Effect of cytolytic infection on maintenance of resistance to HVJ (Sendai virus) in an altered BHK cell culture

Altered baby hamster kidney (BHK-R) cells were serially cultured in the continuous presence of hemagglutinating virus of Japan (HVJ). These cells showed a distinct resistance to superinfection with the homologous HVJ. This resistance of BHK-R cells gradually disappeared after serial passages in the presence of ultraviolet-irradiated HVJ particles which lost infectivity but still preserved hemagglutinating and neuraminidase activities. When BHK-R cells were serially cultured in the presence of a temperature-sensitive mutant of HVJ at non-permissive temperature, the cells also lost the resistance. The resistance of BHK-R cells remained unchanged, even after prolonged incubation in virus-free maintenance medium under the conditions of no cell division. It was suggested that killing of virus-sensitive cells, which were generated during cell proliferation, was required for maintenance of the resistance.     

Temperature-sensitive virus derived from BHK cells persistently infected with HVJ (Sendai virus).

BHK-HVJ cells, a cell line of baby hamster kidney cells persistantly infected with HVJ (Sendai virus), started to produce infectious virus by shifting down the incubation temperature from 38 to 32 C. The virus derived from BHK-HVJ cells, designated as HJV-pB, was effectively neutralized with antibody against wild-type virus (HVJ-W) which was used for the establishment of BHK-HVJ cells. HVJ-pB replicated in eggs at 32 C, but not at 38 C, while HVJ-W grew equally well at both temperatures. When BHK cells infected with HVJ-PB were incubated at 38 C, production of infectious virus, hemagglutinin, and neuraminidase was markedly restrained, whereas a considerable amount of viral nucleocapisid and envelope antigens was detected in the cells by complement fixation tests. These viral activities became detectable immediately after temperature shift-down from 38 to 32 C even at the later stage of infection. HVJ-pB was indistinguishable from HJV-W with respect to particle size, density, and morphological characteristics, but appeared to possess a higher neuraminidase activity and was inactivated more rapidly at 50 C than HVJ-W. HVJ-pB was less cytocidal and could easily cause latent infection in BHK and mouse L cells.     

Carbohydrate structures of HVJ (Sendai virus) glycoproteins

The carbohydrate structures of two membrane glycoproteins (HANA protein and F protein) of HVJ have been determined on materials purified from virions grown in the allantoic sac of embryonated chicken eggs. Both glycoproteins contain fucose, mannose, galactose, and glucosamine but not galactosamine, indicating that their sugar chains are exclusively of the asparagine-linked type. The radioactive oligosaccharide fractions obtained from the two glycoproteins by hydrazinolysis followed by NaB[3H]4 reduction gave quite distinct fractionation patterns after paper electrophoresis. More than 75% of the oligosaccharides from F protein were acidic and separated into at least four components by paper electrophoresis. Only 18% of the oligosaccharide from HANA protein was an acidic single component. These acidic oligosaccharides could not be converted to neutral oligosaccharides by sialidase digestion. Structural studies of the neutral oligosaccharide fractions from HANA and F proteins revealed that both of them are mixtures of a series of high mannose type oligosaccharides and of complex type oligosaccharides with Gal beta 1 leads to (Fuc alpha 1 leads to 3) GlcNAc group in their outer chain moieties.     

Growth of poliovirus in HeLa cells persistently infected with HVJ (Sendai virus)

The growth of poliovirus in a HeLa cell culture persistently infected with the hemagglutinating virus of Japan (HVJ, the Sendai strain of parainfluenza 1 virus) (HeLaHVJ) was studied. Plaques produced by poliovirus on HeLaHVJ cell monolayers were hazier, smaller and fewer than those on HeLa cells. HeLaHVJ cells were indistinguishable from normal HeLa cells with respect to adsorption rate and penetration efficiency of poliovirus. Extracellular yields of poliovirus in HeLaHVJ cells were lower, and the cytopathic changes were less than those in normal HeLa cells, while cell-associated virus growth in HeLaHVJ cells was nearly equal to that in HeLa cells. HeLaHVJ cells responded more effectively to the action of magnesium chloride, which facilitates virus release from infected cells, resulting in an cytopathic effects. No reduction in poliovirus yield could be detected in HeLa cells acutely infected with HVJ. The relationship between the inhibition of the release of poliovirus from HeLaHVJ cells and the persistent infection of the cells with HVJ is discussed.     

