B Cell Profiling in Patients with Pemphigus Vulgaris.

Pemphigus vulgaris is a severe, socially significant autoimmune disease associated with autoantibodies to the desmoglein 3 antigen. The disease affects all age groups, beginning at 18 years of age; the mortality rate of pemphigus can reach as high as 50%, depending on a patient's age and a number of other factors. There is no highly selective or personalized therapy for pemphigus vulgaris at the moment. One of the well-known therapeutic approaches to the disease is to use rituximab, an anti-CD20 antibody that can help achieve B cell depletion in peripheral blood. To solve the problem of nonspecific elimination of B cells in patients with pemphigus vulgaris, it is reasonable to use specific immunoligands, their choice being based on an assessment of the level of autoantibodies specific to each of the fragments of desmoglein. In this work, the proportion of autoreactive B cells in patients diagnosed with pemphigus vulgaris is found to be 0.09-0.16%; a positive correlation was revealed between the antibody level and the number of autoreactive B cells to various fragments of desmoglein.

Optimization of recombinant antibody production based on the vector design and the level of metabolites for generation of Ig- producing stable cell lines.

BACKGROUND: The biopharmaceutical industry is significantly growing worldwide, and the Chinese hamster ovary (CHO) cells are used as a main expression host for the production of recombinant monoclonal antibodies. Various metabolic engineering approaches have been investigated to generate cell lines with improved metabolic characteristics for increasing longevity and mAb production. A novel cell culture method based on the 2-stage selection makes it possible to develop a stable cell line with high-quality mAb production. RESULTS: We have constructed several design options of mammalian expression vectors for the high production of recombinant human IgG antibodies. Versions for bipromoter and bicistronic expression plasmids different in promoter orientation and cistron arrangements were generated. The aim of the work presented here was to assess a high-throughput mAb production system that integrates the advantages of high-efficiency cloning and stable cell clones to stage strategy selection reducing the time and effort required to express therapeutic monoclonal mAbs. Development of a stable cell line using bicistronic construct with EMCV IRES-long link gave an advantage in high mAb expression and long-term stability. Two-stage selection strategies allowed the elimination of low-producer clones by using metabolic level intensity to estimate the IgG production in the early steps of selection. The practical application of the new method allows to reduce time and costs during stable cell line development.

Targeting Extracellular Vesicles to Dendritic Cells and Macrophages.

Targeting protein therapeutics to specific cells and tissues is a major challenge in modern medicine. Improving the specificity of protein therapeutic delivery will significantly enhance efficiency in drug development. One of the promising tools for protein delivery is extracellular vesicles (EVs) that are enveloped by a complex lipid bilayer. EVs are secreted by almost all cell types and possess significant advantages: biocompatibility, stability, and the ability to penetrate the blood-brain barrier. Overexpression of the vesicular stomatitis virus protein G (VSV-G) was shown to promote EV formation by the producer cell. We have developed an EV-based system for targeted delivery of protein cargoes to antigen-presenting cells (APCs). In this study, we show that attachment of a recombinant llama nanobody α-CD206 to the N-terminus of a truncated VSV-G increases the selectivity of EV cargo delivery mainly to APCs. These results highlight the outstanding technological and biomedical potential of EV-based delivery systems for correcting the immune response in patients with autoimmune, viral, and oncological diseases.

Analysis of the Specificity of Auto-Reactive Antibodies to Individual Fragments of the Extracellular Domain of Desmoglein 3 in Patients with Pemphigus Vulgaris.

A method for the analysis of the epitope specificity of auto-reactive antibodies to desmoglein 3 (Dsg3) using competitive ELISA has been developed. It is based on a two-stage solid-phase ELISA with initial "depletion" of auto-reactive antibodies against the studied epitope and subsequent quantitative assessment of antibodies against full-length extracellular domain Dsg3. The proposed approach for assessing the specificity of the autoimmune response in patients with pemphigus vulgaris can provide in the future the possibility to personalize the therapy using plasmapheresis by preliminary selection of the antigenic composition of the extracorporeal immunosorbent.

