[STUDY OF HUMORAL IMMUNE RESPONSE FEATURES BASED ON MODELLING OF ANTIGEN DETERMINANTS OF HEPATITIS C VIRUS BY SYNTHETIC PEPTIDES AND GENETICALLY ENGINEERED POLYPEPTIDES].

AIM: Study of humoral immune response features in patients with acute hepatitis C (AHC) with various disease outcomes based on modelling of antigen determinants of hepatitis C virus (HCV) by synthetic peptides and genetically engineered polypeptides. MATERIALS AND METHODS: 20 patients with icteric form of AHC based on clinical-biochemical presentation and HCV RNA detection by PCR in blood sera during 12 months from the disease onset were included into the study. Antibody seroconversion study was carried out by EIA. Genetically engineered proteins and synthetic peptides were used as antigens. RESULTS: Similarity and differences of humoral immune response against the HCV antigens used in this study depending on the disease outcome (convalescence or chronicity) were shown. Significant difference of the humoral immune response to both HCV core protein and various fragments of the immune dominant region of this protein were detected, that indicates on a link of these features of immune response with perspectives of a more or less favorable disease development. CONCLUSION: The regularities of seroconversion detected allow to consider anti-NS5 IgG as a prognostic marker of the disease chronicity. Such marker, as anti-NS3 IgG, is important for diagnostics, but not for disease outcome prognosis.

[Features of antigen-antibody interaction during use of linear synthetic peptides and multipeptide antigen modeling antigenic determinants of hepatitis A virus].

AIM: To study features of antigen-antibody interaction during use of linear synthetic peptides and multipeptide antigen modelling antigenic determinants of hepatitis A virus (HAV) and to evaluate perspectives for use of heterogeneous tetrameric multipeptide antigens for detection of HAV serological markers. MATERIALS AND METHODS: Linear peptides VP1 and VP3 were synthesized by fluorenylmethyloxycarbonyl (Fmoc)-polyamide solid phase method. MAP4 (VP1+VP3) was synthesized according to 9-Fmoc strategy. Interaction of these peptides with anti-HAV IgM positive sera from patients with HA was studied by noncompetitive and competitive methods of immunoenzyme assay. RESULTS. Using immunoenzyme assay, high heterogeneity of immune response in patients with HA (62 and 67% in two groups) was shown. MAP4 (VP1+VP3), unlike the combination of linear peptides VP1 and VP3, interacted with anti-HAV IgM in 41 - 45% of sera and, at the same time, did not lead to false positive results. CONCLUSION: Population of HAV is not so uniform which is usually assumed. It could be reasonable to use heterogenous multipeptide antigens, including those containing VP1 (11 - 25 a.r.) and VP3 (110 - 121 a.r.), for the development of new assays for HA diagnostics.

[Detection of type specific antibodies to hepatitis C virus NS4 protein in hepatitis C patients by enzyme immunoassay]. / Vyiavlenie tipospetsificheskikh anti-HCNS4-antitel u bol'nykh gepatitom C metodom immunofermentnogo analiza.

A multi-enzyme immmune-assay test system was designed for serotyping of genotypes hepatitis C virus (HCV) and a method of such typing of the serum of patients with hepatitis C was worked out. The above test-system was worked out on the basis of a study of 10 type-specific peptides modeling different fragments from NS4-protein variable region of HCV. The designed test system was evaluated by using a set of 42 serum samples obtained at random from patients with chronic hepatitis C, which had been preliminarily genotyped by polymerase chain reaction. The serotyping makes it possible to identify the type-specific antibodies in the blood sera of patients, including those cases when viremia was absent. Differences in the circulation of HCV in Moscow (Russia) and Vitebsk (Byelorussia) were established by using the designed test-system.

[Seroconversion to various hepatitis C virus antigens in patients with hepatitis C from various sources]. / Issledovanie serokonversii k razlichnym antigenam virusa gepatita C s razlichnymi iskhodami.

A total of 136 patients with acute icteric hepatitis C, including patients with known outcome, were examined. Therefore, 46 serological samples, obtained from 13 patients with subsequent remission, and 63 samples, obtained from 13 patients, who subsequently developed the chronic disease stage, were analyzed. The serum of known outcome patients were examined, by using the immune-enzyme analysis method, to the antibodies of both class IgG, and IgM. Differences in the dynamics of the immune humoral response were established with due regard for a pathological course process, including the acute disease stage. The obtained results are interesting because of their prognostic values.

[Spectrum of antibodies to HCV antigens in patients with different clinical patterns of chronic HCV infection]. / Spektr antitel k razlichnym antigenam HCV pri raznykh variantakh techeniia khronicheskoi HCV-infektsii.

Correlations between the spectra of antibodies to HCV proteins represented by various antigenic determinants and clinical variants of chronic HCV infection were studied. Synthetic peptides core-16, NS4-20, and NS5-23 simulating the immunodominant regions of the core, NS4 and NS5 proteins and recombinant proteins core-114 and NS4-86 were used as antigens. The results indicate that if the serum of an HCV patients contains no IgG to both antigenic determinants of NS4 or to NS5 in combination with any core antigenic determinant, a clinical and biochemical remission is highly probable. Chronic hepatitis C is characterized by the presence of IgG in high titers to both antigenic determinants of NS4 protein, particularly in combination with anti-NS5 IgG in low titers or none at all, or high titers of anti-core-16 IgG in combination with high titers of anti-NS4-20 IgG.