Effects of l-Glutamine Deprivation on Growth of HVJ (Sendai Virus) in BHK Cells

l-Glutamine requirement for viral maturation was found in BHK-HVJ cells, a cell line of baby hamster kidney cells persistently infected with HVJ (Sendai virus). Synthesis of envelope protein in BHK-HVJ cells was markedly suppressed by deprivation of l-glutamine, whereas development of nucleocapsid (S) antigen was less affected. More detailed examination of this phenomenon was carried out by using a cytolytic system. Growth of HVJ in BHK cells cultured in media deprived of various amino acids was investigated, and omission of l-glutamine from culture medium resulted in a marked inhibitory effect on the release of infectious virus and synthesis of envelope protein, although synthesis of virus-specific RNA and nucleocapsid antigen in the cells was readily detected. When l-glutamine was restored to the culture medium, infectious virus and envelope protein could be detected. l-Glutamic acid, l-aspartic acid, or l-alanine could be substituted for l-glutamine. Effects of l-glutamine deprivation on HVJ growth in several other cells were also investigated. The growth of HVJ in the cells other than BHK and FL cells was not suppressed by lack of l-glutamine. Growth of Sindbis virus in BHK cells was also markedly retarded in the absence of l-glutamine.     

Efficient introduction of contents of liposomes into cells using HVJ (Sendai virus)

The conditions for efficient introduction of the contents of liposomes into cells were examined using fragment A of diphtheria toxin (DA) as a marker; one molecule of DA can kill a cell when introduced into the cytoplasm. Liposomes containing DA (DA liposomes) were toxic to cells treated with HVJ (Sendai virus) at 4 degrees C just before exposure to DA liposomes at 37 degrees C, but were not toxic to untreated cells. This toxicity was temperature-dependent. DA outside of liposomes was not toxic to HVJ-treated cells. Results also showed that liposomes could fuse with HVJ at 37 degrees but not at 4 degrees C and that liposomes preincubated with HVJ at 37 degrees C could associate with cells. DA liposomes preincubated with HVJ at 37 degrees C were highly toxic to cells. This toxicity was dependent on the duration of preincubation with HVJ and the dose of HVJ. When plasmid DNA coded herpes simplex virus thymidine kinase was trapped in liposomes and fused with Ltk- cells with HVJ, the thymidine kinase activity was expressed in about 10% of the cells. These data show that naked liposomes fuse efficiently with cells with HVJ and that the contents of the liposomes can be introduced into the cytoplasm 100-10 000 times more efficiently by treatment of the cells or liposomes with HVJ.     

Improved methods using HVJ(Sendai virus) for introducing substances into cells.

When HVJ virions were sonicated in the presence of a given protein, about 0.2%–0.3% of total protein added was recovered in the virions. The protein molecules could be introduced effectively into cells. In this study, fragment A of diphtheria toxin was used as the test protein. More than 96% of L cells were killed after short exposure to the virus suspension containing fragment A diluted so as to contain only about 0.004 μg of fragment A per ml.     

Effects of cytochalasin D on fusion of cells by HVJ (Sendai virus).

Fusion of cells mediated by HVJ was inhibited completely with 5 μg/ml or more of cytochalasin D (CD). With cytochalasin, HVJ-cell interaction at 0 °C proceeded as well as without cytochalasin; HVJ was adsorbed to cell surfaces and the cells agglutinated together. Then the virus particles were enfolded with cell membranes, which resulted in the disappearance of hemadsorption activity on the cell surfaces. When the cell-virus complex was incubated at 37 °C, the early reactions proceeded as well as without cytochalasin; the hemadsorption activity reappeared on the cell surfaces, the viral envelopes fused with cell membranes at the same degree as without cytochalasin, and a stage sensitive to sodium azide appeared as in a control without cytochalasin. But cell-to-cell fusion did not occur in the presence of cytochalasin; cells were dissociated freely from the cell aggregates during incubation. This indicates that cell-to-cell fusion was inhibited but HVJ envelope to cell membrane interactions proceeded well on incubation at 37 °C. These findings suggest that viral envelope-cell membrane fusion and cell-cell fusion are separable, and participation of a cytoskeleton system including microfilaments in the cells is essential for cell-cell fusion.     

