Along with their excellent safety profiles, subunit vaccines are typically characterized by much weaker immunogenicity and protection efficacy compared to whole-pathogen vaccines. Here, we present an approach aimed at bridging this disadvantage that is based on synergistic collaboration between pattern-recognition receptors (PRRs) belonging to different families. We prepared a model subunit vaccine formulation using an influenza hemagglutinin antigen incorporated into poly-(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles adjuvanted with monophosphoryl lipid A (TLR4 agonist) and muramyl dipeptide (NOD2 agonist). The efficacy studies were conducted in comparison to control vaccine formulations containing individual PRR agonists. We show that the complex adjuvant based on TLR4 and NOD2 agonists potentiates proinflammatory cell responses (measured by activity of transcription factors and cytokine production both in vitro and in vivo) and enhances the phagocytosis of vaccine particles up to comparable levels of influenza virus uptake. Finally, mice immunized with vaccine nanoparticles containing both PRR agonists exhibited enhanced humoral (IgG, hemagglutination-inhibition antibody titers) and cellular (percentage of proliferating CD4+ T-cells, production of IFNɣ) immunity, leading to increased resistance to lethal influenza challenge. These results support the idea that complex adjuvants stimulating different PRRs may present a better alternative to individual PAMP-based adjuvants and could further narrow the gap between the efficacy of subunit versus whole-pathogen vaccines.

Technological versatility and the humoral and cellular immune response induction capacity have conditioned wide spread of adenoviral vectors as vaccine and gene therapy drugs. However, vaccination with Sputnik V made a significant portion of the population immune to the types 5 and 26 (Ad5 and Ad26) recombinant human adenovirus vectors, which are some of the most frequently used bases for candidate vaccines. Today, vaccine designers tend to select alternative adenovirus serotypes as platforms to develop vaccines against new pathogens on. A good example is simian adenovirus type 25 (SAd25), which belongs to subgroup E. It is genetically distant from Ad5 and exhibits extremely low seroprevalence in human beings, which makes it an appealing alternative vaccine vector. The purpose of this work was to design and study a new vaccine platform based on simian adenovirus type 25. We relied on the advanced methods of molecular biology and virology to construct and make recombinant adenoviruses; the phylogenetic analysis in the context of this study was enabled with bioinformatic methods. The resulting recombinant adenoviral vector can effectively replicate itself in the HEK293 cell line (human embryonic kidney cells). This work substantiates the expediency of further investigation into the SAd25 vector as a platform for development of the prevention vaccines against various infectious diseases.

Introduction. Adenovirus infection occurs globally in the form of sporadic cases and isolated outbreaks. Human adenovirus type 55 (HAdV-55), endemic in China and South Korea, causes acute respiratory viral infections (ARVI) of varying severity, both among the civilian population and in military units in different countries of the world. Genomic research facilitates reliable identification of HAdV-55. The aim of this study was to identify HAdV isolated in Moscow in 2022, as well as to conduct whole-genome sequencing and comparative genomic research. Materials and methods. HAdV-55 was isolated from a sample of a patient hospitalized with pneumonia and analyzed using restriction fragment length polymorphism analysis and whole-genome sequencing. Bioinformatics comparative analysis was performed on a sample of sequences of 83 isolates. Results. The whole-genome sequencing of first isolated in Russia HAdV-55 was conducted. The sequence of isolate SCV3008:Ad55 was deposited in GenBank (Accession Number PQ641625). Unique mutations in the SCV3008:Ad55 genome were identified, one of which resulted in a conservative T29A substitution in the penton that did not affect its functions. Phylogenetic analysis showed clustering of SCV3008:Ad55 with isolates of clade II, which included representatives of 7 countries on different continents, indicating a wide distribution of HAdV-55. Isolates from endemic regions of China and South Korea formed separate clades. The study of microsatellite length polymorphism in untranslated regions of the genome became an additional tool for distinguishing closely related genomes. Conclusion. The obtained genomic information laid the foundation for further monitoring for HAdV-55 in Russia and demonstrated the informativeness and significance of whole-genome studies for monitoring adenoviruses. The development and implementation of genotyping methods aimed at detecting HAdV-55 and other clinically relevant genotypes will significantly improve the effectiveness of the diagnosis of adenovirus infections with the threat of developing bronchopneumonia.

