INTRODUCTION. Vaccination is the main measure for the primary prevention of human papillomavirus (HPV)-related diseases. The development of novel vaccine candidates is underway worldwide, including in the Russian Federation. At the same time, the clinical introduction of new HPV vaccines is seriously hampered by the lack of clear and unambiguous recommendations for conducting preclinical studies of these vaccines.

AIM. This study aimed to analyse regulatory documents on HPV vaccines, to study the experience of conducting preclinical studies, and to summarise the preclinical approaches that could be recommended for developers and applicants seeking approval for new preventive HPV vaccines, including the vaccines being developed in the Russian Federation.

DISCUSSION. The authors have analysed regulatory documents issued by the World Health Organisation (WHO), the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH), and the Council of the Eurasian Economic Commission (EEC). Additionally, the authors have reviewed the experimental results of preclinical studies of HPV vaccines. The known licensed and pipeline HPV vaccines are similar in terms of their characteristics and constructive features. However, there may be some differences in the HPV serotype coverage and the methods used to produce the HPV L1 capsid protein. To date, studies have confirmed the role of the HPV L1 capsid protein in the development of specific immunity, rendering challenge tests in animal models unnecessary. Papillomatosis modelling may be required for choosing an alternative immunological target or for studying an alternative (non-parenteral) route for vaccine administration. Preclinical study programmes may be supplemented with individual stages of comprehensive assessment of adjuvants and other additives included in novel HPV vaccine compositions.

CONCLUSIONS. The authors have studied the international experience and presented a systemic overview of the methods and approaches used in preclinical studies of HPV vaccines. The authors have formulated recommendations for developers for the planning and organisation of preclinical studies of HPV vaccines (including immunogenicity, toxicity, and local tolerance assessments required for licensing new vaccines).

INTRODUCTION. Respiratory syncytial virus (RSV) is one of the most widespread pathogens that typically cause acute upper and lower respiratory tract infections in children and adults. Monoclonal antibody products have long been used for passive immunoprophylaxis in premature infants with bronchopulmonary dysplasia. However, vaccines have recently been licensed for the prophylactic immunisation of older adults with various risk factors for severe RSV infection (primarily, chronic cardiovascular and respiratory diseases and diabetes mellitus).

AIM. This study aimed to review the current status of the development of vaccines for active immunisation against RSV infection, including the epidemiological rationale for their development, clinical trial results for licensed vaccines, recommendations for vaccination, and promising pipeline vaccines for RSV prevention.

DISCUSSION. Initially hindered by the unique immunopathogenesis of RSV infection and the genetic hypervariability of RSV for a long time, attempts to develop an RSV vaccine succeeded when international researchers managed to identify a conservative neutralising antibody target capable of inducing specific immunity against RSV. This target, the RSV capsid protein stabilised in its prefusion (pre-F) conformation, can mediate viral entry into the cell following a conformational change. Several subunit vaccines based on recombinant pre-F proteins have successfully passed clinical trials and have been approved for the immunisation of older adults. In addition, one of these vaccines has been recommended for use during pregnancy to prevent RSV infection in newborns and infants. Currently, programmes are being implemented to develop novel RSV vaccines based on messenger RNA (mRNA) and non-replicating attenuated influenza vectors. This article examines and summarises the efficacy and safety parameters of two RSV vaccines approved in multiple countries around the world. Both vaccines have satisfactory safety profiles and comparable prophylactic efficacy parameters.

CONCLUSIONS. Prelicensure clinical trials of novel RSV vaccines, including those being developed in the Russian Federation, should include prophylactic efficacy assessments in target patient populations. For vaccines approved by leading international regulators, clinical trials required for approval in the Russian Federation will be limited to bridging studies confirming the immunogenicity and safety of the vaccines.

INTRODUCTION. Chikungunya virus (CHIKV) genotyping involves sequencing fractions of genes encoding E1, E2, and nsP1 proteins or the entire genome of the virus. Available reagent kits or polymerase chain reaction protocols cannot be used for CHIKV genotyping, and nucleic acid sequencing requires expensive equipment and materials, which are not always available. Therefore, it seems promising to use a simpler and more cost-effective restriction fragment length polymorphism (RFLP) method, which has not previously been used for CHIKV genotyping.

AIM. This study aimed to investigate the possibility of using reverse transcription polymerase chain reaction (RT-PCR) and RFLP for CHIKV identification and genotyping.

