Replication Of Animal Viruses Research Articles

Control of animal virus replication by RNA adenosine methylation.

Methylation at the N6-position of either adenosine (m6A) or 2'-O-methyladenosine (m6Am) represents two of the most abundant internal modifications of coding and non-coding RNAs, influencing their maturation, stability and function. Additionally, although less abundant and less well-studied, monomethylation at the N1-position (m1A) can have profound effects on RNA folding. It has been known for several decades that RNAs produced by both DNA and RNA viruses can be m6A/m6Am modified and the list continues to broaden through advances in detection technologies and identification of the relevant methyltransferases. Recent studies have uncovered varied mechanisms used by viruses to manipulate the m6A pathway in particular, either to enhance virus replication or to antagonize host antiviral defenses. As such, RNA modifications represent an important frontier of exploration in the broader realm of virus-host interactions, and this new knowledge already suggests exciting opportunities for therapeutic intervention. In this review we summarize the principal mechanisms by which m6A/m6Am can promote or hinder viral replication, describe how the pathway is actively manipulated by biomedically important viruses, and highlight some remaining gaps in understanding how adenosine methylation of RNA controls viral replication and pathogenesis.

Immunization with Plant-Expressed Hemagglutinin Protects Chickens from Lethal Highly Pathogenic Avian Influenza Virus H5N1 Challenge Infection

Highly pathogenic avian influenza (HPAI) is a striking disease in susceptible poultry, which leads to severe economic losses. Inactivated vaccines are the most widely used vaccines in avian influenza virus (AIV) vaccination programs. However, these vaccines interfere with the serological detection of wild-type AIV infections in immunized populations. The use of vaccines that allow differentiation between infected and vaccinated animals (DIVA strategy) would stop current stamping-out policies. Therefore, novel vaccination strategies are needed to allow improved protection of animals and humans against HPAI virus (HPAIV) infection. The presented study analyzed for the first time the immunogenic capacity of plant-expressed full-length hemagglutinin (rHA0) of HPAIV H5N1 in several vaccine formulations within the highly relevant host species chicken. We were able to express plant-expressed rHA0 at high levels and could show that, when administered with potent adjuvants, it is highly immunogenic and can fully protect chicken against lethal challenge infection. Real-time reverse transcription (RT)-PCR and serological tests demonstrated only marginally increased virus replication in animals vaccinated with plant-derived rHA0 compared to animals immunized with an inactivated reference vaccine. In addition, the use of plant-expressed rHA0 also allowed an easy serological differentiation of vaccinated from AIV-infected animals based on antibodies against the influenza virus NP protein.

The role of RNAi and microRNAs in animal virus replication and antiviral immunity

The closely related microRNA (miRNA) and RNAi pathways have emerged as important regulators of virus-host cell interactions. Although both pathways are relatively well conserved all the way from plants to invertebrates to mammals, there are important differences between these systems. A more complete understanding of these differences will be required to fully appreciate the relationship between these diverse host organisms and the various viruses that infect them. Insights derived from this research will facilitate a better understanding of viral pathogenesis and the host innate immune response to viral infection.

Study of animal viruses in yeast

Yeast is often considered to be a model eukaryotic organism, in a manner analogous to E. coli as a model prokaryotic organism. Yeast has been extensively characterized and the genomes completely sequenced. Despite the small genome size, yeast displays most of features of higher eukaryotes. The facts that most of cellular machinery is conserved among different eukaryotes and that the powerful technologies of genetics and molecular biology are available have made yeast model eukaryotic cells in biological and biomedical sciences including virology. Cumulative data indicate that yeast can be a host for animal viruses. I briefly describe yeast gene expression and review viral replication in yeast. Great discovery include complete replication of animal viruses and production of virus-like particle vaccines in yeast. Current studies on yeast focus on identification of host factors and machinery used for viral replication. The studies are based on traditional yeast genetics and genome-wide identification using a complete set of yeast deletion strains.