Lassa hemorrhagic fever is an acute human infectious disease with high mortality rate and pandemic potential. To date, there are no approved drugs for the specific treatment or prevention of Lassa hemorrhagic fever in the world. The aim of this study was to develop and evaluate the immunobiological properties and preclinical safety of a candidate vaccine for the prevention of Lassa hemorrhagic fever (LHF) based on recombinant human adenoviral vectors. Standard genetic engineering techniques, molecular biology techniques, virological methods, and animal testing procedures were used in the course of the study. A combined vector candidate vaccine for the prevention of Lassa hemorrhagic fever has been designed and characterized. The vaccine is composed of two components for heterologous immunization in a prime-boost regimen. Both components are based on recombinant replication-defective adenovirus vectors. The first component of the vaccine is a recombinant human adenovirus type 26; the second component is a recombinant human adenovirus type 5. Both recombinant vectors contain the codon-optimized sequence of Lassa virus glycoprotein. Two experimental batches of the candidate vaccine were produced under GMP-conditions and analyzed. The results of studies in compliance with appropriate specifications for viral vector vaccines are provided. In preclinical studies in mice, antigen-specific IgG response was detected after immunization with two vaccine components, either separately, or in a prime-boost regimen. The time dynamics of the IgG response was also studied on 42, 77, 119 and 147 days after immunization. At the same time, despite achieving 100% seroconversion, no virus neutralizing antibodies were detected in any of the samples collected from immunized mice. A biodistribution study showed that 24 hours following intramuscular injection of the vaccine components, the DNA of adenovirus vectors was detected only at the site of injection and in regional lymph nodes. Based on preclinical safety assessments (including acute toxicity, chronic toxicity, immunotoxicity, allergenic properties, reproductive toxicity), no contraindications were found for initiation of the candidate Lassa vaccine clinical trials. Taken together, the results demonstrate that the candidate vaccine for prevention of Lassa hemorrhagic fever based on recombinant adenovirus vectors types 26 and 5 is a promising drug for specific immunoprophylaxis.

Background: The SARS-CoV-2 virus continuously acquires mutations, leading to the emergence of new variants. Notably, the effectiveness of global vaccination efforts has significantly declined with the rise and spread of the B.1.1.529 (Omicron) variant. Methods: The study used virological, immunological and histological research methods, as well as methods of working with laboratory animals. In this study, we evaluated the Gam-COVID-Vac (Sputnik V), an adenoviral vaccine developed by the N.F. Gamaleya National Research Center for Epidemiology and Microbiology, and conducted experiments on hemizygous K18-ACE2-transgenic F1 mice. The variants studied included B.1.1.1, B.1.1.7, B.1.351, B.1.1.28/P.1, B.1.617.2, and B.1.1.529 BA.5. Results: Our findings demonstrate that the Sputnik V vaccine elicits a robust humoral and cellular immune response, effectively protecting vaccinated animals from challenges posed by various SARS-CoV-2 variants. However, we observed a notable reduction in vaccine efficacy against the B.1.1.529 (Omicron BA.5) variant. Conclusions: Our results indicate that ongoing monitoring of emerging mutations is crucial to assess vaccine efficacy against new SARS-CoV-2 variants to identify those with pandemic potential. If protective efficacy declines, it will be imperative to develop new vaccines tailored to current variants of the virus.

Despite the widespread accessibility of vaccines and antivirals, seasonal influenza virus epidemics continue to pose a threat to public health. In this study, we constructed a recombinant replication-deficient simian adenovirus type 25 vector carrying the full-length hemagglutinin (HA) of the H1N1 influenza virus, named rSAd25-H1. Both systemic and mucosal humoral immune responses, as well as the protective efficacy, were assessed in mice immunized via the intramuscular (IM) or intranasal (IN) route. A single-dose IM or IN administration of rSAd25-H1 elicited a robust systemic IgG antibody response, including hemagglutination inhibition antibodies. As expected, only IN immunization was able to induce IgA production in serum and respiratory mucosa. Notably, a single dose of rSAd25-H1 at the highest dose (10¹⁰ viral particles) conferred complete protection against lethal homologous H1N1 challenge in mice despite the route of administration. These findings demonstrate the potential of simian adenovirus type 25-based vectors as a promising candidate for intranasal vaccine development targeting respiratory pathogens.