Classical inbred mouse strains have historically been instrumental in mapping immunological traits. However, most of the classical strains originate from a relatively limited number of founder animals, largely within the Mus musculus domesticus subspecies. Therefore, their genetic diversity is ultimately limited. For this reason, it is not feasible to use these mice for exhaustive interrogation of immune signaling pathways. In order to investigate networks through forward genetic analysis, larger genetic diversity is required than is introduced under laboratory conditions. Recently, inbred strains from other mouse subspecies were established such as Mus musculus castaneus and Mus musculus musculus, which diverged from a shared common ancestor with Mus musculus domesticus more than one million years ago. A direct genomic comparison clearly demonstrates the evolutionary divergence that has occurred between wild-derived mice and the classical inbred strains. When compared to classical inbred strains, wild-derived mice exhibit polymorphisms every 100-200 base pairs. Studying the molecular basis of these traits provides us with insight into how the immune system can evolve regulatory features to accommodate environment-specific constraints. Because most wild-derived strains are able to breed with classical inbred mice, they represent a rich source of evolutionarily significant diversity for forward genetic studies. These organisms are an emerging, though still largely unexplored, model for the identification and study of novel immunological genes.

The identification of new SARS-CoV-2 and human protein and gene targets, which may be markers of the severity and outcome of the disease, are extremely important during the COVID-19 pandemic. The goal of this study was to carry out genetic analysis of SARS-CoV-2 RNA samples to elucidate correlations of genetic parameters (SNPs) with clinical data and severity of COVID-19 infection.Material and Methods. The study included viral RNA samples isolated from 56 patients with COVID-19 infection who received treatment at the City Hospital No. 40 of St. Petersburg from 04/18/2020 to 04/18/2021. Patients underwent physical examination with the assessments of hemodynamic and respiratory parameters, clinical risk according to National Early Warning Score (NEWS), computed tomography (CT) of the chest, and laboratory studies including clinical blood analysis, assessment of ferritin, C-reactive protein (CRP), interleukin-6 (IL-6), lactate dehydrogenase (LDH), D-dimer, creatinine, and glucose levels. All patients tested positive for SARS-CoV-2 RNA by polymerase chain reaction (PCR). Single nucleotide polymorphisms (SNPs) in viral RNA were identified through the creation of cDNA libraries by targeted sequencing (MiSeq Illumina). Bioinformatic analysis of viral samples was performed using the viralrecon v2 pipeline with the further annotation via Pangolin and Nextlade. Sampled genomes were visualized using the Integrative Genomics Viewer (IGV) software. Statistical data processing (descriptive statistics and graphical analysis of data relationships from diff erent tables) was performed using a GraphPad device on the Prism 8.01 platform.Results. A comparative analysis of SNP frequencies in the virus genome in samples from deceased and discharged patients was carried out. The SNPs associated with risk of death (OR > 1), neutral SNPs (OR = 1), and protective SNPs (OR < 1) were identifi ed. Patient samples were infected with 14 lines of SARS-CoV-2, fi ve of which (B.1.1.129, B.1.1.407, B.1.1.373, B.1.1.397, and B.1.1.152) were of Russian origin. The SNPs in the samples infected with the strains of non-Russian origin were associated with an increased risk of mortality (OR = 2.267, 95% confi dence interval 0.1594-8.653) compared to the SNPs in the samples obtained from the group of patients infected with the strains of Russian origin. Positive correlations were identifi ed between the average SNP number, nonsynonymous SNPs, and S-protein SNPs with the degree of respiratory failure, total NEWS score, CT-based form of disease, duration of treatment with mechanical ventilation, disease outcome, levels of LDH, glucose, D-dimer, and ferritin, and RNA amount in the PCR test. S-protein SNPs negatively correlated with the leukocyte and neutrophil counts.

Since SARS-CoV-2 first appeared in humans, the scientific community has tried to gather as much information as possible in order to find effective strategies for the containment and treatment this pandemic coronavirus. We reviewed the current published literature on SARS-CoV-2 with an emphasis on the distribution of SARS-CoV-2 in tissues and body fluids, as well as data on the expression of its input receptors on the cell surface. COVID-19 affects many organ systems in many ways. These varied manifestations are associated with viral tropism and immune responses of the infected person, but the exact mechanisms are not yet fully understood. We emphasize the broad organotropism of SARS-CoV-2, as many studies have identified viral components (RNA, proteins) in many organs, including immune cells, pharynx, trachea, lungs, blood, heart, blood vessels, intestines, brain, kidneys, and male reproductive organs. Viral components are present in various body fluids, such as mucus, saliva, urine, cerebrospinal fluid, semen and breast milk. The main SARS-CoV-2 receptor, ACE2, is expressed at different levels in many tissues throughout the human body, but its expression levels do not always correspond to the detection of SARS-CoV-2, indicating a complex interaction between the virus and humans. We also highlight the role of the renin-angiotensin aldosterone system and its inhibitors in the context of COVID-19. In addition, SARS-CoV-2 has various strategies that are widely used in various tissues to evade innate antiviral immunity. Targeting immune evasion mediators of the virus can block its replication in COVID-19 patients. Together, these data shed light on the current understanding of the pathogenesis of SARS-CoV-2 and lay the groundwork for better diagnosis and treatment of patients with COVID-19.