Sofia R. Kozlova

Background: Lipid nanoparticles (LNPs) can activate innate immunity, but the factors shaping repeat-dose reactogenicity remain unclear. We compared systemic, local, and organ-specific reactions after intramuscular administrations of empty LNPs containing ionizable lipids used in mRNA vaccines. Methods: Female BALB/c mice received two intramuscular injections, 2 weeks apart, of LNP-4 (four components, ALC-0315 as the sole ionizable lipid; 59 nm) or LNP-5 (five components, equimolar ALC-0315/SM-102 at the same total ionizable lipid content; 86 nm). Body weight was monitored for 15 days. Blood biochemical parameters, injection-site histology, and morphological and molecular markers in the hypothalamus, liver, lungs, and spleen were assessed 24 h after the second injection by histology, immunohistochemistry (IHC), immunofluorescence (IF), Western blotting, and quantitative PCR (qPCR). Results: Both LNPs were followed by transient body-weight loss, moderate biochemical changes, and local reactogenicity. The strongest organ-specific responses occurred in the liver and hypothalamus. Both LNPs induced hepatic sinusoidal dilation and leukocyte infiltration, but LNP-4 was associated with more myeloid cell numbers and higher inflammatory marker expression. In the hypothalamus, LNP-4 produced broader changes in inflammatory and myeloid marker expression than LNP-5. No marked structural damage was observed in the examined organs. Conclusions: Repeated LNP administration was followed by systemic and local reactogenicity, and organ-specific changes differed between the formulations, possibly reflecting lipid composition, particle size, and lipid dose. Carrier composition should be considered in the design and safety evaluation of LNP-based vaccine delivery systems.

Background/Objectives: Epitope-based mRNA vaccines represent a promising strategy for eliciting protective T-cell immunity against SARS-CoV-2 and as well as for non-infectious mRNA-based vaccines. However, how the structural architecture of vaccine constructs (including epitope arrangement, linker composition, signal peptide presence, and the combination of MHC class I and II epitopes) shapes the quality of T-cell responses remains poorly understood. Methods: Ten tandem minigene mRNA constructs (Cons1–10) encoding different combinations of MHC class I and class II epitopes from SARS-CoV-2 proteins (S, N, M, ORF3a) were designed, encapsulated in lipid nanoparticles, and administered to C57BL/6 mice. Immunogenicity was assessed by cytokine profiling (IFN-γ, IL-2, IL-4, IL-10) and T-cell proliferation assays. Protective efficacy was evaluated in K18-hACE2 transgenic mice challenged with SARS-CoV-2. Results: Constructs lacking a signal peptide and enriched in MHC class I-restricted epitopes induced robust Th1 responses and strong CD8⁺ T-cell proliferation, achieving up to 66% survival following lethal challenge. In contrast, constructs associated with elevated IL-10 and IL-4 production conferred limited protection (11–33%), consistent with functional skewing towards regulatory or Th2-associated immune profiles. Conclusions: These findings establish a direct link between construct design parameters and T-cell polarization quality, and provide a rational framework for next-generation epitope-based mRNA vaccine development.

Background/Objectives: While tick-borne encephalitis virus (TBEV) is genetically relatively conserved, the significant antigenic divergence between its main circulating subtypes hinders the development of broadly effective antiviral treatments and vaccines. Current inactivated TBEV vaccines offer limited cross-protection against heterologous strains, as evidenced by cases among vaccinated individuals in endemic regions. The aim of this study was to design a candidate mRNA vaccine and evaluate the breadth of protective immunity it elicits. Methods: Ten candidate mRNA-PrM/E-LNP vaccines were comparatively evaluated for immunogenicity and protective efficacy in BALB/c mice. Immunogenicity was assessed by measuring antigen-specific IgG titers via ELISA and neutralizing antibody titers against a panel of TBEV strains using a virus-neutralization test. Protective efficiency was determined in a lethal challenge model, where immunized mice were challenged with one of seven distinct TBEV strains. Results: Vaccination with all tested mRNA-PrM/E-LNP candidates conferred 100% survival in mice following a lethal challenge with each of the seven TBEV strains (100 LD₅₀). The construct mRNA-PrM/E—Krasny Yar-8 demonstrated the highest immunogenicity, inducing antigen-specific antibodies with a geometric mean titer (GMT) of 1:6625, as well as the broadest virus-neutralizing activity against both homologous and heterologous TBEV strains in vitro. Conclusions: The mRNA platform represents a promising strategy for developing TBEV vaccines, demonstrating high immunogenicity and cross-protective efficacy against diverse viral strains.

