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PubMed1992

Identification and characterization of a coronavirus packaging signal.

Previously, a mouse hepatitis virus (MHV) genomic sequence necessary for defective interfering (DI) RNA packaging into MHV particles (packaging signal) was mapped to within a region of 1,480 nucleotides in the MHV polymerase gene by comparison of two DI RNAs. One of these, DIssF, is 3.6 kb in size and exhibits efficient packaging, whereas the other, DIssE, which is 2.3 kb, does not. For more precise mapping, a series of mutant DIssF RNAs with deletions within this 1,480-nucleotide region were constructed. After transfection of in vitro-synthesized mutant DI RNA in MHV-infected cells, the virus product was passaged several times. The efficiency of DI RNA packaging into MHV virions was then estimated by viral homologous interference activity and by analysis of intracellular virus-specific RNAs and virion RNA. The results indicated that an area of 190 nucleotides was necessary for packaging. A computer-generated secondary structural analysis of the A59 and JHM strains of MHV demonstrated that within this 190-nucleotide region a stable stem-loop of 69 nucleotides was common between the two viruses. A DIssE-derived DI DNA which had these 69 nucleotides inserted into the DIssE sequence demonstrated efficient DI RNA packaging. Site-directed mutagenic analysis showed that of these 69 nucleotides, the minimum sequence of the packaging signal was 61 nucleotides and that destruction of the secondary structure abolished packaging ability. These studies demonstrated that an MHV packaging signal was present within the 61 nucleotides, which are located on MHV genomic RNA 1,381 to 1,441 nucleotides upstream of the 3' end of gene 1.

Animals↗
PubMed2005

Recombinant, live-attenuated tetravalent dengue virus vaccine formulations induce a balanced, broad, and protective neutralizing antibody response against each of the four serotypes in rhesus monkeys.

Three tetravalent vaccine (TV) formulations of previously described monovalent dengue (DEN) virus vaccine candidates were compared to a tetravalent formulation of wild-type DEN viruses (T-wt) for replication in SCID mice transplanted with human liver cells (SCID-HuH-7) or for replication and immunogenicity in rhesus monkeys. TV-1 consists of recombinant DEN1, -2, -3, and -4, each with a 30-nucleotide deletion in the 3' untranslated region (Delta30). TV-2 consists of rDEN1Delta30, rDEN4Delta30, and two antigenic chimeric viruses, rDEN2/4Delta30 and rDEN3/4Delta30, both also bearing the Delta30 mutation. TV-3 consists of rDEN1Delta30, rDEN2Delta30, rDEN4Delta30, and a 10-fold higher dose of rDEN3/4Delta30. TV-1 and TV-2 were attenuated in SCID-HuH-7 mice with minimal interference in replication among the virus components. TV-1, -2, and -3 were attenuated in rhesus monkeys as measured by duration and peak of viremia. Each monkey immunized with TV-1 and TV-3 seroconverted to the four DEN components by day 28 with neutralization titers ranging from 1:52 to 1:273 and 1:59 to 1:144 for TV-1 and TV-3, respectively. TV-2 induced low antibody titers to DEN2 and DEN3, but a booster immunization after 4 months increased the neutralizing antibody titers to greater than 1:100 against each serotype and elicited broad neutralizing activity against 19 of 20 DEN subtypes. A single dose of TV-2 induced protection against wild-type DEN1, DEN3, and DEN4 challenge, but not DEN2. However, two doses of TV-2 or TV-3 induced protection against DEN2 challenge. Two tetravalent formulations, TV-2 and TV-3, possess properties of a successful DEN vaccine and can be considered for evaluation in clinical trials.

3' Untranslated Regions↗
PubMed1992

Mammalian and viral DNA sequences which interfere with the maintenance of a centromeric vector in yeast.

