Synthesis and Antiviral Evaluation of Analogs of Adenosine-N 1-Oxide and 1-(Benzyloxy)Adenosine

Abstract

The activity of a series of compounds related to adenosine-N ¹-oxide (1) and 1-(benzyloxy)adenosine (42) against vaccinia virus has been determined both in vitro and in a vaccinia mouse tailpox model. Significant activities have been found both in vitro and in vivo for a number of the synthetic compounds.     

Adenovirus E1a interferes with expression of vaccinia viral genes

The 12S and 13S cDNAs of the oncogene E1a encoded by the early region of adenovirus 12 (Ad12) were overexpressed using the T7/encephalomyocarditis (EMC)/vaccinia hybrid expression system. The E1a proteins were stable for at least 12 h in monkey epithelial BSC1 cells. The E1a proteins were recognized by a rabbit polyclonal antibody and displayed phosphorylation patterns similar to those displayed by the E1a proteins expressed in Ad12-transformed cells. Expression of E1a proteins by recombinant vaccinia virus led to inhibition of vaccinia viral protein synthesis which was observed as soon as 6 h after infection. This suppression was mediated by both the 12S and the 13S products of Ad12E1a and to a somewhat lesser extent by the 13S product of Ad2E1a. The inhibition of vaccinia virus gene expression resulted in enhanced survival of vaccinia virus-infected cells. These results suggest that the proteins encoded by the E1a sequester a viral or a cellular product(s) that is essential for the expression of vaccinia virus-encoded genes.     

Studies on Antiviral and Antitumor Antibiotics

Antiviral activity of geodin obtained from a soil fungus was studied employing the Newcastle disease virus—chick embryo fibroblasts culture system. In a plate assay method, the minimum inhibitory concentration was about 9 μg/ml and cytotoxicity was detected at 36 μg/ml. Hemagglutinin synthesis was completely suppressed in a tube assay method when 4 μg/ml of geodin was added after the infection (50 plaque forming units/cell), but at this concentration cytotoxic effect of the antibiotic was observed. At sub-inhibitory concentrations, a dose response was shown in the yield of hemagglutinin and infective virus at 16 hr after the infection, and at this time cytopathic effect was partially or completely arrested depending on the antibiotic concentrations even when complete inhibition of hemagglutinin synthesis was not observed. Geodin did not have any effect on the activity of free virus particles and their adsorption to host cells. The inhibition site of geodin exists somewhere between viral adsorption and viral maturation.     

Synthesis and Antiviral Activities of New Pyrazolo[4,3‐c]quinolin‐3‐ones and Their Ribonucleoside Derivatives

Several new pyrazolo[4,3‐c]quinolin‐3‐one ribonucleosides (5a–g) and their corresponding heterocycle moieties (3a–g) were synthesized and evaluated against vaccinia virus (VV) and herpes simplex virus type 1 (HSV‐1). The derivatives 3c and 3d showed modest inhibitory activity against vaccinia virus reaching 70% at a concentration of 100 µM. All heterocyclic compounds (3a–f) showed a modest inhibition against HSV‐1, reaching the maximal inhibitory effect around 20–30%. The antiviral effects of most of the pyrazolo[4,3‐c]quinolin‐3‐one ribonucleosides (5a–f) on VV and HSV were not impressive.     

Sensitivity of Ribonucleic Acid and Deoxyribonucleic Acid Viruses to Different Species of Interferon in Cell Cultures

Although two deoxyribonucleic acid (DNA) viruses, pseudorabies (PsRV) and vaccinia, are as susceptible as a ribonucleic acid (RNA) virus, vesicular stomatitis (VSV), to interferon when tested in chicken or mouse cells, they are refractory to inhibition in interferon-treated primary rabbit kidney cells and in a continuous line (RK-13) of rabbit kidney cells. Superinfection with VSV of RK-13 cells first infected with PsRV completely blocks the replication of PsRV with no effect on VSV yield. When the same experiment is carried out in RK-13 cells pretreated with 1,000 units of interferon, VSV replication is inhibited, which permits PsRV to replicate normally. These findings demonstrate that in the same cell one virus (PsRV) can be refractory to interferon and a second virus (VSV) can be susceptible. These experiments show that rabbit kidney cell cultures are deficient in the synthesis of resistance factors active against the DNA viruses tested and raise the possibility that separate resistance factors may exist for RNA and DNA viruses. In the case of sequential infection of interferon-treated RK-13 cells with vaccinia and VSV, it was found that not only was vaccinia replication refractory to inhibition by interferon, but also that prior infection with vaccinia was able to partially reverse the effect of the inhibitor on the replication of the VSV used for superinfection. On the basis of these and other data it is postulated that a vaccinia virion component or a replication product of vaccinia virus, or both, enables VSV to escape the inhibiting action of interferoninduced resistance factors.     