Background. The combined or multivalent vaccines are actively used in pediatric practice and offer a series of advantages, including a reduced number of injections and visits to the doctor, simplicity of the vaccination schedule and minimization of side effects, easier vaccine monitoring and storage, and lower vaccination costs. The practice of widespread use of the combined vaccines has shown the potential to increase vaccination coverage against single infections. The mRNA platform has been shown to be effective against the COVID-19 pandemic and enables the development of combined vaccines. There are currently no mRNA-based combined vaccines approved for use in humans. Some studies have shown that different mRNA components in a vaccine can interact to increase or decrease the immunogenicity and efficacy of the combined vaccine. Objectives. In the present study, we investigated the possibility of combining the mRNA vaccines, encoding seasonal influenza and SARS-CoV-2 antigens. In our previous works, both vaccine candidates have shown excellent immunogenicity and efficacy profiles in mice. Methods. The mRNA-LNPs were prepared by microfluidic mixing, immunogenicity in mice was assessed by hemagglutination inhibition assay, enzyme-linked immunoassay and virus neutralization assay. Immunological efficacy was assessed in a mouse viral challenge model. Results. In this work, we demonstrated that the individual mRNA components of the combined vaccine did not affect the immunogenicity level of each other. The combined vaccine demonstrated excellent protective efficacy, providing a 100% survival rate when mice were infected with the H1N1 influenza virus and reducing the viral load in the lungs. Four days after the challenge with SARS-CoV-2 EG.5.1.1., no viable virus and low levels of detectable viral RNA were observed in the lungs of vaccinated mice. Conclusions. The combination does not lead to mutual interference between the individual vaccines. We believe that such a combined mRNA-based vaccine could be a good alternative to separated human vaccinations for the prevention of COVID-19 and influenza.

SARS-CoV-2 variants have evolved over time in recent years, demonstrating immune evasion of vaccine-induced neutralizing antibodies directed against the original S protein. Updated S-targeted vaccines provide a high level of protection against circulating variants of SARS-CoV-2, but this protection declines over time due to ongoing virus evolution. To achieve a broader protection, novel vaccine candidates involving additional antigens with low mutation rates are currently needed. Based on our recently studied mRNA lipid nanoparticle (mRNA-LNP) platform, we have generated mRNA-LNP encoding SARS-CoV-2 structural proteins M, N, S from different virus variants and studied their immunogenicity separately or in combination in vivo. As a result, all mRNA-LNP vaccine compositions encoding the S and N proteins induced excellent titers of RBD- and N-specific binding antibodies. The T cell responses were mainly specific CD4⁺ T cell lymphocytes producing IL-2 and TNF-alpha. mRNA-LNP encoding the M protein did not show a high immunogenicity. High neutralizing activity was detected in the sera of mice vaccinated with mRNA-LNP encoding S protein (alone or in combinations) against closely related strains, but was undetectable or significantly lower against an evolutionarily distant variant. Our data showed that the addition of mRNAs encoding S and M antigens to mRNA-N in the vaccine composition enhanced the immunogenicity of mRNA-N and induced a more robust immune response to the N protein. Based on our results, we suggested that the S protein plays a key role in enhancing the immune response to the N protein when they are both encoded in the mRNA-LNP vaccine.

The development of new and effective antibacterials for pharmaceutical or cosmetic skin care that have a low potential for the emergence and expansion of bacterial resistance is of high demand in scientific and applied research. Great hopes are placed on alternative agents such as bactericidal peptidoglycan hydrolases, depolymerases, etc. Enzybiotic-based preparations are being studied for the treatment of various infections and, among others, can be used as topical formulations and dressings with protein-polysaccharide complexes. Here, we investigate the antibiofilm properties of a novel enzybiotic cocktail of phage endolysin LysSi3 and bacteriocin lysostaphin, formulated in the alginate gel matrix and its ability to control the opportunistic skin-colonizing bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, as well as mixed-species biofilms. Our results propose that the application of SiL-gel affects different components of biofilm extracellular polymeric substances, disrupts the matrix, and eliminates the bacteria embedded in it. This composition is highly effective against biofilms composed of Gram-negative and Gram-positive species and does not possess significant cytotoxic effects. Our data form the basis for the development of antibacterial skin care products with a gentle but effective mode of action.

Mass vaccination campaigns against COVID-19 affected more than 90% of the population in most developed countries. The new epidemiologic wave of COVID-19 has been ongoing since the end of 2021. It is caused by a virus variant B.1.1.529, also known as “Omicron” and its descendants. The effectiveness of major vaccines against Omicron is not known. The purpose of this study is to evaluate the efficacy of the Sputnik V vaccine. The main goal is to assess its protection against hospitalization in the period of Omicron dominance. We conducted our study based on a large clinical center in Moscow (Russia) where 1112 patients were included. We used the case-population method to perform the calculations. The data we obtained indicate that the Omicron variant causes at least 90% of infections in the studied cohort. The effectiveness of protection against hospitalization with COVID-19 in our study was 85.9% (95% CI 83.0–88.0%) for those who received more than one dose. It was 87.6% (95% CI 85.4–89.5%) and 97.0% (95% CI 95.9–97.8%) for those who received more than two or three doses. The effectiveness in cases of more severe forms was higher than for less severe ones. Thus, present study indicates the high protective efficacy of vaccination against hospitalization with COVID-19 in case of Omicron lineage.