SEARCH · PubMed Health

Results for “viral replication”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

PubMed1989

Chronic delta hepatitis: detection of hepatitis delta virus antigen in serum by immunoblot and correlation with other markers of delta viral replication.

To investigate the presence of serum hepatitis delta virus antigen by immunoblot and its correlation with other markers of active viral replication (intrahepatic hepatitis D antigen, IgM antibody to hepatitis D and serum hepatitis D virus RNA), we studied serum samples from 50 patients with chronic hepatitis D virus infection (38 with and 12 without intrahepatic hepatitis D antigen). Of the 38 patients with intrahepatic hepatitis D antigen, 27 (71%) had antigen detectable in serum by immunoblot, whereas only two were reactive by conventional enzyme-linked immunosorbent assay. Thirty-one (82%) patients were also positive for serum hepatitis D virus RNA by spot hybridization and 33 (87%) were positive for IgM anti-hepatitis D virus. All markers were simultaneously present in 24 patients. Circulating hepatitis D antigen was detected in one (8%), IgM anti-hepatitis D in seven (58%) and hepatitis D virus RNA in two (17%) of the 12 patients who had anti-hepatitis D in serum but not detectable hepatitis D antigen in liver. Hepatitis D antigen was not detected in serum of any of the 15 control patients. The results suggest that serum hepatitis D antigen as detected by immunoblot and serum hepatitis D virus RNA are similar in sensitivity for detection of active hepatitis D virus replication during chronic infection and constitute useful, sensitive and noninvasive tests for the diagnosis and monitoring of chronic hepatitis D virus infection.

Adolescent↗

PubMed2006

Possible compartmentalization of hepatitis C viral replication in the genital tract of HIV-1-coinfected women.

BACKGROUND: We estimated the prevalence of hepatitis C virus (HCV) in cervical cytobrush samples from HCV/human immunodeficiency virus (HIV)-coinfected women and analyzed the HCV quasi species in both cytobrush and plasma samples. Possible compartmentalization of viral quasi species in the genital tract and plasma was evaluated by comparison of genetic heterogeneity and use of phylogenetic analysis. METHODS: Paired plasma and cytobrush samples were obtained from 85 HCV/HIV-coinfected women. The presence of HCV in cytobrush samples was evaluated by reverse-transcription polymerase chain reaction of the 5' untranslated region. Viral quasi species were analyzed by cloning and sequencing the highly variable region-1 in 8 patients. RESULTS: HCV was detected in 27% of cytobrush samples. The composition of viral quasi species was different in the 2 body compartments at both the nucleotide and amino acid level. In fact, the mean complexity was significantly lower in cytobrush samples, and a similar trend was observed for the other parameters of heterogeneity. Phylogenetic analysis and amino acid alignment identified several viral variants that were unique to each body compartment. CONCLUSIONS: Our data suggest that the genital and plasma quasi species represent distinct subpopulations, which possibly reflects compartmentalized viral replication. Alternatively, cell carriers harboring viral quasi species in the genital tract that are distinct from those in plasma could transfer the virus through the barrier separating the 2 body sites.

5' Untranslated Regions↗

PubMed1983

Binding of simian virus 40 large T antigen from virus-infected monkey cells to wild-type and mutant viral replication origins.

The binding of purified simian virus 40 (SV40) large T antigen (T) from monkey cells infected with wild-type SV40 virus to viral replication origin-containing DNA fragments was studied by DNase footprinting and restriction endonuclease protection methods. A strong affinity binding site (site 1) of 30 base-pairs and a second, adjacent 40 base-pair lower affinity binding site (site 2), which includes the origin of replication, were detected in these assays. These sites appear identical to those previously noted in similar assays performed with the Ad2 + D2 (D2) T protein. Heating T prior to incubation with DNA significantly increased the binding to these two sites, and the order of binding did not change. Moreover, protection of sequences was observed on both strands in these two sites suggesting that both strands can participate in binding of T to these two sites. Studies with DNAs from two internal site 2 deletion mutants as well as with a DNA fragment lacking the distal 13 base-pairs of site 2 revealed that sequences in the "early" portion of site 2 are sufficient for T binding to the intact site. Furthermore, use of a new assay that measures protection of DNA sequences from specific restriction enzyme cleavage revealed that site 2 can be subdivided into two subsites, 2A and 2B, where 2A corresponds to the above-noted early segment of this locus. In titration experiments, the affinity of 2A for T was greater than that of 2B. Hence, binding to a major portion of the replication initiation sequence (i.e. site 2) is the product of at least two interactions. Finally, analyses performed with DNA from a site 1 deletion mutant, cs1085, revealed that prior binding of T to this locus did not facilitate its binding to site 2. The opposite effect was observed when D2T was employed in these assays. Thus, although similar in many respects, these proteins display a detectable difference in their DNA binding mechanisms.