HN glycoprotein of HVJ (Sendai virus) enhances the selective cytotoxicity of diphtheria toxin fragment A-containing liposomes on subacute sclerosing panencephalitis virus-infected cells

Fragment A of diphtheria toxin-containing liposomes (naked liposomes) selectively kill subacute sclerosing panencephalitis virus-infected cells (SSPE cells) (Exp cell res 132 (1981) 259) [10]. Fragment A-containing liposomes associated with either hemagglutinating and neuraminidase (HN) or fusion (F) glycoprotein of HVJ (Sendai virus) were prepared. These liposomes did not kill normal cultured cells. Fragment A-containing liposomes associated with HN protein were much more cytotoxic than naked liposomes containing fragment A to SSPE cells. Their cytotoxicity to the SSPE cells was influenced by the duration of incubation and the amount of HN protein. Fragment A-containing liposomes associated with F protein had about the same cytotoxicity on SSPE cells as had naked liposomes containing fragment A. Fragment A-containing liposomes associated with wheat germ agglutinin (WGA) were also prepared, but these also had the same toxicity as naked liposomes containing fragment A. The effects of monoclonal antibodies against HN protein on the cytotoxicity on SSPE cells of fragment A-containing liposomes associated with HN were studied. The significance of these results with regard to the actions of HN protein and possible reasons for the selective killing of SSPE cells are discussed.     

The role of extracellular calcium ions in HVJ (Sendai virus)-induced cell fusion

The biochemical and biophysical roles of extracellular calcium ions in HVJ (Sendai virus)-induced cell fusion were studied. (1) Various kinds of cell, such as Ehrlich ascites tumor cells, mouse melanoma cells (B16-CW1 cells) and human epidermoid carcinoma cells (KB cells), could fuse in Ca2+-free medium containing a cheletor, glycoletherdiaminetetraacetic acid, in the same way as in Ca2+-containing medium. (2) The ATP content in Ehrlich ascites tumor cells decreased rapidly when the cells were treated with the virus in Ca2+-free medium but not in Ca2+-containing medium. (3) Intracellular adenine nucleotides leaked out into the reaction medium when the cells were treated with the virus in Ca2+-free medium but not in Ca2+-containing medium. (4) On addition of the virus, O2 consumption of Ehrlich ascites tumor cells decreased in Ca2+-free medium, but not in Ca2+-containing medium. (5) HVJ (Sendai virus) did not affect production of lactate by Ehrlich ascites tumor cells in both Ca2+-free medium and Ca2+-containing medium. These observations suggest that the role of extracellular Ca2+ in virus-induced cell fusion is to maintain the ATP and other intracellular metabolite contents at normal levels instead of triggering the fusion reaction itself.     

Monoclonal antibody to rat brain actin antigenically enhanced with HVJ (Sendai virus) M protein

Monoclonal antibody to rat brain actin was easily produced using HVJ (Sendai Virus) M protein to enhance the antigenicity of the actin. This monoclonal antibody was determined to be IgM with a kappa light chain. By immunoblot analysis the antibody was also shown to react with rat brain actin but not with HVJ M protein on nitrocellulose sheets. Utilizing the antibody, neuronal cytoplasm in the cerebral cortex, the anterior and posterior horns in the spinal cord, the spinal ganglion and astrocytes showed positive immunohistochemical staining by light microscopy. However, Purkinje cells showed variable staining, some staining intensely, while others were negative. All of neurons in specific anatomical locations showed always positive staining but variable intensities. Vascular walls were stained only faintly. By electron microscopy, neuronal cytoplasm showed diffuse positive staining. Other areas showed a positive reaction, including dendrites, the postsynaptic densities, and a few capillary endothelial cells and arterial smooth muscle cells. The results suggest that the HVJ M protein was effective for producing monoclonal antibody to brain actin, and that the antibody could be utilized for the immunohistochemical study of neuronal elements in both normal and pathological conditions.     

