This example of cross-reactivity between Epstein-Barr virus and alpha-synuclein may bear implications for further elucidating infectious or autoimmune mechanisms in PD.