The herpes simplex virus tegument: Interactions and abundance

Abstract

Herpes Simplex Virus (HSV) is the etiological agent of widespread cutaneous epithelial lesions. Its large DNA core is enclosed in an icosahedral capsid that is surrounded by a highly structured, proteinacious, asymmetric compartment referred to as tegument. These components are enveloped by a lipid bilayer derived from host cell organellar membranes, and is studded with glycoproteins.;It has been hypothesized that interactions between the cytoplasmic tail regions of glycoproteins and tegument proteins serve to drive envelopment of the viral nucleocapsid to produce mature virions. In addition these interactions may be important for both the structural integrity of the virion, and maintaining the arrangement of glycoproteins in the envelope. This thesis work seeks to contribute to the understanding of HSV assembly and envelopment by examining the interactions of the glycoprotein B (gB) cytoplasmic tail with the tegument component VP16 and gaining a preliminary characterization of the residues within gB that may mediate this binding.;When the residues QSN (802-804) are mutated to AAA, binding between the two structural components appears heightened. This motif may be important to prevent the virion components from binding too tightly, which would hinder disassembly of the tegument during entry. In addition, when the residues TK (815-816) are mutated to AA, binding of the gB tail to VP16 is abrogated with respect to the unmutated 20 residue tail. We conclude these two residues may play a key role in the interaction of the two HSV structural components.;This thesis also presents a technique for the isolation of nuclear membranes containing enveloped perinuclear virions and shows by three independent means that this preparation excludes mature cytoplasmic virions. This thesis presents a preliminary quantitation of tegument proteins VP16, VP22, and vhs in the perinuclear virion. Data presented here will show that by quantitative Western blot, these tegument proteins are 67, 104, and 50 fold less abundant respectively in the immature virion than in the mature secreted virion. Perinuclear virions were also examined for their infectivity and a plaque forming unit assay revealed that immature particles display less than 3 log fold the infectivity of mature virions.