Animals↗

PubMed1986

[Viral replication and hepatic manifestations in 7 cases of periarteritis nodosa associated with hepatitis B virus].

Viral replication was studied in 7 cases of PAN associated with hepatitis B virus (HBV). Serum and liver were strongly positive for markers reflecting HBV replication (constant high levels of HBe Ag, numerous hepatocytes nuclei reactive for HBc Ag, high DNA-polymerase activity). No cases were found to be positive for delta antigen or antibody. Mild biological and histological signs of liver damage were present in all patients but one. In PAN, high replication might lead to continuous stimulation and formation of circulating immune complexes in antigen excess which deposit in vascular walls with subsequent vasculitis. The demonstration of intense and permanent HBV replication could explain the unsatisfactory results observed with steroids and immunosuppressive drugs. Since steroids have been shown to increase HBV replication, this therapy might contribute to the perpetuation of the immunopathogenic process responsible for PAN. A more rational approach should take advantage of new antiviral drugs inhibiting HBV replication as suggested by preliminary beneficial results.

Adolescent↗

PubMed1973

Herpes simplex virus and human cytomegalovirus replication in WI-38 cells. I. Sequence of viral replication.

A comparison, under standardized conditions, of herpes simplex virus (HSV) and human cytomegalovirus (CMV) revealed differences in viral morphology, in the timing of their infectious cycles, and in several morphological events during those cycles. Structural distinctions between the two viruses included the coating of unenveloped cytoplasmic CMV capsids, but not those of HSV, and a variation in the structure of their cores. Since the two cycles were carried out in the same host cell strain under conditions of one-step growth (input multiplicity = 10 PFU/cell), it was possible to construct time scales locating the major events of each cycle. Comparison of the two showed that HSV replicated and released progeny within 8 h postinfection, whereas CMV required 4 days. These results correlated well with those of concurrent plaque assays. Within the longer CMV cycle, most of the major events appeared retarded to a similar degree, and no obvious limiting step in particle production could be identified. Distinctions between the two cycles included the following: condensation of the chromatin in HSV- but not CMV-infected cells; the greater tendency of HSV to produce membrane alterations; and the appearance of cytoplasmic dense bodies in CMV- but not HSV-infected cells. Identification of these differences even under identical conditions of culture and infection strongly implies that they result from intrinsic differences in the nature of the viruses, and are not caused by variations in experimental conditions.

Cell Line↗

PubMed2002

Degenerate specificity of HTLV-1-specific CD8+ T cells during viral replication in patients with HTLV-1-associated myelopathy (HAM/TSP).

Human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an inflammatory neurologic disease caused by HTLV-1 infection, in which HTLV-1-infected CD4(+) T cells and HTLV-1-specific CD8(+) T cells may play a role in the disease pathogenesis. Patients with HAM/TSP have high proviral loads despite vigorous virus-specific CD8(+) T-cell responses; however, it is unknown whether the T cells are efficient in eliminating the virus in vivo. To define the dynamics of HTLV-1-specific CD8(+) T-cell responses, we investigated longitudinal alterations in HTLV-1 proviral load, amino acid changes in an immunodominant viral epitope, frequency of HTLV-1-specific T cells, and degeneracy of T-cell recognition in patients with HAM/TSP. We showed that the frequency and the degeneracy of the HTLV-1-specific CD8(+) T cells correlated well with proviral load in the longitudinal study. The proviral load was much higher in a patient with low degeneracy of HTLV-1-specific T cells compared to that in a patient with comparable frequency but higher degeneracy of the T cells. Furthermore, in a larger number of patients divided into 2 groups by the proviral load, those with high proviral load had lower degeneracy of T-cell recognition than those with low proviral load. Sequencing analysis revealed that epitope mutations were remarkably increased in a patient when the frequency and the degeneracy were at the lowest. These data suggest that HTLV-1-specific CD8(+) T cells with degenerate specificity are increased during viral replication and control the viral infection.

