This study evaluates the oncolytic potential of the Moscow strain of reovirus against human metastatic melanoma and glioblastoma cells. The Moscow strain effectively infects and replicates within human melanoma cell lines and primary glioblastoma cells, while sparing non-malignant human cells. Infection leads to the selective destruction of neoplastic cells, mediated by functional viral replication. A positive correlation was identified between viral RNA accumulation and tumor cell death, with no replication observed in non-malignant cells. This study highlights the critical roles of cathepsins B, L, and S as mediators of the oncolytic process. The pharmacological inhibition of these enzymes significantly attenuated reovirus-induced cytotoxicity in melanoma and glioblastoma cells. Conversely, PKR production analysis revealed minimal activation in reovirus-infected tumor cells, suggesting that the hyperactivation of the RAS-signaling pathway and subsequent PKR inhibition do not directly contribute to the selective efficacy of reovirus. Moreover, infected tumor cells exhibited features of both apoptotic and non-apoptotic death, emphasizing the intricate mechanisms of reovirus-mediated oncolysis. These findings underscore the therapeutic promise of the Moscow strain of reovirus as a selective and potent oncolytic agent for targeting melanoma and glioblastoma cells.

Introduction. Rotavirus infection causes more than 250 million episodes of acute gastroenteritis annually, of which approximately 130,000 cases in children under 5 years of age are fatal. In this regard, the search for drugs for the treatment of rotavirus infection seems extremely relevant. The aim of the research was to evaluate the antiviral activity of Cytovir ® -3 against human rotavirus on a cellular infection model. Material and methods. The objects of the study were a mixture of active ingredients and individual components, identical in composition and ratio, contained in Cytovir ® -3. The study was carried out using a monkey kidney cell culture MA-104 and a laboratory strain of human group A rotavirus — 568, genotype G3P. Cultural, virological, molecular biological and statistical methods were used during the study. Results and discussion. Analysis of the survival of MA-104 cells in the presence of Cytovir ® -3 showed that in the concentration range from 100 to 200 µg/ml, the drug reproducibly exhibited antiviral activity, which was expressed in increased cell survival compared to the viral control. Cytovir ® -3 in a non-toxic concentration of 150 µg/ml suppressed the reproduction of rotavirus by 1.0-2.0 lg СC₅₀/ml with various schemes of introduction into cell culture at all periods of observation, which was accompanied by a significant decrease in the concentration of viral RNA and a cytoprotective effect.

Introduction. Animal models for SARS-CoV-2 infection, reproducing the clinical features of COVID-19 in humans, are important tools for studying the pathogenesis of the disease, transmission of the pathogen and are indispensable for testing antiviral drugs and vaccines. The aim of the study was to assess the virulence and tissue tropism for golden Syrian hamsters of SARS-CoV-2 strains belonging to different epidemiologically significant variants: Wuhan-like, Delta, Omicron BA.1.1 and Omicron BA.5.2. Materials and methods. Hamsters were intranasally infected with different SARS-CoV-2 strains. Virulence and tissue tropism of SARS-CoV-2 strains were assessed by comparing the dynamics of weight, viral load in organs and histopathological changes in lungs in infected and uninfected animals. Results. The Wuhan-like Dubrovka strain had the greatest virulence for hamsters, which was manifested by the development of severe pneumonia and a delay in weight gain by 14.6%, high virus content in the lungs, nasal passages and brain — 6.2, 5,9 and 3.7 lg TCID50/ml of homogenate, respectively. Presumably, it was the infection of the Wuhan-like virus of the central nervous system that negatively affected the weight and general condition of the animals. When hamsters were infected with viruses belonging to the Delta and Omicron variants, the observed minor weight loss in animals was uninformative, so indicators such as lung histopathology, viral load in the lungs, nasal passages, heart and other organs played a decisive role in assessing the virus pathogenicity. A score assessment of lung histopathology was of particular value in assessing the severity of pneumonia, since it reduced subjectivity in evaluating the results of histological examination and provided a semi-quantitative assessment of the pathological process. Conclusion. Despite the revealed lower virulence for hamsters of viruses belonging to the Delta and Omicron variants compared to the ancestral Wuhan virus, this animal model for COVID-19 retains its value for conducting preclinical trials of antiviral drugs.

