Ultrastructural development of guinea pig cytomegalovirus in cultured guinea pig embryo cells.

The ultrastructural development of guinea pig cytomegalovirus (GPCMV) in guinea pig embryo cells was studied using electron microscopy. Tubular structures were found in nuclei of virus infected cells, followed by the appearance of intranuclear inclusions containing virus nucleocapsids. While some nucleocapsids were enveloped at the inner nuclear membrane, others were released into the cytoplasm where they were associated with, or within, dense matrix which was subsequently enveloped by cytoplasmic membranes to form enveloped dense virions. Dense bodies without virus capsids were formed in the cytoplasm and enveloped in a similar manner. An involvement of the nuclear pores in the release of unenveloped virus capsids from the nucleus to the cytoplasm was postulated. Evidence that the enveloped dense virions and dense bodies shared common envelope antigen(s) was obtained by immunoelectron microscopy. The similarities and differences in the ultrastructural development of GPCMV and other cytomegaloviruses are discussed.     

Epstein-Barr virus in adult T-cell leukemia/lymphoma.

Adult T-cell leukemia/lymphoma (ATLL) is a well-known human T-cell lymphotropic virus type-1-related disease. We studied Epstein-Barr virus (EBV) in the tumor cells of ATLL, to investigate the etiological significance of double infection with these viruses. We used polymerase chain reaction and EBV-encoded small RNA-1 in situ hybridization to investigate the presence of EBV and immunohistochemistry to detect EBV-related oncoproteins, such as EBV-determined nuclear antigen-2 and latent membrane protein. Polymerase chain reaction performed on DNA of frozen specimens from 96 cases of ATLL revealed that the tumor tissue from 21 cases contained EBV DNA. EBV-encoded small RNA-1 in situ hybridization performed on the paraffin sections of the polymerase chain reaction-positive cases indicated EBV in the nuclei of ATLL tumor cells in 16 cases, nine of which were in the pleomorphic nuclei. Latent membrane protein was also detected in the cytoplasm of ATLL tumor cells in 15 cases, and EBV nuclear antigen-2 was observed in the nuclei of ATLL tumor cells in 11 cases. We conclude that EBV was present within tumor cells in about 17% of cases with ATLL and expressed EBV oncoprotein in the tumor cells. It is hypothesized that EBV and human T-cell lymphotropic virus-1 may infect the same T cells in early life and may play a role in the oncogenesis of ATLL.     

Experimental Adenovirus Infection of the Mouse Adrenal Gland: II. Electron Microscopic Observations

A strain of mouse adenovirus, found to have a striking tropism for the weanling mouse adrenal gland, enabled electron microscopic examination of adrenals in various stages of infection. Nucleolar hypertrophy and the successive formation of three types of inclusion bodies in association with nucleoli preceded virion production. Angular crystals of virions formed in the affected nuclei. Virus was released by lysis of nuclear membranes; rapid degeneration of cytoplasmic organelles followed. Rupture of external cell membranes released virus into the extracellular spaces where virions crossed vascular basement membranes to enter endothelial cells. Virions were also phagocytized by inflammatory cells which reentered vascular sinusoids, and by adrenal parenchymal cells. Disruption of virus-laden phagocytic vacuoles in parenchymal cells released virions into the cytoplasm. Typical viral inclusion bodies also formed in vascular endothelial cells and in inflammatory cells, but virion replication was not detected. The possibility that virus directly entered parenchymal cells through the external cell membrane without phagocytosis is discussed.     

Morphological observations of the replication of herpesvirus tamarinus in RL-33 cells

Summary The replication in RL-33 cells (rabbit lung cell line) of herpesvirus tamarinus isolated from cotton-topped marmosets(Saguinus oedipus) was investigated by electron microscopy. In the early stages of infection, ring-shaped and granular structures, and fibrillar materials were recognized in the nucleus. Immature particles were often found in such nuclei. The envelope of the virus was formed by budding through intracytoplasmic membranes, the inner nuclear membrane or the membrane of intracytoplasmic vacuoles. Virus particles which appeared to be budding through the plasma membrane were also observed. Aberrant viral forms were produced by independent budding of both the inner and outer nuclear membranes. The mature particles once enveloped acquired a second envelope by budding through intracytoplasmic double membranes or the outer nuclear membrane. Unusual virus-associated structures were observed in the cytoplasm and nucleus. Virus particles appeared to be released by the process of reverse phagocytosis.With 19 Figures     

