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BACKGROUND: Despite the large-scale development of vaccines against coronavirus infection, there is still no complete information about the antigenic structure of the SARS-CoV-2 virus particles. This article describes a method of obtaining a pure concentrated whole-virion sample that can be used in various studies. AIM: The goal is to develop an optimal method of purification of the inactivated SARS-CoV-2 virus in order to obtain a standard with parameters of purity and antigen content sufficient for structural and immunological studies. MATERIALS AND METHODS: To obtain a pure concentrated virus SARS-CoV-2 we used the sucrose density gradient ultracentrifugation. Fractions with the highest content of viral particles were evaluated based on the concentration of nucleocapsid N and glycoprotein S. The purity of the pooled fractions (the purified sample) was evaluated by the presence of impurity proteins, toxins and bovine serum albumin. RESULTS: The optimal conditions for obtaining the inactivated purified SARS-CoV-2 whole virus were determined. A standard sample of the inactivated SARS-CoV-2 virus was isolated and characterized. CONCLUSIONS: The obtained standard sample can be used in enzyme immunoassay to measure the amount of antigen in whole-virion vaccines against coronavirus infection, as well as in various structural studies of SARS-CoV-2 virus particle.

The severe COVID‐19 pandemic drives the research toward the SARS‐CoV‐2 virion structure and the possible therapies against it. Here, we characterized the β‐propiolactone inactivated SARS‐CoV‐2 virions using transmission electron microscopy (TEM) and atomic force microscopy (AFM). We compared the SARS‐CoV‐2 samples purified by two consecutive chromatographic procedures (size exclusion chromatography [SEC], followed by ion‐exchange chromatography [IEC]) with samples purified by ultracentrifugation. The samples prepared using SEC and IEC retained more spikes on the surface than the ones prepared using ultracentrifugation, as confirmed by TEM and AFM. TEM showed that the spike (S) proteins were in the pre‐fusion conformation. Notably, the S proteins could be recognized by specific monoclonal antibodies. Analytical TEM showed that the inactivated virions retained nucleic acid. Altogether, we demonstrated that the inactivated SARS‐CoV‐2 virions retain the structural features of native viruses and provide a prospective vaccine candidate., SARS‐CoV‐2 virions inactivated with β‐propiolactone were analyzed using transmission electron microscopy (TEM) and atomic force microscopy.The S proteins could be recognized by specific monoclonal antibodies.Analytical TEM showed that the inactivated virions retained nucleic acid.

Vaccines are proven to be an effective tool in prophylaxis of severe COVID-19, but emerging mutated SARS-CoV-2 variants constantly challenge vaccines’ protectivity. We have evaluated the ability of the sera from individuals vaccinated with two variants of inactivated vaccine CoviVac and COVID-19 convalescents (May-December 2020) to neutralize SARS-CoV-2 variants Delta and Omicron. Four groups of serum samples (CoviVac vaccinees; COVID-19 convalescents; mice immunized with CoviVac preparations based on prototype B.1.1 strain and Delta variant) were evaluated in virus neutralization test against SARS-CoV-2 heterologous B.1.1 virus, Delta and Omicron variants. CoviVac preparations based on B.1.1 and Delta induced neutralizing antibodies against SARS-CoV-2 B.1.1 and two variants of concern. We observed a decrease in neutralization capacity in the sera from CoviVac (based on B.1.1 strain) vaccinees: 57.1% samples had detectable neutralizing antibodies against Delta and 61.9% against Omicron variants. Sera samples of all (100%) mice immunized with a candidate vaccine based on the SARS-CoV-2 Delta variant strain had neutralizing antibodies against all tested strains.

Highlights • There were multiple importations and several patterns of spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Russia. • There are no signs of direct virus importations from China. • SARS-CoV-2 variants circulating in Russia mostly contain seven common mutations., Objectives The outbreak of coronavirus disease 2019 (COVID-19) started in December 2019 in China and then spread worldwide over the following months, involving 188 countries. The objective of this study was to determine the molecular epidemiology of the COVID-19 outbreak in Russia. Methods In this study, two severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strains were isolated and genetically characterized. A phylogenetic analysis of all available Russian sequences was then performed and these were compared to the epidemiological data on COVID-19 incidence to evaluate the molecular epidemiology and pattern of virus spread in the territory of Russia. Results and conclusions Whole genome analysis of the isolates obtained in this study and 216 others isolated in Russia revealed a set of seven common mutations when compared to the original Wuhan virus, including amino acid substitutions in spike protein S and nucleoprotein N, possibly affecting their properties. Phylogenetic analysis of all Russian sequences and 8717 sequences from other countries showed multiple importations of the virus into Russia, local circulation, and several patterns of virus spread.

Global polio eradication requires both safe and effective vaccines, and safe production processes. Sabin oral poliomyelitis vaccine (OPV) strains can evolve to virulent viruses and result in poliomyelitis outbreaks, and conventional inactivated poliomyelitis vaccine (Salk-IPV) production includes accumulation of large stocks of neurovirulent wild polioviruses. Therefore, IPV based on attenuated OPV strains seems a viable option. To increase the global supply of affordable inactivated vaccine in the still not-polio free world we developed an IPV made from the Sabin strains–PoliovacSin. Clinical trials included participants 18–60 years of age. A phase I single-center, randomized, double-blind placebo-controlled clinical trial included 60 participants, who received one dose of PoliovacSin or Placebo. A phase II multicenter, randomized, double-blind, comparative clinical trial included 200 participants, who received one dose of PoliovacSin or Imovax Polio. All vaccinations were well tolerated, and PoliovacSin had a comparable safety profile to the Placebo or the reference Imovax Polio preparations. A significant increase in neutralizing antibody levels to polioviruses types 1–3 (Sabin and wild) was observed in PoliovacSin and Imovax Polio vaccinated groups. Therefore, clinical trials confirmed good tolerability, low reactogenicity, and high safety profile of the PoliovacSin and its pronounced immunogenic properties. The preparation was approved for clinical trials involving infants.