Introduction. The antigen complex of opportunistic pathogenic bacteria (ACOPB) has a protective effect against avian influenza viruses, herpes virus type 2, and other viruses that cause acute respiratory viral infections. In the context of the COVID-19 pandemic, an important task is to find out whether ACOPB has a protective effect against SARS-CoV-2. The purpose of the study was to evaluate in vitro the ACOPB virus-inhibitory activity against the Dubrovka laboratory strain of SARS-CoV-2. Materials and methods. The study was performed using Vero cell line CCL-81, human peripheral blood mononuclear cells (PBMCs), mouse monoclonal anti-idiotypic antibodies structurally mimicking biological effects of human interferons (IFNs), the Dubrovka laboratory strain of SARS-CoV-2. The infectivity of the virus was assessed by two methods: by virus titration using cell cultures and the limiting dilution method when the results are assessed by a cytopathic effect; the second method was a plaque assay. The in vitro virus inhibition test was performed using the cell culture susceptible to SARS-CoV-2; the mixture containing a specific dose of the virus and a two-fold dilution of ACOPB was transferred to the cell culture after the ACOPB medication had interacted with the virus at 4C for 2 hours. The ACOPB virus-inhibitory activity against SARS-CoV-2 was assessed by the functional activity of / and IFN receptors (RIFN) in human PBMCs induced in vitro by ACOPB and the ACOPB mixture with the specific dose of SARS-CoV-2. The RIFN expression level was measured by the indirect membrane immunofluorescence test. Results. Hemagglutination assay using chicken, mouse, guinea pig, and human red blood cells was performed for detection of the SARS-CoV-2 inhibitory protein. The lysate of Vero CCL-81 cells infected with SARS-CoV-2 Dubrovka demonstrated the highest hemagglutination activity with guinea pig red blood cells and low titers of hemagglutination in the virus-containing fluid. The virus inhibition test in the Vero CCL-81 cell culture demonstrated that ACOPB inhibited 10 doses of SARS-CoV-2 Dubrovka with the titer 1 : 32, providing 100% protection of the cell culture for 8 days (the monitoring period). ACOPB induced / and RIFN expression on membranes of human PBMCs in in vitro cultures and decreased RIFN / and expression after its interaction with SARS-CoV-2 Dubrovka. Conclusion. The experimental studies including the virus inhibition test in the cell culture susceptible to SARS-CoV-2 Dubrovka and the indirect membrane immunofluorescence assay using monoclonal anti-idiotypic antibodies mimicking IFN-like properties demonstrated that ACOPB had both an immunomodulatory and a virus-inhibitory effect.

As novel SARS-CoV-2 Variants of Concern emerge, the efficacy of existing vaccines against COVID-19 is declining. A possible solution to this problem lies in the development of a live attenuated vaccine potentially able of providing cross-protective activity against a wide range of SARS-CoV-2 antigenic variants. Cold-adapted (ca) SARS-CoV-2 variants, Dubrovka-ca-B4 (D-B4) and Dubrovka-ca-D2 (D-D2), were obtained after long-term passaging of the Dubrovka (D) strain in Vero cells at reduced temperatures. Virulence, immunogenicity, and protective activity of SARS-CoV-2 variants were evaluated in experiments on intranasal infection of Syrian golden hamsters (Mesocricetus auratus). In animal model infecting with ca variants, the absence of body weight loss, the significantly lower viral titer and viral RNA concentration in animal tissues, the less pronounced inflammatory lesions in animal lungs as compared with the D strain indicated the reduced virulence of the virus variant. Single intranasal immunization with D-B4 and D-D2 variants induced the production of neutralizing antibodies in hamsters and protected them from infection with the D strain and the development of severe pneumonia. It was shown that for ca SARS-CoV-2 variants, the temperature-sensitive (ts) phenotype was not obligate for virulence reduction. Indeed, the D-B4 variant, which did not possess the ts phenotype but had lost the ability to infect human lung cells Calu-3, exhibited reduced virulence in hamsters. Consequently, the potential phenotypic markers of attenuation of ca SARS-CoV-2 variants are the ca phenotype, the ts phenotype, and the change in species specificity of the virus. This study demonstrates the great potential of SARS-CoV-2 cold adaptation as a strategy to develop a live attenuated COVID-19 vaccine.