MATERIALS AND METHODS. The experimental study used RNA from CHIKV strains of four genotypes, including the Asian, West African (WAf), and East/Central/South African (ECSA) genotypes, and the Indian Ocean Lineage of the ECSA genotype (ECSA-IOL). The study used RT-PCR followed by DNA restriction and restriction fragment length analysis.

RESULTS. The nsP2 gene fragment of 648 bp in length (positions 3806 to 4453) contains recognition sites for the restriction endonucleases PspEI, PvuII, and DraI. The presence or absence of these sites generates a different combination specific to each of the four CHIKV genotypes. The authors designed primers for amplification of the selected gene region and performed RTPCR and RFLP.

CONCLUSIONS. The RFLP method can be used for rapid CHIKV identification and genotyping. The method provides results within a few hours and does not require high-tech equipment.

INTRODUCTION. The completeness of virus inactivation and the identity of the vaccine strain are essential parameters for the safety and quality of inactivated virus vaccines, which should be controlled during vaccine development and production. Currently, the most promising quality control methods for inactivated virus vaccines are molecular genetic methods, which provide rapid results with high sensitivity and specificity.

AIM. The aim of this study was the development of a real-time quantitative polymerase chain reaction (qPCR) method and an integrated cell culture real-time quantitative polymerase chain reaction (ICC-qPCR) method to assess the completeness of virus inactivation, as well as a reverse-transcription polymerase chain reaction assay coupled with restriction fragment length polymorphism analysis (RT-PCR-RFLP) to confirm the identity of the vaccine virus strain.

MATERIALS AND METHODS. This study used RNA of CHIKV genotypes (three strains of each of the four CHIKV genotypes, including Asian, West African (WAf), and East/Central/South African (ECSA) genotypes, and the Indian Ocean Lineage of the ECSA genotype (ECSA-IOL), which were identified by sequencing prior to analysis). Additionally, the study used the Nika21 CHIKV strain (ECSA genotype), the Nika21 CHIKV strain inactivated with β-propiolactone, and the Nika21 CHIKV strain antigen adsorbed on aluminium hydroxide. The methods used included real-time qPCR, RT-PCR-RFLP, and virus neutralisation.

RESULTS. The study identified a 218 bp fragment of the nsP1 gene (positions 789 to 1006) with restriction endonuclease recognition sites. These sites were present or absent in combinations specific to each of the four CHIKV genotypes. The authors selected primers for amplification of the specified gene region and tested the conditions for real-time qPCR and RT-PCR-RFLP. The study demonstrated the possibility of using the ICC-qPCR method to confirm the completeness of virus inactivation and the RT-PCR-RFLP method to identify the vaccine strain.

CONCLUSIONS. The study showed the advantages of using the ICC-qPCR method to confirm the completeness of antigen inactivation and the RT-PCR-RFLP method to identify the vaccine strain. These methods are more sensitive and faster than traditional culture methods. ICC-qPCR and RT-PCR-RFLP can be used at any stage of the production process for inactivated vaccines.

INTRODUCTION. Marburg and Ebola viruses cause severe haemorrhagic fever in humans and primates. Currently, there are no licensed prophylactic vaccines that can simultaneously prevent the spread or reduce the severity of both diseases caused by these filoviruses. The development of effective prophylactic vaccines requires studies aimed at selecting the most immunogenic forms of protective antigens.

AIM. This study aimed to evaluate humoral immune induction in animals after administration of recombinant adenoviral vectors expressing various forms of Ebola and Marburg virus glycoproteins (GPs).

MATERIALS AND METHODS. Samples of recombinant human adenovirus type 5 (rAd5) were obtained using homologous recombination in Escherichia coli, growth in HEK293 cells, and purification by CsCl gradient ultracentrifugation. The resulting rAd5 samples were characterised in terms of their identity (PCR and whole-genome sequencing), the concentration of viral particles (fluorescence spectroscopy), and the concentration of infectious viral particles (TCID₅₀ assay). Enzyme-linked immunosorbent assay (ELISA) was used to evaluate the GP-specific IgG titres in the sera of immunised mice.

