Willingness to practice medicine and related influential factors among medical undergraduates during COVID-19: a cross-sectional study.

BACKGROUND: As the medical undergraduates constitute the future workforce in China, their career preferences hold a significant bearing on the quality of healthcare services, particularly in light of the ongoing COVID-19 pandemic. We aim to understand the current state of the willingness to practice medicine among medical undergraduates and to analyze the related influential factors. METHODS: During the COVID-19 epidemic, we conducted a cross-sectional survey via an online platform from February 15, 2022, to May 31, 2022, to collect participants' demographic information, psychology, and factors influencing their career choices. The general self-efficacy scale (GSES) was used to evaluate medical students' perceptions of their self-efficacy. Futhermore, we conducted multivariate logistic regression analyses to explore the influencing factors of medical undergraduates' willingness to pursure a caree in medicine. RESULTS: A total of 2348 valid questionnaires were included, and 1573 (66.99%) were willing to practice medicine for medical undergraduates after graduation. The mean GESE scores in the willingness group (2.87 ± 0.54) were significantly higher than those of the unwillingness group (2.73 ± 0.49). The multiple logistic regression showed that several factors were positively associated with willingness to practice medicine as a career, including students' GSES score (OR = 1.87), current major, household income, personal ideals (OR = 1.97), family support (OR = 1.44), high income (OR = 1.77), and social respect (OR = 2.19). Compared with those who were very afraid of COVID-19, students who did not express any fear towards the COVID-19 pandemic had a higher preference for choosing the medical profession as a career. Conversely, students thinking of high tension in the doctor-patient relationship, heavy workload, and long training were less likely to choose medical work after graduation. CONCLUSIONS: The study highlights a noteworthy prevalence of medical undergraduates who expressed their willingness to pursue medicine as a career post-graduation. Several factors, including but not limited to current major, household income, psychological factors, personal preferences, and career needs or preferences, were significantly associated with this willingness. Moreover, the impact of the COVID-19 pandemic on medical students' career choices cannot be overlooked.

Continuous evolution and emerging lineage of seasonal human coronaviruses: A multicenter surveillance study.

The seasonal human coronaviruses (HCoVs) have zoonotic origins, repeated infections, and global transmission. The objectives of this study are to elaborate the epidemiological and evolutionary characteristics of HCoVs from patients with acute respiratory illness. We conducted a multicenter surveillance at 36 sentinel hospitals of Beijing Metropolis, China, during 2016-2019. Patients with influenza-like illness (ILI) and severe acute respiratory infection (SARI) were included, and submitted respiratory samples for screening HCoVs by multiplex real-time reverse transcription-polymerase chain reaction assays. All the positive samples were used for metatranscriptomic sequencing to get whole genomes of HCoVs for genetical and evolutionary analyses. Totally, 321 of 15 677 patients with ILI or SARI were found to be positive for HCoVs, with an infection rate of 2.0% (95% confidence interval, 1.8%-2.3%). HCoV-229E, HCoV-NL63, HCoV-OC43, and HCoV-HKU1 infections accounted for 18.7%, 38.3%, 40.5%, and 2.5%, respectively. In comparison to ILI cases, SARI cases were significantly older, more likely caused by HCoV-229E and HCoV-OC43, and more often co-infected with other respiratory pathogens. A total of 179 full genome sequences of HCoVs were obtained from 321 positive patients. The phylogenetical analyses revealed that HCoV-229E, HCoV-NL63 and HCoV-OC43 continuously yielded novel lineages, respectively. The nonsynonymous to synonymous ratio of all key genes in each HCoV was less than one, indicating that all four HCoVs were under negative selection pressure. Multiple substitution modes were observed in spike glycoprotein among the four HCoVs. Our findings highlight the importance of enhancing surveillance on HCoVs, and imply that more variants might occur in the future.

A dePEGylated Lipopeptide-Based Pan-Coronavirus Fusion Inhibitor Exhibits Potent and Broad-Spectrum Anti-HIV-1 Activity without Eliciting Anti-PEG Antibodies.

