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J. Virol., 07 1997, 5012-5024, Vol 71, No. 7
S Jayachandra, A Baghian and KG Kousoulas
We characterized the glycoprotein K (gK)-null herpes simplex virus type 1
[HSV-1] (KOS) delta gK and compared it to the gK-null virus HSV-1 F- gKbeta
(L. Hutchinson et al., J. Virol. 69:5401-5413, 1995). delta gK and F-gKbeta
mutant viruses produced small plaques on Vero cell monolayers at 48 h
postinfection. F-gKbeta caused extensive fusion of 143TK cells that was
sensitive to melittin, a specific inhibitor of gK- induced cell fusion,
while delta gK virus did not fuse 143TK cells. A recombinant plasmid
containing the truncated gK gene specified by F- gKbeta failed to rescue
the ICP27-null virus KOS (d27-1), while a plasmid with the delta gK
deletion rescued the d27-1 virus efficiently. delta gK virus yield was
approximately 100,000-fold lower in stationary cells than in actively
replicating Vero cells. The plaquing efficiencies of delta gK and F-gKbeta
virus stocks on VK302 cells were similar, while the plaquing efficiency of
F-gKbeta virus stocks on Vero cells was reduced nearly 10,000-fold in
comparison to that of delta gK virus. Mutant delta gK and F-gKbeta
infectious virions accumulated within Vero and HEp-2 cells but failed to
translocate to extracellular spaces. delta gK capsids accumulated in the
nuclei of Vero but not HEp- 2 cells. Enveloped delta gK virions were
visualized in the cytoplasms of both Vero and HEp-2 cells, and viral
capsids were found in the cytoplasm of HEp-2 cells within vesicles.
Glycoproteins B, C, D, and H were expressed on the surface of delta
gK-infected Vero cells in amounts similar to those for KOS-infected Vero
cells. These results indicate that gK is involved in nucleocapsid
envelopment, and more importantly in the translocation of infectious
virions from the cytoplasm to the extracellular spaces, and that actively
replicating cells can partially compensate for the envelopment but not for
the cellular egress deficiency of the delta gK virus. Comparison of delta
gK and F-gKbeta viruses suggests that the inefficient viral replication and
plaquing efficiency of F-gKbeta virus in Vero cells and its syncytial
phenotype in 143TK- cells are most likely due to expression of a truncated
gK.
Copyright © 1997, American Society for Microbiology
Herpes simplex virus type 1 glycoprotein K is not essential for infectious virus production in actively replicating cells but is required for efficient envelopment and translocation of infectious virions from the cytoplasm to the extracellular space
Department of Veterinary Microbiology and Parasitology, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803, USA.
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