Novel Carbocyclic Nucleosides Containing A Cyclobutyl Ring. Guanosine and Adenosine Analogues

Abstract

(1R,cis)-2-(3-Amino-2,2-dimethylcyclobutyl)ethanol (4) was used as a precursor in the synthesis of cyclobutyl nucleoside analogues containing guanine, 8-azaguanine, adenine or 8-azaadenine. All the compounds were evaluated as antiviral agents in a variety of assay systems. Some activity was noted for compound 13, 17, 19 and 20 against vaccinia virus and for compounds 11, 12, 13, 17, 19 and 20 against herpes simplex virus, at concentrations that were up to 10-fold below the cytotoxic concentrations for the host cells.     

LIGHT-MEDIATED INHIBITION OF IN VITRO DEVELOPMENT OF RUDIMENTARY EMBRYOS OF ILEX OPACA

The mature seeds of Ilex opaca Ait. contain rudimentary heart-shaped embryos. When excised embryos of cv. Farage were grown in vitro with a 16-hr photoperiod, only 20 % reached germination size after 13-day incubation, while 75% of the embryos reached the same stage when incubated in darkness. This light inhibitory effect increased with the length of daily light exposure as the daily photoperiod reached 4 hr. Nearly 50% growth reduction resulted as the cultures were preincubated in light continuously for 2 days before a 10-day dark incubation. After 4 days of light incubation the inhibitory effect could no longer be reversed by the subsequent dark incubation. Once the heart-shaped embryos started to grow in darkness they become progressively insensitive to subsequent light inhibition. After a 6-day initial dark incubation the embryos become immune from the inhibitory effect of light. This light inhibitory effect on in vitro embryo growth was universal in all 11 tested cultivars.     

Suppression of Growth of Herpes Simplex Virus in Chick Embryo Fibroblasts at 40 C

Four strains of herpes simplex virus tested all showed inability to form plaques in chick embryo fibroblasts (CEF) at 40 C, while no such suppression of growth was observed with WEE, vaccinia or JE virus in the same cells. The suppression was not due to a complete inhibition of viral growth, because virus-infected CEF bottle cultures consistently showed a small but definite increase of virus titer in 24 hr. When CEF monolayers adsorbing herpes virus were placed at 40 C, the number of infective centers decreased gradually; however, this decrease was much slower than the degradation of free virus at this temperature. Transfer of virus-infected CEF bottle cultures from 35 C to 40 C at any time during a one step growth cycle promptly slowed down subsequent virus replication. When virus-infected CEF bottles were incubated first at 40 C for 24 hr and then transferred to 35 C, a new increase in virus titer took place following a short lag. What stage of virus replication is suppressed at 40 C remains yet to be determined.     

Detection of Amsacta moorei entomopoxvirus and vaccinia virus proteins in cell cultures restrictive for poxvirus multiplication

The titer of Amsacta entomopoxvirus (EPV) protein detected in murine L-929 cells by enzyme-linked immunosorbent assay (ELISA) decreased to within preimmune serum levels by 24 hr after inoculation of the virus which indicates that Amsacta EPV structural protein biosynthesis does not occur in the vertebrate cell line. A viral-induced protein of approximately 100,000 M_r was detected by [³⁵S]methionine incorporation 4 hr after inoculation of Tn-368 cells with Amsacta EPV. Biosynthesis of protein which reacted with vaccina antiserum was detected in Estigmene acrea (BTI-EAA) cells by ELISA 10 hr after inoculation with 10 PFU of virus per cell. The amount of putative vaccinia structural protein detected in BTI-EAA cells increased approximately twofold by 70 hr after virus inoculation. No increase in vaccinia structural protein biosynthesis was detected in BTI-EAA cells inoculated with vaccinia virus previously inactivated by heat and UV light.     

