[Recombinant antibodies to tick-borne encephalitis virus]

A gene encoding the dimeric form of single-chain antibody fragments (scFv) was designed on the basis of the artificial gene coding monomeric scFv to tick-borne encephalitis glycoprotein E. The sequence encoding histidine oligomer was added to 3'-ends of the genes encoding the monomeric and dimeric forms of scFv antibodies. Escherichia coli strains were constructed for the production of monomeric and dimeric antibodies. These antibodies were purified using Ni-NTA resin. The specificity of the purified monomeric and dimeric antibodies in the binding reaction with tick-borne encephalitis virus was shown by ELISA and Western-blot analysis. The identity of glycoprotein E epitope bound by monomeric and dimeric scFv and parental monoclonal antibodies E6B was confirmed by competitive immunoassay.

A study of systems for delivering antigens and plasmid DNA for intranasal immunization against tick-borne encephalitis virus

Our previous studies indicated the possibility for some neurotropic viruses to spread into the brain of immune animals through the olfactory pathway. Thus, nasal mucosa in the olfactory region is likely to be a promising target for mucosal immunization to protect the CNS from neurotropic viral infections. THE MAIN IDEA OF THE RESEARCH: Intranasal immunization inducing mucosal and systemic immune responses blocks the propagation of neurotropic virus into the brain via the olfactory pathway and neutralizes the multiplication of virus in visceral organs, allowing more effective protection against neurotropic infections transmitted by bloodsucking arthropods to be achieved. Thus, study of the efficiency of delivery systems for intranasal immunization against tick-borne encephalitis (TBE) virus is an urgent task in the development of anti-TBE mucosal vaccine. To study intranasal immunization against TBE virus, we have chosen four delivery systems (DSs), namely, (i) biodegradable microparticles, (ii) cationic liposomes, and live attenuated (iii) bacterial and (iv) viral vectors. The gene of TBE virus protein E was inserted into the pcDNA3 plasmid (designated as pcDNA3/E-TBE). Three types of delivery system for plasmid DNA were developed and studied in vitro. The first system, artificial virus-like microparticles (VLP), consists of polyglycan-spermidine complexes that cover pcDNA3/E-TBE DNA. The second system is cationic liposomes with DNA of the plasmid pcDNA3/E-TBE. The third system is an attenuated Salmonella strain containing pcDNA3/E-TBE. The fourth system is a recombinant vaccinia strain with inserted genes of TBE virus proteins C, prM, E, NS1, NS2a, NS2b, and NS3. The DSs were tested in COS-7 and CV-1 cell lines and macrophages by ELISA of cell lysate. The results obtained showed the expression of the E gene in transfected cells, thereby demonstrating that these DSs are suitable for mucosal immunization. High levels of immune response shifted to the Th1 type were detected in BALB/c mice following intranasal immunization with recombinant vaccinia-TBE strain and VLP-pcDNA3/E-TBE. The mice immunized intranasally with recombinant vaccinia-TBE strains were completely protected against intraperitoneal challenge with TBE virus strain Sofjin, whereas intranasal immunization with killed TBE vaccine failed to induce a significant level of protection.

[Molecular construction of experimental combined vaccines]

A method for designing molecular constructions of combined artificial immunogens mimicking viral particles is proposed. Using this method, it is possible to expose antigenic determinants of any viral protein on the surface of such particles and to deliver plasmids containing genes encoding the synthesis of protein antigens to target cells. This approach was used to create the constructions of combined artificial immunogens inducing the production of specific antibodies to HIV-1 and to evaluate the extent and duration of B-cellular immune response depending on the way of antigen exposure to immunocompetent cells.

[Construction and study of antigenic characteristics of recombinant salmonella strain producing TBI protein]

A recombinant strain producing TBI protein (artificial protein containing HIV-1 B and T cell epitopes) was constructed on the base of attenuated Salmonella typhimurium SL7207 strain and BALB/c mice were immunized with this strain in a dose of 10(9) live cells orally or rectally. A single immunization with the recombinant salmonella strain induced humoral and cellular immune response to HIV-1; hence, this strain is a promising candidate for vaccine against HIV.

