- Volume 44, Issue 1, 1979
Volume 44, Issue 1, 1979
- Review Article
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- Articles
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A Fluoroimmunoassay for Measurement and Visualization of Antibody Bound to Surface Antigens of HSV-Infected Cells
More LessSUMMARYAn assay based on quantitative spectrofluorometry of surface immunofluorescence was applied to the study of reactions between antibody and surface antigens of viable HSV-infected cells in suspension. Fluorescence was expressed in terms of photon counts per second. Both the direct and indirect fluorescent antibody techniques proved acceptable for assay of surface reactions, yielding values of specific fluorescence as high as eight times those of controls. Fluorescence microscopy of cell populations assayed by spectrofluorometry allowed for simultaneous visual examination of surface antigens.
Comparison of the fluoroimmunoassay with the 51Cr-release test for cytolytic antibody to HSV-induced surface antigens revealed the latter to be the more sensitive, with antibody titres ranging up to four times those detected by fluoroimmunoassay. General correlation between the two assays was found using both rabbit and human sources of antisera.
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Characterization of Virus DNA Synthesized in KB Cells Infected with Two Temperature-sensitive Mutants of Adenovirus Type 5
More LessSUMMARYKB cells were infected with H5ts36 or H5ts125, two adenovirus type 5 (Ad5) mutants with a temperature-sensitive synthesis of virus DNA. Infection was started at the nonpermissive temperature and at 16 h p.i. the temperature was shifted down to the permissive temperature. Shortly after the shift-down H5ts125-infected cells showed an accumulation of purely single-stranded DNA of virus origin, which was not observed in H5ts36-infected cells. This single-stranded DNA has been characterized by hybridization and sedimentation analysis. It was found that the single-stranded DNA was derived from both complementary strands and consisted of short fragments. The observation that the single-stranded DNA accumulates in H5ts125-infected cells under conditions in which the amount of DNA binding protein is reduced, suggests that the DNA-binding protein is not only involved in initiation, but also in elongation of nascent strands.
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Comparisons of Virulence of Influenza Virus Recombinants in Ferrets in Relation to their Behaviour in Man and their Genetic Constitution
D. Campbell, C. Sweet and H. SmithSUMMARYTwo parent viruses, A/Finland/4/74 (H3N2) and A/Okuda/57 (H2N2), virulent and attenuated respectively for man, showed similar differences of virulence in ferrets as judged by estimations of 50% minimal infectious doses (MID50), the level and persistence of nasal infection, the height and duration of pyrexia and the level of lung infection. In ferrets, two recombinant clones, WRL 94 (H3N2) and WRL 105 (H3N2), were almost as virulent as A/Finland and indistinguishable from one another, a result which agreed well with genetic analysis (Hay et al., 1977); the RNA pieces of these recombinants appeared identical and largely derived from the virulent parent (A/Finland).
The results in ferrets did not agree with tests on clone WRL 94 in small numbers of human volunteers but they were not inconsistent with those on clone WRL 105 in larger numbers. It is possible therefore that careful tests in ferrets may yield more accurate information on the virulence of strains than limited tests in human volunteers.
A rapid test for virulence in ferrets is described. It could be used to screen many additional recombinants thereby yielding information on the genetical basis of virulence and indicating possible vaccine strains for more thorough testing in ferrets and in man.
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Enhanced Proliferation of Endogenous Virus in Chinese Hamster Cells Associated with Microtubules and the Mitotic Apparatus of the Host Cell
More LessSUMMARYChinese hamster ovary cells harbour intracytoplasmic virus-like particles of type A which are closely associated with sites of microtubule formation. We report here the enhanced proliferation of these particles and their release at the cell membrane by using either 5-bromodeoxyuridine or dibutyryl cyclic AMP. The extracellular mature particles are similar in morphology to retroviruses of type B. Close association of the type A virus precursors with microtubule organizing centres, i.e. kinetochores, centrioles and basal bodies, and with microtubules per se, is confirmed by studying the effects of the microtubule inhibitors Colcemid and vincristine sulphate. The role of microtubules in the activation and transport of the intracytoplasmic type A particles is discussed.