— The appearance of mutations in the genes encoding the surface proteins of the new type of coronavirus SARS-CoV-2, when it circulates in the host population, makes it difficult to use monoclonal antibodies for its species identification. In such cases, the choice of conservative genetic targets allows identification by molecular biological methods. In this work, previously developed primers specific to the E- gene fragment were tested to detect a new type of coronavirus on six isolates belonging to different genetic variants (the original Wuhan strain, delta and omicron). The choice of a conservative site of the E gene encoding the small transmembrane protein E as a target for reverse transcription with subsequent amplification (RT-PCR) made it possible to detect coronavirus regardless of its subtypes characterized by antigenic heterogeneity in N- and S-proteins. The possibility of species-level identification of the COVID-19 pathogen circulating in Russia is shown, both in the total reaction volume (in a single test tube) and on biological microarrays.

Although WHO declared an end to the pandemic, COVID-19 remains a significant public health concern worldwide. Modern vaccines often induce either only humoral or only cellular immunity. Furthermore, new emergent epidemiologically significant SARS-CoV-2 variants and their spread considerably reduce the effectiveness of preventive vaccination. Therefore, there is an urgent need to improve the existing vaccines against COVID-19. One of the promising approaches to the solution of the problem is creation of a "universal" vaccine that would have a cross-protective activity against different antigenic variants of the virus. In this respect, the development of live attenuated vaccine is of special interest, as it can activate not only humoral, but also cell-mediated components of immunity, providing long-term immune response and cross-protection against different variants of the virus. This review highlights the existing approaches to producing attenuated SARS-CoV-2 strains and gives an assessment of their prospects for clinical use. Some researchers use methods of genetic engineering and reverse genetics such as site-directed mutagenesis and codon deoptimization for virus attenuation. Others tend to use traditional approaches focusing on producing virus mutants through extended passaging in cell culture under selective conditions. The gained experience demonstrates great prospects for development of highly effective live-attenuated vaccine against COVID-19.

Introduction. Despite the end of the COVID-19 pandemic, the problem of vaccine prevention of this disease appears highly relevant. The emergence and widespread distribution of the Omicron SARS-CoV-2 variant of concern (VOC) and its sublineages has dramatically reduced the efficacy of vaccination. The possible approach to solving this problem is to develop a nasal live attenuated vaccine capable of activating humoral, mucosal, and cell-mediated immunity, providing a prolonged immune response and cross-protection against different VOCs. The aim of the study was to determine the immunization efficacy with attenuated cold-adapted Wuhan-like SARS-CoV-2 D-D2 strain against homologous and heterologous challenges. Materials and methods. The study was conducted on an animal model of coronavirus pneumonia in golden Syrian hamsters. The efficacy of immunization was assessed by comparing the dynamics of weight, viral load in organs and histopathological changes in the lungs in immunized and unimmunized animals. Results. Single intranasal immunization of golden Syrian hamsters with D-D2 strain showed its high immunogenicity: seroconversion was evident in all immunized animals. Wuhan-like D-D2 strain provides highly effective protection of hamsters against the development of productive infection and pneumonia when challenged both with ancestral virus and heterologous strains related to Delta (AY.122) and Omicron (sublineages BA.1.1 and BA.5.2) variants. Conclusion. SARS-CoV-2 attenuation is a promising strategy for the development of a highly effective nasal live COVID-19 vaccine.