Recombinant Fragment of the Extracellular Domain of Human Desmoglein 3 Fused with the Fc-Fragment of Human IgG1 Selectively Adsorbs Autoreactive Antibodies from the Sera of Pemphigus Patients.

Using the recombinant second fragment of the extracellular domain (EC2) of human desmoglein type 3 (Dsg3) as an affinity ligand, an immunosorbent was obtained that selectively binds autoreactive antibodies to this domain from the immune sera of patients with pemphigus. The EC2 protein was obtained in the form of a fusion protein with the Fc-fragment of human IgG1. The production was carried out in CHO cells using the method of transient expression.

Monoclonal Antibodies to PRAME Protein Slow the Development of PRAME-Expressing Tumor.

Two monoclonal antibodies recognizing non-overlapping epitopes of the PRAME protein were injected into immunocompetent mice to study their influence on the growth of subcutaneous tumor nodes. The B16F10 murine melanoma line, either expressing human PRAME protein or bearing only a vector without PRAME gene, were used as transplants. Each of the antibodies showed the ability to suppress tumor growth of a PRAME-expressing tumour, but not a tumor without PRAME.

Recombinant Bispecific Antibodies to the Human ErbB2 Receptor and Interferon-Beta.

The development of and research into new therapies that can selectively and effectively destroy tumor cells that overexpress the ErbB2 receptor is a pressing task. Recently, research into the use of type I interferons in the treatment of cancer has intensified. Cytokine therapy is aimed at activating the cells of the immune system to fight tumors, but it has drawbacks that limit its use because of a number of side effects the severity of which varies depending on the dosage and type of used cytokine. At the moment, a number of studies are being conducted regarding the use of IFNß in oncology. The studies are aimed at mitigating the systemic action of this cytokine. The immunocytokine complex made of a bispecific antibody against the ErbB2 receptor and recombinant IFNß developed in this study underlies the mechanism meant to avoid the systemic action of this cytokine. Part of this study focuses on the development of full-length antibodies that bind to the ErbB2 receptor on the one hand, and bind and neutralize IFNß, on the other hand, which allows us to consider the antibodies as a means of cytokine delivery to tumor cells.

Epitope Analysis of Murine and Chimeric Monoclonal Antibodies Recognizing the Cancer Testis Antigen PRAME.

We investigated the epitope specificity of different monoclonal antibodies recognizing the cancer testis antigen PRAME. Antibody 5D3 binds to the fragment of PRAME corresponding to 160-180 amino acid residues. Antibodies 6H8 and F11 bind to the fragment corresponding to 180-200 amino acid residues of PRAME. These antibodies retained the ability to recognize these PRAME fragments after chimerization.

Production of Recombinant Human Transferrin in Eukaryotic Pichia pastoris Expression System.

The development and manufacturing of serum-free culture media allowing reducing the costs of preparations and standardizing the biotechnological process are important trends in biotechnology. Substitution of protein compounds in the serum-free media with recombinant analogues reduces the risk of contamination with various infectious agents. Human transferrin is a protein component of serum-free media responsible for the transport of Fe3+ ions into cells. We generated a producing strain P. pastoris secreting human transferrin to the culture medium. The use of constitutive GAP promoter and maintenance of medium pH at 6.5 allows attaining maximum level of transferrin expression (20 mg/liter).

The Generation of the Human mAb RabD4 Specific to the Rabies Virus Glycoprotein and Characterization Thereof.

We generated a novel human neutralizing human mAb RabD4 against rabies virus glycoprotein using in vitro stimulation of human peripheral B cells produced by immunized donor. The human mAb RabD4 showed a high antigen-binding activity and virus-neutralizing activity in the FAVN test with the CVS-11 rabies virus.

The Development and Study of Recombinant Immunoglobulin A to Hemagglutinins of the Influenza Virus.

