High seroprevalence of anti-SARS-CoV-2 antibodies in the capital of Chad

Background. Since the start of the COVID-19 pandemic, Chad has had 7,417 confirmed cases and 193 deaths, one of the lowest in Africa. Objective. This study assessed SARS-CoV-2 immunity in N'Djamena. Methods. In August-October 2021, eleven N'Djamena hospitals collected outpatient data and samples. IgG antibodies against SARSCoV- 2 nucleocapsid protein were identified using ELISA. "Bambino Gesu" Laboratory, Rome, Italy, performed external quality control with chemiluminescence assay. Results. 25-34-year-old (35.2%) made up the largest age group at 31.9 12.6 years. 56.4% were women, 1.3 women/men. The 7th district had 22.5% and the 1st 22.3%. Housewives and students dominated. Overall seroprevalence was 69.5% (95% CI: 67.7-71.3), females 68.2% (65.8-70.5) and males 71.2% (68.6-73.8). >44-year-old had 73.9% seroprevalence. Under-15s were 57.4% positive. Housewives (70.9%), civil servants (71.5%), and health workers (9.7%) had the highest antibody positivity. N'Djamena's 9th district had 73.1% optimism and the 3rd district had 52.5%. Seroprevalences were highest at Good Samaritan Hospital (75.4%) and National General Referral Hospital (74.7%). Conclusion. Our findings indicate a high circulation of SARS-CoV- 2 in N'Djamena, despite low mortality and morbidity after the first two COVID-19 pandemic waves. This high seroprevalence must be considered in Chad's vaccine policy.

Proteases of SARS Coronaviruses

Coronaviruses such as SARS and SARS-CoV-2 have established themselves as a global health concern after causing an epidemic and a pandemic in the last twenty years. Understanding the life cycle of such viruses is critical to reveal their pathogenic potential. As one of the essential viral enzymes, SARS proteases are indispensable for the processing of viral polypeptides and for the replication of the virus. SARS-CoV and SARS-CoV-2 encode for 2 viral proteases: the main protease (3CLpro) and the papain-like protease (PLPro), which are conserved among different coronaviruses and are absent in humans. This review summarizes the existing literature on the structure and function of these proteases;highlighting the similarity and differences between the enzymes of SARS and SARS-CoV-2. It also discusses the development of inhibitors to target viral proteases. © 2023 Elsevier Inc. All rights reserved.

Marine drugs as putative inhibitors against non-structural proteins of SARS-CoV-2: an in silico study.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) is an unprecedented pandemic, threatening human health worldwide. The need to produce novel small-molecule inhibitors against the ongoing pandemic has resulted in the use of drugs such as chloroquine, azithromycin, dexamethasone, favipiravir, ribavirin, remdesivir and azithromycin. Moreover, the reports of the clinical trials of these drugs proved to produce detrimental effects on patients with side effects like nephrotoxicity, retinopathy, cardiotoxicity and cardiomyopathy. Recognizing the need for effective and non-harmful therapeutic candidates to combat COVID-19, we aimed to develop promising drugs against SARS-COV-2. DISCUSSION: In the current investigation, high-throughput virtual screening was performed using the Comprehensive Marine Natural Products Database against five non-structural proteins: Nsp3, Nsp5, Nsp12, Nsp13 and Nsp15. Furthermore, standard precision (SP) docking, extra precision (XP) docking, binding free energy calculation and absorption, distribution, metabolism, excretion and toxicity studies were performed using the SchrÓ§dinger suite. The top-ranked 5 hits obtained by computational studies exhibited to possess a greater binding affinity with the selected non-structural proteins. Amongst the five hits, CMNPD5804, CMNPD20924 and CMNPD1598 hits were utilized to design a novel molecule (D) that has the capability of interacting with all the key residues in the pocket of the selected non-structural proteins. Furthermore, 200 ns of molecular dynamics simulation studies provided insight into the binding modes of D within the catalytic pocket of selected proteins. CONCLUSION: Hence, it is concluded that compound D could be a promising inhibitor against these non-structural proteins. Nevertheless, there is still a need to conduct in vitro and in vivo studies to support our findings.

