Characterization of the immediate-early functions of pseudorabies virus

The immediate-early transcripts of pseudorabies virus have been located in a region of the genome situated internally within the inverted repeat between map positions 0.99 and 0.95. A single immediate-early transcript (approximately 6 kb) can be detected both in the cytoplasmic and nuclear fractions of infected, cycloheximide-treated cells. Analysis of the proteins synthesized after removal of cycloheximide from infected cells or after translation in vitro of the RNA isolated from these cells revealed the presence of a single protein (180K) not present in similarly treated, uninfected cells. That this is a virus protein and is specified by the immediate-early region of the genome was shown by selection and translation of mRNA hybridizing with virus DNA from the appropriate region of the genome. The effects of infection of cells with a temperature-sensitive mutant (tsG1) defective in the 180K protein were studied. At the nonpermissive temperature only immediate-early RNA was transcribed and only one virus protein, the 180K protein was synthesized. Inhibition of cellular protein and DNA synthesis was also observed. After shift down of tsG1-infected cells from the nonpermissive to the permissive temperature at 3 hr post infection, a transition to early RNA transcription occurred. However, if the shift down was delayed until 5 hr post infection, transcription of the virus genome was completely inhibited and an abortive infection ensued. Shift of the mutant-infected cells from the permissive to the nonpermissive temperature resulted in a decrease in the rate of accumulation of early and late transcripts, and a resumption of the synthesis of immediate-early RNA and protein. From these as well as from previous results, it is concluded that pseudorabies virus codes for a single multifunctional immediate-early protein which is essential for the transcription of immediate-early to early RNA and is required for the continuous transcription of early (and late) RNA. The immediate-early protein is also self-regulatory; the presence of the functional immediate-early protein represses the transcription of its RNA. In addition, the immediate-early protein of pseudorabies virus appears to play a direct role, under certain conditions, in the inhibition of cellular macromolecular synthesis.

[Developing an avirulent mutant of Aujeszky's disease virus using the effect of 5 bromodesoxyuridine]

Chemicals are being used increasingly in the preparation of vaccines. Thus, an effective vaccine (MK25) against Aujeszky's Disease showing stable genetic characteristics was produced by having 5 iododesoxyuridine exert its action on a particular strain of virus. 5 Bromo-desoxyuridine also has an inhibitory effect on the synthesis of DNA viruses. The development of a new mutant of Aujeszky's Disease virus using this agent is reported. The resulting mutant, MK35, was found to be biologically stable, non-pathogenic for white mice, rabbits, sheep and piglets and, in addition, produced stable immunity in piglets, sheep and rabbits within four days after injection of this mutant.

Photodynamic inactivation of pseudorabies virus with methylene blue dye, light, and electricity

Pseudorabies virus was photoinactivated with a combination of methylene blue dye, light, and electricity. Viral suspensions were mixed with variable amounts of methylene blue dye and then were placed in a current source apparatus. Total inactivation of pseudorabies virus (1.7 X 10(6) 50% tissue culture infective doses per ml) was achieved with constant mixing, a methylene blue dye concentration of 10(-4) M, and an electrical current of 12 microA for 12 min.

Combined effect of acyclovir and amphotericin B on the replication of pseudorabies virus in BHK-21 cells

Acyclovir, known as an antiherpetic agent, showed an inhibitory effect on the propagation of pseudorabies virus in BHK-21 cells. The antiviral effect of acyclovir was observed by plaque reduction, as well as by the inhibition of the virus-stimulated uptake of thymidine by BHK-21 cells. Amphotericin B potentiated the antiviral activity of acyclovir. The optimal concentrations of polyene antibiotic expressing the potentiating effect were lower than required for the induction of K+ leakage from the cells. There was no evident amphotericin B-induced stimulation of thymidine incorporation into infected BHK-21 cells. The model presented may be useful to study the potentiation phenomenon of polyene macrolide antibiotics.