We obtained recombinant variants of human antibody FI6 broadly specific to hemagglutinins of the influenza A virus. On the basis of a bi-promoter (CMV, hEF1-HTLV) vector, we developed genetic constructs for the expression of the heavy and light chains of the immunoglobulins of IgA1-, IgA2m1-, and IgG-isotypes. Following transfection and selection, stable Chinese hamster ovary (CHO) cell lines were produced. The antibodies of IgA1-, IgA2m1-, and IgG-isotypes were purified from culture media. We performed an immunochemical characterization and studied their interactions with influenza A strains of the H1N1- and H3N2-subtypes. It was shown that recombinant FI6 variants of the IgA-isotype retain the properties of the parental IgG antibody to demonstrate specificity to all the strains tested. The strongest binding was observed for the H1N1 subtype, which belongs to hemagglutinins of phylogenetic group I.

The Development and Inmmunochemical Properties of the Dimer of Immunoglobulin A Specific to the Influenza Virus A Hemagglutinin.

We obtained dimeric forms of IgA1- and IgA2m1-isotypes of FI6 antibody broadly specific to hemagglutinins of different subtypes of influenza A virus. It was shown that the dimers of IgA1 isotype are characterized by a higher antigen-binding activity compared to the IgA2m1 dimers. The affinity of IgA1 dimers to the strains of the H1N1 subtype is higher than that of the H3N2 subtype, which correlates with the properties of the parental human FI6 antibody.

Recombinant Monoclonal Antibodies for Rabies Post-exposure Prophylaxis.

Rabies virus is a prototypical neurotropic virus that causes one of the most dangerous zoonotic diseases in humans. Humanized or fully human monoclonal antibodies (mAb) that neutralize rabies virus would be the basis for powerful post-exposure prophylaxis of rabies in humans, having several significant benefits in comparison with human or equine rabies polyclonal immunoglobulins. The most advanced antibodies should broadly neutralize natural rabies virus isolates, bind with conserved antigenic determinants of the rabies virus glycoprotein, and show high neutralizing potency in assays in vivo. The antibodies should recognize nonoverlapping epitopes if they are used in combination. This review focuses on basic requirements for anti-rabies therapeutic antibodies. The urgency in the search for novel rabies post-exposure prophylaxis and methods of development of anti-rabies human mAb cocktail are discussed. The rabies virus structure and pathways of its penetration into the nervous system are also briefly described.

[In vitro Antiviral Activity of Recombinant Antibodies of IgG and IgA Isotypes to Hemagglutinin of the Influenza A Virus].

Seasonal and highly infectious strains of the influenza A and influenza B viruses cause millions of cases of severe complications in elderly people, children, and patients with immune diseases each year. Immunoglobulin A (IgA), which is an active component of humoral immunity, can prevent the spread of the virus in the upper respiratory tract. The preparation and study of the properties of recombinant virus-specific IgA could be an important approach to finding new means of preventing and treating influenza. Based on CHO DG44 cells, we developed stable monoclonal cell lines that produce monomeric and dimeric antibodies FI6-IgA1 and FI6-IgA2m1 to hemagglutinin (HA) of the influenza A virus. When studying the productivity, growth, and stability of the obtained clones, we found that the dimeric form of antibodies of IgA1 isotype is superior to other forms. The dimeric form of IgA antibodies plays a key role in mucosal immunity. Recognizing the prospects of using dimeric IgA as prophylactic and therapeutic mucosal drugs for viral infections, we studied their virus-neutralizing and antiviral activities on MDCK cell culture and compared them with the antibodies of the IgG1 isotype. This study presents the data on antiviral and virus-neutralizing activities of the FI6-IgA1 dimers to seasonal and highly infectious strains of influenza A virus.

Recombinant Antibodies to the Ebola Virus Glycoprotein.