Amino Acid Substitution↗

PubMed2004

Inhibition of hepatitis C virus nonstructural protein, helicase activity, and viral replication by a recombinant human antibody clone.

Hepatitis C virus (HCV) nonstructural protein 3 (NS3), with its protease, helicase, and NTPase enzymatic activities, plays a crucial role in viral replication, and therefore represents an ideal target for the development of anti-viral agents. We have developed a recombinant human antibody (Fab) that reacts with the helicase domain of HCV NS3. The affinity-purified Fab antibody completely inhibited the helicase activity of HCV NS3 at equimolar concentration. To evaluate the effect of the Fab on HCV replication, the clone encoding the Fab gene was put into an expression vector, which converts Fab into a complete IgG1 antibody. Using a DNA-based transfection model, we demonstrated that intracellular expression of this antibody resulted in significant reduction of HCV-negative strand RNA synthesis. Intracellular expression of this antibody into either a stable cell line replicating subgenomic RNA, or a transient full-length HCV replication model, reduced both HCV RNA and viral protein expression. These results support the use of recombinant antibody fragments to inhibit NS3 enzyme as a novel, feasible, and effective approach for inhibiting HCV replication.

Animals↗

PubMed2003

The human cytomegalovirus major immediate-early enhancer determines the efficiency of immediate-early gene transcription and viral replication in permissive cells at low multiplicity of infection.

To determine the effect of the human cytomegalovirus (CMV) major immediate-early (MIE) enhancer or promoter on the efficiency of viral replication in permissive human cells, we constructed recombinant viruses with their human MIE promoter, enhancer, and promoter plus enhancer replaced with the murine CMV components. After a low multiplicity of infection (MOI) (0.01 PFU/cell), recombinant human CMV with the murine CMV promoter replicated like the wild type but recombinant virus with the murine enhancer replicated less efficiently. Immediate-early (IE) viral protein pIE72 (UL123), early viral protein (UL44), and viral DNA synthesis were significantly decreased. The effect of the human CMV enhancer substitution with the murine CMV enhancer was also demonstrated in different cell types by using recombinant virus with the UL127 promoter, driving the expression of green fluorescent protein (GFP). After an MOI of 1, GFP expression was high with the human CMV enhancer and significantly lower with the murine CMV enhancer. Even though at a high MOI (10 PFU/cell), the murine CMV enhancer was as efficient as the human CMV enhancer for the transcription of IE genes in human foreskin fibroblast cells, at lower MOIs, the murine CMV enhancer was less efficient. Proximal and distal chimeras of the human and murine enhancers also replicated less efficiently at a low MOI and expressed lower levels of GFP from the UL127 promoter. These experiments demonstrate that the entire human CMV enhancer has evolved for the efficient expression of the viral IE and early genes in human cells. Possible functions of the human CMV enhancer and promoter at a low MOI are discussed.

Animals↗

PubMed1998

High SDF-1 expression in HIV-1 carriers does not correlate with CD8+ T-cell-mediated suppression of viral replication.