INTRODUCTION The variability of SARS-CoV-2 appeared to be higher than expected, the emergence of new variants raises concerns. The aim of the work was to compare the pathogenicity of the Wuhan and BA.1.1/Omicron variants in BALB/c mice and Syrian hamsters. MATERIALS AND METHODS The study used strains of SARS-CoV-2: Dubrovka phylogenetically close to Wuhan-Hu-1, and LIA phylogenetically close to Omicron, BALB/c mice, transgenic mice B6.Cg-Tg(K18-ACE2)2Prlmn/HEMI Hemizygous for Tg(K18-ACE2)2Prlmn, Syrian golden hamsters. Animals were infected intranasally, pathogenicity was estimated by a complex of clinical, pathomorphological and virological methods. RESULTS Comparative studies of SARS-CoV-2 Dubrovka and LIA strains on animal models demonstrated their heterogeneous pathogenicity. In parallel infection of BALB/c mice with Dubrovka and LIA variants, the infection proceeded without serious clinical signs and lung damage. Infection with the LIA strain resulted to a systemic disease with a high concentration of viral RNA in the lungs and brain tissues of animals. The presence of viral RNA in mice infected with the Dubrovka strain was transient and undetectable in the lungs by day 7 post-infection. Unlike the mouse model, in hamsters, the Dubrovka strain had a greater pathogenicity than the LIA strain. In hamsters infected with the Dubrovka strain lung lesions were more significant, and the virus spread through organs, in particular in brain tissue, was observed. In hamsters infected with the LIA strain virus was not detected in brain tissue. CONCLUSION The study of various variants of SARS-CoV-2 in species initially unsusceptible to SARS-CoV-2 infection is important for monitoring zoonotic reservoirs that increase the risk of spread of new variants in humans.

Introduction. The emergence of new epidemiologically significant variants of SARS-CoV-2 has shifted emphasis to development of a live vaccine, which would be able to provide protection against a wide range of antigenic variants of the virus. The aim of the study was to obtain SARS-CoV-2 variants attenuated through cold adaptation and to provide their biological characterization.Materials and methods. The Dubrovka laboratory strain of SARS-CoV-2 and its variants were cultured on Vero and Calu-3 cells. The virus quantification was performed by virus titration in Vero cells and by real-time reverse transcription-polymerase chain reaction. SARS-CoV-2 virions were analyzed using transmission electron microscopy. Genome sequences of the virus were identified by nanopore sequencing. The attenuation (att) phenotype of SARS-CoV-2 variants was identified using Syrian hamsters as an animal model for COVID-19. Results. Cold-adapted (ca) SARS-CoV-2 variants – Dubrovka-ca-B4 and Dubrovka-ca-D2 were produced by continued passaging of the Dubrovka strain in the Vero cell culture at the temperature being gradually decreased to 23ºC and by subsequent cloning. Up to 20 nucleotide substitutions and 18 amino acid substitutions were detected in genomes of ca-variants. Ca-variants, as distinct from the parent Dubrovka strain, actively replicated at 23ºC, while the Dubrovka-ca-D2 variant had a temperature-sensitive (ts) phenotype (did not replicate at 39ºC). Ca-variants of the virus replicated poorly at 37ºC in the Calu-3 human lung cell culture, which, along with the ts-phenotype, can be a marker of virus attenuation for humans. In the intranasally infected Syrian hamsters, ca-variants of the virus demonstrated an attenuation phenotype: they did not cause loss of appetite, fatigue, drowsiness, did not slow down weight gain, replicating much more slowly in the lungs and brain compared to the virulent Dubrovka strain. Conclusion. The obtained attenuated SARS-CoV-2 ca-variants, Dubrovka-ca-B4 and Dubrovka-ca-D2, should be studied further as candidate vaccine strains for a live attenuated vaccine against COVID-19.