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Production of Tubular Structures in Vero Cells Infected with Herpes Simplex Virus Type 2: Effects of Ultraviolet Light Irradiation and Antimetabolites
More LessSUMMARYIn order to investigate the nature of tubular structures specifically found in herpes simplex virus type 2 (HSV-2)-infected cells, the multiplication of HSV-2 was studied in Vero cells cultured in the presence of varying concentrations of cytosine arabinoside (Ara-C) and cycloheximide (CH), inhibitors of DNA synthesis and protein synthesis respectively. Ara-C, at a concentration of 60 µg/ml, inhibited the multiplication of HSV-2 by more than 99% and also prevented the appearance of tubular structures and virus particles in the nuclei of infected cells. Nevertheless, the synthesis of virus specific surface antigens of HSV-2-infected Vero cells was not reduced, as revealed by the fluorescent antibody technique. On the other hand, 10 µg/ml of CH inhibited both the appearance of tubular structures and virus particles and the synthesis of virus specific surface antigens by more than 99%. These observations strongly suggest that the appearance of tubular structures is one of the late events in the process of virus multiplication.
To measure the comparative genome size needed to produce membrane antigens, tubular structures and infectious centres, the effect of u.v.-inactivation of HSV-2 on these processes was studied. After u.v.-irradiation, the capacity to induce tubular structures was inactivated at a slower rate than the capacity to form infectious centres, but at a faster rate than the induction of surface antigens. Furthermore, more tubular structures could be induced by u.v.-inactivated virus than by the nonirradiated virus which was diluted to the same infectivity as the u.v.-irradiated virus. These results indicate that expression of the entire genome is not required for the production of tubular structures.
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Physicochemical Properties and Restriction Maps of Simian Adenovirus Type 38 DNA
More LessSUMMARYThe sedimentation constant of simian virus type 38 (SV-38) DNA was estimated to be 31.6S. The intrinsic viscosity of DNA was on average 86.5 dl/g and the length of the molecule determined by electron microscopy was 10.6 µm. The average mol. wt., as determined by sedimentation and viscometry, was 21.5 × 106, which agreed well with the value derived from the length of the molecule (21.4 × 106) and with the value of 21.2 × 106 determined by the relative electrophoretic mobility of the DNA fragments produced by restriction endonucleases EcoR1, SalI and BglII.
The buoyant density of the DNA in caesium chloride and caesium sulphate was 1.7185 and 1.4295 g/ml respectively. The melting temperature of the DNA in 1 × SSC was 93.5 °C. The GC content calculated from ρ and Tm values was 59.3%.
BglII cleaves SV-38 DNA at three sites producing four fragments with mol. wt.: A, 9.3 × 106; B, 5.6 × 106; C, 3.3 × 106; and D, 2.9 × 106. After treatment with EcoR1 and SalI, SV-38 DNA is cleaved into five and six fragments respectively, with mol. wt. for EcoR1 fragments: A, 8.2 × 106; B, 6.5 × 106; C, 4.0 × 106; D, 1.27 × 106; and E, 1.07 × 106, and for SalI fragments: A, 6.5 × 106; B, 5.4 × 106; C, 4.2 × 106; D, 2.8 × 106; E, 2.5 × 106 and F, 0.25 × 106. The sequence of fragments within the SV-38 DNA molecules for BglII was deduced to be BDCA, and for EcoR1 - BCEAD.
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Mouse Hybrid Cell Lines produce Antibodies to Herpes Simplex Virus Type 1
More LessSUMMARYA solid-phase radioimmunoassay procedure has been devised for the assay of antibodies produced in the mouse to herpes simplex virus type 1 (HSV-1). It is based on the adsorption of virus to flexible micro-well plates and uses radio-iodine-labelled rabbit antibody against mouse immunoglobulin to assess antibody binding. Using this assay for screening, cell hybrids have been obtained which yield monoclonal antibody to HSV-1. The hybrids are between spleen cells from hyperimmune mice and an immunoglobulin-non-secreting, azaguanine resistant myeloma cell line (NS-1). From 480 hybrid cell lines initially examined, five stable cell lines were obtained which released HSV-1-specific antibody in vitro and in vivo. Mice carrying transplants of these cell lines yield binding titres in serum of up to 1/25000. Both IgG and IgM antibodies were obtained in this way.