[Comparative study of the effectiveness of HBcAg presentation to the immune system using attenuated Salmonella strains, serovars S.enteritidis and S.typhimurium]

In this work the results of obtaining HBcAg-producing attenuated Salmonella strains, serovars S. enteritidis and S. typhimurium, and their comparative study is presented. As revealed in this study, attenuated S. enteritidis strain E-23 and S. typhimurium strain T-10, producing HBcAg, induce cell-mediated and humoral immune response to HBcAg after injected into anovals. After injection S. typhimurium strain T-10 induces a much higher titer of specific antibodies than S. enteritidis strain E-23. The level of specific antibodies induced by recombinant HBcAg seems to correlate with the capacity of salmonellae for survival inside macroorganisms.

Insertion of foreign epitopes in HBcAg: how to make the chimeric particle assemble

Hepatitis B core antigen is one of the most promising protein carriers of foreign epitopes of various human and animal pathogens. Chimeric HBcAg particles can be used as effective artificial immunogenes. Unfortunately, not all chimeric proteins are able to be particulated. The dependence of correct or incorrect folding of chimeric proteins on physical and chemical properties of inserts was studied with the help of ProAnalyst, SALIX and QSARPro computer programs. We have found that insertion of amino acids with high hydrophobicity, large volume, and high beta-strand index prevent self-assembling chimeric proteins. These factors are most important for the C-termini of inserts. Recommendations for obtaining correct folding of chimeric HBcAg particles have been given.

[Construction of original artificial immunogens--candidate vaccines against HIV-1]

An original method for making effective artificial vaccines has been developed. Immunogens are virus-like particles containing a DNA molecule covered with recombinant proteins carrying the pathogen epitopes. The recombinant proteins are exposed on the surface of the particle and are attached to DNA via spermidine-polygluquine-glutathione or galactopyranoside conjugates (depending on the hybrid protein composition). Two variants of artificial immunogens-candidates for antiHIV vaccine have been prepared.

[Isolation and study of recombinant strains of Salmonella typhimurium SL 7207, producing HBcAG and HBcAG-HBs]

Recombinant strains producing hepatitis B virus (HBcAg) core protein and chimeric core protein exposing on its surface the major immunogenic epitope of HBsAg (HBcAg-HBs) were constructed on the base of attenuated S. typhimurium SL 7202 strain. The resultant Salmonella strains produced proteins which were capable of self-assembly into virus-like particles and showed antigenic properties of both core and surface hepatitis B proteins. A single rectal immunization with recombinant S. typhimurium induced humoral and cellular immune response to HBcAg and HBsAg. Specific anti-HBcAg were detected in animal sera and intestinal tissues, which indicated the formation of specific mucosal immunity.

[The development and certification of the Hepabest anti-HBc IgG test system for detecting antibodies to the core antigen of the hepatitis B virus]

The comparison of the newly developed "HepaBest anti-HBc IgG" assay system for the detection of hepatitis B virus (HBV) core antigen with the reference system "ImmunoComb HBc IgG" (Orgenics, France-Israel) and its approbation on 91 serum samples from patients in the Infectious Clinical Hospital were carried out. The coincidence rate of the results obtained with the use of the two assay systems was 87.9%. The system "HepaBest anti-HBc IgG" permitted the detection of patients whose sera contained no other HBV markers, except anti-HBc IgG. This assay system may be recommended for use in clinical and epidemiological investigations for ascertaining the diagnosis.

[Chimeric hepatitis B core antigen particles as a presentation system of foreign protein epitopes]

The paper presents data available in the literature and the author's own experimental findings as to the construction of chimeric hepatitis B core antigen (HBcAg) particles. The problems associated with the design of hybrid HBcAg particles and the ways of solving arising problems are considered. Data from studies of the antigen and immunogenic properties of hybrid HBcAg particles.

