Human eastern equine encephalitis: Immunohistochemistry and ultrastructure

The brain of a 7-year-old boy who died of eastern equine encephalitis (EEE) was examined by immunohistochemical and ultrastructural techniques to dete ct the presence and distribution of viral antigen. A mouse polyclonal antib ody was most effective for demonstrating the presence of antigen previously unreported in this disease in humans. Antigen was localized to the perikar yon and dendrites of neurons; little was detected in glial cells. Cell deat h by apoptosis was conspicuous, but it was primarily identified in glial an d inflammatory cells. Neuronal death was most commonly marked by cytoplasmi c swelling or eosinophilia and nuclear pyknosis. A disassociation between t he degree of inflammation and the presence of antigen was noted, especially in cerebral cortex and spinal cord, presumably where infected cells alread y had been cleared. Ultrastructurally, rare mature viral particles were see n in extracellular spaces.