RESULTS. The authors constructed rAd5 samples, and each construct contained an expression cassette with a GP gene form encoding a full-length GP, a GP without the mucin-like domain, or a GP without both the glycan cap and the mucin-like domain. Each of these forms was studied using the GPs of four filoviruses, including Zaire Ebola virus, Sudan Ebola virus, Bundibugyo Ebola virus, and Marburg virus. Neither of the forms had a critical effect on the rAd5 replicative capacity. Three weeks after immunisation, the highest GP-specific IgG production was induced by the rAd5 samples encoding either the full-length GP or the GP without the mucin-like domain. The GP without both the glycan cap and the mucin-like domain was the least immunogenic antigen regardless of the filovirus species.

CONCLUSIONS. The most promising constructs for the development of filovirus vaccines based on recombinant adenoviral vectors are the constructs that include the genes encoding the fulllength GP or the GP without the mucin-like domain.

INTRODUCTION. Despite existing treatment methods, complete eradication of human immunodeficiency virus (HIV) infection remains an unattainable goal due to the high variability of HIV type 1 (HIV-1). HIV infection necessitates life-long administration of antiretroviral medicinal products, which cause serious adverse drug reactions. The development of gene therapy products based on adeno-associated virus (AAV) vectors encoding broadly neutralising antibodies represents a promising direction for creating long-term therapies capable of countering a wide range of viral variants.

AIM. This study aimed to evaluate the protective efficacy of CombiMab-2, a medicinal product consisting of a combination of three AAV vectors (AAV9-VRC07-523, AAV9-10-1074, and AAV9-PGDM1400) encoding broadly neutralising antibodies against HIV-1, in a humanised mouse model.

MATERIALS AND METHODS. The study used an HIV infection model based on immunodeficient B-NDG mice humanised with human CD4⁺ lymphocytes (1.5×10⁷ cells per animal) from a leukoconcentrate of a healthy donor. The experiment used two groups of mice, including a control group (3 animals) receiving saline solution and an experimental group (5 animals) receiving CombiMab-2. The medicinal product was administered into different muscles as three separate components six weeks prior to infection. The CCR5-tropic HIV-1 strain was obtained by transfecting HEK293FT cells with the pNL4-3(AD8) plasmid encoding the full-length virus. The authors monitored viral loads in the plasma of animals by reverse transcription polymerase chain reaction and CD4⁺ lymphocyte counts in the peripheral blood of animals by flow cytometry for four weeks after infection.

RESULTS. Six weeks after CombiMab-2 administration, the levels of broadly neutralising antibodies in the serum of humanised mice ranged from 0.17 μg/mL to 4.0 μg/mL. In the control group, the viral load reached 10⁵ copies/mL one week after HIV-1 infection and continued to rise over the next three weeks. In the treatment group, infection developed only in one mouse, which had the lowest antibody titre before infection. No viral load was detected in the remaining mice of the treatment group, which indicated that the medicinal product was effective if serum concentrations of broadly neutralising antibodies reached 0.5 μg/mL or higher.

CONCLUSIONS. The tested medicinal product based on three AAV vectors (AAV9-VRC07-523, AAV9-10-1074, and AAV9-PGDM1400) exhibits protective activity against HIV-1 in humanised mice. The presented data allow the authors to consider CombiMab-2 as a promising antiviral agent that can serve as a basis for further pharmaceutical development.

INTRODUCTION. The increasing prevalence of multidrug-resistant strains of pathogens determines the need for fundamentally new antibacterial agents, including bacteriophage preparations. The consistent implementation of phage therapy is hindered by the lack of generally accepted standardised regulatory documents governing the legal and methodological aspects of the production and preclinical and clinical studies of bacteriophage preparations.

AIM. This study aimed to analyse the international experience with the production and lifecycle management of bacteriophage preparations, as well as the main regulatory requirements for the control of their quality, safety, and efficacy.

DISCUSSION. It is difficult to develop virulent bacteriophage preparations in accordance with the existing requirements for other medicinal products because of the biological characteristics of bacteriophages, the wide variety of bacteriophage strains, and the potential for rapid changes both in the bacteriophage population and in the pathogen population. Therefore, it is reasonable to develop streamlined marketing authorisation routes for phage therapies and methods for the assessment of their safety and efficacy. As part of these efforts, it is necessary to assess the adverse events specific to this group of medicinal products, such as the risks of lysogeny, resistance to bacteriophages, and antibiotic resistance gene transfer between bacterial strains. The pharmaceutical development of bacteriophage preparations can be based on several approaches. Many countries worldwide, including the United States, are implementing the concept of Quality by Design, considering approaches based on the Biological Master File, and conducting Expanded Access programmes. The Active Substance Master File procedure allows the submission of a separate document package covering only part of the registration dossier for regulatory approval. Expanded Access programmes provide individual patients with access to innovative medicinal products without approved treatment protocols. In the Russian Federation, the commercial production of bacteriophage medicinal products is conducted in accordance with the quality standards specified in the State Pharmacopoeia of the Russian Federation.

