[Antigenic activity of human herpes virus type 8 proteins coding orfK8.1 and orf65]

A peptide scanning of the sequences of human herpes virus type 8 (HHV-8) proteins coding orfK8.1 and orf65 was made. The antigenic activity of peptides was evaluated by ELISA. The fragment 101-213 aa of orfK8.1-encoded protein was shown to consist of two sites containing linear B-epitopes that had a weak antigenic activity: 121-145 and 177-209 aa. The protein coding orf65 comprised 2 sites at which linear B-cell epitopes 78-110 aa (a weak antigenic activity) and 142-170 aa (a strong antigenic activity) were located.

[Study of the diagnostic potential of various regions of tick-borne encephalitis virus glycoprotien E]

Bioinformation techniques were used to analyze envelope glycoprotein of tick-borne encephalitis virus in order to determine the potential diagnostically significant antigenic clusters. Five selected regions of the amino acid sequence of protein E were retranslated to nucleic sequences, by employing the optimum code for E. coli. The resultant DNA fragments were synthesized by polymerase chain reaction from synthetic oligonucleotides and expressed in E. coli cells. The recombinant antigen replicating the region from 296 to 414 aminoacids demonstrated the most significant antigenic activity. The findings lead to the conclusion that this recombinant protein may be considered as a candidate for the development of a diagnostic assay.

[Comparison of the diagnostic value of recombinant antigens and synthetic peptides that mimic the immunogenic epitopes of the envelop protein gp41 in the enzyme immunodetection of HIV-1 antibodies]

The study was undertaken to comparatively examine the efficiency of HIV antibody detection by enzyme immunoassay using recombinant antigens and synthetic peptides containing the most immunodominant region of the human immunodeficiency virus envelop protein gp41-cytotoxic T-lymphocytic (CTL) epitope. The application of the synthetic peptides that mimic this region has been to be inadequately effective. The recombinant proteins that contain the CTL epitope may be successfully used for the diagnosis of HIV-1, by using enzyme immunoassay as they show a higher sensitivity in detecting antibodies than do the synthetic peptises.

[Test for specific antibodies to virus hepatitis delta based on synthetic peptides]

Solid-phase synthesis of three linear peptides overlapping the major immunodominant epitope of HDAg, which located within amino acid (aa) segment 53-108, and peptide aa 167-179 was carried out. The structure of the peptides corresponded to the sequences of isolates HDV type I. Their antigen reactivity was studied by indirect enzyme immunoassay with sera from patients with hepatitis D and from asymptomatic carriers of anti-delta antibodies. Two B-epitopes located within aa 53-80 and 71-93 appeared to be the most immnunoreactive. The use of these peptides in ELISA allowed anti-delta IGg antibodies to be detected with 95% confidence in serum of patients with hepatitis D and with 87% confidence in serum of asymptomatic carriers of anti-delta antibodies. Analysis of obtained data showed that these peptides can be used in new diagnostic anti-HDV tests.

Characterization of monoclonal antibodies and epitope mapping of the NS4 protein of hepatitis C virus

Recombinant DNA containing sequences of HCV NS4 protein was expressed in Escherichia coli cells. Six hybridoma clones producing monoclonal antibodies (MAB) to recombinant NS4 protein (rNS4), aa 1677-1756, were developed. Mapping with a panel of 33 peptides and reciprocal competitive EIA have shown that MAB obtained revealed five antigen determinants, not described earlier: MAB 3F11 and 3F12-one genotype-independent epitope of NS4A (aa 1700-1707) common for genotypes 1, 2 and 3; MAB 1D11-genotype-independent epitope (aa 1713-1728) and MAB 1D3-genotype (subtype 1b)-specific epitope of NS4B (aa 1711-1731); MAB 6B11 and C1-two conformation-dependent determinants in 5-1-1 region. These data indicate that the 5-1-1 region of NS4 protein has a complex antigenic structure and contains at least eight epitopes, including five, revealed in the present work. MAB obtained recognized native viral protein in the cytoplasm of liver cells of patients with chronic hepatitis C. The positive rates of the immunostaining for NS4 antigen using MAB 6B11, 1D11 and 3F12 were 64, 59 and 50%, respectively. It was found that 6B11 MAB to a conformation-dependent epitope much more actively interacts with native NS4 than with the recombinant protein to which MAB was developed. The epitope recognized by 6B11 MAB is highly immunogenic since it induces the B-cell response in all patients investigated with identified anti-NS4 antibodies in blood serum. The MAB panel obtained in this study may become a useful tool for the diagnostic purposes, for the investigation of NS4B function and for the host-viral interactions at the cell level.

