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At least 127 records · Page 7Linked to original sources
PubMed1993

Dissociation between lymphoproliferative responses and virus replication in mice with different sensitivities to retrovirus-induced immunodeficiency.

Murine AIDS (MAIDS) is induced by a replication-defective virus (BM5d). In susceptible mice (C57BL/6J), inoculation with LP-BM5 murine leukemia virus, which consists of the BM5d virus and replication-competent B-tropic ecotropic (BM5e) and milk cell focus-inducing (BM5-MCF) helper viruses results in the polyclonal proliferation of T and B cells, immunodeficiency, and the expansion of B cells containing the BM5d provirus followed by the development of B-cell lymphomas. Several strains of mice that are resistant to LP-BM5-induced murine AIDS have been identified, and major histocompatibility complex genes as well as non-major histocompatibility complex genes were shown to play a role in this resistance. In the present study, we have examined and compared the replication of the BM5d and BM5e viruses after inoculation of LP-BM5 into sensitive (C57BL/6J) and resistant (C57BL/KSJ) mice. Using a specific polymerase chain reaction, we could detect the BM5d and BM5e proviruses as early as 1 week postinfection in the sensitive mice, and the levels of both viruses increased significantly with the progression of the disease. In contrast, in the resistant C57BL/KSJ mice, replication of BM5d and BM5e was restricted and no BM5d and only very low levels of the BM5e provirus could be detected either at early or late times postinoculation with the LP-BM5 virus mixture. Inoculation with LP-BM5 did not lead to the production of antibodies that could recognize the BM5d-encoded Pr60gag in either the sensitive or resistant mice; however, production of antibodies recognizing the env-related proteins of the helper virus was detected in the resistant but not in the sensitive mice at late times postinfection. Interestingly, inoculation with LP-BM5 increased polyclonal stimulation of spleen cells and decreased mitogen stimulation in both strains of mice. This stimulation of splenocytes persisted in the sensitive mice but decreased after a few weeks in the resistant mice. These results show an early block in BM5d and BM5e replication in the resistant C57BL/KSJ mice and indicate that resistance is a consequence of the inhibition of an onset of the BM5d virus infection and its expansion. However, initial responses to virus infection such as proliferation of spleen cells and response to mitogen are similar in both strains of mice and are therefore not necessarily related to the development of the disease.

Animals↗
PubMed2005

Virus-inducible reporter genes as a tool for detecting and quantifying influenza A virus replication.

The use of influenza A virus-inducible reporter gene segments in detecting influenza A virus replication was investigated. The RNA polymerase I promoter/terminator cassette was used to express RNA transcripts encoding green fluorescence protein or firefly luciferase flanked by the untranslated regions of the influenza A/WSN/33 nucleoprotein (NP) segment. Reporter gene activity was detected after reconstitution of the influenza A virus polymerase complex from cDNA or after virus infection, and was influenza A virus-specific. Reporter gene activity could be detected as early as 6 h post-infection and was virus dose-dependent. Inhibitory effects of antibodies or amantadine could be detected and quantified rapidly, providing a means of not only identifying influenza A virus-specific replication, but also of determining the antigenic subtype as well as antiviral drug susceptibility. Induction of virus-specific reporter genes provides a rapid, sensitive method for detecting virus replication, quantifying virus titers and assessing antiviral sensitivity as well as antigenic subtype.

Animals↗
PubMed1993

Ectromelia virus replication in major target organs of innately resistant and susceptible mice after intravenous infection.