An electron microscopic study of varicella skin lesions

Summary The skin lesions of varicella were studied by electron microscopy. Singlemembrane particles were the only type of viral particles present in the nucleus. Two modes of viral envelopment were observed; budding from the inner nuclear membrane, and budding from vacuole membranes of the cytoplasm. Tubular, filamentous structures, probably an aberrant form of the virus, were often observed in affected nuclei. Nuclear bodies were frequently found and showed abnormal structures in the nuclei of cells near the intraepidermal vesicles. Strands, inclusion-like structures, probably composed of degenerated nuclear materials, were seen in some instances in the cytoplasm. Virions were frequently included in phagosomes of epidermal or dermal macrophages.     

In situ hybridization to detect Epstein-Barr virus DNA in oral tissues of HIV-infected patients

Summary Thirty biopsies of oral mucosal lesions and normal oral mucosa were obtained from 26 HIV-seropositive individuals and studied for virus infections with Epstein-Barr virus-specific DNA probes (EBV). In situ DNA hybridization was carried out on frozen and formalin-fixed, paraffin-embedded tissues. Specifically bound biotinylated virus probes were detected with the streptavidin-gold-silver technique and visualized by standard and interference reflection microscopy. In 9/30 biopsies, EBV DNA was clearly demonstrated in the upper two thirds of oral epithelia. This finding corresponded to peculiar cytopathic effects including ground glass nuclei, basophilic nuclear inclusions, and ballooning of the cytoplasm, which were concentrated in the upper two or three layers of the stratum spinosum. Cytopathic effects together with the demonstration of EBV DNA were demonstrated in seven cases of tongue mucosa, and two cases derived from the gingiva. When comparing clinical and pathological findings with DNA detection rates, we saw 5/9 hairy leukoplakias associated with EBV infections. Four positive cases (two samples from the tongue, two gingival specimens) had not been regarded as hairy leukoplakia clinically. EBV infection of the oral epithelium occurred in male homosexuals (7 cases) and in male/ female intravenous drug abusers (2 cases). Among the nine EBV-positive cases, 2 patients were asymptomatic, 4 patients were grouped into the ARC-, and 3 individuals into the AIDS-category. We conclude that HIV-seropositive patients are particularly prone to develop productive EBV infections in oral epithelia. This infection most frequently appears at the lateral border of the tongue, but may also occur at other sites of the oral cavity, and may already exist in a preclinical stage prior to the development of oral white lesions (hairy leukoplakia).     

Electron microscopic localization of wheat striate mosaic virus in its leafhopper vector, Endria inimica

Electron microscopy of thin sections of salivary glands from wheat striate mosaic virus (WSMV)-infected leafhoppers, Endria inimica (Say), showed for the first time the presence of rhabdovirus particles in the leafhopper vector. These virus particles looked similar to those that have been observed in WSMV-infected wheat. The virions were found in the nuclei of infected cells both in well-defined intranuclear inclusions and in spaces between the inner and outer nuclear membranes. Bundles of particles were also seen in the cytoplasm close to infected nuclei. No particles were found in leafhoppers reared on virus-free wheat.     

Electron microscopic study of Herpesvirus saimiri.

Replication of Herpesvirus saimiri has been studied by electron microscopy in highly permissive primary owl monkey kidney cells (OMK) and less permissive Vero African green monkey kidney cells. In OMK cells, toroid structures were observed in nucleoids of immature and mature virions, and what has been previously described as intranuclear envelopment was shown to be envelopment by budding into intranuclear vesicles, the membranes of which were continuous with the inner nuclear membrane. In the less permissive Vero cells, accumulation of empty cytoplasmic capsids associated with dense osmiophilic material suggested the possibility of cytoplasmic assembly of defective particles. Other unusual structures associated with virus replication in the less permissive Vero cells are described and their possible role in virus morphogenesis is discussed.     

Morphogenesis of bovine parvoviruses and associated cellular changes

Morphogenic features of bovine parvovirus replication and associated cellular alterations in bovine fetal lung and spleen cells were examined by electron microscopy. Morphological evidence of parvoviral replication was detected first at 24 hr after inoculation when empty viral capsids were found in association with the smooth endoplasmic reticulum, in the lumina of nuclear pores, and in the nucleus. At 36 hr empty capsids were found in the parafibrosa of the nucleolus. Few complete virions were seen in the nucleus at 24 and 36 hr postinfection. The ratio of complete to empty virions increased and complete virions predominated 48, 60, and 72 hr after infection. Empty capsids and complete virions measured 20–22 nm in diameter. At 48 and 60 hr complete virions accumulated within the nucleus near nuclear pores, and similar 20–22 nm particles were seen on the cytoplasmic side of the nuclear membrane. The cytoplasm was severely degenerated in cells 72 hr after inoculation, the nuclear membranes were fragmented, and complete virions replaced the heterochromatin. Crystals composed either of empty capsids or complete virions were occasionally seen in the nuclei of different infected cells.     

