Sofiia N. Rizatdinova

In the post-pandemic era, monitoring adaptive immunity of the population to emerging SARS-CoV-2 variants remains an important public health priority. To address this need, we developed a test that can simultaneously assess the neutralization ability of three SARS-CoV-2 variants. A panel of lentiviral pseudoviruses, each bearing the S-protein of different SARS-CoV-2 variants (Wuhan-Hu-1, BA.1, and XBB.1.5) and expressing a unique fluorescent protein (Clover, mRhubarb713, or mRuby3) was generated and used to transduce hACE2-overexpressing cells. The percentage of infected target cells for each variant was quantified via flow cytometry. Co-infection led to a minor reduction in the percentage of infected cells compared to mono-infection controls, confirming the robustness of the assay. We then applied the test to the analysis of human sera samples, which were collected in the Sirius Federal Territory (Russian Federation) and revealed the following: (1) sera collected in 2021 neutralized the Wuhan-Hu-1 variant and demonstrated cross-specificity to the BA.1 variant, but not to the XBB.1.5 variant; (2) sera collected after the Omicron emergence point neutralized Wuhan-Hu-1 and BA.1, and possessed a weak ability to neutralize the XBB.1.5. This assay provides a valuable tool for efficient profiling of humoral immunity and monitoring its development in response to ongoing viral diversity.

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.