Localization of the amino terminus of the hepatitis B virus core antigen within the core particle

The position of the amino terminus of the hepatitis B virus core antigen (HBcAg) within the core particle was studied. For this purpose, three recombinant analogs of HBcAg were designed. One analog, HBcAgR, was identical in amino acid sequences to the core polypeptide of the hepatitis B virus; the second, HBeAgR, differed from the authentic protein in deletion of 39 carboxy-terminal amino acids. The amino acid sequences of the third polypeptide, HBe delta N and of HBeAgR were similar, HBe delta N differed from HBeAgR only in replacement of 3 N-terminal amino acids by 16 amino acids of beta-galactosidase. The HBcAg analogs were compared with respect to their reaction with monoclonal antibody (mAb E1A7) to the amino-terminal linear epitope of hepatitis B virus e antigen. Although able to assemble into virus-like particles, the three analogs of HBcAg, reacted differently with mAb E1A7. It was demonstrated that mAb E1A7 reacted with both native and denatured HBeAgR. HBe delta N was not recognized by mAb E1A7. In contrast, HBcAgR reacted with mAb E1A7 only when denatured. Native HBcAgR did not react with mAb E1A7 when assembled into particles. Thus evidence was obtained that the amino terminus of HBcAg is not exposed on the particle surface.

Design of immunogens as components of a new generation of molecular vaccines

Three new approaches to design effective immunogens are considered. At first, we derived an expression vector from bacteriophage M13 allowing the exposure of short peptides on the virion surface. EIA demonstrates that antibodies against a recombinant phage carrying the antigenic determinant of the HIV-1 gag protein reacted with the 17-kDa core protein of the virus and also with its polyprotein precursor p55 in immunoblotting. In another approach, we chose the hepatitis B core antigen (HBcAg) particle as a vehicle for the presentation of foreign antigenic determinants to the immune system. Chimerical particles of HBcAg containing epitope of the VEE virus were obtained. A vector system for insertion of foreign antigenic determinants and production of both hybrid and wild HBcAg proteins were also obtained. The third approach relies on construction of immunogens from different T- and B-cell epitopes of the HIV-1. We suggested to construct HIV-1 vaccines in a form of the TBI (T- and B-cell epitopes containing Immunogen) with a predetermined tertiary structure, namely, a four-alpha-helix bundle. The gene of the TBI protein consisting of nine HIV-1 epitopes was synthesized and expressed in Escherichia coli cells. Mice immunized with TBI showed humoral and cellular immune responses to HIV-1. Anti-TBI antibodies displayed HIV-1 neutralizing activity. These new approaches offer promise in the development of new effective vaccines.

[Localization of the N-terminal epitope of the HBe antigen of the hepatitis B virus]

A new antigenic site was located at the N-terminus of HBeAg. Comparison of antigenic properties of the recombinant proteins HBeAgR and HBeAg delta N truncated at the N-terminus has lead to this conclusion. The proteins have been studied by ELISA and western-blot analysis using monoclonal antibodies E1A7 and polyclonal antiserum to HBeAg. Polyclonal antiserum to HBeAg binds to HBeAg delta N and HBeAgR while monoclonal antibodies E1A7 interact only with HBeAgR. The data obtained supports evidence that the epitope is located at the N-terminus of HBe-polypeptide chain. It is classified as a sequential type one and at least one amino acid from the Met-Asp-Ile sequence participates in its formation.

[Mutagenesis, induced by phosphotriester analogs of oligonucleotides and directed to the cleavage site of double-spiral DNA]

The mutagenic properties of phosphotriester analogues revealed in course of interaction with linearized plasmid DNA were studied. The plasmid-based model system permitting one to test reliably the induced mutations is proposed. The efficiency of mutagenesis was shown to depend on the length of the oligonucleotide-mutagen and the genotype of the transformed Escherichia coli strain. The possible mechanisms involved in mutagenesis are discussed.