Objectives. To evaluate the effect of cellular genes FLT4, Nup98, and Nup205 on the reproduction of the influenza A virus in A549 human lung cancer cell line.Methods. The work was carried out using the equipment of the center for collective use of the I.I. Mechnikov Research Institute of Vaccines and Sera (Russia). The virus-containing fluid was collected within three days from the moment of transfection and infection and the intensity of viral reproduction was assessed by viral titration and hemagglutination reaction. The viral RNA concentration was determined by real-time reverse-transcription polymerase chain reaction (RT-PCR). To calculate statistically significant differences between groups, the nonparametric Mann–Whitney test was used.Results. In cells treated with small interfering RNAs (siRNAs) targeted at FLT4, Nup98, and Nup205 genes, a significant decrease in their expression and indicators of viral reproduction (virus titer, hemagglutinating activity, viral RNA concentration) was observed at a multiplicity of infection (MOI) = 0.1. Additionally, it was found that a decrease in the expression of target genes using siRNA does not lead to a significant decrease in cell survival. The viral titer in cells treated with siRNA FLT4.2, Nup98.1, and Nup205 on the first day was lower by an average of 1.0 lg, and on the second and third days, by 2.2–2.3 lg, compared to cells treated with nonspecific siRNA. During real-time RT-PCR, a significant decrease in the concentration of viral RNA was observed with siRNA Nup98.1 (up to 190 times) and Nup205 (up to 30 times) on the first day, 26 and 29 times on the second day, and 6 and 30 times on the third day, respectively. For FLT4.2 siRNA, the number of viral RNA copies decreased by 23, 18, and 16 times on the first, second, and third days. Similar results were obtained when determining the hemagglutinating activity of the virus. The hemagglutinating activity on the third day most strongly decreased in cells treated with siRNA Nup205 and FLT4.2 (16 times). In cells treated with siRNA FLT4.1, Nup98.1, and Nup98.2, hemagglutinating activity decreased by 8 times.Conclusions. In the present study, three cellular genes (FLT4, Nup98, and Nup205) were identified—the decrease in the expression of which effectively suppresses viral reproduction— and the original siRNA sequences were obtained. The results obtained are important for creating therapeutic and prophylactic medication, whose action is based on the RNA interference mechanism.

One of the most important steps in the development of drugs and vaccines against a new coronavirus infection is their testing on a relevant animal model. The laboratory mouse, with well-studied immunology, is the preferred mammalian model in experimental medicine. However, mice are not susceptible to infection with SARS-CoV-2 due to the lack of human angiotensin-converting enzyme (hACE2), which is the cell receptor of SARS-CoV-2 and necessary for the entry of the virus into the cell. In present work, it was shown that intranasal administration of the adeno-associated vectors AAV9 and AAV-DJ encoding the hACE2 provided a high level of expression of ACE2 gene in the lungs of mice. In contrast, the introduction of the AAV6 vector led to a low level ACE2 expression. Infection with SARS-CoV-2 of mice expressing hACE2 in the lungs led to virus replication and development of bronchopneumonia on the 7th day after infection. Thus, a simple method for delivering the human ACE2 gene to mouse lungs by intranasal administration of the AAV vector has been proposed. This approach enabled rapid generation of mouse model for studying coronavirus infection.

One of the most important steps in the development of drugs and vaccines against a new coronavirus infection is their testing on a relevant animal model. The laboratory mouse, with well-studied immunology, is the preferred mammalian model in experimental medicine. However, mice are not susceptible to infection with SARS-CoV-2 due to the lack of human angiotensin-converting enzyme (hACE2), which is the cell receptor of SARS-CoV-2 and necessary for the entry of the virus into the cell. In present work, it was shown that intranasal administration of the adeno-associated vectors AAV9 and AAV-DJ encoding the hACE2 provided a high level of expression of ACE2 gene in the lungs of mice. In contrast, the introduction of the AAV6 vector led to a low level ACE2 expression. Infection with SARS-CoV-2 of mice expressing hACE2 in the lungs led to virus replication and development of bronchopneumonia on the 7th day after infection. Thus, a simple method for delivering the human ACE2 gene to mouse lungs by intranasal administration of the AAV vector has been proposed. This approach enabled rapid generation of mouse model for studying coronavirus infection.