[Diagnostic significance of antibody detection to various hepatitis C virus antigens in patients with acute and chronic HCV-infection]. / Diagnosticheskaia znachimost' opredeleniia antitel k razlichnym antigenam virusa gepatita C u patsientov s ostroi i khronicheskoi HCV-infektsiei.

AIM: To examine diagnostic value of antibodies to various HCV antigens in patients with acute and chronic HCV-infection. MATERIAL AND METHODS: Enzyme immunoassay has tested blood sera from 136 patients with icteric acute hepatitis C (AHC) and 45 patients with chronic HCV infection for IgG antibodies to antigens of proteins core, NS4, NS5, HCV. Synthetic peptides core-16, NS4-20, NS5-23 were used as antigens. RESULTS: Patients with icteric AHC had IgG antibodies to antigens of both structural protein core and non-structural proteins NS4, NS5 of HCV as early as the first 10 days of jaundice. Occurrence of anti-core and anti-NS4 increases with the disease duration. Incidence of anti-NS4 correlated with duration of previous intravenous drug addiction. In patients with AHC early in the icteric period anti-core, anti-NS4, anti-NS5 were present less frequently than in patients with chronic HCV infection having elevated levels of AlAT. Significant differences were found neither with the group with normal AlAt nor in the spectrum of the detected antibodies between patients with acute and chronic HCV infection. CONCLUSION: Despite different frequency of anti-core, anti-NS4, anti-NS5 detection in patients with icteric AHC and patients with chronic HCV-infection and high AlAT, their high incidence rate in this or that group and absence of differences by the spectrum of the studied antibodies do not allow the fact of their detection to be a diagnostic marker differentiating acute HCV-infection with chronic one.

[Serological study of hepatitis C virus NS5 protein epitopes and their clinical and diagnostic significance]. / Serologicheskoe issledovanie épitopov belka NS5 virusa gepatita C i ikh znachenie dlia kliniki i diagnostiki.

Three peptides corresponding to the 2295-2317 aa NS5 HCV region and individual parts of this region were synthesized. Antigenic properties of these peptides were investigated. The 2295-2317 aa region contains at least two epitopes of different nature. The full-sized peptide is more promising for the diagnostic studies. Optimal conditions for ELISA with this peptide were defined, allowing the maximum complete utilization of the potentialities of both epitopes.

[Antigenic activity of delta-antigen peptides corresponding to three genotypes of the delta hepatitis virus]. / Antigennaia aktivnost' peptidov del'ta-antigena, sootvetstvuiushchikh trem genotipam virusa gepatita del'ta.

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.

[Use of synthetic peptides as additional antigens for detecting antibodies to hepatitis C virus]. / Ispol'zovanie sinteticheskikh peptidov kak dopolnitel'nykh antigenov dlia vyiavleniia antitel k virusu gepatita C.

Peptide fragments of hepatitis C virus (HCV) nonstructural protein NS4 capable of reacting with anti-HCV in enzyme immunoassay are synthesized. Addition of synthetic peptides to recombinant nucleocapsid HCV antigen absorbed on solid phase notably improves the efficacy of detection of antibodies to HCV in the sera of patients with hepatitis C.

[A comparative study of the diagnostic value of peptides, corresponding to various genomic sequences of the hepatitis delta virus]. / Sravnitel'noe issledovanie diagnosticheskoi tsennosti peptidov, sootvetstvuiushchikh razlichnym genomnym posledovatel'nostiam virusa gepatita del'ta.

A set of 5 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, 76. Free peptides and their conjugates with bovine serum albumin were tested for antigenicity in ELISA. Correlation between the length of the peptide chain and its antigenic activity was noted. Peptides 65-80 and 69-80 demonstrated positive reaction with all sera from acute HDV patients. Both variants of peptide 71-80 reacted with 83% of positive sera. The smaller peptide 73-80 reacted strongly with one positive serum out of five used.

[Inhibition of HIV reproduction in cell culture by 5'-phosphonates of 3'-azido-2',3'-dideoxynucleosides]. / Ingibirovanie reproduktsii virusa immunodefitsita cheloveka v kul'ture kletok 5'-fosfonatami 3'-azido-2',3'-dideoksinukleozidov.

The antiviral activity of 3'-azido-2',3'-dideoxynucleoside 5'-phosphate analogues: 5'-phosphonomethylene-3'-azido-2',3'-dideoxythymidine, 5'-methylphosphonate and 5'-phosphite of 3'-azido-2',3'-dideoxythymidine, 5'-phosphites of 3'-azido-2',3'-dideoxyadenosine and guanosine was investigated in HIV-infected cell cultures (human lymphoblastoid cells). The effectivity of inhibition of HIV-reproduction in cells by these substances was close or even higher than that for the corresponding 3'-azido-2',3'-dideoxynucleosides, whereas their toxicity was lower than that of nucleosides. These substances are supposed to be transported into the cells and to be transformed into the corresponding 5'-triphosphate analogues under the action of cell kinases. It is possible that such agents are terminator substrates of virus reverse transcriptases and thus inhibit the biosynthesis of DNA chains.