Epidemiology of Horsepox. The New Aspects

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.