Stromal cell-derived factor 1 (SDF-1) inhibits T-cell tropic (T-tropic) HIV-1 infection in vitro. In this study, we examined the regulatory role of SDF-1 on HIV-1 replication in peripheral blood mononuclear cells (PBMC) of HIV-infected individuals. We found that the amount of SDF-1 mRNA in freshly isolated PBMC of HIV-1 carriers was higher than in healthy donors. Moreover, PBMC from some asymptomatic carriers (ACs) exhibited high levels of SDF-1 mRNA expression. The level of SDF-1 expression in PBMC did not correlate with the magnitude of CD8+ T-cell-mediated suppression of HIV-1 among ACs SDF-1 inhibited HIV-1 replication at the viral entry step, whereas a single-cycle HIV-1 infection system showed that the major part of the CD8+ T-cell-mediated suppression occurs after intracellular penetration of the virus. Our results suggest that SDF-1 acts as a suppressor of virus replication in a CD8+ T-cell-independent mechanism in HIV-infected individuals.

Base Sequence↗

PubMed1991

Non-replicating deletion mutants of brome mosaic virus RNA-2 interfere with viral replication.

Naturally occurring defective interfering RNAs (DI-RNAs) and satellite RNAs greatly reduce the accumulation of their helper virus in vivo, but often modulate symptom expression in an unpredictable manner. Deletion mutants Nc/S, Na/M and Sa/Nc + M/S, derived from brome mosaic virus (BMV) RNA-2, failed to replicate when co-inoculated with BMV RNAs-1 and -2 to barley protoplasts. However, the inoculum RNA corresponding to these deletion mutants was extremely stable and could have been mistaken for plus-strand progeny had minus-strand progeny analysis been omitted. These results accentuate the need for such tests in evaluating the ability of mutant viral sequences to replicate. One of the mutants, Nc/S, effectively interfered with the accumulation of BMV RNAs-1 and -2 in barley protoplasts. This non-replicating interfering RNA was termed NRI RNA-2 Nc/S. When present with RNAs-1 and -2 at low inoculum amounts (1 microgram), NRI RNA-2 Nc/S reduced replication of RNA-2, the parental RNA, by 63% and preferentially interfered with minus-strand RNA accumulation. At higher levels (4 micrograms), it completely displaced replication of both RNAs-1 and -2. Mutations eliminating translation of a truncated p2a protein from NRI RNA-2 Nc/S did not alleviate the interference effect, demonstrating that a defective replicase protein was not responsible for the decreased accumulation of genomic RNA. At an NRI RNA: genomic RNA inoculum molar ratio of 1:1, NRI RNA-2 Nc/S reduced the accumulation of all helper virus RNAs by 55%. Since this reduction was seen for both wild-type RNA-3 and delta SGP RNA-3, a deletion mutant of RNA-3 that lacks the subgenomic promoter necessary for coat protein expression, it was evident that the effective interference mediated by NRI RNA-2 Nc/S was not mitigated by encapsidation. The ability of the NRI RNAs to mimic satellite DI RNAs in depressing helper virus replication suggests that their expression in transgenic plants may provide a new and widely applicable approach for inducing resistance to viral infection.

Blotting, Northern↗

PubMed1989

Detection of proteins encoded by the pre-S region of hepatitis B virus in the sera of HBsAg carriers: relation to viral replication.

In order to determine the relationship between the presence of pre-S1 and pre-S2 proteins and the level of hepatitis B virus (HBV) replication, a study of 94 HBsAg chronic carriers, 15 anti-HBe positive patients who suffered a viral reactivation and 12 HBeAg, HBV-DNA positive cases under antiviral therapy, has been carried out. Pre-S1 and pre-S2 antigens were detected by RIA using polystyrene beads coated with anti-preS1 or anti-preS2 (Dr W. Gerlich, Göttingen) and 125I-anti-HBs as tracer. The presence of pre-S1 and pre-S2 antigens was detected in 74 (79%) and 85 (90%), respectively, out of the 94 HBsAg chronic carriers included. The level of these antigens was significantly higher in HBeAg, HBV-DNA positive patients than in the other patients (p less than 0.05). Among anti-HBe positive patients suffering a reactivation, a significant increase of pre-S1 and pre-S2 levels was observed, concurring with ALT exacerbation and HBV-DNA positivity. After reactivation, the level of pre-S antigens returned to the basal values. A significant decrease in pre-S antigen levels (p less than 0.05) among patients who respond to recombinant interferon therapy was observed, while no changes were detected among non-responder cases. The detection of pre-S1 and pre-S2 antigens in serum is more frequent in those patients with high viral replication. Furthermore, among anti-HBe carriers with a viral reactivation, synthesis of pre-S antigens takes place again.