Divergent mutations of Delta and Omicron variants: key players behind differential viral attributes across the COVID-19 waves.

The third SARS-CoV-2 pandemic wave causing Omicron variant has comparatively higher replication rate and transmissibility than the second wave-causing Delta variant. The exact mechanism behind the differential properties of Delta and Omicron in respect to infectivity and virulence is not properly understood yet. This study reports the analysis of different mutations within the receptor binding domain (RBD) of spike glycoprotein and non-structural protein (nsp) of Delta and Omicron strains. We have used computational studies to evaluate the properties of Delta and Omicron variants in this work. Q498R, Q493R and S375F mutations of RBD showed better docking scores for Omicron compared to Delta variant of SARS-CoV-2, whereas nsp3_L1266I with PARP15 (7OUX), nsp3_L1266I with PARP15 (7OUX), and nsp6_G107 with ISG15 (1Z2M) showed significantly higher docking score. The findings of the present study might be helpful to reveal the probable cause of relatively milder form of COVID-19 disease manifested by Omicron in comparison to Delta variant of SARS-CoV-2 virus. Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-023-00823-0.

Structural and non-structural proteins in SARS-CoV-2: potential aspects to COVID-19 treatment or prevention of progression of related diseases.

Coronavirus disease 2019 (COVID-19) is caused by a new member of the Coronaviridae family known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). There are structural and non-structural proteins (NSPs) in the genome of this virus. S, M, H, and E proteins are structural proteins, and NSPs include accessory and replicase proteins. The structural and NSP components of SARS-CoV-2 play an important role in its infectivity, and some of them may be important in the pathogenesis of chronic diseases, including cancer, coagulation disorders, neurodegenerative disorders, and cardiovascular diseases. The SARS-CoV-2 proteins interact with targets such as angiotensin-converting enzyme 2 (ACE2) receptor. In addition, SARS-CoV-2 can stimulate pathological intracellular signaling pathways by triggering transcription factor hypoxia-inducible factor-1 (HIF-1), neuropilin-1 (NRP-1), CD147, and Eph receptors, which play important roles in the progression of neurodegenerative diseases like Alzheimer's disease, epilepsy, and multiple sclerosis, and multiple cancers such as glioblastoma, lung malignancies, and leukemias. Several compounds such as polyphenols, doxazosin, baricitinib, and ruxolitinib could inhibit these interactions. It has been demonstrated that the SARS-CoV-2 spike protein has a stronger affinity for human ACE2 than the spike protein of SARS-CoV, leading the current study to hypothesize that the newly produced variant Omicron receptor-binding domain (RBD) binds to human ACE2 more strongly than the primary strain. SARS and Middle East respiratory syndrome (MERS) viruses against structural and NSPs have become resistant to previous vaccines. Therefore, the review of recent studies and the performance of current vaccines and their effects on COVID-19 and related diseases has become a vital need to deal with the current conditions. This review examines the potential role of these SARS-CoV-2 proteins in the initiation of chronic diseases, and it is anticipated that these proteins could serve as components of an effective vaccine or treatment for COVID-19 and related diseases. Video Abstract.

Insilico Screening for Identification of Hits against SARS-Cov-2 Variant of Concern B.1.617 and NSP12 Mutants by Molecular Docking and Simulation Studies

