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S O Viazov

Publications and source records attributed to S O Viazov.

At least 19 recordsLinked to original sources
PubMed2001

Performance characteristics of a transcription-mediated nucleic acid amplification assay for qualitative detection of hepatitis C virus RNA.

The detection of hepatitis C virus (HCV) RNA by nucleic acid amplification techniques is the method of choice to differentiate between ongoing and past infection, and can be used to monitor the course of HCV infection. In this study, we evaluated the performance characteristics of a newly developed transcription-mediated amplification (TMA)-based assay, the VERSANT HCV RNA qualitative assay, which was designed to qualitatively detect HCV RNA. Samples tested by the TMA assay included 100 HCV antibody negative sera; serial dilutions of an HCV genotype 1a panel; the WHO HCV RNA standard 76/790; an HCV genotyping panel; and 150 clinical specimens, including sera from patients who had received alpha interferon (IFN) treatment or liver transplants. TMA test results were compared with the Cobas Amplicor HCV polymerase chain reaction (PCR) assay. The analytical specificity of the HCV TMA assay was > 98%. No carry-over contaminations were observed. The assay demonstrated an analytical sensitivity of 100% at 41 HCV RNA copies/mL (genotype 1a panel) and 5 IU/mL (WHO standard), respectively. HCV genotypes and subtypes did not affect the results. Qualitative RNA detection by diagnostic Amplicor PCR and TMA was in agreement in > 97% of all 150 clinical samples tested. In our study, the TMA-based assay proved to be a specific and sensitive method for qualitative HCV RNA detection. The test may turn out to be an attractive alternative to already established techniques for HCV RNA amplification in routine clinical laboratories.

Enzyme-Linked Immunosorbent Assay↗
PubMed2000

Genotyping of hepatitis C virus isolates using CLIP sequencing.

Determination of hepatitis C virus (HCV) genotypes and subtypes has become increasingly important for the clinical management and prognosis of HCV infections. The aim of the present study was to assess the specificity and reliability of a newly developed, commercially available HCV genotyping kit (TRUGENE HCV 5'NC genotyping kit). This technique utilizes PCR fragments previously generated by the diagnostic Roche AMPLICOR HCV test, which are subsequently subjected to simultaneous PCR amplification and direct sequencing (CLIP sequencing) of the 5' noncoding region (5'NCR). HCV isolates from 100 randomly chosen patients were genotyped by both the TRUGENE HCV 5'NC genotyping kit and DNA enzyme immunoassay (DEIA). Typing results obtained by both methods were in complete concordance in 91% of the cases. HCV RNA from the samples with discordant genotype assignment in both assays was additionally amplified with primers from the HCV core and NS5B regions. Phylogenetic analysis of the obtained sequences supported the results obtained from DEIA in six cases and CLIP sequencing in two cases. In the former six cases, the TRUGENE HCV 5'NC genotyping kit could not correctly differentiate between subtypes of genotypes 1 and 2 due to the high conservation of the 5'NCR. However, since there was not any misclassification between HCV genotypes 1 and non-1 types, the results obtained with this system are, in general, reliable and can be used in clinical practice. The TRUGENE HCV 5'NC genotyping kit in our hands proved to be a fast and convenient technique that might be an attractive option for HCV genotyping in laboratories already using the Roche AMPLICOR HCV test for diagnostic reverse transcription-PCR.

5' Untranslated Regions↗
PubMed2000

Sequence heterogeneity of TT virus and closely related viruses.

TT virus (TTV) is a recently discovered infectious agent originally obtained from transfusion-related hepatitis. However, the causative link between the TTV infection and liver disease remains uncertain. Recent studies demonstrated that genome sequences of different TTV strains are significantly divergent. To assess genetic heterogeneity of the TTV genome in more detail, a sequence analysis of PCR fragments (271 bp) amplified from open reading frame 1 (ORF1) was performed. PCR fragments were amplified from 5 to 40% of serum specimens obtained from patients with different forms of hepatitis who reside in different countries (e.g., China, Egypt, Vietnam, and the United States) and from normal human specimens obtained from U.S. residents. A total of 170 PCR fragments were sequenced and compared to sequences derived from the corresponding TTV genome region deposited in GenBank. Genotypes 2 and 3 were found to be significantly more genetically related than any other TTV genotype. Moreover, three sequences were shown to be almost equally related to both genotypes 2 and 3. These observations suggest a merger of genotypes 2 and 3 into one genotype, 2/3. Additionally, five new groups of TTV sequences were identified. One group represents a new genotype, whereas the other four groups were shown to be more evolutionary distant from all known TTV sequences. The evolutionary distances between these four groups were also shown to be greater than between TTV genotypes. The phylogenetic analysis suggested that these four new genetic groups represent closely related yet different viral species. Thus, TTV exists as a "swarm" of at least five closely related but different viruses. These observations suggest a high degree of genetic complexity within the TTV population. The finding of the additional TTV-related species should be taken into consideration when the association between TTV infections and human diseases of unknown etiology is studied.

