Herpes simplex virus infection of the human sensory neuron

Abstract

Herpes simplex virus (HSV) type 1 was used to infect cultures of human embryonic dorsal root ganglion cells. Infected cultured were studied by electron microscopy. Viral nucleocapsids were observed to be internalized into neuronal cells bodies and neuritic extensions by fusion of the viral envelope and the plasma membrane. No signs of internalization by endocytosis were noted. Nucleocapsids were transported in neurites and were within 2 hrs postinfection found located near the microtubules and close to the nuclear pores in the perikaryon. A primary envelopment of nucleocapsids occurred at the inner lamina of the nuclear membrane and virions appeared between the two laminae. Presence of non-enveloped nucleocapsids outside the nuclear membrane and in close contact with the endoplasmic reticulum suggested that nucleocapsids could pass to the cytoplasmic side probably by de-envelopment at the outer nuclear membrane. A secondary envelopment occurred at the endoplasmic reticulum where the virions also became enclosed in transport vesicles. Enveloped virus appearing in the cytoplasm of neurons and neuritic extensions was always found only inside these transport vesicles. During their passage through the cytoplasm the virion-transport vesicle complexes were surrounded by smaller lysosome-like vesicles possibly derived from the Golgi apparatus. Fusion reactions between vesicles with virions and the smaller vesicles seemed to occur. We discuss if in this way the virion-transport vesicle complexes might be provided with glycosyl transferases and substrates necessary for maturation and completion of glycosylation of the viral envelope glycoproteins. The transport vesicles seemed essential for egress of virions from the infected cell by releasing virus when fusing with the plasma membrane.

Local modulation of plus-end transport targets herpesvirus entry and egress in sensory axons

“…For example, some neurotropic viral pathogens, such as poliovirus, enter axons by endocytosis and subsequently traverse the axon in the endosome (25). However, by transmission electron microscopy (TEM), herpesvirus capsids are typically observed directly in the cytosol subsequent to entry into axons (15,26,27). Similarly, we see membrane-free capsids in axons in our culture model by TEM (data not shown).…”

“…Although transmission electron microscopy studies of herpesviruses infections in sensory neurons support a model of viral entry by fusion at the host cell plasma membrane, endocytosis of virions can result in productive infections in some cell types (15,16). To determine whether axonal transport of capsids was associated with endosome transport, sensory neurons and nonneuronal cells present in the disassociated neural culture were together infected with the GFP-capsid virus after labeling of the endocytic pathway with a TMR-dextran fluid-phase marker.…”

HSV trafficking and development of gene therapy vectors with applications in the nervous system

“…Within neurons, HSV-1 nucleocapsid and tegument proteins travel in a retrograde manner to the neuronal cell body where the viral genome is released into the nucleus. [96][97][98] The transport of alphaherpesvirus nucleocapsids along axons has been estimated to occur at rates of 0.5-3.5 mm/s, 99 suggesting that transport is an active process. While the exact mechanism of HSV transport along axons has yet to be elucidated, recent studies have identified viral and host cell components that contribute to this process.…”

Binding of herpes simplex virus to cellular heparan sulphate, an initial step in the adsorption process

“…Binding to the cell, and fusion of the viral envelope and the plasma membrane of the cell by which penetration is accomplished (Fuller & Spear, 1987;Lycke et al, 1988;Morgan et al, 1968), includes activities of glycoproteins B, C, D and H (Cai et al, 1988;Campadelli-Fiume et al, 1990;Desai et al, 1988;Kfihn et al, 1990;Ligas & Johnsson, 1988;Muggeridge et al, 1990), but it has not been established whether and how the glycoproteins interact and whether nonglycosylated envelope proteins are involved also in the attachment of the virion to the plasma membrane (Langeland et al, 1990;Spear, 1985).…”