Animal virus replication and RNAi-mediated antiviral silencing in Caenorhabditis elegans

The worm Caenorhabditis elegans is a model system for studying many aspects of biology, including host responses to bacterial pathogens, but it is not known to support replication of any virus. Plants and insects encode multiple Dicer enzymes that recognize distinct precursors of small RNAs and may act cooperatively. However, it is not known whether the single Dicer of worms and mammals is able to initiate the small RNA-guided RNA interference (RNAi) antiviral immunity as occurs in plants and insects. Here we show complete replication of the Flock house virus (FHV) bipartite, plus-strand RNA genome in C. elegans. We show that FHV replication in C. elegans triggers potent antiviral silencing that requires RDE-1, an Argonaute protein essential for RNAi mediated by small interfering RNAs (siRNAs) but not by microRNAs. This immunity system is capable of rapid virus clearance in the absence of FHV B2 protein, which acts as a broad-spectrum RNAi inhibitor upstream of rde-1 by targeting the siRNA precursor. This work establishes a C. elegans model for genetic studies of animal virus-host interactions and indicates that mammals might use a siRNA pathway as an antiviral response.

Role of adenovirus type 5 early region 3 in the pathogenesis of ocular disease and cell culture infection.

Experimental animal virus replication models make it possible to study the role of viral gene products in adenovirus (Ad)-induced ocular disease. This study tested the hypothesis that the early region 3 (E3) of the human Ad genome plays an important role in the pathogenesis of Ad-induced ocular disease. Both Ad5 wt300, a genetically defined E3+ parent, and Ad5 dl327, a deletion mutant without E3 (E3-), replicated in ocular-derived cell cultures. Ad5 E3+ and Ad8 replicated more efficiently than did Ad5 E3- in cornea and conjunctival cell cultures. Lacrimal gland-derived cell cultures supported human Ad8 replication significantly more efficiently than did either Ad5 E3+ or Ad5 E3-. After intrastromal and topical inoculation of rabbits with either Ad wt300 or Ad dl327, a specific immune response was elicited that coincided with the appearance of subepithelial opacities that mimicked human disease both clinically and histologically. The clinical features (i.e., conjunctivitis, iritis, and corneal edema) were not significantly different for Ad5 E3(+)- and Ad5 E3(-)-induced ocular infection. Ad5 E3(+)- and Ad5 E3(-)-inoculated eyes shed virus for up to 7 and 5 days, respectively, and occasionally established persistent and/or latent infections in corneal, conjunctival, and, infrequently, lacrimal gland cells. Both Ad5 E3+ and Ad5 E3- spread from virus-inoculated animals to the cornea and conjunctiva of normal animals. Under current experimental conditions, expression of the E3 gene does not appear to affect the degree of virulence in ocular disease induced by Ad5 in the rabbit eye model. Deletion of the E3 gene from Ad5 does not make the model more like human disease.

In vivo replication of the hamster polyomavirus genome and generation of specific deletions in the process of lymphomagenesis.

Hamster polyomavirus (HaPV) causes lymphomas when injected into newborn hamsters. These tumors are virus-free but accumulate large amounts of deleted extrachromosomal viral genomes. In order to identify the major sites of virus replication in animals, we have monitored the HaPV DNA present in different organs at various times after injection. The data demonstrate that viral replication preferentially occurs in lymphoid organs. Lymphoma-associated viral genomes display specific deletions. PCR analysis shows that such viral genomes are the only variants detectable in infected animals, suggesting that they are generated by a specific cellular mechanism. We have tested the possible role of the lymphoid cell-specific V(D)J recombination activity in the generation of these specific variants. Our results indicate that this mechanism is not solely responsible for the viral genome rearrangement, if involved at all.