Adult↗

PubMed1989

Mammalian tissue culture growth, viral replication, and cultivation using serum replacement factor.

Variability, cost, and availability of fetal bovine serum are in question; thus, we examined whether using a serum replacement factor in multiple mammalian tissue cultures could support not only cell growth, but also viral replication, expression, and retention of phenotypic markers. By using a serum replacement in defined media, we demonstrated multipassage cell growth of several different cell lines and viral cultivation and replication equivalent to fetal bovine serum. Moreover, by supplementing media with a serum replacement factor we observed at least a 28% financial savings.

Animals↗

PubMed1990

The BamHI J fragment (0.706 to 0.737 map units) of pseudorabies virus is transcriptionally active during viral replication.

The BamHI J fragment of the pseudorabies virus (PRV) genome has not been associated with any viral transcripts during viral replication. In this report, data are presented to show that a portion of BamHI-J is transcribed during a productive infection. Four oligo(dT)-cellulose-selected RNA species were detected by hybridization with probes derived from BamHI-J. These RNAs were partially colinear, and they were transcribed in the opposite orientation with respect to the immediate-early gene (IE180) of PRV. At least one of the transcripts overlapped (antisense) the coding sequence of IE180 by 450 nucleotides. Expression of these RNAs was sensitive to phosphonoacetic acid, indicating that they are transcripts of PRV late genes. There were several similarities between these RNAs and the latency-associated transcripts detected in the trigeminal ganglia of swine latently infected with PRV (A. K. Cheung, J. Virol. 63: 2908-2913, 1989).

Animals↗

PubMed2004

A loss of viral replicative capacity correlates with altered DNA polymerization kinetics by the human immunodeficiency virus reverse transcriptase bearing the K65R and L74V dideoxynucleoside resistance substitutions.

Mechanisms governing viral replicative capacity are poorly understood at the biochemical level. Human immunodeficiency virus, type 1 reverse transcriptase (HIV-1 RT) K65R or L74V substitutions confer viral resistance to 2',3'-dideoxyinosine (ddI) in vivo. The two substitutions never occur together, and L74V is frequently found in patients receiving ddI, while K65R is not. Here we show that recombinant viruses carrying K65R and K65R/L74V display the same resistance level to ddI (about 9.5-fold) relative to wild type. Consistent with this result, purified HIV-1 RT carrying K65R RT or K65R/L74V substitutions exhibits an 8-fold resistance to ddATP as judged by pre-steady state kinetics of incorporation of a single nucleotide into DNA. Resistance is due to a selective decrease of the catalytic rate constant k(pol): 22-fold (from 7.2 to 0.33 s(-1)) for K65R RT and 84-fold (from 7.2 to 0.086 s(-1)) for K65R/L74V RT. However, the K65R/L74V virus replication capacity is severely impaired relative to that of wild-type virus. This loss of viral fitness is correlated to a poor ability of K65R/L74V RT to use natural nucleotides relative to wild-type RT: 15% that of wild-type RT for dATP, 36% for dGTP, 50% for dTTP, and 25% for dCTP. The order of incorporation efficiency is wild-type RT > L74V RT > K65R RT > K65R/L74V RT. Processivity of DNA synthesis remains unaffected. These results explain why the two mutations do not combine in the clinic and might give a mechanism for a decreased viral fitness at the molecular level.

Cells, Cultured↗

PubMed1988

Markers of viral replication in patients with chronic hepatitis B virus infection.