We previously identified a lipopeptide, EK1C4, by linking cholesterol to EK1, a pan-CoV fusion inhibitory peptide via a polyethylene glycol (PEG) linker, which showed potent pan-CoV fusion inhibitory activity. However, PEG can elicit antibodies to PEG in vivo, which will attenuate its antiviral activity. Therefore, we designed and synthesized a dePEGylated lipopeptide, EKL1C, by replacing the PEG linker in EK1C4 with a short peptide. Similar to EK1C4, EKL1C displayed potent inhibitory activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses. In this study, we found that EKL1C also exhibited broad-spectrum fusion inhibitory activity against human immunodeficiency virus type 1 (HIV-1) infection by interacting with the N-terminal heptad repeat 1 (HR1) of viral gp41 to block six-helix bundle (6-HB) formation. These results suggest that HR1 is a common target for the development of broad-spectrum viral fusion inhibitors and EKL1C has potential clinical application as a candidate therapeutic or preventive agent against infection by coronavirus, HIV-1, and possibly other class I enveloped viruses.

Exploring the worldwide impact of COVID-19 on conflict risk under climate change.

Objectives: Understand whether and how the COVID-19 pandemic affects the risk of different types of conflict worldwide in the context of climate change. Methodology: Based on the database of armed conflict, COVID-19, detailed climate, and non-climate data covering the period 2020-2021, we applied Structural Equation Modeling specifically to reorganize the links between climate, COVID-19, and conflict risk. Moreover, we used the Boosted Regression Tree method to simulate conflict risk under the influence of multiple factors. Findings: The transmission risk of COVID-19 seems to decrease as the temperature rises. Additionally, COVID-19 has a substantial worldwide impact on conflict risk, albeit regional and conflict risk variations exist. Moreover, when testing a one-month lagged effect, we find consistency across regions, indicating a positive influence of COVID-19 on demonstrations (protests and riots) and a negative relationship with non-state and violent conflict risk. Conclusion: COVID-19 has a complex effect on conflict risk worldwide under climate change. Implications: Laying the theoretical foundation of how COVID-19 affects conflict risk and providing some inspiration for the implementation of relevant policies.

Structure-Based Design of Potent Peptidomimetic Inhibitors Covalently Targeting SARS-CoV-2 Papain-like Protease.

The papain-like protease (PLpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays a critical role in the proteolytic processing of viral polyproteins and the dysregulation of the host immune response, providing a promising therapeutic target. Here, we report the structure-guide design of novel peptidomimetic inhibitors covalently targeting SARS-CoV-2 PLpro. The resulting inhibitors demonstrate submicromolar potency in the enzymatic assay (IC50 = 0.23 µM) and significant inhibition of SARS-CoV-2 PLpro in the HEK293T cells using a cell-based protease assay (EC50 = 3.61 µM). Moreover, an X-ray crystal structure of SARS-CoV-2 PLpro in complex with compound 2 confirms the covalent binding of the inhibitor to the catalytic residue cysteine 111 (C111) and emphasizes the importance of interactions with tyrosine 268 (Y268). Together, our findings reveal a new scaffold of SARS-CoV-2 PLpro inhibitors and provide an attractive starting point for further optimization.

Clinical characteristics and host immunity responses of SARS-CoV-2 Omicron variant BA.2 with deletion of ORF7a, ORF7b and ORF8.

BACKGROUND: The pathogenicity and virulence of the Omicron strain have weakened significantly pathogenesis of Omicron variants. Accumulating data indicated accessory proteins play crucial roles in host immune evasion and virus pathogenesis of SARS-CoV-2. Therefore, the impact of simultaneous deletion of accessory protein ORF7a, ORF7b and ORF8 on the clinical characteristics and specific immunity in Omicron breakthrough infected patients (BIPs) need to be verified. METHODS: Herein, plasma cytokines were identified using a commercial Multi-cytokine detection kit. Enzyme-linked immunosorbent assay and pseudovirus neutralization assays were utilized to determine the titers of SARS-CoV-2 specific binding antibodies and neutralizing antibodies, respectively. In addition, an enzyme-linked immunospot assay was used to quantify SARS-CoV-2 specific T cells and memory B cells. RESULTS: A local COVID-19 outbreak was caused by the Omicron BA.2 variant, which featured a deletion of 871 base pairs (∆871 BA.2), resulting in the removal of ORF7a, ORF7b, and ORF8. We found that hospitalized patients with ∆871 BA.2 had significantly shorter hospital stays than those with wild-type (WT) BA.2. Plasma cytokine levels in both ∆871 BA.2 and WT BA.2 patients were within the normal range of reference, and there was no notable difference in the titers of SARS-CoV-2 ancestor or Omicron-specific binding IgG antibodies, neutralizing antibody titers, effector T cells, and memory B cells frequencies between ∆871 BA.2 and WT BA.2 infected adult patients. However, antibody titers in ∆871 BA.2 infected adolescents were higher than in adults. CONCLUSIONS: The simultaneous deletion of ORF7a, ORF7b, and ORF8 facilitates the rapid clearance of the BA.2 variant, without impacting cytokine levels or affecting SARS-CoV-2 specific humoral and cellular immunity in Omicron-infected individuals.

