Electron microscopic study of Herpesvirus saimiri

Establishment and characterization of two primary breast cancer cell lines from young Indian breast cancer patients: mutation analysis

Two novel triple negative breast cancer cell lines, NIPBC-1 and NIPBC-2 were successfully established from primary tumors of two young breast cancer patients aged 39 and 38 years respectively, diagnosed as infiltrating duct carcinoma of breast. Characterization of these cell lines showed luminal origin with expression of epithelial specific antigen and cytokeratin 18 and presence of microfilaments and secretary vesicles, microvilli, tight junctions and desmosomes on ultra-structural analysis. Both the cell lines showed anchorage independent growth and invasion of matrigel coated membranes. Karyotype analysis showed aneuploidy, deletions and multiple rearrangements in chromosomes 7, 9, X and 11 and isochromosomes 17q in both the cell lines. P53 mutational analysis revealed no mutation in the coding region in both the cell lines; however NIPBC-2 cell line showed presence of heterozygous C/G polymorphism, g.417 C > G (NM_000546.5) resulting in Arg/Pro allele at codon 72 of exon 4. Screening for mutations in BRCA1&2 genes revealed presence of three heterozygous polymorphisms in exon 11 of BRCA1 and 2 polymorphisms in exons 11, and14 of BRCA2 gene in both the cell lines. Both the cell lines showed presence of CD 44+/24-breast cancer stem cells and capability of producing mammosphere on culture. The two triple negative breast cancer cell lines established from early onset breast tumors can serve as novel invitro models to study mechanisms underlying breast tumorigenesis in younger age group patients and also identification of new therapeutic modalities targeting cancer stem cells.

Three-dimensional visualization of gammaherpesvirus life cycle in host cells by electron tomography

Gammaherpesviruses are etiologically associated with human tumors. A three-dimensional (3D) examination of their life cycle in the host is lacking, significantly limiting our understanding of the structural and molecular basis of virus-host interactions. Here, we report the first 3D visualization of key stages of the murine gammaherpesvirus 68 life cycle in NIH 3T3 cells, including viral attachment, entry, assembly, and egress, by dual-axis electron tomography. In particular, we revealed the transient processes of incoming capsids injecting viral DNA through nuclear pore complexes and nascent DNA being packaged into progeny capsids in vivo as a spool coaxial with the putative portal vertex. We discovered that intranuclear invagination of both nuclear membranes is involved in nuclear egress of herpesvirus capsids. Taken together, our results provide the structural basis for a detailed mechanistic description of gammaherpesvirus life cycle and also demonstrate the advantage of electron tomography in dissecting complex cellular processes of viral infection.

Putative site for the acquisition of human herpesvirus 6 virion tegument

The virion of human herpesvirus 6 (HHV-6) contains a very distinct tegument layer, occupying the space between the nucleocapsid and the virion envelope. Ultrastructural analyses of thymocytes infected with HHV-6 revealed the presence of intranuclear spherical compartments, approximately 1.5 microns in diameter, in which tegumentation seems to take place. These compartments, termed tegusomes, were bounded by two membranes and contained ribosomes, consistent with their derivation by cytoplasmic invagination into the nucleus. Capsids located within the nucleus outside the tegusomes were all naked, while those located in the cytoplasm were uniformly tegumented. In contrast, capsids present inside the tegusomes contains teguments of variable thicknesses. In addition, nucleocapsids were documented in the process of budding into the tegusomes. We thus suggest that the tegusomes represent a cellular site in which HHV-6 virions acquire their tegument.

Fine structure of EBV-infected keratinocytes in oral hairy leukoplakia

We evaluated biopsy specimens of 42 cases of clinically suspected oral hairy leukoplakia for the pattern and frequency of ultrastructural alterations specific to epithelial cells infected with Epstein-Barr virus. Some structures could clearly be identified as Epstein-Barr virus at different stages of assembly, but other intranuclear and cytoplasmic alterations were not conclusively identifiable as any known structure. Keratinocytes producing Epstein-Barr virus contained intranuclear particles of different size and shape; some of them were arranged in a monodispersed pattern and others formed arrays. In contrast, both lesional keratinocytes not producing virus and keratinocytes in uninvolved mucosa contained intranuclear particles reminiscent of perichromatin granules. The nuclei of productive cells also contained marginated chromatin, tubular structures, and, occasionally, crystalline and fibrillar formations as well as enveloped virus. Formations of electron-dense bilayers were seen on both sides of the nuclear membrane. In the cytoplasm of productive cells we observed aggregates of parallel tubules and enveloped electron-dense bodies. Although many of these observations are of diagnostic and pathobiological significance, the morphogenesis, composition, and function of alterations with uncertain morphological identification remain unclear.