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The Replication of Frog Virus 3 in an Amphibian Cell Line (XTC-2) Derived from Xenopus laevis
More LessSUMMARYFrog virus 3 (FV3) has been demonstrated to replicate in a Xenopus laevis cell line, XTC-2. The virus has been titrated in XTC-2 cells by plaque assay, but the efficiency of plaquing is lower than in minnow or hamster cells. The rate of replication is greater in XTC-2 cells than in BHK cells and this has been correlated with the appearance of virus specific polypeptides in infected cells. Electron microscope observations have shown that FV3 replicates in the cytoplasm of XTC-2 cells and that the virus may leave the cell by budding at the plasma membrane.
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The Physico-chemical Characterization of Bovine Ephemeral Fever Virus as a Member of the Family Rhabdoviridae
More LessSUMMARYThis study of the physico-chemical properties of bovine ephemeral fever virus was initiated to establish whether or not it should be classified as a rhabdovirus. In contrast to the regular bullet-shaped morphology of some rhabdoviruses the virus particles are often cone-shaped or slight variants from bullet-shaped. The virion contains single-stranded RNA sedimenting at 42S and six proteins with mol. wt. of 164, 101, 64, 53, 43 and 29 × 103. The protein P101 is located on the surface of the virus and is glycosylated. It is removed by treatment of the virus particles with trypsin. Protein P64, the nucleoprotein, was found to be a phosphoprotein, like the N protein of rabies virus, whereas in vesicular stomatitis virus NS is the phosphorylated protein.
Virus harvests contain defective-interfering particles. The particles are short cone-shaped forms about one-third the length of the infectious virion and similar in morphology to defective-interfering particles of vesicular stomatitis virus. These particles interfere with the replication of bovine ephemeral fever virus but not with the Indiana serotype of vesicular stomatitis virus. They contain single-stranded RNA sedimenting at 18 to 20S. The particles appear to have a protein composition identical to that found in the virus particle.
The physico-chemical properties of bovine ephemeral fever virus justify its inclusion in the family Rhabdoviridae. The protein composition differs in detail from that found for vesicular stomatitis and rabies viruses, but is similar to that found for Obodhiang and kotonkan, two rabies serogroup viruses isolated from insects in Africa.
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Determinants of Spontaneous Recovery and Persistence in MDCK Cells Infected with Lymphocytic Choriomeningitis Virus
More LessSUMMARYMDCK cells that normally would have been killed by standard lymphocytic choriomeningitis (LCM) virus were saved either by pre- or co-infection with defective interfering (DI) virus. The ability of these spared cells to produce virus-specific antigen (as well as infectious virus) and resist being killed by standard virus challenge was followed for at least 35 days. During this period both types of cultures displayed unique cycling patterns for the above characteristics. The most striking difference was the longevity of the infections. Cultures exposed to DI particles prior to standard virus became persistently infected, while co-infection with both virus types led to spontaneous curing with no trace of the previous infection. The basis for these dissimilar outcomes was traced to a hitherto undetected non-defective LCM virus (called SP) in the DI virus stocks used to preinfect MDCK cells. SP virus was not present in standard virus stocks but arose in long-term persistently infected L cells that had been initially infected with standard virus. Cloned SP virus shared species-specific antigens with standard virus, was resistant to inhibition by DI virus and was capable of turning self-curing cultures into cultures persistently synthesizing both DI and SP virus.
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Protein Synthesis in Bunyamwera Virus-infected Cells
More LessSUMMARYIn Vero cells infected with Bunyamwera virus there is a rapid inhibition of cell RNA and protein synthesis to levels of 30 and 3% respectively of the control rate, both the rate of inhibition and the time lag before its initiation being multiplicity dependent. Using u.v.-irradiated virus, investigation of the mechanism of inhibition of host cell protein synthesis indicates that synthesis of new virus components is required for inhibition to occur. Quantitative comparison of the proteins synthesized in infected cells shows that at higher m.o.i. synthesis of virus, as well as cellular proteins, is inhibited. Bunyamwera virus-infected Vero cells synthesized three virus-specific proteins identified as the structural virion proteins. Nucleoprotein is synthesized predominantly early in infection while the major envelope glycoprotein and the minor glycoprotein are synthesized predominantly late in the infection cycle.