We constructed a recombinant plasmid by inserting into the pRS314 yeast centromeric plasmid vector the mouse DNA sequence responsible for the maintenance in transgenic mice of plasmid p12B1 (1). Such constructs could constitute convenient shuttle vectors between yeast and mouse cells. However, the recombinant molecule could not be established as a stable plasmid in Saccharomyces cerevisiae. A region with a limited similarity to the yeast centromere (CEN element) is present in this mouse sequence as well as in two other sequences subsequently identified in a data bank search using the CEN consensus. One of them is localized in Bovine Papillomavirus Type 1 DNA, and the other one in the human beta-globin locus. Once inserted in pRS314, these two sequences showed the same inhibitory effect on plasmid maintenance as the p12B1 mouse DNA fragment. This effect appears to depend on the simultaneous presence in the construct of one of the "CEN-like regions" and of an authentic CEN element. Non-centromeric yeast plasmids carrying one of the three sequences could replicate autonomously, and were even stabilized to a significant extent. These results identify in the genomes of higher eukaryotes and their viruses a family of sequences which cannot be simply cloned in centromeric yeast vectors.

Animals↗
PubMed1976

Defective-interfering particles of Semliki Forest Virus: structural differences between standard virus and defective-interfering particles.

Serial passaging of Semlike Forest virus in BHK cells at a constant input multiplicity of 50 p.f.u./cell resulted in a 4 log10 drop in yield of infectious virus by passage 9. An interference analysis showed that this drop was due to the presence of defective-interfering (DI) particles. Attempts were made to separate the DI particles from standard virus by equilibrium and velocity centrifugation. Only equilbrium centrifugation on CsCl resolved the DI particles (identified by interference analyses) from standard virus. The buoyant density of the DI particles (1.23 g/ml) was higher than that of standard virus (p = 1-20 g/ml). No difference was observed between the structural porteins of standard virus and DI particles. Analysis of the RNA of standard virus and DI particles showed that whereas standard virus contained only 42S RNA (mol. wt. approx. 4-2 X 10(6), DI particles contained two small pieces of RNA of mol. wt. 0.81 and 0-75 X 10(6) respectively. Infectivity assays showed that these low mol. wt. species were not only non-infectious but also interfered with the infectivity of 42S RNA from standard virus. Nucleocapsids derived from purified DI particles had a buoyant density 0-02 g/ml greater than the nucleocapsids from standard virus. Analysis of the RNA from DI nucleocapsids showed it to be entirely of the low mol. wt. class. To account therefore for the density difference not only between DI particles and standard virus but also between their respective nucleocapsids we propose that each SFV DI particle contains several molecules of the low mol. wt. RNA species.

Cell Line↗
PubMed1993

Interference with superinfection and with cell killing and determination of host range and growth kinetics mediated by feline leukemia virus surface glycoproteins.

The functions of the surface glycoproteins (SU) of feline leukemia viruses (FeLVs) are of interest since these proteins mediate virus infection and interference and are critical determinants of disease specificity. In this study, we examined the biochemical and genetic determinants of SU important to virus entry and cell killing. In particular, we developed and used vesicular stomatitis virus (VSV)/FeLV pseudotype virus interference assays to determine interference subgroupings and assess mechanisms of host cell restriction. We also assessed roles of SU in virus growth kinetics and in the inhibition of cell killing caused by superinfection with cytopathic virus. Subgroup classification by VSV/FeLV pseudotype assay was in agreement with that defined previously by focus interference assay and was found to be determined by changes near the N terminus of SU for FeLV subgroups A (FeLV-A) and C. Virus host range restriction was found to be mediated at the level of virus entry in most cases, although postentry events mediated restriction in the failure of a subgroup A-like, T-cell cytopathic and immunodeficiency-inducing clone (FeLV-FAIDS-EECC) to replicate in feline fibroblasts. FeLV-FAIDS-EECC-induced cell killing was also inhibited by prior infection with one of two FeLV-A isolates. This inhibition could be conveyed by as few as four amino acid changes near the N terminus of the FeLV-A SU and also appeared to be mediated at a postentry level. Lastly, the SU-coding sequence was also found to determine differences in growth kinetics of viruses within the same subgroup. These studies demonstrate that subtle alterations in the FeLV SU, particularly in the N-terminal region, impart multiple significant functional differences which distinguish virus variants.

Amino Acid Sequence↗
PubMed1986

Combined vaccination with live oral polio vaccine and the bovine rotavirus RIT 4237 strain.

