In the last 10 years, scientists' interest in the horsepox pathogen has increased sharply due to the obtaining of its chimeric copy and the discussion of whether it was used to create early smallpox vaccines and the dangers of technologies that allow the restoration of extinct pathogens of dangerous infections.The aim of the work is to summarize the materials on modern studies of the horsepox virus.The source base of the study is English-language scientific literature available via the Internet.The research method is an analysis of scientific sources on horsepox from the general to the specific. We considered the area of distribution of the virus, its epidemiological danger, phylogenetic relationship, data on the sequencing of the horsepox virus genome and the likelihood of its use in the creation of the first vaccines, as well as obtaining its chimeric copy, on the basis of which a new smallpox vaccine was created – TNX-801.Results and discussion. The horsepox virus belongs to the poxvirus family, the orthopoxvirus genus. Classical horsepox has previously been reported only in Europe (France), Mongolia, and Kenya. The complete nucleotide sequence of the horsepox virus genome MNR-76 isolated in Mongolia has been determined. In addition to genes common to all orthopoxviruses, it includes intact genes specific only to this virus, the homologues of which are fragmented in the genome of other orthopoxviruses. Phylogenetic analysis of a number of orthopoxviruses was performed and a phylogenetic tree was constructed based on the conserved central region of the genome and some of the more variable terminal regions. The data obtained indicate that horsepox virus is most closely related to vaccinia virus and rabbitpox virus strains. Although horsepox is currently considered extinct, its pathogen may persist in unknown reservoirs. The data on the sequencing of the horsepox virus genome, strain MNR-76, suggest that horsepox virus could have served as the basis for the first smallpox vaccines. A chimeric copy of the horsepox virus was obtained using synthetic biology, which was used to create a new smallpox vaccine, TNX-801. On its basis, a recombinant vaccine against SARS-CoV-2 was constructed. The restoration of "extinct viruses" using synthetic biology methods has led to intense debates about the benefits and risks of such research.Conclusion. It cannot be ruled out that the use of modern genetic engineering technologies may lead not only to the development of effective vaccines, but also to the production of new orthopoxviruses pathogenic for humans and animals, or to the reintroduction of smallpox, which is especially dangerous in the context of the virtual absence of smallpox immunity in the population and international control over experiments in the synthetic biology of dangerous pathogens.

Epidemic vector-borne viral infections pose a serious threat to public health worldwide. There is currently no specific preventive treatment for most of them. One of the promising solutions for combating viral fevers is development of vector vaccines, including MVA-based vaccines, which have virtually no adverse side effects. The safety of the MVA strain and absent reactogenicity of recombinant MVA vaccines have been supported by many clinical trials.The article focuses on test results for similar preventive products against viral fevers: Crimean-Congo hemorrhagic fever, Rift Valley fever, yellow fever, Chikungunya and Zika fevers.Their immunogenicity was evaluated on immunocompetent and immunocompromised white mice; their protective efficacy was assessed on immunocompromised white mice deficient in IFN-α/β receptors, that are used for experimental modeling of the infection. Nearly all the new recombinant vaccines expressing immunodominant antigens demonstrated 100% protective efficacy. It has been found that although the vaccine expressing Zika virus structural proteins induced antibodies against specific viral glycoproteins, it can be associated with high risks when used for prevention of Zika fever in individuals who had dengue fever in the past, due to the phenomenon known as antibody-dependent enhancement of infection, which can occur in diseases caused by antigenically related flaviruses. For this reason, the vaccine expressing non-structural protein 1 (NS1) was developed for vaccination against Zika fever.The yellow fever vaccine developed on the MVA platform had immunogenicity similar to that of the commercial 17D vaccine, outperforming the latter in safety.