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Effect of Undiluted Passage on the Polypeptides of Measles Virus
More LessSUMMARYMeasles virus induces a large polypeptide (L; mol. wt. 180 K), a large glycopolypeptide (H; mol. wt. 80 K), a nucleocapsid associated polypeptide (P; mol. wt. 70 K), a nucleocapsid polypeptide (N; mol. wt. 60 K), a second glycopolypeptide (F0; mol. wt. 60 K), a matrix or membrane polypeptide (M; mol. wt. 37 K) and a small polypeptide (S; mol. wt. 15 K). The second glycopolypeptide (F0) appears to be cleaved in purified measles virus. Defective interfering particles accumulate during passage of measles virus leading to a decrease in the amounts of virus-specific protein synthesized in infected cells. Even in the best preparations of purified measles virus, host proteins are always detected and these become more predominant in preparations with low infectivity.
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Feline Syncytium-forming Virus: DNA Provirus Size and Structure
More LessSUMMARYAn infectious DNA assay has been used to investigate the size and structure of the genome of feline syncytium-forming virus (FSFV). The dose response between DNA extracted from FSFV-infected cells and plaque number on feline embryo cells followed two-hit kinetics and the mol. wt. of the proviral DNA was estimated as approx. 6 × 106.
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Enzyme-assisted Purification of two Phloem-limited Plant Viruses: Tobacco Necrotic Dwarf and Potato Leafroll
Y. Takanami and S. KuboSUMMARYTobacco necrotic dwarf (TNDV) and potato leafroll (PLRV), viruses which are normally phloem-limited and are transmitted by aphids in the persistent manner, were successfully purified using Driselase, an enzyme that macerates plant tissue. Frozen tissue of Physalis floridana infected with TNDV or PLRV was homogenized in buffer containing Driselase and incubated with shaking. The virus particles were then purified by clarifying extracts with chloroform and n-butanol, precipitation of virus with polyethylene glycol, differential centrifugation and density-gradient sedimentation. The average yield of TNDV purified without the enzyme was 0.5 mg/kg of fresh tissue and of that purified with the enzyme was 4.7 mg. Yield of PLRV purified using the enzyme was 1.3 mg/kg. The sedimentation coefficients of both TNDV and PLRV were s 20, w = 115S. Enzyme treatment had no influence on the infectivity of the viruses, assessed either using tobacco mesophyll protoplasts or using aphids fed through membranes. The enzyme method described here may be useful for purification of other phloem-limited viruses.
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Initial Interaction of Human Fibroblast and Leukocyte Interferons with FS-4 Fibroblasts
More LessSUMMARYHuman FS-4 cells were exposed to human fibroblast interferon for various times and further incubated in the absence of interferon until challenged with vesicular stomatitis virus. Addition of antibody to fibroblast interferon at the time of removal of interferon did not alter the development of the antiviral state. If cells were exposed to interferon for 45 min at either 0 or 37 °C, they developed resistance upon subsequent incubation at 37 °C. However, less resistance developed if the cells were initially incubated at 0 °C. Our results indicate that a single interaction of fibroblast interferon with susceptible cells, either at 0 or 37 °C, is sufficient for the subsequent development of an antiviral state, at least in the short term experiment.
The kinetics of development of the antiviral state were compared with fibroblast and leukocyte interferon. The rise in the degree of antiviral resistance was steeper and maximal levels of resistance were reached sooner when FS-4 cells were incubated with increasing concentrations of fibroblast interferon than with leukocyte interferon. This suggests a greater affinity of fibroblast interferon for these cells.
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Interferon Induction by Viruses. II. Sindbis Virus: Interferon Induction Requires One-Quarter of the Genome – Genes G and A
More LessSUMMARYWe have measured the amounts of interferon formed by chick cells ‘aged’ in vitro in response to different amounts of infectious wild-type Sindbis virus. Our results suggest that one plaque-forming unit is enough to induce maximum interferon formation. With higher m.o.i. the yield of interferon is less.
To inactivate the interferon-inducing activity of Sindbis virus, four times more u.v.-radiation was needed than to inactivate the infectivity of the virus. This suggests that only 25% of the virus genome need be intact in order to induce interferon. Temperature-sensitive Sindbis virus mutants from the three RNA+ complementation groups, C, D and E, gave rise to interferon in chick cells incubated at a non-permissive temperature. Similarly, mutants from two of the RNA− groups, B and F, gave rise to interferon, but not mutants from groups G and A.