Effect of emulsifiers on influenza type a virus infection, in vivo and in vitro studies

Results of in vitro studies carried out by other investigators suggest that insecticide emulsifiers enhance the replication of animal viruses possessing a single-stranded RNA genome. Based on this observation and on epidemiological findings, it has been postulated that insecticide emulsifiers and related compounds may be etiologically involved in Reye's syndrome. Reye's syndrome is an enigmatic pernicious disease of childhood causally associated with an antecedent viral infection, usually influenza, and putatively associated with exposure to environmental chemicals. The present study was carried out to assess the effects of emulsifiers on infection in vivo with influenza type A virus, a virus possessing a single-stranded RNA genome, using the suckling mouse as host, and in vitro using a susceptible line of mammalian cells. Three coded emulsifiers retrospectively identified as Atlox 3409F, Toximul MP8, and Triton X-100 were assayed at concentrations of 1.0, 2.5, 5.0, and 10.0 ppm. None of the emulsifiers enhanced the plaquing efficiency of influenza A/PR/8/34 (HON1) virus in Madin-Darby canine kidney cells (less than a twofold increase), nor did percutaneous application of these emulsifiers at a concentration of 21 parts per thousand in peanut oil enhance the lethality of influenza A/PR/8/34 (HON1) virus infection. Indeed, peanut oil alone, and in combination with the emulsifiers, lowered lethality relative to mice that were treated percutaneously in parallel with physiologic saline.

Effect of halothane on the replication of animal viruses

Five RNA- and two DNA-containing viruses were propagated in Vero cells and tested for their ability to replicate in the presence of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane), a commonly used inhalational anesthetic. Halothane did not affect poliovirus replication at any anesthetic concentration tested, but all other viruses were either partially or totally inhibited by clinical doses of the anesthetic. Replication of Sendai virus, simian virus 40, vesicular stomatitis virus, and herpes simplex virus type 1 were moderately inhibited by halothane exposure. At concentrations of 2.2% (vol/vol) halothane, peak virus titers were reduced by ca. 2 orders of magnitude for vesicular stomatitis virus and simian virus 40, 3.5 orders of magnitude for Sendai virus, and 4 orders of magnitude for herpes simplex virus. Newcastle disease virus and measles virus were the most susceptible to exposure to halothane. Total inhibition of the replication of these viruses occurred at 1.6 to 2.0% halothane. All of the viruses whose replication was susceptible to the action of halothane were inhibited in a concentration-dependent manner. Furthermore, with the exception of simian virus 40, the inhibition of the replication of all viruses was reversible after halothane removal, although total recovery of virus synthesis was not observed unless the culture medium was changed or the pH was adjusted after anesthetic removal.

Does the cytoskeleton play a significant role in animal virus replication?

Evidence which has accumulated over the past decade implicating various elements of the cytoskeleton in the replication of animal viruses is discussed in this speculative review. In particular, the interactions of adenovirus types 2 and 5 and reovirus type 1 with microtubules are emphasized. Further, a review is presented of associations between poxviruses, polioviruses, papovaviruses and other enveloped viruses with both the 100 Å filament and microfilament components of the cytoskeleton. Finally, tentative conclusions are drawn as to the significance of these interactions between viruses and virus subparticles with the cytoskeletons of infected cells.

Proteolytic events in replication of animal viruses.

Proteolytic events in replication of animal viruses.

Replication of Animal Viruses in Differentiating Muscle Cells: Vaccinia and Herpes Simplex Virus Type 1

Cells cultured from the breast muscles of 11 to 12-day-old chick embryos were infected in the undifferentiated mitotic myoblast stage or in the terminally differentiated non-mitotic myotube stage with one of two DNA viruses, vaccinia and herpes simplex virus type 1 (HSV-1). DNA synthesis was measured and production ov virus-specific DNA detected in cells infected as myoblasts or myotubes by isotope labelling, autoradiographic and buoyant density centrifugation techniques. Furthermore, fully fused myotubes resemble myoblasts in their ability to support productive infection by these DNA viruses although DNA replication and nuclear division have ceased in myotubes and only minimum levels of host-cell DNA polymerase activity are present.