[Antiviral activity of modified RNAses]

Antiviral activity of pancreatic RNase and RNase from Act.rimosus modified by various dextran derivatives was studied with respect to aphthosa and Ayzeku disease viruses. Antiviral activity of pancreatic RNase modified by dextran m-aminobenzylhydroxymethyl ether was lower than biological activity of RNase from Act.rimosus modified by the same dextran. Antiviral activity of pancreatic enzyme modified by dialdehyde dextran also changed insignificantly. Modification by dextran hydroxyethylsulfonylanisole ether, dextran m-aminobenzylhydroxymethyl ether in the presence of pyridine or dextran sulfate resulted in a more pronounced increase in antiviral activity of pancreatic enzyme. Therefore, biological activity of the modified nucleases depended on the nature of the enzyme and dextran modifying it.

[Electron microscopic study of the in vitro effect of dipyridamol on the pseudorabies virus]

Dipyridamole at a concentration of 50 microM/ml displays no activity on adsorption and penetration of pseudorabies virus in chicken embryonal cells. Furthermore, first stages of virus replication take place within the nucleus, whereas incomplete virus cores defective in DNA content are found within the nucleoplasm at times when the regular viral replication has been finished in controls. Defective pseudorabies virus particles lacking in DNA-content of the core, can be observed at the end of normal replication time. Consequently, the antiviral activity of dipyridamole may be due to blocking of the synthesis or of the incorporation of infectious viral DNA into the virus core.

[On the biological action of transition metal complexes. 3. About the antiviral activity of cis-dichloro diammine platinum (II) (author's transl)]

The coordination compound cis-dichlorodiammineplatinum(II) (cis-DDP) was shown by Rosenberg et al. (17) to exhibit antitumour activity. Several authors have indicated limited virustatic properties of cis-DDP against bacterial, oncogenic, avipox and paramyxo viruses. In our investigations, cis-DDP significantly showed an antiviral action in vitro against enveloped DNA and RNA viruses, such as vaccinia, pseudorabies, herpes simplex type 1, Newcastle disease, influenza A/fowl plague, influenza A/Victoria 3/75, influenza A/Jena 48/78, influenza B/Johannesburg and vesicular stomatitis viruses. Out of the group of nonenveloped viruses, adenovirus type 4 and 5 were inhibited, whereas no inhibition against naked cardiovirus Mengo could be estimated. The antiviral action was proved against extracellular virus by dialysis experiments with vaccinia virus and also during the replication cycles of enveloped viruses. In trials with cell-free viruses the plaque reduction of all sensitive viruses mentioned above amounted to 100 per cent in comparison to the untreated controls caused by virus inactivation with loss of infectivity in contact with several concentrations of cis-DDP. On the other hand, the addition of the compound for one hour only immediately after infection or up to 8 hrs later produced a complete depression of further multiplication of vaccinia virus. Likewise, the replication of influenza virus A/FPV or VSV was inhibited whereas the multiplication of adenoviruses was not influenced in a comparable manner.

[On the biological action of transition metal complexes. 4. The antiviral activity of metallocene dichlorides of titanium and molybdenum (author's transl)]

In view of the fact that bis cyclopentadienyl metal dihalides are known to be anti-tumour drugs, we have investigated the antiviral activity of this type of coordination compounds. Bis cyclopentadienyl titanium dichloride (a) has shown significant antiviral efficiency in vitro against representatives of a nuber of enveloped DNA and RNA viruses. Inhibition of orthopoxvirus (vaccinia), herpes virus (pseudorabies), orthomyxoviruses (influenza A/fowl plague [FPV], influenza A/Victoria 3/75, influenza A/jena 48/78 and influenza B/Johannesburg), paramyxovirus (Newcastle disease [NDV]) and rhabdovirus (vesicular stomatitis [VSV]) was observed after direct contact with the compound under loss of infectivity up to 100%. Regarding the group of unenveloped viruses only adenovirus type 4 became influenced but not type 5. No antiviral activity could be found against the cardiovirus Mengo. The compound bis cyclopentadienyl molybdenum dichloride failed to show an antiviral action versus vaccinia, influenza A/FPV and influenza viruses B/Johannesburg. Application of the inhibitor (a) during the replication of vaccinia and influenza viruses A/FPV in cell cultures produced an additional effect of inhibition of virus multiplication. On the other hand, adenovirus type 4 and VSV replication was not affected by titanocene dichloride.