SARS-CoV-2 induces cardiomyocyte apoptosis and inflammation but can be ameliorated by ACE inhibitor Captopril.

Although the clinical manifestation of COVID-19 is mainly respiratory symptoms, approximately 20% of patients suffer from cardiac complications. COVID-19 patients with cardiovascular disease have higher severity of myocardial injury and poor outcomes. The underlying mechanism of myocardial injury caused by SARS-CoV-2 infection remains unclear. Using a non-transgenic mouse model infected with Beta variant (B.1.351), we found that the viral RNA could be detected in lungs and hearts of infected mice. Pathological analysis showed thinner ventricular wall, disorganized and ruptured myocardial fiber, mild inflammatory infiltration, and mild epicardia or interstitial fibrosis in hearts of infected mice. We also found that SARS-CoV-2 could infect cardiomyocytes and produce infectious progeny viruses in human pluripotent stem cell-derived cardiomyocyte-like cells (hPSC-CMs). SARS-CoV-2 infection caused apoptosis, reduction of mitochondrial integrity and quantity, and cessation of beating in hPSC-CMs. In order to dissect the mechanism of myocardial injury caused by SARS-CoV-2 infection, we employed transcriptome sequencing of hPSC-CMs at different time points after viral infection. Transcriptome analysis showed robust induction of inflammatory cytokines and chemokines, up-regulation of MHC class I molecules, activation of apoptosis signaling and cell cycle arresting. These may cause aggravate inflammation, immune cell infiltration, and cell death. Furthermore, we found that Captopril (hypotensive drugs targeting ACE) treatment could alleviate SARS-CoV-2 induced inflammatory response and apoptosis in cardiomyocytes via inactivating TNF signaling pathways, suggesting Captopril may be beneficial for reducing COVID-19 associated cardiomyopathy. These findings preliminarily explain the molecular mechanism of pathological cardiac injury caused by SARS-CoV-2 infection, providing new perspectives for the discovery of antiviral therapeutics.

A Case Series of Persistent SARS-CoV-2 Infection in Immunocompromised Pediatric Patients.

Diagnosis and management of SARS-CoV-2 infection in immunocompromised patients are extremely challenging. These patients can have atypical clinical courses, and there is a paucity of data regarding clinical features, diagnostic findings, and the safety and efficacy of available therapeutic agents used to treat COVID-19 in these patients. In this case series, we report atypical COVID-19 presentations in 4 immunocompromised pediatric patients who were admitted with acute respiratory failure after an initial diagnosis of COVID-19 a few weeks earlier. All patients included in this cohort showed persistent worsening respiratory symptoms for several weeks before hospital presentation. While they manifested common COVID-19 sequelae, they also had rare COVID-19-related pathognomonic and radiographic features developed along their hospital course. Multiple therapeutic agents were used in their COVID-19 management, including corticosteroids, remdesivir, and monoclonal antibodies. All three patients who have received concurrent therapy with remdesivir, hydrocortisone, and monoclonal antibodies survived, and only one patient died as a direct complication of COVID-19 ARDS with secondary pulmonary mucormycosis. Our outcomes suggest the potential benefit of remdesivir use in combination with hydrocortisone and monoclonal antibodies in the management of severe COVID-19 ARDS in this group, as well as the importance of close surveillance and early administration of broad empirical antimicrobial and antifungal coverage if clinically indicated in this high-risk population.