The kinetics of ectromelia virus replication in the spleen and liver and of alpha/beta interferon production in the spleen were determined during the first 3 days after intravenous infection with the virulent Moscow strain in resistant C57 BL/6 and susceptible DBA/2 mice. Virus replication in the spleen as measured by assays for virus DNA and infectious centers was suppressed in C57BL/6 mice relative to DBA/2 mice within the first 1 or 2 days of infection. Infectious centers increased in DBA/2 mice but not in C57 BL/6 mice. Differences in virus replication between strains were less discrete when spleens were assayed for infectious virus than when they were assayed for infectious centers because infectious centers of most C57 BL/6 mice had more infectious virus than infectious centers of DBA/2 mice. Virus replication in the liver, the major target organ, as measured by virus DNA and infectious virus assays, was suppressed in C57 BL/6 mice relative to DBA/2 mice 3 days after infection but not before that interval. The results indicate that genetic control of ectromelia virus replication begins within the first 1 or 2 days of infection in the spleen but is delayed in the liver and that genetic control is directed at the prevention of virus spread more than at virus replication.

Animals↗
PubMedDate not supplied

[Induction of alphavirus ts-mutations by N-methyl-N-nitro-N-nitrosoguanidine added to the replicating virus].

The possibility of producing ts mutants of Sindbis and eastern equine encephalomyelitis (EEE) virus by treatment of replicating virus with N-methyl-N-nitro-N-nitrosoguanidine was studied. N-methyl-N-nitro-N-nitrosoguanidine added in a concentration of 20 micrograms/ml to chick fibroblast cultures infected with Sindbis virus for 4 hours was shown to induce ts mutations in the virus. Under similar conditions no ts mutants of EEE virus could be obtained. The content of ts mutants in the mutagenized populations of Sindbis virus was 7.9%. Eight ts mutants were isolated. Their temperature-sensitive defect was expressed to various degrees. The plaque-forming efficiency at 40 degrees C/35 degrees C ranged from 6.3 X 10(-2) to 1.7 X 10(-8), and the yield from 5.6 X 10(-2) to 2.8 X 10(-4).

Alphavirus↗
PubMed1996

Vaccinia virus replication is independent of cellular HSP72 expression which is induced during virus infection.

HSP72 is dramatically induced in the ovaries of vaccinia virus (VV)-infected mice and associates with VV proteins. In order to investigate the role of HSP72 during vaccinia virus replication, we have constructed a recombinant vaccinia virus encoding the major inducible cellular HSP72 (VV-HSP72+) and examined the replication characteristics of this virus. VV-HSP72+ exhibited growth kinetics identical to and peak titers very similar to those of control viruses, both in vitro and in vivo. In particular, replication of VV-HSP72+ was identical to that of control viruses in the HSP72-negative cell line Y3.Ag.1.2.3, and overexpression of HSP72 had no effect on the virulence of VV infection in normal or immunocompromised mice. We conclude that while VV infection results in the induction of the major inducible 72-kDa HSP, VV replication proceeds normally in the absence of this protein. It is unclear whether another celluar chaperone is required to facilitate virus replication in place of HSP72 in Y3.Ag.1.2.3 cells or whether HSP expression plays no role in virus replication, but is simply a component of the generalized stress response to virus infection.

Animals↗
PubMed2006

Characterization of white spot syndrome virus replication in in vitro-cultured haematopoietic stem cells of freshwater crayfish, Pacifastacus leniusculus.

Replication of White spot syndrome virus (WSSV) was investigated in haematopoietic cells (hpt cells) derived from haematopoietic tissue (hpt) of freshwater crayfish, Pacifastacus leniusculus. Temperature and type of inoculum for virus replication were studied. The cell culture remained viable at a wide range of temperatures ranging from 4 to 25 degrees C. WSSV replicated in cells, as evidenced by in situ hybridization, RT-PCR and by the presence of virions visualized with an electron microscope. Moreover, the results showed that the infectivity of WSSV to hpt cells is dependent on temperature and a supplemented growth factor (cytokine) astakine. WSSV replicated more rapidly at higher temperatures than at lower temperatures. No virus replication was observed at 4 degrees C. Detectable WSSV-infected cells were present as early as 36 h post-inoculation, demonstrated by in situ hybridization or RT-PCR of VP28 expression at 25 degrees C. Hpt cells can survive a few weeks at 25 or 16 degrees C and longer than several months at 4 degrees C.

Animals↗
PubMed1988

Combined effects of fasting and diet on interferon production and virus replication in calves infected with a vaccine strain of infectious bovine rhinotracheitis virus.