Human coronaviruses (HCoVs), including severe acute respiratory syndrome coronavirus (SARS-CoV) and 2019 novel coronavirus (2019-nCoV), also known as SARS-CoV-2, have caused global epidemics with high morbidity and mortality. Active research on finding effective drugs against 2019-nCoV/SARS-CoV-2 is going on. In silico screening represents the best approach for hits identification and could shorten the time and reduce cost compared to de novo drug discovery. Recently, CoV2 mutations have been a big concern in India, particularly on non-structural proteins (NSPs) and Spike Protein (B.1.617) which are the key targets that play a pivotal role in mediating viral replication and transcription. Herein, this study analyzed the NSPs and spike's structural aspects of mutant strains of SARS-CoV-2. The three-dimensional structures of NSPs and S Spike proteins were retrieved from the protein data bank or modeled. And a dataset of an antiviral compound library containing 490,000 drug-like ligands and structurally diverse biologically active scaffolds was used for our studies. Initially, the molecular alignment was performed for library compounds with the reference drug molecule to find targets that match the field points. Antiviral compounds having a similarity score >0.6;were selected for further docking studies with wild and mutant NSPs and S Spike protein of SARS-CoV-2 variant B.1.617. The docking studies identified a potent analog MA-11, which exhibited the highest binding affinity towards wild and mutant proteins. Further, molecular dynamics simulation studies of selected compounds confirmed their perfect fitting into NSP12 and spike active sites and offer direction for further lead optimization and rational drug design.

Detection of IgA and IgG Antibodies against the Structural Proteins of SARS-CoV-2 in Breast Milk and Serum Samples Derived from Breastfeeding Mothers.

Background: COVID-19 vaccination or natural infection is associated with the development of immunity. The search of IgA and IgG antibodies against all the structural proteins (spike, nucleocapsid, membrane, and envelope) of SARS-CoV-2 in breastfeeding mothers is associated with immunity that can help the newborn avoid development of the infection. Methods: In this study, we analyzed 30 breastfeeding women that provided samples of breast milk and serum and evaluated the presence of IgA, total IgG, and subclasses against the structural proteins of SARS-CoV-2. Results: We reported a high seroprevalence to IgA (76.67-100%) and negativity to IgG against all analyzed proteins in breast milk. Seroprevalence in serum samples was around 10-36.67% to IgA and 23.3-60% to IgG. Finally, we detected the presence of the subclasses IgG1, IgG2, and IgG4 against all the structural proteins of SARS-CoV-2. Conclusions: This work provides evidence of the presence of IgA and IgG antibodies against the four structural proteins of SARS-CoV-2 in breast milk and serum samples derived from breastfeeding women, which can confer immunity to the newborn.

Emetine, a potent alkaloid for the treatment of SARS-CoV-2 targeting papain-like protease and non-structural proteins: pharmacokinetics, molecular docking and dynamic studies.

The main objective of this study is to find out the anti-SARS-CoV-2 potential of emetine by using molecular docking and dynamic simulation approaches. Interestingly, molecular docking studies suggest that Emetine showed significant binding affinity toward Nsp15 (-10.8 kcal/mol) followed by Nsp12 (-9.5 kcal/mol), RNA-dependent RNA polymerase, RdRp (-9.5 kcal/mol), Nsp16 (-9.4 kcal/mol), Nsp10 (-9.2 kcal/mol), Papain-like protein (-9.0 kcal/mol), Nsp13 (-9.0 kcal/mol), Nsp14 (-8.9 kcal/mol) and Spike Protein Receptor Domain (-8.8 kcal/mol) and chymotrypsin-like protease, 3CLpro (-8.5 kcal/mol), respectively, which are essential for viral infection and replication. In addition, molecular dynamic simulation (MD) was also performed for 140 ns to explore the stability behavior of the main targets and inhibitor complexes as well as the binding mechanics of the ligand to the target proteins. The obtained MD results followed by absolute binding energy calculation confirm that the binding of emetine at the level of the various receptors is more stable. The complex EmetineNSP15, mechanistically was stabilized as follows: Emetine first binds to the monomer, after, binds to the second inducing the formation of a dimer which in turn leading to the formation of complex that simulation stabilizes it at a value less than 5 Å. Overall, supported by the powerful and good pharmacokinetic data of Emetine, our findings with clinical trials may be helpful to confirm that Emetine could be promoted in the prevention and eradication of COVID-19 by reducing the severity in the infected persons and therefore can open possible new strategies for drug repositioning. Communicated by Ramaswamy H. Sarma.

Antivirals virtual screening to SARS-CoV-2 non-structural proteins.

