Double-stranded RNAs are promising adjuvants for enhancing immunogenicity of vaccines

Background. The most effective way to prevent infectious diseases is vaccination. Adjuvants contribute to the optimization of the immune response of vaccines. Double-stranded ribonucleic acids (dsRNAs) from natural sources are promising, but insufficiently studied adjuvants. The aim of the work was to study the adjuvant activity of dsRNA obtained from the killer strain of Saccharomyces cerevisiae using two models of induction of a specific immune response. Materials and methods. In the experiments, the substance of the drug Ridostin containing dsRNA, 21.72% (produced by Institute of Medical Biotechnology of the State Research Center of Virology and Biotechnology "Vector”), was used. A specific immune response was modeled using ovalbumin (OVA) or the substance of the EpiVacCorona vaccine (EVC). The experiments were carried out in 200 female BALB/c mice. Mice of the experimental groups were injected twice with antigen and adjuvant together with a 28-day interval, mice of the comparison group — with antigen only. On the 10th day after the second immunization, blood samples were collected to determine the level of specific antibodies using enzyme immunoassay. The results were evaluated by calculation of the average geometric titers of specific antibodies against OVA or EVC. Results. OVA or EVC administered twice induced the specific antibodies in mice in dose-dependent titers. The combined administration of antigen and dsRNA increased the strength of the immune response. The highest stimulating effect of dsRNA was observed in the dose of 100 µg/mouse administered into mice immunized with OVA (1 µg/mouse) or in the dose of 50 µg/mouse in mice immunized with EVC substance (0.25 of a human dose per mouse). Conclusion. The data obtained indicate that the substance of dsRNA exerts adjuvant properties, which gives reason to consider dsRNA as a promising adjuvant for peptide vaccines. © 2022, Central Research Institute for Epidemiology. All rights reserved.

Immunogenicity and protectivity of the peptide vaccine against SARS-CoV-2

Background. In 2020, the pandemic caused by novel coronavirus infection has become one of the most critical global health challenges during the past century. The lack of a vaccine, as the most effective way to control the novel infection, has prompted the development of a large number of preventive products by the scientific community. We have developed a candidate vaccine (EpiVacCorona) against novel coronavirus infection caused by SARS-CoV-2 that is based on chemically synthesized peptides conjugated to a carrier protein and adsorbed on aluminum hydroxide and studied the specific activity of the developed vaccine. Aims — study of the immunogenicity and protectivity of the peptide candidate vaccine EpiVacCorona. Methods. The work was performed using standard molecular biological, virological and histological methods. Results. It was demonstrated that EpiVacCorona, when administered twice, spaced 14 days apart, to hamsters, ferrets, and non-human primates (african green monkeys, rhesus macaques) at a dose of 260 μg, which is equal to one inoculation dose for humans, induces virus-specific antibodies in 100% of the animals. Experiments in hamsters showed this vaccine to be associated with the dose-dependent immunogenicity. The vaccine was shown to accelerate the elimination of the virus from the upper respiratory tract in ferrets and prevent the development of pneumonia in hamsters and non-human primates following a respiratory challenge with novel coronavirus. Conclusions. The results of a preclinical specific activity study indicate that the use of EpiVacCorona has the potential for human vaccination. © 2021 Izdatel'stvo Meditsina. All rights reserved.

A SINGLE BLIND, PLACEBO-CONTROLLED RANDOMIZED STUDY OF THE SAFETY, REACTOGENICITY AND IMMUNOGENICITY OF THE "EPIVACCORONA" VACCINE FOR THE PREVENTION OF COVID-19, IN VOLUNTEERS AGED 18-60 YEARS (PHASE I-II)

Vaccination of the population is one of the most effective countermeasures in responding to the pandemic caused by novel coronavirus infection. Therefore, scientists all over the world have been working to develop effective and safe vaccines. We have developed a synthetic peptide vaccine, EpiVacCorona, against novel SARS-CoV-2 coronavirus, which is a suspension for intramuscular administration containing a composition of chemically synthesized peptide immunogens of the S protein of SARS-CoV-2 coronavirus conjugated to a carrier protein and adsorbed on aluminum hydroxide. Phase I-II clinical trials of the vaccine have started that consist of two stages: Stage 1 is an open study of the safety, reactogenicity, and immunological activity of the vaccine with the involvement of 14 volunteers aged 18-30 years;Stage 2 is a single blind, comparative, randomized placebo-controlled study with the involvement of 86 volunteers. The study involved volunteers aged 18-60 years;the vaccine was injected intramuscularly twice, spaced 21 days apart between injections. All local reactions in response to vaccine administration were mild, such as a short-term pain at the injection site. There were no signs of development of local or systemic adverse reactions. The two-dose vaccination scheme induced the production of antibodies, specific to the antigens that make up the vaccine, in 100% of the volunteers. Seroconversion with a neutralizing antibody titer >= 1:20 was reported in 100% of the volunteers 21 days following the second immunization dose. No seroconversion was reported in the groups of volunteers vaccinated with a placebo. The peptide-based EpiVacCorona Vaccine has low reactogenicity and is a safe, immunogenic product.