A study was undertaken to investigate the combined effects of fasting and different diets on interferon (IFN) production and virus replication measured in nasal secretions of calves inoculated with a vaccine strain of infectious bovine rhinotracheitis virus. Four groups of calves were inoculated intranasally with infectious bovine rhinotracheitis virus. Two groups were inoculated 24 hours after onset of a 3-day fast; upon refeeding, 1 group was fed a maintenance diet (M diet) of hay, and the other was fed a higher energy diet (HE diet) of hay and concentrate. Nonfasted control groups were fed the M diet or the HE diet. Overall IFN production was highest (P less than 0.01) in nonfasted calves fed the M diet throughout the study and lowest in nonfasted calves fed the HE diet. Fasted calves refed the HE diet produced consistently and significantly more IFN than did nonfasted calves fed this diet. Fasted calves refed the M diet, however, produced significantly less IFN, compared with control calves fed the M diet throughout the study. Overall mean virus excretion was similar in all groups; therefore, the amount of virus replication per se did not account for the differences in IFN production, nor did greater IFN production result in less virus excretion. Serum cortisol concentrations and immune responses were not significantly affected by fasting or diet.

Animals↗
PubMed2005

Reduced expression of the rotavirus NSP5 gene has a pleiotropic effect on virus replication.

Rotavirus RRV gene 11 encodes two non-structural proteins, NSP5 and NSP6. NSP5 is a phosphorylated non-structural protein that binds single- and double-stranded RNA in a non-specific manner. Transient expression of this protein in uninfected cells has provided evidence for its participation in the formation of electron-dense cytoplasmic structures, known as viroplasms, which are thought to be key structures for the replication of the virus. NSP6 is a protein of unknown function that seems not to be essential for virus replication in cell culture. To study the function of NSP5 in the context of a viral infection, the expression of RRV gene 11 was silenced by RNA interference. Reduction in the synthesis of NSP5, as shown by immunoblot and immunofluorescence assays, correlated with a reduction in the number and size of viroplasms and with an altered intracellular distribution of other viroplasm-associated proteins. Silencing of gene 11 also resulted in a reduced synthesis of viral RNA(+) and double-stranded RNA and of all viral proteins, as well as in a decreased production of infectious virus. A similar phenotype was observed when the NSP5 coding gene of the lapine rotavirus strain Alabama was silenced. The fact that the NSP5 gene of rotavirus Alabama lacks the AUG initiator codon for a complete NSP6 protein, suggests that the described phenotype in gene 11-silenced cells is mostly due to the absence of NSP5. The data presented in this work suggest that NSP5 is a key protein during the replication cycle of rotaviruses.

Animals↗
PubMed1997

The cysteine residues of the M2 protein are not required for influenza A virus replication.

The M2 protein of influenza A virus functions as an ion channel. It contains three cysteine residues: cysteines 17 and 19, which form disulfide bonds in the ectodomain, and cysteine 50 which is acylated. To understand the role of these cysteine residues in virus replication, we used reverse genetics to create influenza viruses in which the individual cysteines were mutated and a virus in which all three cysteines were changed to serine. The M2 cysteine mutants that lacked either of the cysteine residues in the ectodomain and the mutant that lacked all three residues had appreciably lower amounts of M2 oligomers than did the wild-type virus when examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. None of the mutants, however, were defective in replication, either in vitro or in ferrets and mice. These findings demonstrate that noncovalent interactions are sufficient for the M2 protein to form functional oligomers for virus replication and that its cysteine residues are dispensable for influenza virus replication in vitro and in vivo.

Amino Acid Substitution↗
PubMed1994

Hepatitis C virus antibody and hepatitis C virus replication in chronic hepatitis B patients.