In March 2020, the World Health Organization (WHO) declared coronavirus disease-19 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a pandemic. Since then, the search for a vaccine or drug for COVID-19 treatment has started worldwide. In this regard, a fast approach is the repurposing of drugs, primarily antiviral drugs. Herein, we performed a virtual screening using 22 antiviral drugs retrieved from the DrugBank repository, azithromycin (antibiotic), ivermectin (antinematode), and seven non-structural proteins (Nsps) of SARS-CoV-2, which are considered important targets for drugs, via molecular docking and molecular dynamics simulations. Drug-receptor binding energy was employed as the main descriptor. Based on the results, paritaprevir was predicted as a promising multi-target drug that favorably bound to all tested Nsps, mainly adipose differentiation-related protein (ADRP) (-36.2 kcal mol-1) and coronavirus main proteinase (Mpro) (-32.2 kcal mol-1). Moreover, the results suggest that simeprevir is a strong inhibitor of Mpro (-37.2 kcal mol-1), which is an interesting finding because Mpro plays an important role in viral replication. In addition to drug-receptor affinity, hot spot residues were characterized to facilitate the design of new drug derivatives with improved biological responses.

SARS-CoV-2 infection: a global outbreak and its implication on public health.

BACKGROUND: A novel corona virus is formally named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which results in causing coronavirus disease 2019 (COVID-19). It is the latest prevalent pandemic worldwide when compared to other infectious diseases like Avian flu, Middle East respiratory syndrome and severe acute respiratory syndrome (SARS). MAIN BODY: Coronavirus disease 2019 (COVID-19) is currently occurring pandemic over world. It was emerged in Wuhan, China, in the end of December 2019 and spreading across worldwide. As the coronavirus is spreading easily through direct contact with infected people droplets, inhalation, and also air droplets, it hit up a huge amount of population even reported with death. Still, with small amounts of asymptomatic transmission between people it spreads throughout the globe. People need special care to protect from the transmission of disease. However, there are no drugs so far that shows efficacy; there is an immediate need for the development of vaccines. In order to decrease the COVID-19 cases, organizations rapidly involve in the preparation of vaccine and many vaccines have been developed by various countries. The governments took safety measures to control the spread of virus and also to minimize morbidity and mortality rate to least possible. CONCLUSION: The purpose of this review article is to increase our understanding of COVID-19 and facilitate the people to take a move in facing challenges of the world.

COVID-19-associated lung microvascular endotheliopathy: a "from the bench" perspective

Rationale: Autopsy and biomarker studies suggest that endotheliopathy contributes to coronavirus disease (COVID-19)-associated acute respiratory distress syndrome. However, the effects of COVID-19 on the lung endothelium are not well defined. We hypothesized that the lung endotheliopathy of COVID-19 is caused by circulating host factors and direct endothelial infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Objectives: We aimed to determine the effects of SARS-CoV-2 or sera from patients with COVID-19 on the permeability and inflammatory activation of lung microvascular endothelial cells. Methods: Human lung microvascular endothelial cells were treated with live SARS-CoV-2;inactivated viral particles;or sera from patients with COVID-19, patients without COVID-19, and healthy volunteers. Permeability was determined by measuring transendothelial resistance to electrical current flow, where decreased resistance signifies increased permeability. Inflammatory mediators were quantified in culture supernatants. Endothelial biomarkers were quantified in patient sera. Measurements and Main Results: Viral PCR confirmed that SARS-CoV-2 enters and replicates in endothelial cells. Live SARS-CoV-2, but not dead virus or spike protein, induces endothelial permeability and secretion of plasminogen activator inhibitor 1 and vascular endothelial growth factor. There was substantial variability in the effects of SARS-CoV-2 on endothelial cells from different donors. Sera from patients with COVID-19 induced endothelial permeability, which correlated with disease severity. Serum levels of endothelial activation and injury biomarkers were increased in patients with COVID-19 and correlated with severity of illness. Conclusions: SARS-CoV-2 infects and dysregulates endothelial cell functions. Circulating factors in patients with COVID-19 also induce endothelial cell dysfunction. Our data point to roles for both systemic factors acting on lung endothelial cells and viral infection of endothelial cells in COVID-19-associated endotheliopathy.