We conclude that no pre-formed inducer of interferon is present in Sindbis virus. It appears, however, that genes G and A represent a special one-quarter of the genome which must be functional in order to synthesize an interferon-inducing moiety. We suggest that this moiety is a double-stranded RNA molecule formed after synthesis of a segment of RNA complementary to the genome.
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Replication of Two Influenza Virus Strains and a Recombinant in HEF and LEP Cells
More LessSUMMARYThe replication of influenza viruses A/NWS-D, A/WS-MK and their r12 recombinant in human embryo fibroblast (HEF) and human diploid fibroblast (LEP) cell lines was studied. In HEF cells virus NWS-D and recombinant r12 induced synthesis of virus-specific macromolecules and produced infectious virions; virus WS-MK induced synthesis of virus complementary RNA (cRNA), virion RNA (vRNA), proteins, RNP and non-infectious virions, but haemagglutinin cleavage was impaired and the virions formed contained uncleaved haemagglutinin. In LEP cells, infectious virions were formed only by virus NWS-D; viruses WS-MK and r12 induced synthesis of virus cRNA, vRNA, proteins and RNP; virus r12 had the haemagglutinin cleaved, whereas in virus WS-MK this process was impaired; neither virus WS-MK nor r12 was capable of forming virions. Analysis of the recombinant r12 genome showed that it had only inherited a single gene from NWS-D, the one coding for neuraminidase, having inherited all others (P1, P2, P3, HA, NP, M, NS) from WS-MK. The data obtained suggested that the inability of virus WS-MK to form infectious virions in HEF cells is due to the character of its neuraminidase, which is incapable of participating in haemagglutinin cleavage. The deficient reproduction of this virus in the other host-cell system (LEP) is apparently associated with some characteristics of another protein (other proteins) of this virus.
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Rotavirus Polypeptides
More LessSUMMARYRotavirus infected monkey kidney cells (LLC-MK2) have been labelled with 35S-methionine in the presence of actinomycin D. The cells have been lysed with SDS and the polypeptides separated by discontinuous polyacrylamide gel electrophoresis. Rotavirus polypeptides began to appear 4 to 5 h p.i.; incorporation was maximum at 8 h, but all the polypeptides were still being made 15 to 18 h p.i. Tissue culture adapted calf rotavirus particles were labelled with 35S-methionine and the polypeptides compared with cell associated rotavirus polypeptides. There were four inner coat, four outer coat and three non-structural polypeptides. Several of the outer coat polypeptides have altered mol. wt. on maturation. The polypeptides of rotavirus from seven species (human, pig, calf, lamb, mouse, foal and rabbit) have been compared and their mol. wt. calculated. The polypeptides fell into the same relative groupings for each virus, but there were variations in the mol. wt. of most comparable polypeptides. The polypeptides of tissue culture adapted and non-adapted calf rotavirus from the same original isolate varied only in one of the non-structural polypeptides.
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Expression of Retrovirus-associated 8S RNA in Mammalian Cells
More LessSUMMARYA comparative study of the expression of retrovirus-associated 8S RNA was made in different mammalian cells. This RNA is found in cultured cells from all mammalian species analysed but its expression varies. An increase of 8S RNA is observed in sarcoma virus-transformed cells as compared to control uninfected cells or cells infected with leukaemia virus. No increased quantities of 8S RNA were detected in cells transformed by SV40 or by methylcholanthrene. These data show that the level of 8S RNA was augmented following transformation by sarcoma viruses.