We assessed hepatitis C virus infection in 156 chronic hepatitis B patients using second-generation hepatitis C virus antibody (anti-HCV). Active virus replication was further investigated in anti-HCV-positive cases by means of polymerase chain reaction assay for the detection of serum hepatitis C virus RNA. Anti-HCV prevalence was higher in patients negative for hepatitis B e antigen (HBeAg) (10/48, 21%) than in HBeAg-positive patients (10/108, 9%) (p < 0.05), and the reactivity (cut-off index) in anti-HCV enzyme-linked immunosorbent assay of the positive cases was significantly higher in HBeAg-negative patients (4.1 +/- 0.1) than in -positive ones (3.6 +/- 0.6) (p < 0.05). The prevalence of hepatitis C virus RNA in anti-HCV-positive cases was also higher in the HBeAg-negative group (9/10, 90%) than in the -positive group (3/10, 30%) (p < 0.01). Viremia was found in association with high reactivity in anti-HCV ELISA (cut-off index > 3.5) in both groups. Nine (90%) of 10 such cases were viremic in the HBeAg-negative group compared with three (43%) of seven in the HBeAg-positive group (p < 0.05). These results suggest that hepatitis C virus replication may be influenced by hepatitis B virus replicative states, indicating possible interference between hepatitis B and C viruses.

Adult↗
PubMed1990

Monitoring hepatitis B virus replication.

Serum hepatitis B virus DNA is the best marker for monitoring hepatitis B virus replication in the liver. Data are presented on the sensitivity, specificity and application of a standardized solution hybridization assay for the quantitation of hepatitis B viral DNA in serum. The assay is linear over several orders of magnitude in sample concentration and is equivalent in sensitivity and specificity to classic filter hybridization methods employing [32P]DNA probes and autoradiography. The assay provides clinically relevant information for monitoring viral replication before, during and after antiviral therapy.

DNA, Viral↗
PubMed1984

2-5A accumulates to high levels in interferon-treated, vaccinia virus-infected cells in the absence of any inhibition of virus replication.

We investigated the effects of interferon treatment on virus yield, protein synthesis, and the 2-5A system in vaccinia virus-infected HeLa, L929, and CV1 cells. Under the culture conditions used, vaccinia virus replication was relatively insensitive to the antiviral effects of interferon. In L929 and HeLa cells, interferon at 400 reference units (r.u.) per ml had little effect on viral protein synthesis, the virus-induced inhibition of host protein synthesis, or virus yield: 2,000 to 20,000 r.u./ml were required to inhibit these. Despite this, high levels (up to 5 microM) of 2-5A [ppp(A2'p)nA; n greater than or equal to 2] were found during vaccinia infection of all of these types of cells treated with 400 r.u. of interferon per ml, i.e., at interferon concentrations too low to inhibit significantly virus growth. High levels (up to 5 microM) were also found in non-interferon-treated HeLa cells (which have a high constitutive level of 2-5A synthetase) in which vaccinia virus replicates perfectly well. It can be concluded that high levels of 2-5A per se have no necessary antiviral effect on vaccinia virus in these systems. These results are in marked contrast to those obtained here and previously with encephalomyocarditis virus. For example, in HeLa cells less than 20 nM 2-5A accumulated, but virus replication was inhibited by 50 r.u. of interferon per ml (Silverman et al., Eur. J. Biochem. 124:131-138, 1982). The characteristic cleavage of rRNA by the 2-5A-dependent RNase was delayed relative to 2-5A accumulation in the vaccinia virus-infected cells. This delay was not the result of either defective 2-5A or of a stable virus-induced inhibition of the 2-5A-dependent RNase; 2-5A extracted from the cells had full biological activity when assayed by activation of the 2-5A-dependent RNase in cell extract, and the 2-5A-dependent RNase extracted from the vaccinia virus-infected cells was fully active in vitro. The basis for the delay remains to be determined. High levels of 2-5A were not observed when late (DNA synthesis-dependent) vaccinia transcription was inhibited by either cycloheximide or cytosine arabinoside. The only known activator of the 2-5A synthetase is double-stranded RNA. The presence of 2-5A therefore implies the natural occurrence of double-stranded structures in late viral RNA in intact vaccinia virus-infected cells.

Adenine Nucleotides↗