Herpes simplex virus infection of the human sensory neuron

Summary 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 post-infection 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.     

Growth of an autonomously replicating parvovirus (feline panleukopenia): Kinetics and morphogenesis

Summary Feline embryo (FEmb) cell cultures, in which 90 percent of cells were dividing (cycling), were synchronized, by serum deprivation, to the degree that 88 per cent of the cells divided within a 12 hour period. When such cultures were infected with feline panleukopenia virus (FPV) at a multiplicity of infection of 5.7, a maximum level of cell associated virus was attained 28 hours post-infection (p.i.). There was a tendency for virus to remain cell associated in that cell lysis did not begin until 40 hours p.i.The genesis of FPV inclusion bodies was studied by light microscopy. Inclusions were intranuclear, weakly basophilic and Feulgen positive; they were first observed 8 hours p.i., and increased to be present in 90 percent of cells by 40 hours. Mitosis was markedly inhibited in FPV infected monolayers.The earliest changes observed by electron microscopy of infected cells were the presence of virus particles within nuclei, progressive chromatin margination, and nucleolar changes involving apparent segregation of the fibrillar and granular components. Virus particles measured 20 nm in diameter, and appeared either uniformly electron dense or possessed a dense margin and a pale center; many of the latter contained a single, central, dark spot. Virions ultimately became closely packed in all areas unoccupied by other nuclear components. In some nuclei a linear arrangement of virions was noted, but paracrystalline arrays were not seen.Other changes observed in infected nuclei included the presence of nucleolar remnants sometimes in the form of solid or hollow bodies comprised of nucleolar granules or filaments; distension of the space between the two membranes of the nuclear envelope; and the presence of aggregates of abnormal, electron dense material within the nucleus. Discontinuities of the plasma membrane and swelling of cytoplasmic organelles were commonly seen in cells showing advanced nuclear changes, but at least the inner membrane of the nuclear envelope generally remained intact. The characteristic, well defined inclusions of light microscopy were not observed by electron microscopy, and thus probably represented a preparation (shrinkage) artifact.With 11 Figures     

Electron microscopical study of initial and final stages of fowl plague virus-replication in chick embryo cells

Summary Cellular uptake of fowl plague virus occurs 10–30 minutes after inoculation of chick embryo cells. The penetration of the virions is by pinocytosis (viropexis); fusion with the cellular membrane has not been observed. After pinocytosis the virions become gradually disintegrated. Budding of newly formed virions from the cellular membrane starts 3 hours post inoculation (p. i.) and reaches its maximum 8 hours p. i. At the same time budding takes place into electron microscopically empty and autophagic vacuoles. Eight hours p. i. about 3 per cent of the infected cells show budding of virions from the surface and into cytoplasmic vacuoles. Labelling of the cellular membrane with ruthenium red demonstrated that these cytoplasmic vacuoles are not simple cross-sections of invaginations of the cellular membrane. Cluster-like structures were found at 6 hours p. i. in the nuclei of infected cells; however, the suggestion that the clusters develop from nucleoli could not be confirmed.With 6 Figures     

Viral Behavior of Paracrystalline Inclusions in Osteoclasts of Paget's Disease of Bone

Fresh tissues from six patients with Paget's disease of bone were examined ultrastructurally to investigate whether the characteristic paracrystalline inclusions in pagetic osteoclasts revealed viral behavior. These inclusions appeared as microfil-amentous aggregates in both nuclei and cytoplasm of the osteoclasts in all six cases. The filamentous elements of the inclusions with a diameter of 11-15 nm showed tubular structures with a central electron-lucent zone measuring 5-7 nm in diameter. Viral budding-like structures containing these inclusions were found at the peripheral cytoplasm or cell processes in the ruffled border of some pagetic osteoclasts in two cases. The inclusions in the budding-like structures were often arrayed in a parallel fashion on the cytoplasmic side of the cell membranes of extruded cytoplasm or cell processes. Virion-like particles were also found in the extracellular spaces of the ruffled border. Marked nuclear degeneration was often seen in pagetic osteoclasts of three cases, although other nuclei in the same osteoclasts appeared normal. The degenerated nuclei showed nuclear ring formation where destroyed nuclear membranes were seen and disappearance of nuclear matrices was noted. Since the modifications were always associated with the accumulation of abundant inclusions, they were probably caused by the inclusions. These findings suggested that the inclusions showed viral behavior in pagetic osteoclasts, and that the nuclear modifications were caused by virus infection.     