Serum samples from 56 patients with biopsy-proven chronic B viral hepatitis without superimposed delta hepatitis were analyzed for the various markers of viral replication, including serum hepatitis B e Ag (HBeAg), hepatitis B virus deoxyribonucleic acid (HBV-DNA), and hepatitis B core antigen (HBcAg) in the liver tissues. Twenty-seven patients had persistent viral hepatitis (PH) and 29 patients had chronic active hepatitis (CAH) with or without cirrhosis. HBV-DNA was identified in the sera of 81% of patients with PH and 60% of patients with CAH. Significantly higher levels of HBV-DNA were found in patients with PH than in those with CAH. Both HBeAg in serum and HBcAg in liver correlated positively with serum HBV-DNA. Nine patients had serum HBV-DNA in the absence of HBeAg (four had anti-HBe), and seven of these nine patients had stainable HBcAg in the liver (two did not have staining). None of these patients had hepatic HBcAg in the absence of serum HBV-DNA. When these patients were stratified according to their epidemiologic background, serum HBV-DNA was present in a significantly higher number of male homosexuals than in any other groups. This was unrelated to their status of human immunodeficiency viral serology.

Chronic Disease↗

PubMed1996

Characterization of human papillomavirus-11 mRNAs expressed in the context of autonomously replicating viral genomes.

We have previously adapted an experimental system which supports autonomous replication of human papillomavirus-11 (HPV-11) genomic DNA in a human squamous carcinoma cell line (SCC-4) following electroporation of linearized viral DNA. This system allows evaluation of HPV-11 transcription in the context of replicating viral genomes. RNA was isolated from cells following transfection, and first-strand cDNA was produced by reverse transcription using HPV-11-specific primers. The cDNAs were amplified using the polymerase chain reaction, and resulting DNA products were cloned and sequenced. Transcripts were identified that utilize the same splice donor and acceptor sites as transcripts characterized previously from human lesions. Three previously unreported splice junctions that employ novel combinations of those splice sites were also identified. We also detected these newly identified transcripts in laryngeal papillomas. A modified version of the 5' rapid amplification of cDNA ends method was used to identify transcriptional start sites of several of the HPV-11 transcripts. The family of mRNAs characterized in this replication system have the potential to encode all of the major HPV-11 E-region proteins described to date. The data support the utility of this system as an experimental model for examining mechanisms of viral replication and transcription.

Base Sequence↗

PubMed2005

Virus factories: associations of cell organelles for viral replication and morphogenesis.

Genome replication and assembly of viruses often takes place in specific intracellular compartments where viral components concentrate, thereby increasing the efficiency of the processes. For a number of viruses the formation of 'factories' has been described, which consist of perinuclear or cytoplasmic foci that mostly exclude host proteins and organelles but recruit specific cell organelles, building a unique structure. The formation of the viral factory involves a number of complex interactions and signalling events between viral and cell factors. Mitochondria, cytoplasmic membranes and cytoskeletal components frequently participate in the formation of viral factories, supplying basic and common needs for key steps in the viral replication cycle.

Animals↗

PubMed2005

Relocalization of the Mre11-Rad50-Nbs1 complex by the adenovirus E4 ORF3 protein is required for viral replication.

Adenovirus replication is controlled by the relocalization or modification of nuclear protein complexes, including promyelocytic leukemia protein (PML) nuclear domains and the Mre11-Rad50-Nbs1 (MRN) DNA damage machinery. In this study, we demonstrated that the E4 ORF3 protein effects the relocalization of both PML and MRN proteins to similar structures within the nucleus at early times after infection. These proteins colocalize with E4 ORF3. Through the analysis of specific viral mutants, we found a direct correlation between MRN reorganization at early times after infection and the establishment of viral DNA replication domains. Further, the reorganization of MRN components may be uncoupled from the ability of E4 ORF3 to rearrange PML. At later stages of infection, components of the MRN complex disperse within the nucleus, Nbs1 is found within viral replication centers, Rad50 remains localized with E4 ORF3, and Mre11 is degraded. The importance of viral regulation of the MRN complex is underscored by the complementation of E4 mutant viruses in cells that lack Mre11 or Nbs1 activity. These results illustrate the importance of nuclear organization in virus growth and suggest that E4 ORF3 regulates activities in both PML nuclear bodies and the MRN complex to stimulate the viral replication program.

Acid Anhydride Hydrolases↗