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.

Many viruses are known to trigger endoplasmic reticulum (ER) stress in host cells, which in turn can develop a protective unfolded protein response (UPR). Depending on the conditions, the UPR may lead to either cell survival or programmed cell death. One of three UPR branches involves the upregulation of Xbp1 transcription factor caused by the unconventional cytoplasmic splicing of its mRNA. This process is accomplished by the phosphorylated form of the endoribonuclease/protein kinase Ire1/ERN1. Here, we show that the phosphorylation of Ire1 is up-regulated in HeLa cells early in enterovirus infection but down-regulated at later stages. We also find that Ire1 is cleaved in poliovirus- and coxsackievirus-infected HeLa cells 4–6 h after infection. We further show that the Ire1-mediated Xbp1 mRNA splicing is repressed in infected cells in a time-dependent manner. Thus, our results demonstrate the ability of enteroviruses to actively modulate the Ire1-Xbp1 host defensive pathway by inducing phosphorylation and proteolytic cleavage of the ER stress sensor Ire1, as well as down-regulating its splicing activity. Inactivation of Ire1 could be a novel mode of the UPR manipulation employed by viruses to modify the ER stress response in the infected cells.

We present the results of a randomized, double-blind, placebo-controlled, multi-center clinical trial phase I/II of the tolerability, safety, and immunogenicity of the inactivated whole virion concentrated purified coronavirus vaccine CoviVac in volunteers aged 18–60 and open multi-center comparative phase IIb clinical trial in volunteers aged 60 years and older. The safety of the vaccine was assessed in 400 volunteers in the 18–60 age cohort who received two doses of the vaccine (n = 300) or placebo (n = 100) and in 200 volunteers in 60+ age cohort all of whom received three doses of the vaccine. The studied vaccine has shown good tolerability and safety. No deaths, serious adverse events (AEs), or other significant AEs related to vaccination have been detected. The most common AE in vaccinated participants was pain at the injection site (p < 0.05). Immunogenicity assessment in stage 3 of Phase II was performed on 167 volunteers (122 vaccinated and 45 in Placebo Group) separately for the participants who were anti-SARS-CoV-2 nAB negative (69/122 in Vaccine Group and 28/45 in Placebo Group) or positive (53/122 in Vaccine Group and 17/45 in Placebo Group) at screening. On Day 42 after the 1st vaccination, the seroconversion rate in participants who were seronegative at screening was 86.9%, with the average geometric mean neutralizing antibody (nAB) titer of 1:20. A statistically significant (p < 0.05) increase in IFN-γ production by peptide-stimulated T-cells was observed at Days 14 and 21 after the 1st vaccination. In participants who were seropositive at screening but had nAB titers below 1:256, the rate of fourfold increase in nAB levels was 85.2%, while in the participants with nAB titers > 1:256, the rate of fourfold increase in nAB levels was below 45%; the participants who were seropositive at screening of the 2nd vaccination did not lead to a significant increase in nAB titers. In conclusion, inactivated vaccine CoviVac has shown good tolerability and safety, with over 85% NT seroconversion rates after complete vaccination course in participants who were seronegative at screening in both age groups: 18–60 and 60+. In participants who were seropositive at screening and had nAB titers below 1:256, a single vaccination led to a fourfold increase in nAB levels in 85.2% of cases. These findings indicate that CoviVac can be successfully used both for primary vaccination in a two-dose regimen and for booster vaccination as a single dose in individuals with reduced neutralizing antibody levels.

Background/Objectives: The World Health Organization (WHO) recommends the use of attenuated Sabin strains for the production of inactivated poliovirus vaccine (IPV), offering improved biosafety while retaining immunogenicity. To better characterize the antigenic composition of Sabin strain-based IPV (sIPV), including both the protective D-antigen and the non-protective H-antigen forms, we developed a method for purifying D- and H-antigens forms. Methods: D- and H-antigens of poliovirus Sabin strains types 1, 2, and 3 were purified using gradient ultracentrifugation and used to generate antigen-specific polyclonal antibodies. Results: The generated polyclonal antibodies demonstrated high specificity with neutralizing titers of antibodies against Sabin type 1 poliovirus—1:2048, against Sabin type 2 poliovirus—more than 1:2048, against Sabin type 3 poloivirus—1:2048. Conclusions: This antigen-specific antibody approach provides a valuable tool for routine quality control in sIPV manufacturing, enabling accurate quantification of immunogenic components and detection of potentially immunogenic degradation products during vaccine storage and distribution. Antibodies to the D-antigen allow assessment of immunogenic, neutralizing epitopes, while antibodies to the H-antigen provide a tool for detecting non-neutralizing components. This antigen-specific antibody approach offers a valuable tool for studying the antigenic structure of sIPV and for improving the accuracy of ELISA-based antigen quantification.

Objectives: Most antiviral vaccines are created by inactivating the virus using chemical methods. The inactivation and production of viral vaccine preparations after the irradiation of viruses with accelerated electrons has a number of significant advantages. Determining the integrity of the genome of the resulting viral particles is necessary to assess the quality and degree of inactivation after irradiation. Methods: This work was performed on the Sabin 2 model polio virus. To determine the most sensitive and most radiation-resistant part, the polio virus genome was divided into 20 segments. After irradiation at temperatures of 25 °C, 2–8 °C, −20 °C, or −70 °C, the amplification intensity of these segments was measured in real time. Results: The best correlation between the amplification cycle and the irradiation dose at all temperatures was observed for segment 3D, left. Consequently, this section of the poliovirus genome is the least resistant to the action of accelerated electrons and is the most representative for determining genome integrity. The worst dependence was observed for the VP1 right section, which, therefore, cannot be used to determine genome integrity during inactivation. The electrochemical approach was also employed for a comparative assessment of viral RNA integrity before and after irradiation. An increase in the irradiation dose was accompanied by an increase in signals indicating the electrooxidation of RNA heterocyclic bases. The increase in peak current intensity of viral RNA electrochemical signals confirmed the breaking of viral RNA strands during irradiation. The shorter the RNA fragments, the greater the peak current intensities. In turn, this made the heterocyclic bases more accessible to electrooxidation on the electrode. Conclusions: These results are necessary for characterizing the integrity of the viral genome for the purpose of creating of antiviral vaccines.

Introduction. Since the development of inactivated polio vaccines, different stages of the production process have been changed and improved. Current production of inactivated polio vaccines based on both wild and attenuated strains includes several technological stages, one of which is the concentration of the virus-containing liquid, which ensures poliovirus concentration, and purification of the virus-containing liquid from a significant part of the ballast components.Research objective is to compare the characteristics of ultrafiltration membranes and select the membranes that provide optimal value of purification and concentration of poliovirus type 1 (Sabin strain).Materials and methods. Laboratory ultrafiltration systems from two manufacturers with 50, 100, and 300 kDa membranes were used for the concentration. Results were evaluated by the content of total protein, which is the main stress for the subsequent purification stages, the value of infectious virus titer in the concentrate, and the content of D-antigen as the target product.Results and discussion. Obtained results demonstrated that the content of the target product (the highest D-antigen content) and purification from impurity proteins (the total protein content in the concentrate) were most optimal when a membrane with a cut-off of 300 kDa was used for concentration. The study also evaluated the real cut-off components by various membranes to determine the composition of the protein load on the target product.Conclusion. In terms of quality of the resulting target product and the manufacturability of the production process, the use of a 300 kDa membrane is the most appropriate when working out the technology for manufacturing inactivated polio vaccine based on Sabin strains of poliovirus and the Vero line as a producing culture.