Glioblastoma multiforme (GBM) accounts for almost half of all primary malignant brain tumors in adults and has a poor prognosis. Here we demonstrated the oncolytic potential of the L-16 vaccine strain of measles virus (MV) against primary human GBM cells and characterized the genetic patterns that determine the sensitivity of primary human GBM cells to oncolytic therapy. MV replicated in all GBM cells, and seven out of eight cell lines underwent complete or partial oncolysis. RNA-Seq analysis identified about 1200 differentially expressed genes (FDR < 0.05) with at least two-fold expression level change between MV-infected and uninfected cells. Among them, the most significant upregulation was observed for interferon response, apoptosis and cytokine signaling. One out of eight GBM cell lines was defective in type I interferon production and, thus, in the post-interferon response, other cells lacked expression of different cellular defense factors. Thus, none of the cell lines displayed induction of the total gene set necessary for effective inhibition of MV replication. In the resistant cells, we detected aberrant expression of metalloproteinase genes, particularly MMP3. Thus, such genes could be considered intriguing candidates for further study of factors responsible for cell sensitivity and resistance to L-16 MV infection.

Influenza is a widespread respiratory infection, accompanied by damage to the lower respiratory tract of a person, and can lead to severe complications, up to a fatal outcome. Currently existing therapeutic agents and vaccines do not provide fully effective protection against influenza viruses. The development and creation of drugs based on the mechanism of RNA interference in the context of this problem is a promising direction. The aim of this study is to select and experimentally substantiate cellular target genes for miRNAs whose knockdown suppresses viral reproduction. A549 cells (human lung adenocarcinoma) were transfected with small interfering RNAs. After 4 hours, the transfected cells were infected with the influenza virus pri MOI = 0.1; 0.01 and 0.001. The virus-containing liquid was sampled within three days from the moment of transfection and the intensity of the dynamics of viral reproduction was assessed by the CPD titration method. The use of all small interfering RNAs at MOI = 0.1 resulted in a significantly significant decrease in the viral titer relative to non-specific control. Similar results were obtained at MOI = 0.01 and 0.001. The most effective siRNA ISSINUP98, since when using it, at MOI = 0.1, the viral titer values decreased by 1.7 lg TCD50/ml and by 3 lg TCD50/ml at MOI = 0.01 on the third day. The results showed that miRNAs directed to human cellular genes FLT4, Nup98 and Nup205, whose derivatives play an important role in the life cycle of the influenza virus, effectively reduce its reproduction in vitro. Thus, the studied genes and their products are potential targets for the development of anti-influenza drugs.

Objectives. Evaluation of changes in the viral activity of influenza A/WSN/33 after complex knockdown of combinations of cellular genes FLT4, Nup98 and Nup205 in human lung cell culture A549. Methods. The work was carried out using the equipment of the Center for Collective Use of the I. Mechnikov Research Institute of Vaccines and Sera, Russia. The authors performed transfection of combinations of small interfering ribonucleic acid (siRNA) complexes that cause simultaneous disruption of the expression of cellular genes FLT4, Nup98, and Nup205. Within three days from the moment of transfection and infection, the supernatant fluid and cell lysate were taken for subsequent viral reproduction intensity determination using the titration method for cytopathic action. The dynamics of changes in the concentration of viral ribonucleic acid (vRNA) was determined by real-time reverse transcription polymerase chain reaction (real-time RT-PCR). The nonparametric Mann–Whitney test was used to calculate statistically significant differences between groups. Results. Using all of the combinations of siRNA complexes, cell viability did not decrease below the threshold level of 70%. In cells treated with complex FLT4.2 + Nup98.1 + Nup205 at the multiplicity of infection (MOI) equal to 0.1, a significant decrease in viral reproduction by 1.5 lg was noted on the first day in relation to nonspecific and viral controls. The use of siRNA complexes at MOI 0.01 resulted in a more pronounced antiviral effect. The viral titer in cells treated with siRNA complexes FLT4.2 + Nup98.1 and Nup98.1 + Nup205 decreased by 1.5 lg on the first day. In cells treated with complexes FLT4.2 + Nup205 and FLT4.2 + Nup98.1 + Nup205, it decreased by 1.8 and 2.0 lg on the first day and by 1.8 and 2.5 lg on the second day, respectively, in relation to nonspecific and viral controls. When conducting real-time RT-PCR, a significant decrease in the concentration of vRNA was noted. At MOI 0.1, a 295, 55, and 63-fold decrease in the viral load was observed with the use of siRNA complexes FLT4.2 + Nup98.1, Nup98.1 + Nup205, and FLT4.2 + Nup98.1 + Nup205, respectively. On the second day, a decrease in vRNA was also observed in cells treated with complex A. A 415-fold decrease in vRNA on the third day was noted in cells treated with complex FLT4.2 + Nup205. At MOI 0.01, the concentration of vRNA decreased 9.5 times when using complex B relative to nonspecific and viral control. Conclusions. The study showed a pronounced antiviral effect of siRNA combinations while simultaneously suppressing the activity of cellular genes (FLT4, Nup98, and Nup205), whose expression products are playing important role in the viral reproduction process, and obtained original designs of siRNA complexes. The results obtained are of great importance for the creation of emergence prophylactic and therapeutic drugs, whose action is based on the mechanism of RNA interference.