CONCLUSIONS. There are fundamental differences in the approaches to phage therapy and its regulation around the world and in the Russian Federation. It is reasonable to supplement the current national guidelines for the safety and efficacy evaluation of bacteriophage preparations, in particular, to specify the requirements for conducting preclinical studies.

INTRODUCTION. The stability assessment of biological medicinal products (BMPs) requires special approaches and regulatory requirements. Therefore, BMPs require relevant national guidelines, which are an important prerequisite for the assurance of the safe and effective use of BMPs.

AIM. This study aimed to analyse national and international requirements for the stability assessment of BMPs in order to use the results to inform future development of a unified regulatory approach to estimating and confirming shelf-life periods for BMPs.

DISCUSSION. Most biotechnological medicinal products (BTMPs) are proteins and are highly sensitive to environmental factors by nature. Therefore, the shelf life of a BTMP is established on the basis of real-time stability studies. Stability testing under accelerated and stress conditions is conducted to support shelf-life claims and to characterise the mechanism of protein structure degradation. The results of accelerated and stress studies can be used to select the most sensitive stability-indicating parameters and testing methods. National and international regulatory authorities have developed specialised guidelines for stability studies of BMPs of various origins, and the stability assessment approaches in the regulatory system of the Eurasian Economic Union (EAEU) are harmonised with international standards. Special considerations associated with the stability of vaccines imply that stability studies of vaccines should not only establish shelf life but also investigate stability after reconstitution and after short-term temperature excursions from the recommended cold-chain conditions.

CONCLUSIONS. Special stability testing considerations for various groups of BMPs (including BTMPs and immunobiologicals) indicate the need to develop and improve the system of requirements for BMP stability assessment. This will facilitate the optimisation of the life cycle of BMPs in the Russian Federation and the other EAEU member states.

INTRODUCTION. The quality evaluation of live anthrax vaccines will benefit from the implementation of alternative testing methods that are capable of specific identification of the Bacillus anthracis spore antigen using the appropriate diagnostic products that are authorised in the Russian Federation for the detection of B. anthracis spores.

AIM. This study aimed to investigate the applicability of immunofluorescence analysis to the identification of live anthrax vaccines and compare this method with immunochromatography.

MATERIALS AND METHODS. The study used commercial batches of a live anthrax vaccine and Russian diagnostic products, including diagnostic dry adsorbed fluorescent anti-anthrax spore immunoglobulins and an immunochromatographic assay (ICA) reagent kit for rapid detection and identification of B. anthracis spores (ICA system for B. anthracis). For smears and ICA system reactions, the authors prepared working solutions of bacterial suspensions at spore concentrations typical of the B. anthracis STI-1 vaccine strain. The spore concentrations were achieved using the pharmacopoeial reference standard (RS) for the opacity of bacterial suspensions of 10 international units (IU). Identification reactions involved the registration of immune complex formation.

RESULTS. Immunofluorescence tests of the live anthrax vaccine demonstrated bright greenish-yellow envelope fluorescence with an intensity score of 3+ to 4+ for smears stained with diagnostic immunoglobulins at 1:32 and 1:64 dilutions. Immunochromatographic tests of the live anthrax vaccine detected the spore antigen at vaccine concentrations of 10⁹ and 10⁸ spores/mL, with the test strips showing two distinct dark-pink lines indicative of immunoprecipitation. According to the results obtained using the selected methods, the tested microbial culture was confirmed as B. anthracis.

CONCLUSIONS. Immunochromatography and immunofluorescence tests with appropriate diagnostic preparations are convenient and reliable tools for the species-specific detection of B. anthracis STI-1 spores in the live anthrax vaccine. The results obtained in the anthrax vaccine identification tests provide a basis for recommending the above methods as supplementary alternatives to Ziehl–Neelsen bacteriological staining, which is currently prescribed by the State Pharmacopoeia of the Russian Federation.