[Determination of type-specific synthetic peptide antibodies to hepatitis delta virus ]

Nine peptides from immunodominant (53-68 and 65-80 aa) and hypervariable (201-213 aa) regions derived from delta antigen sequences corresponding to 3 HDV genotypes were synthesized. Type specificity of antibodies to the resultant peptides was evaluated by indirect enzyme immunoassay with sera from patients with hepatitis D and asymptomatic carriers of anti-delta antibodies. Analysis of the results showed that HDV circulating in the Central Volga region belongs to type I in the majority of cases. High heterogeneity and changeability of HDV genome during the period of transition from acute forms to asymptomatic carriership was revealed. Possibility of circulation of new hybrid HDV strains causing mixed infection in Russia is discussed.

[Determination of hepatitis G virus markers in various risk groups]

Study of prevalence of hepatitis G virus (HGV) markers in different risk groups showed the presence of HGV RNA in 3.2% blood donors, 24.2% patients with hepatitis C (HCV), and 28% patients with hemophilia. HGV antibodies were detected in 11.3% donors, 16.0% patients with HCV, 13.4% patients with hemophilia, and 8.5% HIV-infected subjects. Anti-E1 HGV were more often detected in the absence of HGV RNA. Antibodies to HGV E2 protein were significantly more often detected in adult HCV patients but not in adolescent patients aged 8-15 years.

[Diagnostic possibilities of an immunoenzyme test-system for determining the spectrum of antibodies to structural and nonstructural hepatitis C virus antigens]

A new enzyme immunoassay EIA-HCV-Spectr test system constructed on the base of recombinant proteins and synthetic peptides allows separate detection of antibodies to E1/E2, core, HS3, NS4, and NS5 antigens of hepatitis C virus (HCV). The system is highly specific and more sensitive than the test systems used in screening studies, which allows its use as a final test for antiHCV antibodies. Antibodies to various HCV antigens were analyzed using this test system in patients with acute and chronic hepatitis C and asymptomatic donors with antiHCV. In acute hepatitis C during the first-second week after clinical manifestation, antibodies to nonstructural virus proteins are detected 3-4 times less often than in chronic hepatitis C. Acute hepatitis C is characterized by the presence of antibodies only to core antigen (66%). In chronic condition combinations of antibodies to structural and nonstructural HCV antigens predominate: core + NS4, core + NS3 + NS4, core + NS3 + NS5, core + NS4 + NS5, and core + NS3 + NS4 + NS5. In asymptomatic donors with antiHCV and in patients with chronic hepatitis C the spectra of antibodies were similar in 45.7% cases.

[Antigenic activity of delta-antigen peptides corresponding to three genotypes of the delta hepatitis virus]

Six synthetic peptides from immunodominant region 65-80 aa derived from the sequences of delta-antigen corresponding to 3 HDV genotypes were obtained. Their antigenic activities were assessed by indirect enzyme immunoassay with sera of patients with hepatitis D and of asymptomatic carriers of anti-delta antibodies. Differences in antigenic characteristics of full-size 65-80 and truncated 71-80 aa peptides corresponding to three HDV genotypes were revealed. The diagnostic significance of synthetic 65-80 aa fragments is shown.