Benzoxazolone-5-sulphonanilides, 1-(benzoxazolone-5'-sulphonyl)-benzotriazoles and 4-hydroxy-3,2'-diaminobenzenesulphonanilides with antiviral activity

benzoxazolone-5-(2'-nitro)-sulphonanilides were synthesized by acylation of o-nitroanilines with benzoxazolone-5-sulphochloride or 3-methylbenzoxazolone-5-sulphochloride. The nitro group in these compounds was subjected to reduction and the resulting amino derivatives were cyclysed to yield the corresponding 1-(benzoxazolone-5'-sulphonyl)-benzotriazoles. Decyclization of the oxazolone cycle of benzoxazolone-5-(2'-amino)-sulphonanilides resulted in 4-hydroxy-3,2'-diaminobenzenesulphonanilides. In vitro testing of the antiviral activity of the compounds obtained during successive synthetic steps revealed that some of them exhibited marked antiviral effect against toga, orthomixo, oncorna and herpes viruses.

[On the biological action of transition metal complexes. 1. The antiviral activity of palladium aminopyridin-complexes (author's transl)]

Some aminopyridine complexes of palladium and PdCl2 showed an antiviral in vitro activity against enveloped DNA and RNA viruses such as vaccinia virus, pseudorabies virus, NDV and FPV. In contrast, naked RNA virus as mengovirus was not affected. The compounds were compatible for chicken embryo as well as FL cells in concentrations of 100-250 microM. The therapeutical index calculated from the maximally tolerated dose and the concentration causing a 50 per cent plaque reduction was determined with more than 45 for vaccinia virus, for example.

[Comparative study of the antiviral activity of pancreatic and microbial RNAse]

The efficacy of pancreatic RNase with microbial enzymes (RN-ases) of Act. rimosus and Bacillus intermedius) was studied comparatively in vitro in a transplantable cell culture of the swine embryokidney with respect to the aphthosa virus (AV) and the virus of the Aujeszky disease (VAD). The VAD proved to be most sensitive to RNases. RNase of Bac. intermedius showed the highest antiviral efficacy. The enzymes were active in vivo, when the albino mice and newborn rabbits were infected with the AV, the RNase of Bac. intermedius being also most active in this case.

Laboratory evaluation of selected disinfectants as virucidal agents against porcine parvovirus, pseudorabies virus, and transmissible gastroenteritis virus

Of a variety of disinfectants evaluated, only sodium hypochlorite and sodium hydroxide inactivated porcine parvovirus (PPV) after a 5-minute incubation period. After the same incubation time, pseudorabies and transmissible gastroenteritis viruses were inactivated by all of the disinfectants tested. When the incubation time was increased to 20 minutes, 2% glutaraldehyde and a double-strength concentration of a commercial formaldehyde preparation also inactivated PPV. Formaldehyde vapor and ultraviolet radiations inactivated PPV also, but relatively long exposure times were required.

Sensitivity of viruses to phosphorylated 9-(2-hydroxyethoxymethyl)guanine revealed in TK-transformed cells

Vaccinia and pseudorabies viruses are resistant to ACV [Acyclovir or 9-(2-hydroxyethoxymethyl)guanine] in normal cells. However, both viruses are sensitive in thymidine kinase (TK)-transformed cells in which the resident HSV-specific TK is able to phosphorylate the drug. This demonstrates the sensitivity of these viruses to phosphorylated ACV and suggests a wider antiviral activity for the phosphorylated drug.

Differentiation of vaccine strains and field isolates of pseudorabies (Aujeszky's disease) virus: trypsin sensitivity and mouse virulence markers

Five cloned virulent North American field isolates and 2 European vaccine strains of pseudorabies (PR) viruses were compared by their sensitivity to trypsin and their virulence for mice. Marked differences in trypsin sensitivity were detected between and among virulent and vaccine PR viruses. These differences were distinct enough to characterize a virus as either sensitive or resistant to trypsin. This test also differentiated 2 virulent viruses which were previously shown to be indistinguishable on the basis of their sensitivity to thermal inactivation. Mouse virulence was evaluated by comparing the mean times-to-death of mice infected with individual viruses. Three distinct levels of virulence were observed. The two vaccine viruses were differentiated from each other and from virulent virus. Mice infected with the vaccine viruses required 23 to 118 hours longer to die than mice which were infected with virulent virus. A significant difference of 5.6 hours (P less than .005) was also detected between mice infected with 2 different field viruses. When viruses were described according to their marker profiles, 5 of 6 possible combinations were revealed. The 2 vaccine viruses could be described by separate profiles and virulent viruses could be described by 1 of 3 profiles.