Genetic conservation across SARS-CoV-2 non-structural proteins - Insights into possible targets for treatment of future viral outbreaks.

The majority of SARS-CoV-2 therapeutic development work has focussed on targeting the spike protein, viral polymerase and proteases. As the pandemic progressed, many studies reported that these proteins are prone to high levels of mutation and can become drug resistant. Thus, it is necessary to not only target other viral proteins such as the non-structural proteins (NSPs) but to also target the most conserved residues of these proteins. In order to understand the level of conservation among these viruses, in this review, we have focussed on the conservation across RNA viruses, conservation across the coronaviruses and then narrowed our focus to conservation of NSPs across coronaviruses. We have also discussed the various treatment options for SARS-CoV-2 infection. A synergistic melding of bioinformatics, computer-aided drug-design and in vitro/vivo studies can feed into better understanding of the virus and therefore help in the development of small molecule inhibitors against the viral proteins.

Capabilities of Double-Resonance LPG and SPR Methods for Hypersensitive Detection of SARS-CoV-2 Structural Proteins: A Comparative Study.

The danger of the emergence of new viral diseases and their rapid spread demands apparatuses for continuous rapid monitoring in real time. This requires the creation of new bioanalytical methods that overcome the shortcomings of existing ones and are applicable for point-of-care diagnostics. For this purpose, a variety of biosensors have been developed and tested in proof-of-concept studies, but none of them have been introduced for commercial use so far. Given the importance of the problem, in this study, long-period grating (LPG) and surface plasmon resonance (SPR) biosensors, based on antibody detection, were examined, and their capabilities for SARS-CoV-2 structural proteins detection were established. Supersensitive detections of structural proteins in the order of several femtomoles were achieved by the LPG method, while the SPR method demonstrated a sensitivity of about one hundred femtomoles. The studied biosensors are compatible in sensitivity with ELISA and rapid antigen tests but, in contrast, they are quantitative, which makes them applicable for acute SARS-CoV-2 infection detection, especially during the early stages of viral replication.

Binding of SARS-CoV-2 Structural Proteins to Hemoglobin and Myoglobin Studied by SPR and DR LPG.

One of the first clinical observations related to COVID-19 identified hematological dysfunctions. These were explained by theoretical modeling, which predicted that motifs from SARS-CoV-2 structural proteins could bind to porphyrin. At present, there is very little experimental data that could provide reliable information about possible interactions. The surface plasmon resonance (SPR) method and double resonance long period grating (DR LPG) were used to identify the binding of S/N protein and the receptor bind domain (RBD) to hemoglobin (Hb) and myoglobin (Mb). SPR transducers were functionalized with Hb and Mb, while LPG transducers, were only with Hb. Ligands were deposited by the matrix-assisted laser evaporation (MAPLE) method, which guarantees maximum interaction specificity. The experiments carried out showed S/N protein binding to Hb and Mb and RBD binding to Hb. Apart from that, they demonstrated that chemically-inactivated virus-like particles (VLPs) interact with Hb. The binding activity of S/N- and RBD proteins was assessed. It was found that protein binding fully inhibited heme functionality. The registered N protein binding to Hb/Mb is the first experimental fact that supports theoretical predictions. This fact suggests another function of this protein, not only binding RNA. The lower RBD binding activity reveals that other functional groups of S protein participate in the interaction. The high-affinity binding of these proteins to Hb provides an excellent opportunity for assessing the effectiveness of inhibitors targeting S/N proteins.

Modelling the Transitioning of SARS-CoV-2 nsp3 and nsp4 Lumenal Regions towards a More Stable State on Complex Formation.