Base Sequence↗
PubMed1993

[Synthesis and antigenic activity of peptides from core- and NS3-proteins of hepatitis C virus].

We synthesized the 20-34 and 22-34 fragments of the core and 1269-1282 fragment of the NS3 protein of the hepatitis C virus. The peptides were prepared by the solid-phase synthesis using activated esters and symmetrical anhydrides of Boc-amino acids. Peptide 20-34 demonstrated positive reaction in ELISA with all individual sera from HCV chronic patients. Peptide 1269-1282 reacted with 33% patients sera.

Amino Acid Sequence↗
PubMed1993

[Localization of an immunodominant site in the hepatitis delta viral antigen using synthetic peptides].

A set of 8 peptides from the immunodominant region (65-80 aa) of delta-antigen was prepared by solid-phase synthesis. Peptide 71-80 was synthesized in two variants--with different amino acid residues in positions 73, 74 and 76. Free peptides and their conjugates with bovine serum albumin were tested for antigenicity in ELISA. The correlation between the peptide chain's length and its antigenic activity was noted. Peptides 65-80 and 69-80 displayed a positive reaction with all individual sera and pools of sera from HDV chronic patients. Both variants of the peptide 71-80 reacted with 100% of sera pools but only with 83% of individual sera. Smaller peptides from the same 65-80 region (73-80, 69-78, 71-78, 71-76) did not bind to any anti-delta positive serum. All synthesized peptides reacted strongly with rabbit antisera raised to the conjugate of peptide 65-80 with bovine albumin. These findings suggest that delta-antigen contains multiple highly immunogenic epitopes associated with the single immunodominant site between 69 and 80 amino acid residues.

Amino Acid Sequence↗
PubMed1992

[Synthesis and antigenic activity of peptides of the nucleocapsid protein of the hepatitis delta virus].

Hepatitis delta virus (HDV), a recently discovered infectious agent, participates in severe, often lethal forms of acute and chronic hepatitis and liver cirrhosis. Based on theoretical analysis of secondary structure, hydrophilicity and acrophilicity data, several regions of HDV antigen, presumably containing B-epitopes, have been revealed and the corresponding peptides have been synthesized by the solid phase method. All the peptides obtained reacted with the respective antipeptide rabbit sera. The peptides and their conjugates with BSA or KLH were used for ELISA with individual and pooled anti-HD-positive sera from patients with chronic delta hepatitis. The high antigenicity of the peptide 65-80 shows that one of the antigenically active regions of HDAg is situated between these amino acid residues and that the peptide may be used for detection of anti-HD antibodies in patients blood sera.

Amino Acid Sequence↗
PubMed1991

[Chronic hepatitis delta--the course and approaches to therapy].

Variants of chronic hepatitis delta (CHD) course were studied in 94 patients. Slow progress (for decades) occurred most frequently, while rapid progress to hepatic cirrhosis (for 1-2 years) or benign course presenting as greater than 3-year remission were rare findings. In addition to routine therapeutic modalities, except corticosteroids, 43 CHD patients received recombinant alpha 2-interferon (reaferon). Follow-up results evaluated separately for hepatic cirrhosis and free of it CHD patients support clinical promise of Soviet recombinant alpha 2-interferon against CHD.

Adolescent↗
PubMed1984

[Use of a radioimmune method for determining HBsAg in preparations of human gamma-globulin].

The work presents the results of studies made with a view to improve the method of testing gamma-globulin preparations for the presence of hepatitis B virus surface antigen (HBsAg) by means of radioimmunoassay (RIA). The work shows that this method requires the use of specially selected negative control samples made up of pooled gamma-globulin samples. Standard RIA techniques intended for detecting the presence of HBsAg in human plasma and blood serum is not suitable for the analysis of the preparations of human gamma-globulin.

Hepatitis B↗
PubMedDate not supplied

[Comparative study of antigens specific for hepatitis B in transfected cell cultures].

A comparative study of antigens detected in the livers of patients with hepatitis B. in the mesonephros of the human tissue--chick embryo system infected with the agents isolated from the blood of hepatitis patients, as well as antigens detectable in cell cultures transfected by the DNA isolated from these tissues was carried out. The results are in favour of the hypothesis on the integrational nature of serum hepatitis.

Animals↗
PubMedDate not supplied

[Detection of TT DNA virus (TTV) in blood donors and patients with hepatitis of unclear etiology].

A new human infective agent: TT virus (TTV) has been recently identified. The polymerase chain reaction detected TTV DNA in the sera of 5 (31.3%) out of 16 children with acute hepatitis, 5 (17.2%) out of 29 children and 3 (14.3%) out of 21 adults with liver diseases of unknown etiology, and 18 (13.2%) out of 136 free-of-charge blood donors. These results indicate a high prevalence of TTV infection in Russia and absence of an obvious correlation between this infection and nonA, nonB, nonC hepatitis in examined patients. Phylogenetic analysis of amplified fragments of viral DNA from 3 patients selected at random showed that the isolated strains belong to subtype 1a, most prevalent in the world.

Adult↗