Currently, there are no approved therapies for targeted prevention and treatment of Ebola hemorrhagic fever. In the present work, we describe the development of a eukaryotic expression system for the production of three full-length chimeric antibodies (IgG1-kappa isotypes) GPE118, GPE325, and GPE534 to the recombinant glycoprotein of the Ebola virus (EBOV GP), which is a key factor in the pathogenicity of the disease. The immunochemical properties of the obtained antibodies were studied by immunoblotting and indirect, direct, and competitive ELISA using the recombinant EBOV proteins rGPdTM, NP, and VP40. The authenticity of the antibodies and the absence of cross-specificity with respect to the structural proteins NP and VP40 of the Ebola virus were proved. The epitope specificity of the resulting recombinant antibodies was studied using commercial neutralizing antibodies against the viral glycoprotein. The recombinant antibodies GPE118, GPE325, and GPE534 were shown to recognize glycoprotein epitopes that coincide or overlap with the epitopes of three well-studied neutralizing anti-Ebola virus antibodies.

New monoclonal antibodies to the Ebola virus glycoprotein: Identification and analysis of the amino acid sequence of the variable domains.

We determined the nucleotide and amino acid sequences of variable domains of three new monoclonal antibodies to the glycoprotein of Ebola virus capsid. The framework and hypervariable regions of immunoglobulin heavy and light chains were identified. The primary structures were confirmed using massspectrometry analysis. Immunoglobulin database search showed the uniqueness of the sequences obtained.

[Neutralizing Monoclonal and Chimeric Antibodies to Human IFN-γ].

Autoiminune disorders are chronic diseases characterized by abnormal immune response directed against self-antigens that leads to tissue damage and violation of its normal functioning. Such diseases often result in disability or even death of patients. Nowadays a number of monoclonal antibodies to pro-inflammatory cytokines and their receptors are successfully used for the targeted treatment of autoimmune diseases. One of the perspective targets in autoimmune disease therapy is interferon gamma, a key cytokine in Th1 cells differentiation, activation of macrophages, and inflammation. In the present work, 5 monoclonal antibodies to human IFN-γ were obtained. For the development of potential therapeutic agent, we have performed neutralizing activity and affinity analysis of the antibodies. Based on the data obtained, the monoclonal antibody F1 was selected. This antibody has a dissociation constant 1.7 x 10(-9) M and IC90 = 8.9 ± 2.0 nM measured upon antibody inhibition of the IFN-γ-induced HLA-DR expression on the surface of U937 cells. We have constructed a bicistronic vector for the production of recombinant chimeric Fab fragment F1 chim in E. coli cells. The recombinant chimeric Fab fragment Fl chim neutralizes IFN-γ activity in vitro and has a dissociation constant 1.8 x 10(-9) M.

[Production of antibodies to aflatoxins].

A panel of ten monoclonal antibodies to aflatoxins B1, B2, and G2 was produced and comprehensively characterized. The affinity and cross reactivity of these antibodies were determined using the methods of direct, indirect, and competitive ELISA. The structures of monoclonal antibody genes were comprehensively studied and the variable and constant domains of the antibody genes were cloned and sequenced. Sequencing analysis confirmed the results of isotyping the light and heavy antibody chains obtained by ELISA. Variable and constant fragments of the antibody genes were cloned into a bicistron expression vector for the recombinant Fab' fragment for one of the antibodies expressed in Escherichia coli and purified. Thus, data were obtained that can be useful for the development of an aflatoxin detection system on the basis of the described monoclonal antibodies and the creation of recombinant antibodies with changed parameters of specificity using protein engineering methods.

[Recombinant full-size human antibody to Ebola virus].

A full-size human antibody to Ebola virus was constructed by joining genes encoding the constant domains of the heavy and light chains of human immunoglobulin with the corresponding DNA fragments encoding variable domains of the single-chain antibody 4D1 specific to Ebola virus, which was chosen from a combinatorial phage display library of single-strand human antibodies. Two expression plasmids. pCH1 and pCL1, containing the artificial genes encoding the light and heavy chains of human immunoglobulin, respectively, were constructed. Their cotransfection into the human embryonic kidney cell line HEK293T provided the production of a full-size recombinant human antibody. The affinity constant for the antibody was estimated by solid-phase enzyme-linked immunoassay to be 7.7 x 10(7) +/- 1.5 x 10(7) M(-1). Like the parent single-chain antibody 4DI, the resulting antibody bound the nucleoprotein of Ebola virus and did not interact with the proteins of Marburg virus.