During coronavirus infection, three non-structural proteins, nsp3, nsp4, and nsp6, are of great importance as they induce the formation of double-membrane vesicles where the replication and transcription of viral gRNA takes place, and the interaction of nsp3 and nsp4 lumenal regions triggers membrane pairing. However, their structural states are not well-understood. We investigated the interactions between nsp3 and nsp4 by predicting the structures of their lumenal regions individually and in complex using AlphaFold2 as implemented in ColabFold. The ColabFold prediction accuracy of the nsp3-nsp4 complex was increased compared to nsp3 alone and nsp4 alone. All cysteine residues in both lumenal regions were modelled to be involved in intramolecular disulphide bonds. A linker region in the nsp4 lumenal region emerged as crucial for the interaction, transitioning to a structured state when predicted in complex. The key interactions modelled between nsp3 and nsp4 appeared stable when the transmembrane regions of nsp3 and nsp4 were added to the modelling either alone or together. While molecular dynamics simulations (MD) demonstrated that the proposed model of the nsp3 lumenal region on its own is not stable, key interactions between nsp and nsp4 in the proposed complex model appeared stable after MD. Together, these observations suggest that the interaction is robust to different modelling conditions. Understanding the functional importance of the nsp4 linker region may have implications for the targeting of double membrane vesicle formation in controlling coronavirus infection.

Design of a multi-epitope-based vaccine consisted of immunodominant epitopes of structural proteins of SARS-CoV-2 using immunoinformatics approach.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has shown rapid global spread and has resulted in a significant death toll worldwide. In this study, we aimed to design a multi-epitope vaccine against SARS-CoV-2 based on structural proteins S, M, N, and E. We identified B- and T-cell epitopes and then the antigenicity, toxicity, allergenicity, and similarity of predicted epitopes were analyzed. T-cell epitopes were docked with corresponding HLA alleles. Consequently, the selected T- and B-cell epitopes were included in the final construct. All selected epitopes were connected with different linkers and flagellin and pan-HLA DR binding epitopes (PADRE) as an adjuvant were used in the vaccine construct. Furthermore, molecular docking was used to evaluate the complex between the final vaccine construct and two alleles, HLA-A*02:01 and HLA-DRB1*01:01. Finally, codons were optimized for in silico cloning into pET28a(+) vector using SnapGene. The final vaccine construct comprised 11 CTL, HTL, and B-cell epitopes corresponding to 394 amino acid residues. In silico evaluation showed that the designed vaccine might potentially promote an immune response. Further in vivo preclinical and clinical testing is required to determine the safety and efficacy of the designed vaccine.

Computational Methodology for Discovery of Potential Inhibitory Peptides

In 2020, a new pandemic caused by a coronavirus has impacted the economic and public health landscape on a global level. Named SARS-CoV-2, it causes COVID-19 and, in two years, has caused thousands of deaths. Among its viral particles, SARS-CoV-2 has an important structural protein called Spike (S), and its entry into human cells is mediated by an interaction between the Spike and the human receptor Angiotensin Converting Enzyme 2 (ACE2). This S/ACE2 binding depends on the cleavage of the Spike into three parts (S1, S2 and S2') by host cell proteases. For this, the S protein undergoes a conformational change that exposes a cleavage site between the S1 and S2 domains, being initially cleaved by the Furin enzyme. The S2 part is cleaved by TMPRSS2 (Transmembrane Serine Protease II) to expose the fusion peptide, promoting endocytic entry of the virus. TMPRSS2 can be inhibited by clinically approved serine protease inhibitors, making it a promising target for the treatment of viral infections. Consequently, our objective was to look for peptides that weren't described as inhibitors for SARS-CoV-2 but can be repositioned. In this paper, we propose a computational method to collect, filter, simulate protein-peptide interaction and identify the best hits based on the pattern of interactions. In addition to the main contribution of the paper that is the method, another contribution of this work is the proposal of candidate peptides. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Recent progresses in rapid detection of novel coronavirus SARS-CoV-2