Impaired potency of neutralizing antibodies against cell-cell fusion mediated by SARS-CoV-2.

The SARS-CoV-2 Omicron subvariants have dominated the pandemic due to their high transmissibility and immune evasion conferred by the spike mutations. The Omicron subvariants can spread by cell-free virus infection and cell-cell fusion, the latter of which is more effective but has not been extensively investigated. In this study, we developed a simple and high-throughput assay that provides a rapid readout to quantify cell-cell fusion mediated by the SARS-CoV-2 spike proteins without using live or pseudotyped virus. This assay can be used to identify variants of concern and to screen for prophylactic and therapeutic agents. We further evaluated a panel of monoclonal antibodies (mAbs) and vaccinee sera against D614G and Omicron subvariants, finding that cell-cell fusion is substantially more resistant to mAb and serum inhibition than cell-free virus infection. Such results have important implications for the development of vaccines and antiviral antibody drugs against cell-cell fusion induced by SARS-CoV-2 spikes.

Evaluating the Safe-Haven Abilities of Bitcoin and Gold for Crude Oil Market: Evidence During the COVID-19 Pandemic.

The COVID-19 pandemic poses a serious threat to investors in the crude oil market. Furthermore, investors have an increasing need to find a safe haven in their investment portfolios when facing unprecedented risks in crude oil markets during the COVID-19 pandemic. According to a review of the literature, there are contradictory findings on which investment is the safer haven for the oil market. Therefore, this paper aims to evaluate whether bitcoin is a safer haven for the crude oil market than the commonly used gold during the COVID-19 pandemic. Three spillover measurements based on the time, and frequency domains, and a network framework are employed to quantify the return spillover effects among bitcoin, gold and three major crude oil futures markets. We divide the sample into two periods, pre-COVID-19 and post-COVID-19. The results show that bitcoin has a weak safe-haven effect on the crude oil market only over a short period, while gold maintains a good safe-haven ability for crude oil futures across various time horizons (frequencies), both before and after the outbreak of the COVID-19 pandemic. The findings of this study have important implications for policy-makers, crude oil producers and global investors. In particularly, investors cannot ignore the importance of bitcoin and gold in selecting more profitable portfolio policies when searching for safe-haven assets.

Association between nitrogen dioxide concentration and hypertension hospitalization: A multicenter time-series analysis in Xinxiang, China

Hypertension is a common chronic disease, and air pollution is strongly associated with hypertension hospitalization. However, the association between nitrogen dioxide (NO2)1 concentration and hypertension hospitalization has rarely been studied. We collected daily data on hypertension hospitalizations, air pollutants, and meteorology from January 1, 2016 to October 31, 2021. After controlling for the effects of seasonal and long-term trends, weather conditions, weekdays, holidays, and during the novel coronavirus crown epidemic, a generalized additive model with over discrete Poisson regression was used to simulate the association between NO2 concentration and hypertension hospitalizations while quantifying hypertension hospitalizations, hospital stays, and hospital costs attributable to NO2. The results showed that each 10 μg/m3 increase in NO2 concentration was significantly associated with the relative risk (RR) of hypertension admission in Xinxiang, with the greatest effect at lag04 (RR = 1.107;95% confidence interval, 1.046–1.172). Hypertension hospitalizations attributed to NO2 during the study period accounted for 9.70% (484) of the total hypertension hospitalizations, equivalent to 4202 hospital days and 338.55 thousand United States dollars (USD). Increased NO2 concentration increases the risk of hypertension hospitalization in Xinxiang, which poses a significant health and economic burden to society and patients. The findings of this study provide a basis for developing stricter environmental pollutant standards.

Intranasal booster using an Omicron vaccine confers broad mucosal and systemic immunity against SARS-CoV-2 variants.