A clinical trial was carried out in 3-month-old infants to assess whether concomitant oral administration of live polio and rotavirus RIT 4237 vaccines would reduce their immunogenicities as a result of mutual interference. One hundred and sixty breast-fed male and female infants were randomly allocated to four study groups to receive in a blind fashion the poliovirus vaccine, the RIT 4237 vaccine, a combination of both vaccines or a placebo preparation. Antibody titres were measured in pre- and postvaccination serum samples by the ELISA test and the neutralizing antibody test (NT) for rotavirus and by the NT for polioviruses types 1 and 3. The percentage of subjects with immune responses to rotavirus in the placebo group was low, indicating the absence of wild rotavirus circulation in the population. Antibody responses against polio types 1 and 3 were found in about a quarter of the infants receiving a placebo because the study was performed during a polio vaccination campaign when vaccine viruses are known to circulate. The results showed that 73% of seroconversion was obtained when RIT 4237 was administered alone and that the responses to polioviruses types 1 and 3 were good. However, simultaneous administration of polio and RIT 4237 vaccines caused a significant reduction of the antibody response to rotavirus but not to polioviruses types 1 and 3.

Antibodies, Viral↗
PubMed1993

Herpes simplex virions interfere with the expression of human papillomavirus type 18 genes.

Papillomaviruses are believed to play an important role in the development of genital carcinoma. Herpes simplex virus (HSV) has been proposed as a cofactor. Here we show that HSV-1 interferes with the expression of human papillomavirus (HPV-18) genes in HeLa cells by reducing the amount of papillomaviral mRNA. By 7 h after HSV-1 infection, expression was reduced by a factor of 50. Experiments with the HSV-1 mutant tsK, with cycloheximide and with u.v.-irradiated virus indicated that the reduction was not due to newly made immediate early, early or late HSV-1 gene products but rather to a component of the virion. Replication of the HSV-1 is therefore not required for the reduction of the HPV-18 mRNA. The HSV-1 strain 17+, which has only a very weak virion host shutoff function, still specifically decreased the level of the papillomaviral mRNA suggesting that either the decrease is due to a new HSV-1 function or that the HPV-18 mRNA is especially sensitive to the low residual host shutoff activity of strain 17+. Experiments with the virus 17(41-), in which the host shutoff function is inactivated by a mutation in the UL41 gene, showed clearly that it is the host shutoff function which is responsible. The papillomaviral mRNA therefore appears to be hypersensitive to the herpesvirus host shutoff function.

Gene Expression Regulation, Viral↗
PubMed1980

Alterations in virus protein synthesis and capsid production in infection with DI particles of herpesvirus.

High multiplicity, undiluted passage of equine herpesvirus type 1 (EHV-1) in L-M cells resulted in the rapid production of virus particles whose genome was genetically less complex, contained more reiterated DNA sequences and exhibited a greater buoyant density (rho = 1.724 g/ml) than the DNA (rho = 1.716 g/ml) of standard virus. These data and the finding that these particles inhibited the replication of standard virus in interference assays confirmed that these were defective interfering (DI) particles (Henry et al. 1979). Additional evidence for this has been obtained from the pattern of cyclic fluctuation in infectious virus titre through 17 serial passages as well as from the pronounced variation in the particle to plaque ratio for each passage. Total particle production was markedly reduced in cells infected with virus preparations containing DI particles and quantification of major cell-associated EHV-1 capsid species by electron microscopy and analysis in Renografin density gradients indicated that this reduction occurred at the level of capsid assembly. Although total capsid production was reduced in cells infected with DI particle preparations, the synthesis of I (immature) capsids increased relative to that of L (empty) capsids and these alterations in the assembly of capsid species could be related to changes in the synthesis of capsid proteins. In cells infected with EHV-1 preparations rich in DI particles, the synthesis of major capsid protein 150000 was greatly reduced, whereas core protein 46000, a major component of I capsids, was overproduced as compared to standard virus infection. Capsids produced in cells infected with virus preparations rich in DI particles were identical in polypeptide composition to those made in standard virus infection.

Animals↗
PubMed1990

The human immunodeficiency virus type 2 vpr gene is essential for productive infection of human macrophages.