Vaccination against COVID-19 is the most effective method of controlling the spread of SARS-CoV-2 and reducing mortality from this disease. The development of vaccines with high protective activity against a wide range of SARS-CoV-2 antigenic variants remains relevant. In this regard, evaluation of the effectiveness of physical methods of virus inactivation, such as ultraviolet irradiation (UV) of the virus stock, remains relevant. This study demonstrates that the UV treatment of SARS-CoV-2 completely inactivates its infectivity while preserving its morphology, antigenic properties, and ability to induce the production of virus-neutralizing antibodies in mice through immunization. Thus, the UV inactivation of SARS-CoV-2 makes it possible to obtain viral material similar in its antigenic and immunogenic properties to the native antigen, which can be used both for the development of diagnostic test systems and for the development of an inactivated vaccine against COVID-19.

An assessment was made of high- and low-risk human papillomaviruses (HPVs) prevalence in the Russian Federation. Clinical samples (urogenital swabs) were obtained from male and female patients of different ages with supposed urogenital HPV infection living in different regions of the Russian Federation in 2019 (n = 12 945). HPV genotyping was performed using a real-time PCR Kvant-21 kit (DNA-Technology, Russia), which allows differentiating between the high-risk HPV types 31, 35, 52, 33, 68, 45, 82, 51, 39, 58, 66, 26, 53, 59, 56, 73, 16, and 18 and low-risk HPV types 6, 11, and 44. In the clinical samples obtained from 5013 patients, 8593 HPV strains were detected with HPV monoinfection being observed in 3057 patients and mixed infection in 1956 patients. It was shown that, in the Russian Federation, the dominant HPV-types are HPV16, 13.8% (95% CI 13.0–14.5); HPV6, 10.7% (10.0–11.3); HPV51, 6.8% (6.3–7.3); HPV44, 6.8% (6.2–7.3); HPV53, 6.3% (5.8–6.8); HPV31, 5.6% (5.2–6.2); HPV56, 5.5% (5.0–6.0); and HPV52, 5.4% (5.0–5.9), while the percentage of other types varied from 5 to 0.4%. The age, gender, and regional distribution of different HPV types has been described. The results of monitoring circulating HPV strains will allow the effectiveness to be predicted of HPV vaccines of different composition in the Russian Federation and may be used to a great extent in the development of Russian HPV vaccines.