Mechanism of Vaccinia Virus Release and Its Specific Inhibition by N1-Isonicotinoyl-N2-3-Methyl-4- Chlorobenzoylhydrazine

The release of vaccinia virus from RK-13 cells and its specific inhibition by N(1)-isonicotinoyl-N(2)-3-methyl-4- chlorobenzoylhydrazine (IMCBH) was studied. Intracellular naked vaccinia virus (INV) was wrapped by intracytoplasmic membranes, forming an intracellular double-membraned virion. Wrapped virions migrated to the cell surface, where the outer virion membrane presumably fused with the plasma membrane, releasing virus surrounded by the inner membrane, referred to as extracellular enveloped vaccinia virus (EEV). At no time was there any evidence that vaccinia virus acquired an envelope by budding of naked virus from the cytoplasmic membrane. Naked virus and double-membraned virus each constituted about one-third of intracellular virus at 8 and 12 h postinfection (p.i.). Beginning at 16 h p.i., the proportion of intracellular virus occurring as double-membraned virus steadily decreased to 1% at 24 h while the proportion of naked virus rose to 87%. IMCBH inhibited the formation of the double-membraned virion and the appearance of EEV while not affecting the production of INV. IMCBH had no effect on INV infectivity or polypeptide composition, on vaccinia virus-specified membrane-associated proteins or glycoproteins, or on hemadsorption. The presence of IMCBH until 4 h p.i. did not decrease the amount of EEV at 48 h p.i., whereas less than 10% of the normal 48-h EEV yield was obtained if the drug was present during the first 16 h p.i. Cell cultures infected at very low multiplicities showed a rapid virus dissemination in the absence of the drug, whereas the presence of IMCBH very effectively inhibited this spread. We conclude that vaccinia virus is liberated via a double-membraned intermediate as an enveloped virion and that it is this extracellular enveloped virus that is responsible for dissemination of infection.     

Quantitative Studies on Fabrics as Disseminators of Viruses: IV. Virus Transmission by Dry Contact of Fabrics

Cotton and woolen fabrics and fabrics of synthetic fibers were exposed by direct contact (pipette) and by aerosolization to poliovirus and to vaccinia virus in separate experiments, allowed to dry for 16 hr at 25 C in 35% relative humidity, and randomly tumbled with sterile swatches of the same fabrics for 30 min. By use of a HEp-2 cell assay system, up to 10^3.5 CCID₅₀ of poliovirus per ml and 10^4.4 CCID₅₀ of vaccinia virus per ml were recovered from the originally sterile fabrics as early as 1 to 10 min after contact. Maximum transfer of both viruses was achieved with wool blanket material, although high titers of vaccinia virus were recovered from all fabrics tested. Poliovirus placed on the fabrics in an aerosol tended to be transferred to the sterile fabrics at a greater rate than when it was placed on the fabrics by direct contact. The method of exposure had essentially no effect on the rate of transfer of vaccinia virus.     

In vivo dose-response of insects to Hz-2V infection

Background

Vaccinia virus, the prototype member of the family Poxviridae, was used extensively in the past as the Smallpox vaccine, and is currently considered as a candidate vector for new recombinant vaccines. Vaccinia virus has a wide host range, and is known to infect cultures of a variety of cell lines of mammalian origin. However, little is known about the virus tropism in human leukocyte populations. We report here that various cell types within leukocyte populations have widely different susceptibility to infection with vaccinia virus.

Results

We have investigated the ability of vaccinia virus to infect human PBLs by using virus recombinants expressing green fluorescent protein (GFP), and monoclonal antibodies specific for PBL subpopulations. Flow cytometry allowed the identification of infected cells within the PBL mixture 1–5 hours after infection. Antibody labeling revealed that different cell populations had very different infection rates. Monocytes showed the highest percentage of infected cells, followed by B lymphocytes and NK cells. In contrast to those cell types, the rate of infection of T lymphocytes was low. Comparison of vaccinia virus strains WR and MVA showed that both strains infected efficiently the monocyte population, although producing different expression levels. Our results suggest that MVA was less efficient than WR in infecting NK cells and B lymphocytes. Overall, both WR and MVA consistently showed a strong preference for the infection of non-T cells.

Conclusions

When infecting fresh human PBL preparations, vaccinia virus showed a strong bias towards the infection of monocytes, followed by B lymphocytes and NK cells. In contrast, very poor infection of T lymphocytes was detected. These finding may have important implications both in our understanding of poxvirus pathogenesis and in the development of improved smallpox vaccines.     