The highly contagious SARS-CoV-2 Omicron subvariants severely attenuated the effectiveness of currently licensed SARS-CoV-2 vaccines based on ancestral strains administered via intramuscular injection. In this study, we generated a recombinant, replication-incompetent human adenovirus type 5, Ad5-S-Omicron, that expresses Omicron BA.1 spike. Intranasal, but not intramuscular vaccination, elicited spike-specific respiratory mucosal IgA and residential T cell immune responses, in addition to systemic neutralizing antibodies and T cell immune responses against most Omicron subvariants. We tested intranasal Ad5-S-Omicron as a heterologous booster in mice that previously received intramuscular injection of inactivated ancestral vaccine. In addition to inducing serum broadly neutralizing antibodies, there was a significant induction of respiratory mucosal IgA and neutralizing activities against Omicron subvariants BA.1, BA.2, BA.5, BA.2.75, BF.7 as well as pre-Omicron strains Wildtype, Beta, and Delta. Serum and mucosal neutralizing activities against recently emerged XBB, BQ.1, and BQ.1.1 could also be detected but were much lower. Nasal lavage fluids from intranasal vaccination contained multimeric IgA that can bind to at least 10 spike proteins, including Omicron subvariants and pre-Omicron strains, and possessed broadly neutralizing activities. Intranasal vaccination using Ad5-S-Omicron or instillation of intranasal vaccinee's nasal lavage fluids in mouse nostrils protected mice against Omicron challenge. Taken together, intranasal Ad5-S-Omicron booster on the basis of ancestral vaccines can establish effective mucosal and systemic immunity against Omicron subvariants and multiple SARS-CoV-2 variants. This candidate vaccine warrants further development as a safe, effective, and user-friendly infection and transmission-blocking vaccine.

The whole-of-society approach of mass COVID-19 vaccination in China: a qualitative study.

BACKGROUND: Many countries have an inefficient vaccination system, which hinders global exit from the COVID-19 pandemic. It is vital to summarize COVID-19 vaccination practices in countries with high vaccination coverage and provide implications for other countries. This study aimed to investigate China's COVID-19 vaccination system and to summarize its implementation experience from a health system perspective. METHODS: We conducted key informant interviews in five representative cities of China in late 2021. Guided by the health systems framework proposed by WHO, we developed our interview guidelines which included seven building blocks-leadership and governance, health workforce, vaccination service delivery, vaccination mobilization and communication, financing, access to vaccines, and information systems. Semi-structured interviews and COVID-19 vaccination policy documents were collected and coded using a thematic analysis approach. RESULTS: A total of 61 participants (nine vaccination programme directors of the local Center for Disease Control and Prevention, four government staff and 48 vaccination service workers) were interviewed. We found that China adopted a whole-of-society approach with adequate government engagement and linked health and non-health sectors to promote COVID-19 vaccination. Key measures included the collaboration of multiple systems and departments from a governance perspective, allocating sufficient health workers and resources, large-scale vaccination mobilization and communication, expansion of vaccine financing channels, localized production and digital information systems. With the vaccination system strengthening, the two-doses vaccination coverage reached 89.5% for the total population but relatively lower coverage for older adults as of July 2022. CONCLUSIONS: Our study highlights the importance of a government-led whole-of-society approach to promote mass vaccination. The low vaccination coverage among older adults should be paid the greatest attention to. The experiences and lessons from China may serve as a reference for other countries.

Ethnic Differences in Response to COVID-19: A Study of American-Asian and Non-Asian College Students.

Asian American students have experienced additional physical and emotional hardships associated with the COVID-19 pandemic due to increased xenophobic and anti-Asian discrimination. This study investigates different coping patterns and risk factors affecting Asian and non-Asian college students in response to COVID-19 challenges by studying the differences in their responses within four domains after the onset of the pandemic: academic adjustment, emotional adjustment, social support, and discriminatory impacts related to COVID-19. We first employed a machine learning approach to identify well-adjusted and poorly adjusted students in each of the four domains for the Asian and non-Asian groups, respectively. Next, we applied the SHAP method to study the principal risk factors associated with each classification task and analyzed the differences between the two groups. We based our study on a proprietary survey dataset collected from U.S. college students during the initial peak of the pandemic. Our findings provide insights into the risk factors and their directional impact affecting Asian and non-Asian students' well-being during the pandemic. The results could help universities establish customized strategies to support these two groups of students in this era of uncertainty. Applications for international communities are discussed.