The improved efficient method for introducing macromolecules into cells using HVJ (Sendai virus) liposomes with gangliosides

Macromolecules such as DNA and RNA can be entrapped within liposomes associated with gangliosides by reverse-phase evaporation. When these liposomes are incubated with HVJ2 (Sendai virus), they deliver their contents into cultured cells efficiently. More than 95% cells of a Ltk- cell line (thymidine kinase-deficient cells) transiently expressed thymidine kinase activity by thymidine kinase gene transfer using HVJ liposomes with gangliosides. Stable transformants could be obtained efficiently from various cell lines by use of HVJ liposomes containing the neoR gene. The neo+ transformants were obtained at frequencies of about 0.2-1.0, 0.06-0.25, and 0.06-0.1% in monolayers of L, CHO-Kl, and HeLa-S3 cells, respectively. Moreover, in Ehrlich ascites tumor cells which grow in suspension, the frequency was more than 0.01%. On introduction of plasmid pTK4 into Ltk- cells, about 0.5-1.0% TK+ transformants were obtained. Cosmid DNA containing the neoR gene (about 45 kbp) was also introduced into L cells by this method and neo+ transformants were obtained at a frequency of 0.1%. When rat liver mRNA was introduced into L cells by HVJ liposomes with gangliosides, immunoprecipitation studies showed that the L cells secreted rat albumin and some other proteins into the cultured medium. Moreover, using erythrocyte membrane vesicles containing IgM that had been incubated with HVJ empty liposomes with gangliosides, the IgM could be introduced into all the L cells.     

Ultraviolet light-induced increase in tumor cell susceptibility to TNF-dependent and TNF-independent natural cell-mediated cytotoxicity

Previously we demonstrated that two consecutive in vitro irradiations of MCA 102 cells with high doses of UVC light (610 and 457 J/m2) resulted in a selection of a permanent line MCA 102UV that manifested high sensitivity to natural cell-mediated cytotoxicity (NCMC). In the present study analysis of the effector cells involved in lysis of these tumor cells was performed by comparing the cytotoxicity of normal spleen cells which mediated both NK and NC cell activity with (a) normal spleen cells in which NC activity was neutralized by anti-TNF Abs (NK+,NC-), (b) NK-depleted or NK-deficient spleen cells (NK-,NC+), and (c) NK-deficient or -depleted spleen cells with NC activity neutralized by anti-TNF Abs (NK-,NC-). Results of these studies indicate that lysis of the original MCA 102 tumor cells was relatively low and was mediated by NC cells. UV irradiation significantly increased MCA 102 tumor cell sensitivity to lysis by both NK and NC cells. Analysis of the mechanisms involved in UV-induced NK sensitivity revealed that UV irradiation increased tumor cell susceptibility to lytic NK-derived granules. NC sensitivity of MCA 102UV tumor cells was associated with their increase in sensitivity to TNF and selection of MCA 102UV cells for resistance to rTNF resulted in a decrease in their susceptibility to NC cells. To determine how fast UV-induced sensitivity to NCMC and rTNF can be established, 51Cr-labeled MCA 102 cells were irradiated in vitro with 38-304 J/m2 of UVC light and their sensitivity to lysis by spleen cells and rTNF was tested immediately in an 18-hr cytotoxicity assay. UV treatment with the same doses was repeated 12 days later. The data obtained showed that tumor cell sensitivity to NCMC and TNF appeared shortly after UV irradiation, was stable, and was further substantially augmented by the second round of UV treatment. Thus, in vitro UV irradiation of tumor cells could be an effective modulator of tumor cell sensitivity to TNF-dependent and TNF-independent cell-mediated cytotoxicity.