In vitro micropropagation of Acacia nilotica subsp. indica Brenan via cotyledonary nodes

Cotyledonary node explants of Acacia nilotica subspecies indica Brenan, differentiated multiple shoots on Gamborg et al.' s medium (B₅, Gamborg et al. 1968) supplemented with cytokinins like N⁶-benzyladenine, 6-(, -Dimethylallylamino)-purine, kinetin or zeatin. Of the four, BA supported maximum multiple shoot differentiation; the highest average number of shoots (6.3) per expiant was in 1.5 mg/l. The number of shoots was further enhanced by (i) using nodal explants of in vitro regenerated shoots as microcuttings, and (ii) repeated subculture of the original expiants (stumps) on the same medium after excising the shoots. Thus, over seven hundred shoots could be obtained from a single cotyledonary node explant. Individual shoots, when transferred to 2 mg/l indole-3-acetic acid augmented medium organised healthy roots in 100% cultures. Such test tube grown plantlets have been successfully transferred to soil, where they grow well up to eight weeks.Abbreviations 2iP 6-(, -Dimethylallylamino)-purine - AC activated charcoal - B₅ Gamborg et al. 's medium with 0.8% agar + 3 % sucrose - BA,N⁶ benzyladenine - CW coconut water - FAA formalin-aceticacid-alcohol - IAA indole-3-acetic acid - IBA indole-3-butyric acid - Kn kinetin - NAA -naphthaleneacetic acid - NOA -naphthoxyacetic acid     

Mode of action and antifungal properties of two cold-adapted chitinases

The mode of action of two chitinases from the Antarctic Arthrobacter sp. strain TAD20 on N-acetyl-chitooligomers and chitin polymers has been elucidated. Identification of the length of chitin oligomers following enzymatic hydrolysis was verified by using HPLC-based analysis. It was observed that the length of the oligomer is important for enzyme action. The enzymes cannot effectively hydrolyze chitin oligomers with a degree of polymerization lower than four. ArChiA is an endochitinase which hydrolyzes chitin substrates randomly, whereas ArChiB is an exochitinase which degrades chitin chains and N-acetyl-chitooligomers from the nonreducing end, releasing N-N-diacetyl-chitobiose. ArChiB (100 g/ml) inhibited spore germination and hyphal elongation of the phytopathogenic fungus Botrytis cinerea by 15% and 30%, respectively. A more pronounced effect was observed with ArChiA (100 g/ml) resulting in 70% inhibition of spore germination and 60% inhibition of germ tube elongation. A slight additive effect was observed, when the two enzymes were used in combination, only on the inhibition of germ tube elongation.Communicated by G. Antranikian     

Sequential Formation of Vaccinia Virus Proteins and Viral Deoxyribonucleic Acid Replication

In vaccinia virus-infected cell cultures, cellular protein synthesis was inhibited 50% at 2 hr postinfection (PI) and 80 to 90% by 4 hr PI. Input virus was responsible for this inhibition. Five early proteins, coded for by the viral genome, could be detected at 2 to 3 hr PI. Normally, their synthesis did not continue beyond 6 hr PI, at which time synthesis of a different set of proteins began. When DNA replication was blocked, synthesis of these early proteins continued until 9 to 12 hr PI. The bulk of the proteins which were incorporated into mature virus were synthesized at 8 hr PI and thereafter. The time of their formation was close to the time at which virus maturation occurred. However, 15% of the protein found in mature virus was synthesized early in the infectious cycle. The quantity of “early viral protein” which was not incorporated into mature virus was almost as large as the quantity of viral protein which did appear in mature virus. The “early” and “late” proteins could be shown to have separate and distinct immunological properties. The role of this large quantity of “early” protein is discussed.     

Effect of Rifamycins and Related Antibiotics on the Deoxyribonucleic Acid-Dependent Ribonucleic Acid Polymerase of Vaccinia Virus Particles

A number of compounds related to rifampin which act as expected in the Escherichia coli system have been tested for their ability to inhibit the vaccinia particle deoxyribonucleic acid-dependent ribonucleic acid (RNA) polymerase in vitro. Some compounds are inactive even at concentrations of 500 mug/ml, others are able to produce partial inhibition, and others strongly inhibit the enzyme activity at 150 mug/ml or less. The inhibition, where present, operates immediately but appears to be at least partially reversible. At least one compound which is without effect against bacterial RNA polymerase is a potent inhibitor of the viral RNA polymerase. As the enzyme activity of rifampin-resistant mutants of vaccinia virus is inhibited to the same extent as that of the wild type, the observed in vitro effect on vaccinia virus RNA polymerase is not identical with the in vivo effect specifically directed against a vaccinia-specified protein.