Ultrastructural analysis of primary rat neurons infected by HSV-1 17+. Micrographs show a primary enveloped virion in the perinuclear cleft (A), secondary envelopment in the cytosol (B), an enveloped virion within a vesicle (C) and a naked nucleocapsid (C, inset) in the axon, or two enveloped virions in a growth cone (D). Black triangles indicate enveloped virions, white triangles denote naked nucleocapsids. Bars: 200 nm in panel A, 1 μm in panels B and D, 300 nm in panel D, and 100 nm in panel C, inset.