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Results for “VIRAL INTERFERENCE”

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At least 559 records · Page 31Linked to original sources
PubMedDate not supplied

[Effect of the method of passage on the biological properties of attenuated alphavirus strains].

Experiments with attenuated clones of Venezuelan equine encephalomyelitis virus and Eastern equine encephalomyelitis virus were carried out to study the regularities in changes of biological properties of virus in "undiluted" passages and in passages by subcultivation of small doses. In the latter case the biological activity of the virus remained at the initial low level but in "undiluted" passages it increased, due to accumulation in the population of clones with altered plaque phenotype and increased reproductive potential. In a number of cases this virus had a higher level of residual virulence than the original one. The evidence that the main source of virus variability in the "undiluted" passages lies, in genetic interaction in which defective virus takes part, is presented. Mixed infection with participation of defective interfering particles and the genetic interaction occurring in it are considered to be the mechanism which is conducive to restoration of biological activity of alphaviruses.

Alphavirus↗
PubMed1982

RNA synthesis in the L cell-SV5 system.

Comparative analysis of the ribonucleoprotein RNA synthesis was performed in two persistently infected L cell systems. In the first (LSV5-I), cells were infected with the cloned standard SV5 virus, in the second (LSV5-II), infecting virus had been enriched with defective interfering particles (DIP). The LSV5(I) system in its 40th-42nd passages was similar to LSV5(II) at the 2nd-3rd passage levels. There was shown that the ribonucleoprotein 3H-RNA synthesized falls into two classes: the minor corresponding to 50S viral RNA and the major revealing predominantly low molecular RNA. The decrease of the synthesis of the heavy viral RNA fraction and the prevalence of the low molecular RNA promoted the limitation of infection, the survival of cells and prolonged the carrier state. The possible correlation between low molecular RNA synthesis and DIP formation in the L cell-SV5 system is discussed.

Animals↗
PubMedDate not supplied

[Defective interfering mumps virus produced by chronically infected cell cultures].

HEp-2 and L-41 culture chronically infected with mumps virus at late passage levels produced 10(2)--10(3) PFU/ml small-plaque slow-replicating virus and defective interfering particles (DIP) in significant amounts. The DIP were characterized by the polypeptide composition similar to that of the virus, the presence of subgenome sise of RNA, and marked interfering activity with regard to the original mumps virus.

Animals↗
PubMedDate not supplied

[Properties of influenza virus isolated from the bodies of mice at different stages of experimental influenza].

The results of the study of persistent influenza infection in S57BL mice developing after inoculation with influenza virus enriched with defective-interfering (DI) particles are presented. Regular isolation of the virus from lung tissues of the infected animals for 45 days after infection was observed. At later intervals after infection (2-8 months), the lungs and spleens yielded 8 virus strains differing from the original by their pathogenicity for mice, and thermostability of hemagglutinin. Examinations by gel electrophoresis of a strain isolated 6 months after inoculation revealed changes in the mobility of M and NS proteins which could produce some phenotypic changes of the virus in the course of persistent infection.

Animals↗
PubMedDate not supplied

[Properties of the rabies virus long persisting in cell cultures].

Properties of rabies virus (RV) persisting in chronically infected cultures (CIC): HEp-2--RV and BHK-RV were studied. RV from the HEp-2-RV system retained its pathogenicity for mice for more than 3 years of observation. RV from the BHK-RV system lost this property after 50 passages in CIC. Both RV variants from CIC formed plaques in CER cells, showed marked immunogenic activity in mice, had no interferon-inducing activity in BHK-21 cells, and were not temperature-sensitive. Electron microscopic examinations of CIC culture fluids showed virions of bullet-like, oval, or spherical shapes.

Animals↗
PubMedDate not supplied

[Use of the plaque method to reveal the phenomenon of autointerference in influenza virus].

The paper describes a simple and convenient method for qualitative and quantitative evaluation of the capacity of influenza virus for autointerference consisting in the lack or considerable reduction of the cytolytic effect of the virus under agar overlay at a high multiplicity of infection. Some experimental and theoretical arguments assuming the role of defective interfering particles in the formation of the observed phenomenon. It is assumed that the detection of autointerference under agar may be used as an additional criterion for detection of non-plaque-forming strains of influenza virus, tentative determination of their interfering capacity as well as for the establishment of biological relationships of viruses.

Defective Viruses↗
PubMed1993

Expression of mouse furin in a Chinese hamster cell resistant to Pseudomonas exotoxin A and viruses complements the genetic lesion.

RPE.40 is a strain of mutated CHO-K1 cells with elevated resistance to Pseudomonas exotoxin A, Sindbis virus, and Newcastle disease virus. Virus resistance is due to an inability to cleave precursor viral membrane glycoproteins and produce infectious virions. Transfection of RPE.40 cells with cDNA for mouse furin causes them to lose all resistance and become as sensitive as wild-type cells to the toxin and viruses. Transfection of RPE.40 cells with cDNA for the related yeast protease Kex2 reduces their resistance to the toxin and viruses, but does not completely eliminate it.

ADP Ribose Transferases↗
PubMed2003

Local gene knockdown in the brain using viral-mediated RNA interference.

Conditional mutant techniques that allow spatial and temporal control over gene expression can be used to create mice with restricted genetic modifications. These mice serve as powerful disease models in which gene function in adult tissues can be specifically dissected. Current strategies for conditional genetic manipulation are inefficient, however, and often lack sufficient spatial control. Here we use viral-mediated RNA interference (RNAi) to generate a specific knockdown of Th, the gene encoding the dopamine synthesis enzyme tyrosine hydroxylase, within midbrain neurons of adult mice. This localized gene knockdown resulted in behavioral changes, including a motor performance deficit and reduced response to a psychostimulant. These results underscore the potential of using viral-mediated RNAi for the rapid production and testing of new genetic disease models. Similar strategies may be used in other model species, and may ultimately find applications in human gene therapy.

Animals↗
PubMed2005

Cross-inhibition to heterologous foot-and-mouth disease virus infection induced by RNA interference targeting the conserved regions of viral genome.

RNA interference (RNAi) is the process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of messenger RNA in animal and plant cells. In mammalian cells, RNAi can be triggered by 21-23 nucleotide duplexes of small interfering RNA (siRNA). Strategies to inhibit RNA virus multiplication based on the use of siRNAs have to consider the high genetic polymorphism exhibited by this group of virus. Here we described a significant cross-inhibition of foot-and-mouth disease (FMD) virus (FMDV) replication in BHK-21 cells by siRNAs targeted to various conserved regions (5'NCR, VP4, VPg, POL, and 3'NCR) of the viral genome. The results showed that siRNAs generated in vitro by human recombinant dicer enzyme gave an inhibition of 10- to 1000-fold in virus yield of both homologous (HKN/2002) and heterologous (CHA/99) isolates of FMDV serotype O at 48 h post-infection (hpi). The inhibition extended to at least 6 days post-infection. For serotype Asia1, the virus yield in YNBS/58-infected cells examined at 12, 24, and 48 hpi decreased by approximately 10-fold in cells pretreated with HKN/2002-specific siRNAs, but there was no significant decrease at 60 hpi. The inhibition was specific to FMDV replication, as no reduction was observed in virus yield of pseudorabies virus, an unrelated virus. Moreover, we also demonstrated an enhanced viral suppression could be achieved in BHK-21 cells with siRNA transfection after an infection had been established. These results suggested that siRNAs directed to several conserved regions of the FMDV genome could inhibit FMDV replication in a cross-resistance manner, providing a strategy candidate to treat high genetic variability of FMDV.

3' Untranslated Regions↗