The human immunodeficiency virus (HIV) genetic determinant(s) responsible for tropism in human T cells or macrophages are not well defined. We studied the role of the HIV type 2 (HIV-2) nef and vpr genes in viral tropism. HIV-2 mutants, lacking either vpr or nef genes, or both vpr and nef, were obtained by site-specific mutagenesis of a biologically active HIV-2 proviral clone (HIV-2sbl/isy), which is infectious in both human T cells and macrophages. Viral progeny carrying mutations of nef, vpr, or of both nef and vpr genes replicated more efficiently than the parental virus in primary human peripheral blood cells and in the human Hut 78 T-cell line. In contrast, the HIV-2 nef- mutant infected human macrophages as efficiently as the parental virus, whereas viruses lacking the vpr gene either alone or in conjunction with the lack of the nef gene did not replicate in macrophages. Thus, some lack of nef in HIV-2 enhances viral replication in T cells and does not interfere with viral replication in primary macrophages, whereas vpr is essential for replication of HIV-2 in human macrophages. Because the parental HIV-2sbl/isy cloned virus also infects rhesus macaques, the use in animal studies of these HIV-2 mutants with differences in cell tropism and rates of replication will be highly useful in understanding the mechanism of viral infectivity and possibly pathogenicity in vivo.

Cell Transformation, Viral↗
PubMedDate not supplied

Cotransfection of mutated forms of human immunodeficiency virus type 1 Gag-Pol with wild-type constructs can interfere with processing and viral replication.

OBJECTIVES: We wished to generate a number of genetic constructs containing mutations in the protease (PR) and reverse transcriptase (RT) genes of the Gag-Pol of human immunodeficiency virus type 1 (HIV-1) and to transfect these constructs into COS-7 cells to determine their effect on wild-type (wt) viral replication. RESULTS: The mutated Gag-Pol polyproteins were incorporated into viral particles. Gag-Pol proteins that were mutated in PR as well as combinations of mutations in PR and RT inhibited the production of fully processed and infectious viral particles when these constructs were coexpressed with the infectious HIV-1 molecular clone pBH10. Viral particles produced after cotransfection of COS-7 cells with both pBH10 and infectious constructs containing Gag-Pol, mutated in PR alone or in both RT and PR, showed abnormal processing and lower infectivity. Complementation experiments in which pBH10 mutated in PR was coexpressed with wt Gag-Pol showed that the latter could be incorporated into the viral particles that were generated. COS-7 cells stably transfected with Gag-Pol, mutated in PR or in both PR and RT, and subsequently transfected with pBH10, produced levels of p24 and RT activity that were substantially diminished in comparison with levels produced by cells transfected with wt pBH10 alone. CONCLUSIONS: These results suggest that trans-dominant effects were potentially responsible for the observed inhibition of viral replication.

Animals↗
PubMed2006

Intracellular-diced dsRNA has enhanced efficacy for silencing HCV RNA and overcomes variation in the viral genotype.

RNA interference (RNAi) can be used to inhibit viral replication in mammalian cells and therefore could be a powerful new antiviral therapy. Small interfering RNA (siRNA) may be effective for RNAi, but there are some technical problems that must be solved in each case, for example, predicting the effective siRNA target site and targeting heterogeneous sequences in a virus population. We show here that diced siRNA generated from long double-stranded RNA (dsRNA) is highly effective for inducing RNAi in HuH-7 cells harboring hepatitis C virus (HCV) replicons and can overcome variations in the HCV genotype. However, in mammalian cells, long dsRNA induced an interferon response and caused cell death. Here we describe an improvement of this method, U6 promoter-driven expression of long hairpin-RNA with multiple point mutations in the sense strand. This can efficiently silence HCV RNA replication and HCV protein expression without triggering the interferon response or cell death normally caused by dsRNA. In conclusion, intracellular-diced dsRNA efficiently induces RNAi, and, despite the high rate of mutation in HCV, it should be a feasible therapeutic strategy for silencing HCV RNA.

Base Sequence↗
PubMed2004

Recent advances in rhinovirus therapeutics.