No direct role for Epstein-Barr virus in American hepatocellular carcinoma

Epstein-Barr virus (EBV) was recently linked to hepatocellular carcinogenesis in Japanese patients. It is not clear whether EBV infection is also associated with hepatocellular carcinoma (HCC) occurring in American patients. We studied 41 cases of HCC from the Los Angeles area for evidence of EBV infection by in situ hybridization, immunohistochemistry, and polymerase chain reaction methods. Of 41 cases, 16 were seropositive for hepatitis B virus surface antigen (39%), 9 of 29 tested were seropositive for hepatitis C virus antibody (31%); in total, 22 cases were seropositive for hepatitis B virus and/or hepatitis C virus (53%). Of 41 cases, 1 was positive for EBV-encoded small nonpolyadenylated RNA (EBER)-1 (2%) by in situ hybridization. By immunohistochemistry, two cases were positive for EBV nuclear antigen (EBNA)-1 (5%), one was positive for the transactivating immediate early BZLF1 (ZEBRA) (2%), and none was positive for latent membrane protein-1. None of the 41 cases was positive for latent membrane protein-1 and EBV nuclear antigen (EBNA)-4 DNAs by polymerase chain reaction assay. All four positive cases showed rare EBER-1-, ZEBRA-, or EBNA-1- positive cells (<0.1%); in none of these cases was there expression of any other EBV viral genes. In the one case each that was positive for EBER-1 and ZEBRA, both of which occurred in patients of non-Asian ethnicity, the staining was limited to infiltrating small lymphocytes, and tumor cells were negative. In the two cases that were positive for EBNA-1, both of which occurred in patients of Asian ethnicity, the staining was limited to tumor cells, and infiltrating small lymphocytes were negative. Our study indicates that rare cases of American HCC may contain EBV-infected cells, but it is unlikely that EBV plays a major role in the carcinogenesis of HCC.     

Detection of Epstein-Barr virus infection in the epithelial cells and lymphocytes of non-neoplastic tonsils by in situ hybridization and in situ PCR

Summary.  Non-neoplastic tonsils were analyzed for detection of Epstein-Barr virus (EBV)-positive cells by in situ hybridization and in situ PCR. EBV-encoded small nuclear RNA 1(EBER1)-positive cells were found in 28.2% of the tonsils and were evenly localized in the extrafollicular area and within germinal centers. Latent membrane protein 1 (LMP1)-positive cells were also dispersed in the extrafollicular and germinal center. Using in situ DNA-DNA hybridization, the EBV-positive signals were observed in the upper epithelial cell layers of the tonsils. In addition, in situ PCR detected EBV DNA-positive cells in the lower epithelial cell layers and lymphoid cells. Accepted December 1, 1997 Received September 16, 1997     

A light and electron microscopic examination of budgerigar fledgling disease virus in tissue and in cell culture

Morphological changes induced by a newly described avian virus in budgerigar (Melopsittacus undulatus) tissues were examined with light and electron microscopes. Infected cells viewed with the light microscope were found to have enlarged nuclei containing marginated chromatin. Cytoplasmic contents were frequently clear in appearance. Tissues affected included skin, feather, follicle, kidney, uropygial gland, crop, lung, liver, heart, bone marrow, spleen and brain. Serum from infected birds contained viral particles. No tumours were found in affected birds. Electron microscopy demonstrated viral particles that were naked, predominantly icosehedral, and 42-49 nm in diameter. Occasional elongate forms of the virions were seen in kidney tissue. Small groups of virions were occasionally enclosed within nuclear and cytoplasmic membranes. Viral particles were observed in chicken embryo fibroblast cultures 18 hours post-inoculation. The particles first appeared in swollen nuclei and subsequently were found in the cytoplasm of more senescent cells. Cytoplasmic disruption and swollen rough endoplasmic reticulum were also observed in infected cells. Negatively stained preparations of the fluid from infected chicken embryo fibroblast cultures contained typical cubic viral particles as well as elongate forms similar to those seen in excised tissue preparations.     

