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The eradication of smallpox has become one of the greatest successes of modern health science. This great achievement was made possible thanks to the widespread vaccination of the population. The last case of human infection with smallpox virus occurred in 1977. In 1980, at the 33rd session of the World Health Assembly, routine vaccination against that infection was recommended to be discontinued due to severe post-vaccination complications. However, humanity remains vulnerable to other orthopoxvirus infections closely related to smallpox virus. Recently, the cases of human infection with ortopoxviruses such as monkeypox virus, cowpox virus, vaccinia virus have become more frequent. Also, cases of infection of people with previously unknown orthopoxvirus species are recorded. Zoonotic orthopoxviruses pathogenic for humans, circulating in nature, require a detailed study and monitoring of the emergence of new strains. Their occurrence against the background of the cessation of planned vaccination of the population against smallpox virus can lead to the emergence of new highly pathogenic viruses. This review contains information on cases of human infection with orthopoxviruses around the world for the period 2008–2018. It also describes epidemiological anamnesis and the relations between cases of human infection in different countries due to the spread of viruses over a wide area, the movement of people between countries, population contacts with domestic and wild animals. Also, this paper provides information on the infection of people with previously unknown strains of orthopoxviruses.

The modern approach to developing attenuated smallpox vaccines usually consists in targeted inactivation of vaccinia virus (VACV) virulence genes. In this work, we studied how an elevated production of extracellular enveloped virions (EEVs) and the route of mouse infection can influence the virulence and immunogenicity of VACV. The research subject was the LIVP strain, which is used in Russia for smallpox vaccination. Two point mutations causing an elevated production of EEVs compared with the parental LIVP strain were inserted into the sequence of the VACV A34R gene. The created mutant LIVP-A34R strain showed lower neurovirulence in an intracerebral injection test and elevated antibody production in the intradermal injection method. This VACV variant can be a promising platform for developing an attenuated, highly immunogenic vaccine against smallpox and other orthopoxvirus infections. It can also be used as a vector for designing live-attenuated recombinant polyvalent vaccines against various infectious diseases.

Vaccinia virus had played a key role in the global smallpox eradication. However, in case of mass vaccination with various Vaccinia virus strains severe side effects were revealed sometimes ending up with lethal outcomes, especially in immunocompromised humans. Hence, in 1980 the World Health Organization recommended to cancel smallpox vaccination after declaring about smallpox eradication. Over the last 40 years, human population virtually lost immunity not only against smallpox, but also against other zoonotic orthopoxvirus infections, such as monkeypox, cowpox, buffalopox, and camelpox. All of them pose a represent increasing threat to human health and heighten a risk of emerging highly contagious viruses due to natural evolution of previous zoonotic orthopoxviruses. In order to prevent development of small outbreaks into spreading epidemics and, thus, to decrease a risk of emergence due to natural evolution of highly pathogenic for humans orthopoxviruses, efforts should be applied to develop safe new generation live vaccines based on Vaccinia virus with target virulence genes inactivation. These strains should be examined in laboratory animal models inoculated via different routes. Currently, Vaccinia virus often becomes attenuated to create live recombinant vaccines due to inserting target DNA sequences into the virus virulence genes resulting in their inactivation. Vaccinia virus strain LIVP used in the Russian Federation as smallpox vaccine as well as derivative attenuated variant LIVP-GFP created by using genetic engineering methods with inactivating its thymidine kinase gene were examined. Such viruses were intracerebrally inoculated into suckling mice at doses of 101 or 102 PFU/animal for neurovirulence assessment. Adult mice were infected intranasally, subcutaneously or intradermally at doses of 107 or 108 PFU/animal and clinical manifestations were analyzed for 14 days. On the 28th day after the onset, blood serum samples were collected from individual mice to measure virus specific antibody level by using ELISA. It was shown that recombinant Vaccinia virus strain LIVP-GFP displayed markedly lowered neurovirulence and pathogenicity for mice as compared to parental LIVP. Finally, intradermal route turned out to demonstrate the most safe and effective profile for immunization with both examined Vaccinia virus strains.