Background: Influenza is one of the most common infectious diseases, which affect the lower respiratory tract, and can lead to serious complications including death. It is known that currently available therapeutic agents and vaccines do not provide 100% protection against influenza viruses. The development of drugs based on the RNA interference mechanism in the context of this problem is a promising area. This paper aims to assess the effect of FLT4, Nup98, and Nup205 cellular gene knockdown on the reproduction of influenza A virus in human lung cell culture. Materials and methods: Influenza virus strain A/WSN/1933 (St. Jude's Children's Research Hospital, USA) was used in this work as well as A549 cell culture (human lung adenocarcinoma, ATCC® CCL-185, USA) and MDCK cell culture (dog kidney cells, Institut Pasteur, France). Small interfering RNAs (siRNAs) (Syntol, Russia) were synthesized for targeting of the FLT4, Nup98, and Nup205 genes. Lipofectamin 2000 (Invitrogen, USA) was used for transfection. After 4 hours, the transfected cells were infected with the influenza virus at MOI = 0.1. Virus-containing fluid was collected within three days from the moment of transfection and the intensity of viral reproduction was assessed by CPE titration and hemagglutination reactions. Viral RNA concentration was determined by RT-PCR. Mann-Whitney U test was used for statistical analysis. Results: In cells treated with siRNA for FLT4, Nup98, and Nup205 genes, there was a significant decrease in the expression of target genes and indicators of viral reproduction (virus titer, hemagglutinating activity, viral RNA concentration) at MOI = 0.1, although the cell survival rate did not decrease significantly. On the first day, the viral titer in cells treated with declared siRNA was lower, on average, by 1 Lg, and on the second and third days, by 2.2-2.3 Lg, compared to cells treated with nonspecific siRNA. During RT-PCR, a significant decrease in the concentration of viral RNA with Nup98.1 and Nup205 siRNA was detected: up to 190 times and 30 times on the first day; 26 and 29 times on the second day; 6 and 30 times on the third day, respectively. For FLT4.2 siRNA, the number of viral RNA copies has decreased 23, 18, and 16 times on the first, second, and third days. Similar results were obtained while determining the hemagglutinating activity of the virus. The hemagglutinating activity decreased mostly (by 16 times) in cells treated with Nup205 and FLT4.2 siRNAs on the third day. In cells treated with FLT4.1, Nup98.1, and Nup98.2 siRNAs, the hemagglutinating activity decreased by 8 times. Conclutions: We identified a number of genes such as FLT4, Nup98, and Nup205, the decrease in the expression of which can effectively suppress viral reproduction. The original siRNA sequences were also obtained. These results are important for the creation of therapeutic and prophylactic agents, whose action is based on the RNA interference mechanism.

The aim of the study was to analyze genetic characteristics of strains belonging to group A rotaviruses (RVA) circulating in Moscow in 2015–2020, including rare strains non-typeable by polymerase chain reaction (PCR).Materials and methods. A total of 289 stool samples were tested; the samples were collected from children aged 1 month to 17 years, hospitalized with acute gastroenteritis. Immunochromatography and real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assays were used for detection of rotaviruses in the samples. The rotavirus genome sequencing was performed using the Sanger technique and nanopore sequencing.Results and discussion. RVA RNA was detected in 131 clinical samples, and the G/[P] genotype was identified in 125 samples. The general profile showed prevalence of RVA strains with the G9P[8]I1 genotype (37%) followed by G3P[8]I2, G4P[8]I1, G2P[4]I2, G1P[8]I1, and G3P[8]I1 variants (18, 15, 11, 5, and 2%, respectively). Seven (5%) isolates were identified as GxP[8]. In 2015–2020, the region reported a decline in G4P[8]I1 genotype prevalence (from 39% to 9%) and an increase in the proportion of the G9P[8]I1 genotype (from 6% to 37%) as compared to 2009–2014. In 2018–2020, a large number of cases with the previously unknown DS-1-like reassortant strain with the G3P[8]I2 genotype were reported; the above strain has become widely common worldwide in the recent years. Nanopore sequencing was performed to analyze the genome of the G3P[8]I2 strain and the rare G4P[6]I1 strain. It was found that the G4P[6]I1 strain was phylogenetically related to porcine rotaviruses.Conclusion. In the recent years, the genetic diversity of RVA circulating in the Moscow Region has changed significantly. The obtained results prove the importance of continuous monitoring of rotavirus infection and selective sequencing of RVA genes to fine-tune data of the type-specific real-time RT-PCR. The ever-changing genetic composition of the circulating RVA strains calls for regular optimization of RVA genotyping systems based on real-time RT-PCR.