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Acute and Latent Infection of Sensory Ganglia with Herpes Simplex Virus: Immune Control and Virus Reactivation
SUMMARYThe role of antiviral antibody in controlling the acute and latent phases of herpes simplex virus (HSV) infection in sensory ganglia of mice was studied in vitro and in vivo. Organ cultures of ganglia inoculated in vitro with HSV produced infectious virus for at least 3 weeks. In the presence of antiviral antibody, the titre of virus was markedly reduced, but the infection was not eliminated. Similarly, passive administration of antibody to HSV-infected immunodeficient (nude) mice reduced the virus titre but did not eliminate the acute phase of the ganglionic infection. Suppression of the cell-mediated immune response in latently infected immunocompetent mice by treatment with cyclophosphamide and/or X-irradiation resulted in reactivation of HSV in up to 70% of the animals. Reactivation was demonstrated by recovering infectious virus in cell-free homogenates of ganglia and eye globes and by finding virus antigens in ganglia by immunofluorescent staining. Reactivation occurred both in vitro and in vivo in the presence of high concentrations of neutralizing antibody. It is concluded that antibody alone is not sufficient to eliminate the acute phase of the ganglionic infection and that cytotoxic agents known to suppress the host’s cellular immune response can reactivate virus in the presence of neutralizing antibody.
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Evidence for Herpes Simplex Virus Type-selective Receptors on Cellular Plasma Membranes
More LessSUMMARYHerpes simplex virus type 1 (HSV-1) interfered with the adsorption of subsequently added homotypic but not heterotypic HSV, suggesting that the cellular receptors involved were type-selective. Both infective and u.v.-irradiated virus could block the attachment of virions to cellular surface receptors. The adsorption rate was studied by assaying non-adsorbed infective virus remaining in the fluid medium and cell-associated 3H-thymidine labelled HSV, and HSV mutants assayed in presence of phosphonoformic acid (PFA). The adsorption profiles indicated that GMK AH-1, Vero and SIRC cells all exhibited more HSV type 1-than type 2-selective receptors while HeLa S3 cells displayed more receptors with affinity for type 2 than for type 1. On HEp-2 and human embryonic lung cells HSV type 1- and type 2-selective receptors were about equally represented.
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Production of Human Lymphoblastoid Interferon by Namalwa Cells Cultured in Serum-free Media
More LessSUMMARYThe human lymphoblastoid cell line, Namalwa, can be cultured in serum-free media to cell densities of 3 to 4 × 106 cells per ml. These cultures produce up to 10000 units of interferon per ml when induced with Newcastle disease virus, strain B1. Maximum accumulation of interferon was obtained at approx. 13 h post-induction.
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Characterization of Interferon Messenger RNA from Human Lymphoblastoid Cells
More LessSUMMARYAfter treatment with Sendai virus, Namalwa cells form large amounts of interferon. RNA extracted from treated whole cells or from their polysomes was injected into Xenopus laevis oocytes and the interferon formed was titrated. The results show that the amount of interferon mRNA was maximal by 9 h after treatment of the cells with Sendai virus and then declined. Sucrose gradient centrifugation of the mRNA gave substantial purification and showed that its size was 12 S.
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Comparison of the Antigens Produced by Foamy Virus in a Cytolytic and a Persistent Infection of HEp2 Cells
More LessSUMMARYThe antigens from cytolytic infections of HEp2 cells by type I simian foamy virus produced two multicomponent precipitation lines when tested by immunodiffusion with the homologous hyperimmune rabbit antiserum. The antigens obtained from a non-productive infection of MK5 virus in HEp2 cells produced only those precipitation lines which corresponded with the inner lines obtained from the cytolytic infection. Similarly, hyperimmune rabbit antiserum against antigens extracted from the persistent infection lacked the antibody which was responsible for the outer lines of precipitation. Indirect immunofluorescence with acetone-fixed and unfixed cells using the homologous and heterologous sera confirmed the absence of antigens in the persistent infection and showed that an antigen is produced in the persistently infected cells which is either absent or present in very small amounts in cytolytically infected cells. Neutralization experiments and ether treatment suggested that the missing antigens in the persistent infection were the envelope components of foamy virus. It is proposed that the persistent infection has properties in common with some infections by RNA tumour viruses.
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Ribonuclease Activity of Preparations of Human Lymphoblastoid Interferon
More LessSUMMARYCrude human lymphoblastoid interferon has less ribonuclease activity than equivalent primary leukocyte interferon and ribonuclease was eliminated when it was purified. The methods used differed from those that had failed to eliminate similar activity from leukocyte interferon. This result makes it unlikely that exogenous ribonuclease plays a major role in the antiviral action of interferon preparations.