Ebola outbreak in eastern parts of the Democratic Republic of the Congo in 2018–2020 proved that the virus remains highly hazardous for humans, and the outbreak in West Africa in 2014–2016, which was the largest Ebola outbreak in history, showed that it could be imported to other continents, including Russia. In 1993 the Federal State Budgetary Institution “48th Central Scientific Research Institute” of the Russian Ministry of Defence developed a specific equine immunoglobulin for emergency prophylaxis of Ebola in risk groups. The evaluation and improvement of the product’s properties is an important area in the development of biological defence technologies.The aim of the study was to examine the properties of the equine anti-Ebola immunoglobulin which had been stored for a long time at 2–8 °C.Materials and methods: the authors studied batches of heterologous anti-Ebola immunoglobulin that had been stored for 17–22 years. The properties of the product were evaluated according to the requirements of the State Pharmacopoeia of the Russian Federation, 14th ed. (Ph. Rus. 14 ed.). The specific activity of the product was determined in a plaque reduction neutralisation test using Ebola virus and African green monkey kidney cells (GMK-AH-1(D)). Immunoglobulin molecular parameters were determined by size-exclusion high-performance liquid chromatography using the test methods described in the European Pharmacopoeia 9.6 and Ph. Rus. 14 ed.Results: the storage of anti-Ebola immunoglobulin for 17–22 years at 2–8 °C resulted in a four-fold reduction of the level of virus-neutralising antibodies against Ebola, decrease in the proportion of monomers from 98 to 74–90%, increase in the proportion of dimers and polymers, and formation of immunoglobulin molecules’ fragments. Signs of toxicity for mice were observed in one of the three product batches. Conclusions: the obtained results suggest the need to perform more studies to test the quality of antiEbola immunoglobulin batches that were stored for shorter periods of time in order to assess the stability of their initial characteristics.

The experiment on guinea pigs shows that Ingavirin, when administered orally in a single dose of 15 mg/kg on the 4 th day after vaccination with TEOVac, reduces accumulation of vaccine virus in organs and tissues of animals without affecting the immunogenicity of the vaccine. This efficacy is less pronounced when it is used together with TEOVac. When administered three times orally on days 6, 7, and 8 after immunization, Ingavirin reduces the level of vaccine virus in the blood, liver, and oral mucosa by a factor of 2 or more. Ingavirin is almost as effective as Arbidol, but less effective than Ridostin. These data indirectly indicate the possibility of using ingavirin along with ridostin to prevent post-vaccination reactions during immunization with TEOVac, and also give grounds to consider ridostin, ingavirin, and arbidol as a means of treating post-vaccination reactions.

Clinical trials of tabletted pox vaccine revealed development of tonsillitis as a postvaccinal reaction in some volunteers: ulceronecrotic lesions in the tonsils, lymphadenitis, hyperthermia and asthenia. The main cause of the local inflammatory reactions was activation of the host opportunistic microflora including hemolytic streptococci and Staphylococcus aureus. For the treatment of the infectious complications systemic antimicrobials, such as benzylpenicillin, amoxicillin, ampicillin, cefazolin and fluoroquinolones (ciprofloxacin) in combination with the symptomatic therapy were used. The treatment course of 9 days provided complete elimination of the postvaccinal reactions, the specific antibody generation being not affected.

Haemorrhagic fever caused by the Ebola virus is a highly hazardous infectious disease with a mortality rate of 50– 90 %. Heterologous immunoglobulins with a high virus-neutralizing titer are an important element of the WHO-endorsed set of measures for emergency prevention and treatment of the disease. Specific activity of these products is largely determined by their fractional composition, and, in particular, by molecular mass distribution (MMD). The size-exclusion-high-performance liquid chromatography (SEC-HPLC) has traditionally been used for determination of the MMD of the target protein in human immunoglobulin-based products. The use of this method for evaluation of molecular parameters of heterologous immunoglobulin requires confirmation of its specificity, accuracy and precision, and establishment of the chromatographic system suitability criteria in the context of a new test object.The aimof the study was to test the applicability of the SEC-HPLC method to the assessment of molecular parameters of anti-Ebola immunoglobulin derived from horse serum.Materials and methods: three batches of purified equine anti-Ebola immunoglobulin were used in the study. Normal equine and human immunoglobulins of the IgG isotype were used as reference standards. The HPLC test procedures described in the European Pharmacopoeia 9.6 and State Pharmacopoeia of the Russian Federation, 14th ed., were used for determination of monomers and other immunoglobulin fractions. An Agilent 1260 Infinity (Agilent, USA) HPLC system with a diode array detector and an Agilent Bio SEC-3 HPLC column were used for quality evaluation of the tested products.Results: the resolution factor between IgG monomer and dimer peaks (1.69 and 2.10), and the chromatographic column efficiency (>2000) make it possible to use the SEC-HPLC system for evaluation of molecular parameters of heterologous immunoglobulin. The study demonstrated reproducibility of the test procedure.Conclusions: the study confirmed the applicability of the SEC-HPLC procedure for evaluation of molecular parameters of anti-Ebola immunoglobulin derived from horse serum. It demonstrated the compliance of the purified immunoglobulin to the national and international quality requirements in terms of «Molecular parameters».