Flaviviruses are single-stranded RNA viruses that have emerged in recent decades and infect up to 400 million people annually, causing a variety of potentially severe pathophysiological processes including hepatitis, encephalitis, hemorrhagic fever, tissues and capillaries damage. The Flaviviridae family is represented by four genera comprising 89 known virus species. There are no effective therapies available against many pathogenic flaviviruses. One of the promising strategies for flavivirus infections prevention and therapy is the use of neutralizing antibodies (NAb) that can disable the virus particles from infecting the host cells. The envelope protein (E protein) of flaviviruses is a three-domain structure that mediates the fusion of viral and host membranes delivering the infectious material. We previously developed and characterized 10H10 mAb which interacts with the E protein of the tick-borne encephalitis virus (TBEV) and many other flaviviruses’ E proteins. The aim of this work was to analyze the structure of E protein binding sites recognized by the 10H10 antibody, which is reactive with different flavivirus species. Here, we present experimental data and 3D modeling indicating that the 10H10 antibody recognizes the amino acid sequence between the two cysteines C92-C116 of the fusion loop (FL) region of flaviviruses’ E proteins. Overall, our results indicate that the antibody-antigen complex can form a rigid or dynamic structure that provides antibody cross reactivity and efficient interaction with the fusion loop of E protein.

Introduction. Following the successful eradication of smallpox, mass vaccination against this disease was discontinued in 1980. The unvaccinated population continues to be at risk of infection due to military use of variola virus or exposure to monkeypox virus in Africa and non-endemic areas. In cases of these diseases, rapid diagnosis is of great importance, since the promptness and effectiveness of therapeutic and quarantine measures depend on it. The aim of work is to develop a kit of reagents for enzyme-linked immunosorbent assay (ELISA) for fast and highly sensitive detection of orthopoxviruses (OPV) in clinical samples. Materials and methods. The efficiency of virus detection was evaluated by single-stage ELISA in the cryolisate of CV-1 cell culture samples infected with vaccinia, cowpox, rabbitpox, and ectromelia viruses, as well as in clinical samples of infected rabbits and mice. Results. The method of rapid ELISA was shown to allow the detection of OPV in crude viral samples in the range of 5.0 1025.0 103 PFU/ml, and in clinical samples with a viral load exceeding 5 103 PFU/ml. Conclusions. The assay involves a minimum number of operations and can be performed within 45 minutes, which makes it possible to use it in conditions of a high level of biosecurity. Rapid ELISA method was developed using polyclonal antibodies, which significantly simplifies and reduces the cost of manufacturing a diagnostic system.

Introduction. Yellow fever (YF) remains one of the most common natural focal infectious diseases in the world. In connection with the increasing tourist flow to countries endemic for YF, the discovery of stable populations of Aedes aegypti and Ae. albopictus which are the main vectors of the yellow fever virus (YFV), in the southern regions of Russia, and the fact that in medical institutions in our country it is possible to obtain a live attenuated vaccine against YF, but there is no way to evaluate the effectiveness of vaccination, the question arises of the development and implementation of diagnostic kits for detecting antibodies (AB) to the pathogen by enzyme immunoassay (ELISA). The aim of this study was to develop a method for detecting specific IgG antibodies to the E protein of YFV by ELISA and assessing its diagnostic characteristics. Materials and methods. A specific cDNA was synthesized by reverse transcription on an RNA template of YFV isolated on a cell culture of Aedes albopictus clone C6/36, and a fragment of the genome coding the YFV E protein was amplified and subsequently cloned into the plasmid pET160 (Thermo Fisher Scientific, USA). The resulting gene fragment was used as a DNA template to obtain a recombinant analog of the third domain of the YFV E protein in Escherichia coli cells (BL-21(DE3)). Next, the immunogenicity of the obtained antigen was evaluated and the analysis conditions were optimized. Results. The optimal conditions for the production of the obtained recombinant E protein of YFV were determined, its specificity was confirmed by immunological methods (Western blot and ELISA), sorption buffers and blocking solutions were selected, and sensitivity and specificity of detection of antibodies to YFV using the recombinant antigen were assessed. Conclusion. A method for the detection of specific IgG antibodies to the YFV E protein by ELISA was developed. This diagnostic kit can be used both to study the protective properties of the YF vaccine and to detect imported cases of infection in non-endemic areas.

Разработка метода одновременного выявления серологических маркеров лихорадки денге

The annual number of reported human cases of flavivirus infections continues to increase. Measures taken by local healthcare systems and international organizations are not fully successful. In this regard, new approaches to treatment and prevention of flavivirus infections are relevant. One promising approach is to use monoclonal antibody preparations. The mouse mAb 10H10 is capable of interacting with viruses belonging to the genus Orthoflavivirus which are pathogenic to humans. ELISA and molecular modeling data can indicate that mAb 10H10 recognizes the fusion loop region of E protein. The KD of interaction between the mAb 10H10 and recombinant analogs of the E protein of the tick-borne encephalitis (TBEV), Zika (ZIKV) and dengue (DENV) viruses range from 1.5 to 4 nM. The aim of this study was to map the epitope of this antibody using phage display technology. After three rounds of biopanning, 60 individual phage clones were chosen. The amino acid sequences of the selected peptides were conveniently divided into five groups. Based on the selected peptides, bacteriophages were obtained carrying peptides on the surfaces of the pIII and pVIII proteins, which were tested for binding to the antibody in ELISA. Thus, the epitope of the mAb 10H10 is the highly conserved region 98-DRGWGNXXGLFGK-110 of the flavivirus E protein. The structures of the complexes of the identified peptides with the antibody paratope are proposed using the molecular docking and dynamics methods.

Background. Squalene represents a promising basis for the development of novel adjuvant compositions with efficacy comparable to traditional adjuvants but with an improved safety profile. Objective. To develop a novel squalene based adjuvant composition and evaluate its ability to enhance the humoral immune response against three different viral antigens — the receptor binding domain (RBDd) of the SARS CoV 2 Delta variant S protein, domain III (WDIII) of the West Nile virus E surface protein, and the surface glycoprotein (trGPM) of the Marburg virus. Materials and methods. The adjuvant was prepared as an oil-in-water emulsion containing squalene, lecithin and Tween 80, followed by ultrasonic homogenization. BALB/c mice were immunized with two intramuscular injections 14 days apart. Specific IgG antibody titers were determined by ELISA. Statistical analysis was performed using the Mann–Whitney U-test. Results. The ASV24 emulsion remained stable for 12 months. When immunized with the WDIII antigen produced in the prokaryotic E. coli system, the adjuvant activity of ASV24 was comparable to that of aluminum hydroxide. For the RBDd antigen produced in Chinese hamster ovary (CHO) cells, a trend toward higher titers was observed in the ASV24 group (3.6 × 10⁶) compared to aluminum hydroxide (9.6 × 10⁵), although no statistically significant differences were found. A pronounced advantage of ASV24 was demonstrated for trGPM, also produced in CHO cells: the mean reciprocal titer was 1,5 orders of magnitude higher than that in the aluminum hydroxide group. Conclusion. The ASV24 adjuvant composition is stable, and its efficacy can surpass that of aluminum hydroxide when using complex multimeric antigens produced in eukaryotic expression systems. These findings suggest that ASV24 is a promising adjuvant for the development of subunit vaccines.