Human rhinoviruses are the major causative agents of the common cold. Because there are greater than 100 viral serotypes, little immunological protection is afforded to humans by prior rhinovirus exposure, which accounts for the high incidence of infection. In most cases, rhinovirus leads to a short self-limiting illness. However, for asthmatics, the elderly and immunocompromised patients, rhinovirus infection can lead to life-threatening complications. This has spurred a consistent effort over recent decades to identify effective treatments and preventions for rhinovirus infection. While some work has focused on alleviating the symptoms induced as a result of inflammatory pathways stimulated by rhinoviruses, the majority of the research has been focused on limiting or preventing viral infection altogether. Various approaches have been taken to halt rhinovirus infection. Prevention of virus-cell interaction has been the aim of research on viral capsid binders and cell receptor blockers. Interference with correct viral protein processing is the goal of the design and testing of protease inhibitors. Current work is attempting to interfere with viral RNA replication by testing silencing RNA molecules. In this review, we will discuss recent advances in the development and testing of human rhinovirus therapeutics.

Antiviral Agents↗
PubMed2000

Anti-(herpes simplex virus) activity of 4'-thio-2'-deoxyuridines: a biochemical investigation for viral and cellular target enzymes.

The antiviral activity of several nucleoside analogues is often limited by their rapid degradation by pyrimidine nucleoside phosphorylases. In an attempt to avoid this degradation, several modified nucleosides have been synthesized. A series of 4'-thio-2'-deoxyuridines exhibits an anti-[herpes simplex virus (HSV)] activity significantly higher (20-600 times) than that shown by the corresponding 4'-oxy counterpart. We investigated the mode of action of these compounds and we found that: (i) several 4'-thio-2'-deoxyuridines are phosphorylated to the mono- and di-phosphates by HSV-1 thymidine kinase (TK) more efficiently than their corresponding 4'-oxy counterpart; (ii) both are inhibitors of cellular thymidylate synthase; (iii) 4'-thio-2'-deoxyuridines are resistant to phosphorolysis by human thymidine phosphorylase; (iv) both 4'-oxy- and 4'-thio-2'-deoxyuridines are phosphorylated to deoxyribonucleotide triphosphate in HSV-1-infected cells and are incorporated into viral DNA; (v) 4'-thio-2'-deoxyuridines are better inhibitors than their 4'-oxy counterparts of [(3)H]thymidine incorporation in HSV-1-infected cells; (vi) 4'-thio-2'-deoxyuridines are not recognized by HSV-1 and human uracil-DNA glycosylases. Our data suggest that 4'-thio-2'-deoxyuridines, resistant to pyrimidine phosphorylase, can be preferentially or selectively phosphorylated by viral TK in HSV-infected cells, where they are further converted into triphosphate by cellular nucleotide kinases. Once incorporated into viral DNA, they are better inhibitors of viral DNA synthesis than their corresponding 4'-oxy counterpart, either because they are not recognized, and thus not removed, by viral uracil-DNA glycosylase, or because they preferentially interfere with viral DNA polymerase.

Antiviral Agents↗
PubMed1985

In vivo interference between pathogenic and non-pathogenic viruses.

The interference among viruses is a well-documented biological phenomenon, both in animals and tissue culture systems. In two of our previous in vivo experiments and in four independent animal experiments, which are described in this presentation, interferences were successfully used to influence the outcomes of viral diseases by using non-pathogenic viruses. In this study, four pathogenic viruses were studied in their natural hosts, and against these viruses, in different combinations, 15 non-pathogenic viruses were tested. There was great variation in mutual effects among pathogenic and non-pathogenic viruses. In our four experiments, the viruses were either simultaneously inoculated or the non-pathogenic viruses were preinoculated. Newcastle disease vaccine (Strain H) had remarkable effects in the development of mouse ascites-associated lymphoma virus. The 50% mortality rate in mice caused by a vaccine strain of rabies virus was reduced to 15% using avian encephalitis virus. The clinical manifestations of rabbit myxoma virus effects were significantly delayed by Newcastle disease vaccine (Strain H). The 72% mortality rate due to Rous sarcoma virus in chickens was decreased to 33.3% when the animals were preinoculated with avian bursa virus vaccine.

Animals↗