The effect of antibody on latent pseudorabies virus infection in vitro

Cytosine arabinoside (Ara C) inhibited the synthesis of pseudorabies virus when Vero cells were infected at a multiplicity of infection of 0.0001-0.05 PFU per cell. On removal of Ara C, infectious virus reappeared after a latent period of 3-5 days. The activation of latent virus was not influenced by elevating the temperature to 40 degrees C at the time of Ara C removal but it was prevented by antiviral antibody. When antiviral IgG was added into the culture fluid of cells either during the incubation with Ara C, or after removal of the inhibitor, the number of infectious centres was reduced to about 10%. The role of antiviral IgG in the maintenance of latency is discussed.

Comparison of pseudorabies virus inactivated by bromo-ethylene-imine, 60Co irradiation, and acridine dye in immune assay systems

Pseudorabies virus infections among animals, especially swine, have become prevalent in the United States in the past few years. The disease in swine is now economically important. Test systems and antigens are being developed for use in control and disease suppression efforts. Pseudorabies virus was inactivated by three methods: chemically, with bromo-ethylene-imine; physically, with 60Co irradiation; and chemically and physically, with 3,9-diaminoacridine dye followed by exposure to white visible light. The antigenicities of the preparations were determined in the presence of specific antibody in immunodiffusion tests and through immunoelectrophoresis. The latter technique permitted quantitation of either antigen or antibody. In the electrophoretic patterns, the antigenic mass in bromo-ethylene-imine preparations was estimated to be 42 mg/ml, the same as in the untreated control material. After 60Co irradiation, 22 mg/ml was present, in comparison with 50 mg/ml in the untreated control antigen. In contrast, 67 mg/ml was present in the acridine dye-light-treated preparation, in comparison with 58 mg/ml in the untreated control material. A possible explanation for the acridine dye-light-treated preparation values is that photodynamic inactivation interferes with viral maturation during the replicative cycle within cells, with a resulting production of a greater amount of antigen, at least some of which is in the form of defective particles.

Antiviral activity of dipyridamole derivatives

Among 46 novel pyrimido [5.4-d] pyrimidine derivatives, 26 compounds were found to exhibit antiviral activity as revealed in a test programme against Mengo, Coxsackie B1, fowl plague, vaccinia and pseudorabies viruses, as concerns inhibition of plaque formation and of infectious virus yield. Attempts to disclose structure-activity relationships by discriminant analysis pointed to a possible importance of hydrophobic substitution for the antiviral effectiveness against Mengo virus of the derivatives investigated.

[Experimental study of the antiviral properties of antibiotic 6734-21]

The effect of antibiotic 6734-21 on the viruses of variolovaccine, Herpes simplex, influenza and classical avian plague was studied on various experimental models. Antibiotic 6734-21 inhibited development of the variolovaccine virus in the tissue culture, in chick embryos, in rabbits with variolovaccine infection, as well as the development of the viruses of Herpes simplex, Aueski, and Newcastle diseases in the tissue culture. It had a virulicidic effect on the viruses of variolovaccine, influenza and classical avian plague.

Stability of pseudorabies virus during freeze-drying and storage: effect of suspending media

The effect of suspending media on the stability of pseudorabies virus upon freeze-drying and subsequent storage was studied. A variety of media was tested, including: sodium glutamate; sucrose; lactose; lactalbumin hydrolysate; peptone; a combination of sucrose, dextran, and glutamate; and various combinations of sucrose, glutamate, and potassium phosphates. Suspending media containing glutamate, either alone or in combination with sucrose and either dextran or phosphates, afforded the greatest degree of protection during the freeze-drying process and upon storage. Some possible functions of these additives in preventing injury to the virus during freezing and drying have been suggested.

