The study of pathogenic viruses has always posed significant biosafety challenges. In particular, the study of highly pathogenic viruses requires methods with low biological risk but relatively high sensitivity and convenience in detection. In recent years, pseudoviruses, which consist of a backbone of one virus and envelope proteins of another virus, have become one of the most widely used tools for exploring the mechanisms of viruses binding to cells, membrane fusion and viral entry, as well as for screening the libraries of antiviral substances, evaluating the potential of neutralizing monoclonal antibodies, developing neutralization tests, and therapeutic platforms. During the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), pseudotyped virus-based assays played a pivotal role in advancing our understanding of virus–cell interactions and the role of its proteins in disease pathogenesis. Such tools facilitated the search for potential therapeutic agents and accelerated epidemiological studies on post-infection and post-vaccination humoral immunity. This review focuses on the use of pseudoviruses as a model for large-scale applications to study enveloped viruses.

The binding properties of synthetic and recombinant peptides derived from N-terminal part of ACE2, the main receptor for SARS-CoV-2, were evaluated. Additionally, the ability of these peptides to prevent virus entry in vitro was addressed using both pseudovirus particles decorated with the S protein, as well as through infection of Vero cells with live SARS-CoV-2 virus. Surprisingly, in spite of effective binding to S protein, all linear peptides of various lengths failed to neutralize the viral infection in vitro. However, the P1st peptide that was chemically “stapled” in order to stabilize its alpha-helical structure was able to interfere with virus entry into ACE2-expressing cells. Interestingly, this peptide also neutralized pseudovirus particles decorated with S protein derived from the Omicron BA.1 virus, in spite of variations in key amino acid residues contacting ACE2.

Background. Research in oncology assumes establishment and usage of xenograft animal models, meeting the requirements of humanity and rationality. Although praised as promising field of research, preclinical studies of low-molecular-weight inhibitors, antitumor monoclonal antibodies, vaccines, cellular therapy products, CAR-T cells entail continuous control of tumor growth dynamics. Luciferase detection of bioluminescence requires injection of a reporter substrate. However, injections not only are laborious, time-consuming and expensive, but are also stressful for animals. Thus, a vast variety of new visualization methods is employed, including proteins of the far-red spectrum.Objective. The study aimed to compare detection efficiency of tumor growth dynamics in mice models of cervical cancer, applying a commercially available line of fluorescent red protein derivatives of Katushka clade and Renilla luciferase, that is commonly used in in vivo studies. Design and methods. Xenograft mice models were derived injecting modified HeLa cell line, that expresses fluorescent reporter proteins: Katushka, Katushka2S, TurboRFP, TurboFP650 and Renilla enzyme. Results. Spectral properties and emission wavelength of far-red fluorescent protein Katushka and Katushka2S outlines these markers within RFP derivatives lineage as outstanding instrument for in vivo tumor visualization.Conclusion. Detection of fluorescent far-red reporters Katushka and Katushka2S can be considered as a credible alternative to Renilla luciferase bioluminescence in experimental models in vivo on the part of immunotherapy research.

INTRODUCTION. The main risk to the clinical translatability of preclinical results for anticancer medicinal products is posed by the difficulty of simulating clinical conditions in an experimental model. With only 5% of product candidates proving clinically effective, the search for new approaches to the preclinical development of anticancer medicinal products is currently an active area of research in medicine.AIM. This study aimed to provide methodological support for planning experiments with modelling of neoplastic processes through analysis and classification of the methods used in preclinical studies of the efficacy of anticancer medicinal products in vivo.DISCUSSION. This article reviews the development of animal tumour models and the selection of cell lines and their testing for tumourigenicity and viability on a step-by-step basis. According to the study results, imaging systems, vital staining, and fluorescence- and luminescence-based methods can be used to assess the efficacy of anticancer medicinal products in both solid tumour models and haematological malignancy models. The article presents a schematic representation of the main types of mouse cancer models. However, no single animal species is universally suitable for in vivo cancer modelling. Researchers selecting models and considering their advantages and disadvantages should pay special attention to the similarity of disease mechanisms in animal models and humans at the tissue and molecular level, keeping in mind the aims of their research.CONCLUSIONS. The results of this comparative analysis of methods for preclinical efficacy evaluation of anticancer medicinal products are essential for designing experimental studies and ensuring the reliability of the results obtained. Choosing the correct research method will increase the chances of obtaining experimental data that can be successfully translated into clinical practice.