Further observations on the morphogenesis of human rotavirus in MA 104 cells

Human rotavirus "KUN" strain was cultivated in a fetal rhesus monkey kidney cell line, MA 104 cells. Four types of virus particles in cells infected with KUN strain were clearly identified: nucleoid cores, single-shelled particles, double-shelled particles, and membrane band, "enveloped" particles. "Enveloped" particles were found only in the thin sections of infected cells. When first visible, the virus precursors appeared at the ribosome free membrane of rough endoplasmic reticulum (RER), increasing in size while simultaneously being coated with nucleocapsid, inner shell. Single-shelled particles were also synthesized within bundles of filaments of viroplasm in the cytoplasma. During subsequent virus maturation two types of "budding" processes were observed. Double-shelled particles arising at the RER membrane entered the cisternae of the RER through an exocytosis-like process. In contrast, the "enveloped" particles developed in the cisternae by being completely enclosed with RER membrane, and later during cytolysis released the single-shelled particles. These "enveloped" virus particles appeared to be the result of inefficient virus maturation at the last stage of outer capsid formation.

Mixed infection with human cytomegalovirus and human polyomavirus (BKV)

Mixed infection, the infection of a single cell by two distinguishable viruses, has been demonstrated electron microscopically in human embryo lung (HEL) and human embryo kidney (HEK) cells infected with human cytomegalovirus (HCMV) and human polyomavirus (BKV). There was no evidence of enhancement of HCMV by BKV in either cell system; however, in HEL cells under certain conditions, HCMV enhanced the growth rate of BKV. Since both BKV and HCMV are often found in the urine of immunosuppressed patients, the enhancement of BKV by HCMV may be of clinical significance.

Characterization of marrow-derived adherent cells. Evidence against an endothelial subpopulation

Cultured, marrow-derived, adherent cells (MDAC) provide a microenvironment which supports the proliferation of haemopoietic stem cells (HSC) for extended periods in vitro. Morphological characterization suggested that MDAC populations consisted of a variety of cell types, including mononuclear phagocytes, fibroblastoid cells, fat cells and vascular endothelial cells. Recently performed functional characterization studies suggest that they consist largely of collagen-producing, fibroblastic cells. MDAC were not, however, examined systematically for endothelial cell characteristics. Unrecharged cultures of MDAC, shown in parallel studies to support in vitro haemopoiesis, were examined for endothelial cell markers. These included the presence of Weibel-Palade bodies and synthesis of factor VII related antigen. They were also examined biochemically for synthesis of basement membrane (type IV) collagen. The results of these investigations were negative in all cultures examined. It is thus concluded that vascular endothelial cells are not present as a significant component of the unrecharged MDAC population and do not, therefore, contribute to the functional haemopoietic microenvironment in vitro or in vitro.

Morphogenesis of human rotavirus type 2 Wa strain in MA 104 cells

Morphogenesis of human rotavirus type 2 Wa strain in MA 104 cells was observed. The virus antigen in the cytoplasm was detected by indirect immunofluorescence twelve hours after infection. The cytopathic effect occurred 24 hours after infection when virus particles were detected by EM in the culture fluid as well as in thin sections of the infected cells. Virus particles were observed in the dilated RER, nuclear envelope (perinuclear space), viroplasm, and a lysosome-like body. Three types of virus particles were noted: double-shelled particles 75-85 nm in diameter, single-shelled particles 64-68 nm in diameter and electron-dense nucleoids or cores 32-40 nm in diameter. The outer shell of virus particles was acquired by budding through the membrane of the dilated RER. Tubular structures, similar in diameter to the single-shelled particles, were found in the cytoplasm and nucleus of infected MA 104 cells. Bundles of filaments or the leaflet-like inclusion bodies of membrane-bounded bundles of filaments were found in the cytoplasm and seemed to be associated with virus particles.

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

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.

Ultrastructural studies on the replication of herpes virus ateles-73 in owl monkey kidney cells

The replicative cycle of herpesvirus ateles, strain 73 (HVA-73), was examined in the electron microscope and compared to that of other herpesviruses known to be oncogenic. A relatively slow replicative cycle of HVA-73 in owl monkey kidney (OMK) cells allowed us to distinguish cytoplasmic and nuclear stages of replication, comprising virus uptake, transport, maturation, and extrusion. Virus uptake was observed within 10 hours of infection and occurred both as a result of fusion between virus and cell membranes and by phagocytosis. Morphologic evidence for the transfer of viral DNA from nuclecapsids to the nucleus at the nuclear membrane is presented. This is shown by the location of numerous empty capsids in front of nuclear pores early during infection. Towards the end of the eclipse phase, at about 48 hougs after infection, two different types of nuclear inclusion bodies were observed. Progeny nucleocapsids were detected in the nucleus at the same time. The envelopment of nucleocapsids occurred both at the nuclear membrane and at proliferating Golgi lamellae in the cytoplasm. Each site of envelopment is associated with the maturation of a characteristic, morphologically distinguishable virus particle. The assembly of HVA-73 resembled that of other oncogenic herpesviruses.