The problems of oncological disease treatment are considered relevant and timely issues of the current research programs. Since monotherapy is increasingly clear to be less effective than combination therapy, the novel studies seek for advancement of current treatments and development of new ones employing oncolytic immunotherapy being among the most rapidly evolving approaches. Modern genetic engineering techniques enable new applications of oncolytic viruses in the frames of combined cancer therapy. These applications are feasible, due to the abilities of oncolytic viruses to destruct tumor cells, like as by changing susceptibility of cancer cells to anti-tumor drug, and upon the whole body, thus overcoming the mechanisms conferring immunoresistance of tumor cells. In the present work, we have developed a recombinant vaccinia virus which is a promising platform for designing the antitumor drugs. The following modifications of viral genome were made by means of genetic engineering: gene encoding granulocyte-macrophage colony-stimulating factor was inserted into the region of viral thymidine kinase gene; viral A34R gene encoding a membrane glycoprotein, was replaced by A34R gene with two nucleotide substitutions resulting into D110N and K151E mutations which cause increased proportion of extracellular enveloped virions during the virus reproduction. Some properties of the recombinant virus were studied in vitro. The virus was shown to produce granulocyte-macrophage colony stimulating factor, and high numbers of extracellular enveloped virions. The genome modifications had no effect upon viral replication.

Melanoma is a tumor that forms as a result of malignant transformation of melanin-producing pigment cells (melanocytes). It is the most aggressive form of skin cancer and is characterized by high resistance to chemotherapeutic drugs, which results in a need to explore alternative methods for this disease therapy. Currently, new approaches to cancer treatment are being intensely developed, oncolytic immunotherapy being one of them. This approach consists in using viruses as targeted tumor-specific cytolytic agents capable of stimulating both tumor-specific and nonspecific immune responses. A considerable body of research is currently aimed on improving the immunostimulatory properties of viruses by inserting the genes encoding immunomodulatory proteins or tumor-specific antigenic determinants into viral genomes. For melanoma, the highest number of tumor-associated antigens (TAAs) has been identified, which serve as the basis for the development of anti-tumor DNA vaccines. The immunogenicity and efficacy of these drugs, however, remain low. The bottlenecks in using DNA vaccines to treat cancer are considered to be imperfect design of polyepitope constructs, as well as inefficient delivery of therapeutic molecules directly to the target cells. A partial solution to these problems may be represented by the use of oncolytic viruses as vectors for the delivery of artificial immunogens. The recombinant vaccinia virus was obtained by transient dominant selection. The cytolytic activity of the obtained virus was tested using the MTT assay. The oncolytic activity of the virus was assessed in the mouse xenograft model obtained using malignant SK-Mel-28 cells. This paper reports the production of a recombinant L-IVP_oncoM virus, the oncolytic virus for the delivery of anticancer therapeutic genes into the cells, on the basis of the vaccinia virus strain L-IVP. Toward this end, the gene encoding the Granulocyte-macrophage colony-stimulating factor (GM-CSF) and the artificial gene encoding a polyepitope immunogen containing the epitopes of the antigens over-expressed in melanoma cells were inserted into the virus genome. These insertions were located in the proximity of the genes encoding thymidine kinase (J2R) and viral growth factor (C11L), respectively. The properties of L-IVP_oncoM were studied in in vitro experiments using cell cultures of various origin and in the in vivo experiments using the mouse xenograft model. The basic experiments to assess the biological properties of the obtained L-IVP_oncoM, which are necessary to characterize the oncolytic virus, have been carried out.

Introduction . Currently, new directions in cancer therapy are actively developing, one of which is oncolytic immunotherapy. This approach would be to use of viruses as cancer specific cytolytic agents capable of stimulating both the tumor-specific and non-specific immune response. The objective paper was obtain a recombinant vaccinia virus containing genes encoding immunostimulating molecules and study oncolytic and immunostimulating properties of recombinant virus. Material and methods . MTT test, ELISA, methods of transient dominant selection. Results . The recombinant vaccinia virus (L-IVP_oncoB) were obtained with deletion of the gene encoding thymidine kinase and had an integrated gene encoding GM-CSF. Also the virus have deletion of the gene encoding viral growth factor and integrated genes encoding synthetic tumor-specific polyepitopic immunogens. It was shown that the modifications made to the viral genome did not affect the growth characteristics of the virus when cultured on CV-1 and 4647 cell cultures, and the cytopathogenic efficacy of the virus was determined in relation to cancer cultures of cells of various genesis. In in vivo experiment, it was revealed that the polyepitopic construct in the genome L-IVP_oncoB is able to initiate a change in the profile of cytokines. Discussion . The obtained data characterized L-IVP_oncoB as a promising cytopathogenic and immunostimulating agent and showed the need for further study of its properties as means of oncolytic immunotherapy. Conclusion. The basic experiments on the evaluation of the biological properties of the obtained L-IVP_oncoB, which are necessary for the characterization of the oncolytic virus, have been carried out.