Similarities and Differences in the Development of Laboratory Strains and Freshly Isolated Strains of Herpes Simplex Virus in HEp-2 Cells: Electron Microscopy

Abstract

HEp-2 cells infected with two laboratory strains (mP and MP) and two freshly isolated strains (F and G) of herpes simplex virus were fixed at intervals between 4 and 50 hr postinfection and sectioned, and were then examined with the electron microscope. These studies revealed the following. (i) All four strains caused identical segregation of nucleoli and aggregation of host chromosomes at the nuclear membrane. (ii) The development of MP virus could not be differentiated from that of its parent mP strain. (iii) There were quantitative differences between laboratory (mP) and freshly isolated (F) type 1 strains. Thus, cells infected with F contained numerous nuclear crystals of nucleocapsids and relatively few cytoplasmic structures containing enveloped nucleocapsids. Conversely, cells infected with mP or with MP virus contained numerous cytoplasmic structures with enveloped nucleocapsids and relatively few nuclear crystals of nucleocapsids. (iv) There were qualitative differences between type 2 strain (G) isolated from genital lesions and type 1 strains. Thus, cells infected with the G strain contain numerous filaments in nuclei and unenveloped and partially enveloped nucleocapsids in the cytoplasm. Of particular interest is the finding that cytoplasmic membranes in apposition to nucleocapsids were thickened and bent as if they were enveloping the particle. The significance of the qualitative differences in the development of the four strains is discussed.

Hexagonal Arrangement of Filaments in Herpes Simplex Virus Type 2‐Infected Cells

“…Those filamentous and lattice structures, observed by several investigators [1,[3][4][5], have been thought to be characteristic of type 2 HSV-infected cells [1,4]. This was also the case with our HSV isolates.…”

“…Filamentous structures and lattice structures have been observed in the nuclei of cells infected with type 2 but not with type 1 herpes simplex virus (HSV) [1,[3][4][5]. Although the nature of both structures are unknown, the latter structures are considered to represent cross sections of the former [1].…”

The morphogenesis of herpes simplex virus type 1 in infected parental mouse L fibroblasts and mutant gro29 cells

“…Reduplication of membranes at envelopment of budding viral particles ensures the continuity of the membranes. The envelope is essential for infectivity, and maximal glycoprotein expression corresponds with maximal levels of infectious virus isolated from cells (38, 39). Confirming the present immunocytochemical results, different expression of HSV‐1 glycoproteins depending on the origin of the host cells was observed both by flow cytometric analysis (39) and immunoscanning electron microscopy (40) together with an always higher labelling density of gD than that of gC (40).…”

Electron Microscopy of Porcine Cytomegalovirus in Pig Lung Macrophage Cultures

“…Another difference between the present results and the development of PCMV in vivo was the small number of nucleocapsids located free in the cytoplasm of PLM. In herpes simplex virus one of the qualitative differences in the development of types 1 and 2 viruses was the finding that HEp-2 cells infected with type 2 virus contained numerous naked and partially enveloped nucleocapsids in the cytoplasm (11). Since strain B 4 of PCMV examined in PLM by electron microscopy was isolated from the same nasal mucosa as was used in our previous study of PCMV in vivo (13,14), the differences could not have been caused by different properties of the viral strains.…”