Inconsistent association of Epstein-Barr virus with CD56 (NCAM)-positive angiocentric lymphoma occuring in sites other than the upper and lower respiratory tract

We previously described nine cases of angiocentric lymphoma of a possible natural killer (NK)-cell lineage with a surface CD3− CD56+ phenotype occurring in sites other than the upper and lower respiratory tract. This study was performed to investigate the association of Epstein-Barr virus (EBV) with these lymphomas, using the polymerase chain reaction (PCR) for the presence of EBV-DNA, in situ hybridization (ISH) for EBV-encoded small RNAs (EBERs) and immunohistology for EBV-determined nuclear antigen-2 (EBNA-2) and latent membrane protein-1 (LMP-1) in paraffin sections. PCR and ISH produced almost identical results, and EBERs were identified in the nuclei of the lymphoma cells of three cases, two of which exhibited LMP-1 in the cytoplasm of tumour cells without EBNA-2 expression. Molecular genetic analysis revealed EBV to be incorporated into these three EBER-positive cases either clonally or biclonally. It was revealed by re-evaluation of their morphology with the established EBV status on each case that, in contrast to the rather variable and irregular cellular composition of the EBV- positive tumours, the EBV-negative tumours stood out because of their remarkably uniform 'blastoid' appearance, and could be grouped as blastic NK-cell lymphoma. The relationship of the EBV-positive cases with nasal NK-cell tumours has yet to be clarified.     

Ultrastructural studies on the replication of herpes simplex virus in PK and XTC-2 cells

Ultrastructural changes showed the following characteristics of restricted replication of herpes simplex virus 1 (HSV 1) strains MA and HSZP in PK and XTC-2 cells: 1) minimal cytopathic changes in PK cells as compared to more pronounced alterations in XTC-2 cells; 2) formation of single nucleocapsids or their absence in the nuclei of PK cells infected with the HSZP strain; 3) lack of budding and envelopment and absence of reduplication of the nuclear membrane; 4) persistence of partially uncoated virions within the endocytic vacuoles in the cytoplasm of PK cells; and 5) formation of dense inclusion bodies in addition to the presence of defective virions in the cytoplasm of XTC-2 cells and vacuolation of their cytoplasmic membranes. The replication of HSV 1 in PK and XTC-2 cells seemed to be blocked at both early and late stages of virus replication. At low multiplicity of infection, no virus particles were formed.     

EB病毒编码的RNA及EB病毒潜在膜蛋白在中线T淋巴瘤中的表达

应用免疫组化和原位杂交技术及抗ＥＢ病毒潜在膜蛋白（ＬＭＰ－１）单克隆抗体和ＥＢ病毒编码的ＲＮＡ（ＥＢＥＲ－１）探针对９例中线Ｔ淋巴瘤（ＭＴＬ）进行了ＥＢ病毒（ＥＢＶ）检测。结果显示：８例肿瘤细胞核ＥＢＥＲ－１阳性；７例肿瘤细胞膜和胞浆ＬＭＰ－１阳性。结果表明：（１）ＥＢＶ与我国的ＭＴＬ存在密切关系，很可能在其发病中起着重要作用；（２）ＥＢＶ在ＭＴＬ的检出率高于全身其它部位和其它类型的周围型Ｔ淋巴瘤；（３）ＥＢＥＲ－１原位杂交和ＬＭＰ－１免疫组化在检测ＭＴＬ中ＥＢＶ方面都很敏感、可靠，而后者更经济简便。     

Epstein-Barr virus in pyothorax-associated pleural lymphoma.

Pleural B-cell lymphoma was found in five patients with a history of pyothorax that was the sequelae of tuberculosis 35 to 47 years previously. Epstein-Barr virus (EBV) DNA was detected in all five pleural tumors by polymerase chain reaction and Southern blot hybridization. The lymphoma cells were shown to express the latent membrane protein-1 and the EBV-encoded nuclear antigen-2 by immunocytochemistry and EBV-encoded small RNA by in situ hybridization. Three cases were shown to be EBV subtype A, whereas the remaining two were subtype B, as determined by differences in the EBV-encoded nuclear antigen-2 nucleotide sequence. The patients also had high titers of antibodies against EBV. These findings suggest that EBV is causally associated with the pleural lymphomas that originate at the site of chronic inflammation and fibrosis with a latent period of more than 40 years.