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Loss of Proviral DNA Sequences in a Revertant of Kirsten Sarcoma Virus-transformed Murine Fibroblasts
More LessSUMMARYA previously described revertant cell line (K-BALB SR1212), derived as a single cell clone from a clonal line of murine fibroblasts (K-BALB) transformed by a nonproductive infection with the Kirsten strain of murine sarcoma virus, has normal morphology and growth kinetics and, unlike the transformed parent cell line, lacks a sarcoma virus that can be rescued. We report here that this reversion correlates with low to undetectable levels of expression of cellular Ki-MSV-specific RNA and a reduction of proviral sequences in the cell DNA to a level equivalent to that found in the uninfected BALB cells with a normal phenotype. The data indicate that phenotypic reversion has occurred as a consequence of the loss of part or all of the sarcoma provirus, either by chromosomal rearrangement or provirus excision.
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Further Studies of the Antigenic Properties of H3N2 Strains of Influenza A Isolated from Swine in South East Asia
More LessSUMMARYH3N2 strains of influenza A isolated from swine in Hong Kong were compared with human strains of H3N2 influenza A variants in reciprocal HI tests using ferret sera. One isolate from swine was indistinguishable from A/Hong Kong/68, one set of viruses isolated in 1976 and 1977 was most related to A/Hong Kong/68 but was not identical to it, two isolates from 1976 were ‘bridging strains’ that cross-reacted equally with the contemporary variants A/Victoria/3/75 and A/Texas/1/77, similarly to a small number of recent human isolates, and two isolates from 1977 were similar to A/Victoria/3/75. These general relationships were supported by neuraminidase inhibition tests. The findings confirm and extend previous results indicating that swine may be a reservoir of old and novel variants of influenza A H3N2 strains related to those that infect man.
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Protection of Mice Against Infection with Wild-type Mengo Virus and an Interferon Sensitive Mutant (IS-1) by Polynucleotides and Interferons
More LessSUMMARYSingle-stranded polynucleotide preparations [tRNA, poly(rI) plus poly(ho5C)-copolymer] which protect mice against picornavirus infections without inducing interferon, protected mice equally against infection with an interferon-sensitive mutant (IS-1) of Mengo virus and with wild-type virus (IS +). Poly(rI).poly(rC) and mouse macrophage interferon [i.e. serum from mice treated with poly(rI).poly(rC)] protected mice equally against infections with the two viruses, but fibroblast interferon protected better against infection with the interferon-sensitive mutant than with the wild-type virus. These and other results indicate that: Mengo virus has a genetic locus affecting sensitivity to fibroblast but not macrophage interferon; these two types of interferon have different mechanisms of action against Mengo virus infections in mice; Mengo virus genes controlling sensitivity to fibroblast interferon may modulate disease since infection in vivo induces only fibroblast interferon; the antiviral activity of the single-stranded polynucleotides is unlikely to be mediated by induction of either macrophage or fibroblast interferon.
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Production of Vesicular Stomatitis Virus with Low Infectivity by Interferon-treated Cells
More LessSUMMARYIn cultures of Ly cells treated with 10 or 30 reference units/ml of mouse interferon there was a 30 to 200 times reduction in the production of infectious vesicular stomatitis virus (VSV); virus particle production, as measured by VSV particle associated virus RNA, virus protein, and virus transcriptase, was inhibited by, at most, six times. These results suggested that interferon-treated cells produce VSV particles with low infectivity and resemble the findings in interferon-treated cells infected with murine leukaemia viruses.
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Orthopoxvirus Strains Defective in Surface Antigen Induction
Hiroko Amano, Y. Ueda and I. TagayaSUMMARYVarious strains of vaccinia, variola, whitepox, monkeypox and cowpox viruses were examined for their capacity to induce a specific early antigen detectable on the surface of infected cells. The Elstree strain of vaccinia, two strains of variola minor and white variants of cowpox and monkeypox viruses lacked the capacity to induce the antigen. Variation of the parent cowpox and monkeypox viruses to white variants was always accompanied by the loss of the antigen-inducing capacity.
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Volume 13 (1971)
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Volume 12 (1971)
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Volume 11 (1971)
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Volume 10 (1971)
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Volume 9 (1970)
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Volume 8 (1970)
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Volume 7 (1970)
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Volume 6 (1970)
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Volume 5 (1969)
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Volume 4 (1969)
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Volume 3 (1968)
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Volume 2 (1968)
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Volume 1 (1967)