The global pandemic coronavirus pneumonia（COVID-19）,the disease infected by the new coronavirus（SARS-CoV-2）,is extremely contagious.It is mainly spread among people through respiratory droplets, aerosols, direct or indirect contact, fecal-oral transmission, and cold chain transportation.Especially, patients who are in the incubation period or have no obvious symptoms already have the ability to infect others.SARS-CoV-2 is a positive-sense single-stranded RNA virus, with a single linear RNA segment.Each SARS-CoV-2 virion is 60-140 nm in diameter.Like other coronaviruses, SARS-CoV-2 has four structural proteins, known as the spike（S）, envelope（E）,membrane（M）,and nucleocapsid（N） proteins.To date, a variety of detection methods for the SARS-CoV-2 have been developed based on the virus structural basis and etiological characteristics, which would provide an effective guarantee for the diagnosis of COVID-19 patients and the control of the epidemic.In order to help for the early diagnosis and prevention of COVID-19,the pathogenic characteristics and recent progresses of detection base on nucleic acid, immunology and biosensors of the SARS-CoV-2 are reviewed in this paper.

Structural insights into the activity regulation of full-length non-structural protein 1 from SARS-CoV-2.

Non-structural protein 1 (Nsp1) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major virulence factor and thus an attractive drug target. The last 33 amino acids of Nsp1 have been shown to bind within the mRNA entry tunnel of the 40S ribosomal subunit, shutting off host gene expression. Here, we report the solution-state structure of full-length Nsp1, which features an α/ß fold formed by a six-stranded, capped ß-barrel-like globular domain (N-terminal domain [NTD]), flanked by short N-terminal and long C-terminal flexible tails. The NTD has been found to be critical for 40S-mediated viral mRNA recognition and promotion of viral gene expression. We find that in free Nsp1, the NTD mRNA-binding surface is occluded by interactions with the acidic C-terminal tail, suggesting a mechanism of activity regulation based on the interplay between the folded NTD and the disordered C-terminal region. These results are relevant for drug-design efforts targeting Nsp1.

Characteristics of the Immune Response to the Spectrum of Viral Antigens SARS-CoV-2 in Dynamics

Introduction. The COVID-19 pandemic caused by highly contagious SARS-CoV-2 coronavirus is still at its peak. As this infection is being studied, new diagnostic methods are emerging and existing ones are being optimized. The production of antibodies against a variety of SARS-CoV-2 antigens is being intensively studied to understand the basic mechanisms of humoral immunity and protective functions of antibodies. Purpose. To study dynamics of formation and maintenance of antibodies to three main antigens (S, N, M) of SARS-CoV-2 virus. Materials and methods. Seventy-five respondents with COVID-19 infection of different severity took part in the study: mild form – 22 persons, moderate form – 26 persons, severe form – 20 persons. Control group consisted of 7 seronegative sera collected from healthy volunteers. To confirm the presence of antibodies to SARS-CoV-2 virus we used commercial test-systems manufactured by Vector-BEST "SARS-CoV-2-IgG-ELISA-BEST" (Russian Federation);"SARS-CoV-2-NP-ELISA-G" produced by Republican Scientific and Practical Center of Epidemiology and Microbiology (Republic of Belarus);as well as newly developed immunoassay "home-made" lia-test (a nitrocellulose membrane with applied S, N, M antigens of SARS-CoV-2 virus). Results. Nine months after the disease, antibodies to S antigen persisted in 92.6% of respondents with a mild form of the disease, and in 100% of those with moderate and severe forms. The N antigen remains seropositive in 48.1%, 48% and 65% of patients with mild, moderate and severe COVID-19, respectively. Positive tests for M protein are 26%, 44%, and 55% with increasing severity of infection. Conclusion. Production of antibodies to S-, N-, and M-proteins of SARS-CoV-2 virus occurs with regard to individual characteristics of the immune system. By the end of 9 months of follow-up, the respondents with moderate and severe forms of coronavirus infection retained antibodies to S-protein in 100% of cases. For N-and M-proteins, significantly fewer seropositive respondents were detected (48%, 65%, and 44% 55%, respectively). Patients who had a mild form of infection retained antibodies to S, N, and M antigens in 92.6%, 48.1% and 26% of cases, respectively. Thus, antibodies to S-protein of SARS-CoV-2 virus, which, as a rule, is the main antigenic component of commercial test systems, persist in the human body for the longest time. © 2022, Professionalnye Izdaniya. All rights reserved.