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Objectives. To develop an effective technology for the cultivation of Chinese hamster ovary (CHO) cells stably producing GamP2C5 antibody which is a component I of the GamCoviMab candidate drug for emergency prevention and therapy of infection caused by SARS-CoV-2 virus; to select optimal cultivation parameters and to scale this technology in production.Methods. The study was performed on CHO GamP2C5 (clone 78) cell culture, producing a single-domain antibody fused to the Fc fragment of human IgG1 GamP2C5. Different culture media and supplements were used. Cells were cultured in Erlenmeyer flasks, Biostat® RM 20 wave-mixed bioreactor, Ambr® 250 mini bioreactors, STR 200 stirred-tank bioreactor.Results. Using molecular-genetic and biotechnological methods, a stable clone producer of CHO GamP2C5 antibody, clone 78, was obtained. Then a technique was worked out for the cultivation of the obtained clone producer on different culture media. The most suitable cultivation regimes, culture media, and optimal supplements were selected. This technology was tested in laboratory conditions in a 10-L reactor, and then successfully scaled up for production at the MedGamal Branch of the Gamaleya National Research Center for Epidemiology and Microbiology.Conclusions. This study demonstrates the fundamental feasibility of developing and scaling up a culture technology, in order to produce a drug based on a modified single-domain antibody with virus neutralizing activity against different strains of SARS-CoV-2 virus.

Monitoring of the proportion of immune individuals and the effectiveness of vaccination in a population involves evaluation of several important parameters, including the level of virus-neutralising antibodies. In order to combat the COVID-19 pandemic, it is essential to develop approaches to detecting SARS-CoV-2 neutralising antibodies by safe, simple and rapid methods that do not require live viruses. To develop a test system for enzyme-linked immunosorbent assay (ELISA) that detects potential neutralising antibodies, it is necessary to obtain a highly purified recombinant receptor-binding domain (RBD) of the spike (S) protein with high avidity for specific antibodies.The aim of the study was to obtain and characterise a SARS-CoV-2 S-protein RBD homodimer and a recombinant RBD-expressing cell line, as well as to create an ELISA system for detecting potential neutralising antibodies.Materials and methods: the genetic construct was designed in silico. To generate a stable producer cell line, the authors transfected CHO-S cells, subjected them to antibiotic pressure, and selected the optimal clone. To isolate monomeric and homodimeric RBD forms, the authors purified the recombinant RBD by chromatographic methods. Further, they analysed the activity of the RBD forms by Western blotting, bio-layer interferometry, and indirect ELISA. The analysis involved mono clonal antibodies GamXRH19, GamP2C5, and h6g3, as well as serum samples from volunteers vaccinated with Gam-COVID-Vac (Sputnik V) and unvaccinated ones.Results: the authors produced the CHO-S cell line for stable expression of the recombinant SARS-CoV-2 S-protein RBD. The study demonstrated the recombinant RBD’s ability to homodimerise after fed-batch cultivation of the cell line for more than 7 days due to the presence of unpaired cysteines. The purified recombinant RBD yield from culture broth was 30–50 mg/L. Monomeric and homodimeric RBD forms were separated using gel-filtration chromatography and characterised by their ability to interact with specific monoclonal antibodies, as well as with serum samples from vaccinated volunteers. The homodimeric recombinant RBD showed increased avidity for both monoclonal and immune sera antibodies.Conclusions: the homodimeric recombinant RBD may be more preferable for the analysis of levels of antibodies to the receptor-binding domain of the SARS-CoV-2 S protein.

Objectives. To develop a technology for obtaining recombinant antibodies in a suspension culture of human HEK293 cells using transduction with recombinant adenovirus serotype 5 (rAd5) carrying genes expressing heavy and light chains of antibodies on the example of two broadspectrum anti-influenza antibodies 27F3 and CR9114.Methods. Ad5-27F3-H, Ad5-CR9114-H, and Ad5-27F3-L recombinant adenoviruses carrying the 27F3 antibody heavy chain gene, CR9114 antibody heavy chain gene, and 27F3 light chain gene, respectively, were generated using the AdEasy™ Adenoviral vector system. To accumulate preparative amounts of recombinant r27F3 and rCR9114 antibodies, the HEK293 suspension cell line was transduced with recombinant adenoviruses carrying genes for heavy and light chains of antibodies. The cells were cultured in a wave-type bioreactor. Chromatography was used to purify recombinant antibodies from the culture medium. After analyzing the molecular weights of purified antibodies using protein electrophoresis, their ability to interact with influenza A and B viruses was analyzed using the Western blot technique, while their ability to neutralize influenza A and B viruses was evaluated using the virus neutralization assay.Results. A method for the accumulation and purification of recombinant r27F3 and CR9114 antibodies from the culture medium of a suspension culture of human cells following transduction with its recombinant adenoviruses carrying the genes for heavy and light chains of these antibodies was developed. The ability of the r27F3 antibody to interact with and neutralize influenza A viruses of group 1 (except influenza A virus subtype H2) and group 2 was shown. The ability of the rCR9114 antibody to interact with influenza A viruses of group 1 and influenza B viruses, as well as to neutralize influenza A viruses of group 1, was demonstrated.Conclusions. A technology for obtaining recombinant antibodies in a suspension culture of HEK293 cells using transduction with recombinant adenoviruses carrying genes expressing heavy and light chains of antibodies was developed along with a confirmation of their specificity.

Adeno-associated virus vectors are among the most promising ones for the delivery of transgenes to various organs and tissues. Recombinant adeno-associated virus (rAAV) is able to transduce both dividing and non-dividing cells, has low immunogenicity, and is able to provide long-term expression of transgenes. Modern technologies make it possible to obtain rAAV for in vivo use, but they are not without drawbacks associated with laboriousness, scalability difficulties, and high cost, therefore, improvement of technological schemes for obtaining rAAV is an urgent issue. The aim of the study was to compare different technological approaches to rAAV production based on different conditions of the transfected HEK293 cell line cultivation on a laboratory scale. Materials and methods: HEK293 cell culture, AAV-DJ Packaging System, PlasmidSelect Xtra Starter Kit were used in the study. The technologies were compared using a model rAAV vector with a single-domain antibody transgene fused to the Fc-fragment of IgG1 specific to botulinum toxin. HEK293 cells were transfected with supercoiled plasmid DNA isolated by three-step chromatographic purification. The identity of the rAAV preparation was determined by electrophoresis, immunoblotting, and real-time polymerase chain reaction. Results: the study demonstrated the efficiency of the chromatographic method for obtaining a supercoiled form of plasmid DNA that can be used for efficient transfection of cell culture in order to produce rAAV. The study compared the following processes of rAAV production: using transient transfection and cultivation of the transfected HEK293 cell suspension in Erlenmeyer flasks, adherent culture in T-flasks, and adherent culture in a BioBLU 5p bioreactor on a matrix of Fibra-Cel disks. Conclusions: the data obtained showed the possibility of using the described approaches to purification of plasmid DNA, cell transfection, and cultivation of the transfected cells under various conditions to obtain rAAV samples that expresses the antibody gene. The BioBLU 5p reactor with Fibra-Cel discs was used for the first time to produce preparative quantities of rAAV on a laboratory scale, which increased the adherent surface area during cell culture and transfection, and, as a result, increased the yield of the target product.