Replication of animal viruses in differentiating muscle cells: influenza virus A.

Cells were cultured from the breast muscle of 11- to 12-day-old chick embryos and were grown under conditions optimal for the development of the cells into terminally differentiated, fused myotubes. Myotubes were infected with influenza virus A/Ann Arbor/6/60(H2N2) at high multiplicity, and synthesis of virus-specific proteins and RNAs was detected by haemadsorption, fluorescence microscopy and/or isotope labelling and electrophoresis techniques. Provided that myotubes were maintained at temperatures below 39 degrees C after infection, production of virus components and yield of infectious virus in these cells was similar to those observed in infected chick kidney cells. However, if cells were maintained at temperatures of 39 degrees to 40 degrees C after infection, virus nucleoprotein was prominent in the nuclei, and synthesis of virus-specific polypeptides and of plus-strand RNA was reduced about fourfold to 20-fold compared to that detected at lower temperatures. Moreover, infectious virus was not produced when temperatures of 39 to 40 degrees C were used during virus replication. The results demonstrate that under suitable conditions avian myotubes formed in culture resemble epithelioid cells in their ability to support the productive replication of influenza virus.

Biological activity in ribonucleoprotein fractions of influenza virus

A profusion of journal articles has appeared in recent years on the molecular mechanisms of animal virus replication. Much of this work is so highly specialized that, all too frequently, only those scientists who are engaged in research on the same family of viruses have the interest and background necessary for following the complexities of the mechanisms being described in this chapter. Review articles help to provide the required background information, but almost all of them are highly exhaustive treatments of individual virus families. Articles that attempt to present comprehensible overviews of the molecular biology of animal viruses as a whole are extremely rare. This chapter is an attempt to bring more order to the seemingly bewildering variety of information now available on animal virus replicative processes. The diagram on replicative pathways is presented in this chapter, together with explanations in the text, to make animal virus replicative processes and comparisons of these processes among virus families better understood by a wider audience.

Chloroquine mediated alterations in mammalian cell metabolism and viral replication.

Chloroquine is an effective antimalarial drug that has also been successfully employed clinically in treating lupus erythematosus (1), as well as rheumatoid arthritis (2). A number of studies performed to examine the biological effects of chloroquine have revealed a diversity of activities. Some of the drug effects included a stabilization of lysosomal membranes (3), an activation of E. coli tyrosine transfer ribonucleic acid (RNA) (4), binding to bacterial deoxyribonucleic acid (DNA) with an alteration of the polymerase reactions (5-8) and an inhibition of a number of metabolic enzymes such as alcohol dehydrogenase (9) and succinic dehydrogenase (10). There is a relative paucity of information describing the effects of chloroquine on mammalian cell metabolism and no information on the effects of this drug on the replication of animal viruses. Since chloroquine is employed clinically as well as for investigative purposes, this study sought to examine the effect of this drug on mammalian cell biosynthetic ...

Biochemistry of animal virus replication.

Biochemistry of animal virus replication.

Replication of animal viruses as studied by electron microscopy

Replication of animal viruses as studied by electron microscopy

Erratum: Specific Inhibition of Replication of Animal Viruses

In the article "Specific inhibition of replication of animal viruses" by I. Tamm and H. J. Eggers [ Science 142, 24 (4 Oct. 1963)], reference ( 64 ) in line 43, column 2, page 28, should be to H. J. Eggers and I. Tamm, in preparation, not to Nature 199, 513 (1963); reference ( 64 ) in line 2, column 2, page 29, is correct as it stands. There is an error in Fig. 8. The nucleosides should have been depicted In their β-D configuration and not in their β-L configuration.

SPECIFIC INHIBITION OF REPLICATION OF ANIMAL VIRUSES.

SPECIFIC INHIBITION OF REPLICATION OF ANIMAL VIRUSES.