Fluorosugars inhibit biological properties of different enveloped viruses

Both 2-deoxy-2-fluoro-D-glucose and 2-deoxy-2-fluoro-D-mannose were found to be potent inhibitors of the synthesis of infectious Semliki forest and fowl plague virus in chicken embryo cells and also of pseudorabies virus grown in rabbit kidney cells. It was found that the pseudorabies virus-mediated cell fusion and the synthesis of functional hemagglutinin of fowl plague virus were blocked. In all cases the 2-deoxy-2-fluoro-D-mannose-caused inhibition was stronger than the 2-deoxy-2-fluoro-D-glucose- or 2-deoxy-D-glucose-mediated blocks. Studies on the virus-specified proteins from Semiliki forest virus-infected cells grown in the presence of the inhibitors show that the target of the fluorosugar action, parallel to the well-studied effects of 2-deoxy-D-glucose, is the glycoprotein biosynthesis.

The effect of temperature and urea on virulent and attenuated strains of pseudoabies virus

Out of 10 virulent strains of pseudorabies virus (PRV), 9 proved to be resistant and 3 out of 4 attenuated strains were sensitive to the temperature of 53 degrees C. No differences were found between attenuated and virulent strains of PRV in their rate of inactivation of 2 M urea; its inactivating effect was enhanced by increasing the temperature. The t (effect of temperature) and u (effect of urea) markers proved unsuitable for a sufficient characterization of PRV strains.

Streptovirudins, new antibiotics with antibacterial and antiviral activity. I. Culture taxonomy, fermentation and production of streptovirudin complex

A new antibiotic complex has been isolated from cultures of Streptomyces strain No. JA 10124. On the basis of taxonomic studies, the producing microorganism is described as Streptomyces griseoflavus (Krainsky, 1914) Waksman et Henrici, 1948, subsp. thuringiensis subsp. nov., type strain JA 10124. The antibiotic complex, designated as streptovirudin, was isolated from extracts of both mycelium and culture filtrate. It is a white amorphous material which consists of ten closely related components including streptovirudins A, B, C, D and E. The streptovirudin complex exhibits antibiotic activity against Gram-positive bacteria, mycobacteria, and various DNA- and RNA-viruses.

Streptovirudins -- new antibiotics with antiviral activity. The antiviral spectrum and inhibition of Newcastle disease virus in cell cultures

Streptovirudins are new antibiotics isolated as a mixture of several structurally related compounds from fermentations of Streptomyces griseoflavus (Krainsky) Waksman et Henrici var. thuringensis JA 10124. They possess antiviral activity against RNA and DNA viruses cultivated in chick embryo cells, namely Sindbis, fowl plague, Newcastle disease (NDV), pseudorabies, vaccinia and sheep abortion viruses. The naturally formed streptovirudin complex, in concentrations of 20-2.5 mug/ml inhibited the viral cytopathic effect and caused 100 percent plaque reduction. Mengo, Coxsackie B1-B5, ECHO 30 and 33, and polio (wild and attenuated types 1, 2, and 3) viruses grown in FL cells were not sensitive in the agar-diffusion plaque-inhibition test. The antibiotics failed to show a direct virucidal effect on the NDV virion itself or to influence virus adsorption and penetration processes. Addition of streptovirudin complex during a one-step growth cycle of NDV from 0-4 hours after virus adsorption resulted in complete suppression of virus yield. The antibiotic complex consists of two main groups: I - A1, B1, C1, D1, E1 and II - A2, B2, C2, D2, E2, each of which possess antiviral activity.

Synergic action of distamycin A and hydroxyurea on the reproduction of DNA viruses in cell cultures

The antiviral activity of the combination of distamycin A (DA) Pand hydroxyurea (HU) on the reproduction of vaccinia and pseudorabies viruses was investigated. The drug combination exerted a significant synergic inhibitory effect on the vaccinia virus yield and on the plaque formation in chick embryo cells. Similar experiments on pseudorabies virus showed an additive effect. The possible mechanism of the mutual enhancement of the antiviral activity is discussed.