Spike glycoprotein and host cell determinants of SARS-CoV-2 entry and cytopathic effects.

SARS-CoV-2, a betacoronavirus, is the cause of the COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein trimer mediates virus entry into host cells and cytopathic effects (syncytium formation). We studied the contribution of several S glycoprotein features to these functions, focusing on those that differ among related coronaviruses. Acquisition of the furin cleavage site by the SARS-CoV-2 S glycoprotein decreased virus stability and infectivity, but greatly enhanced syncytium-forming ability. Notably, the D614G change found in globally predominant SARS-CoV-2 strains increased infectivity, modestly enhanced responsiveness to the ACE2 receptor and susceptibility to neutralizing sera, and tightened association of the S1 subunit with the trimer. Apparently, these two features of the SARS-CoV-2 S glycoprotein, the furin cleavage site and D614G, have evolved to balance virus infectivity, stability, cytopathicity and antibody vulnerability. Although the endodomain (cytoplasmic tail) of the S2 subunit was not absolutely required for virus entry or syncytium formation, alteration of palmitoylated cysteine residues in the cytoplasmic tail decreased the efficiency of these processes. As proteolytic cleavage contributes to the activation of the SARS-CoV-2 S glycoprotein, we evaluated the ability of protease inhibitors to suppress S glycoprotein function. Matrix metalloprotease inhibitors suppressed S-mediated cell-cell fusion, but not virus entry. Synergy between inhibitors of matrix metalloproteases and TMPRSS2 suggests that both host proteases can activate the S glycoprotein during the process of syncytium formation. These results provide insights into SARS-CoV-2 S glycoprotein-host cell interactions that likely contribute to the transmission and pathogenicity of this pandemic agent.IMPORTANCE The development of an effective and durable SARS-CoV-2 vaccine is essential for combating the growing COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein is the main target of neutralizing antibodies elicited during virus infection or following vaccination. Knowledge of the spike glycoprotein evolution, function and interactions with host factors will help researchers to develop effective vaccine immunogens and treatments. Here we identify key features of the spike glycoprotein, including the furin cleavage site and the D614G natural mutation, that modulate viral cytopathic effects, infectivity and sensitivity to inhibition. We also identify two inhibitors of host metalloproteases that block S-mediated cell-cell fusion, a process that contributes to the destruction of the virus-infected cell.

Somatically hypermutated antibodies isolated from SARS-CoV-2 Delta infected patients cross-neutralize heterologous variants.

SARS-CoV-2 Omicron variants feature highly mutated spike proteins with extraordinary abilities in evading antibodies isolated earlier in the pandemic. Investigation of memory B cells from patients primarily with breakthrough infections with the Delta variant enables isolation of a number of neutralizing antibodies cross-reactive to heterologous variants of concern (VOCs) including Omicron variants (BA.1-BA.4). Structural studies identify altered complementarity determining region (CDR) amino acids and highly unusual heavy chain CDR2 insertions respectively in two representative cross-neutralizing antibodies-YB9-258 and YB13-292. These features are putatively introduced by somatic hypermutation and they are heavily involved in epitope recognition to broaden neutralization breadth. Previously, insertions/deletions were rarely reported for antiviral antibodies except for those induced by HIV-1 chronic infections. These data provide molecular mechanisms for cross-neutralization of heterologous SARS-CoV-2 variants by antibodies isolated from Delta variant infected patients with implications for future vaccination strategy.

SARS-CoV-2 Omicron XBB subvariants exhibit enhanced fusogenicity and substantial immune evasion in elderly population, but high sensitivity to pan-coronavirus fusion inhibitors.

Numerous emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariants have shown significant immune evasion capacity and caused a large number of infections, as well as vaccine-breakthrough infections, especially in elderly populations. Recently emerged Omicron XBB was derived from the BA.2 lineage, but bears a distinct mutant profile in its spike (S) protein. In this study, we found that Omicron XBB S protein drove more efficient membrane-fusion kinetics on human lung-derived cells (Calu-3). Considering the high susceptibility of the elderly to the current Omicron pandemic, we performed a comprehensive neutralization assessment of elderly convalescent or vaccine sera against XBB infection. We found that the sera from elderly convalescent patients who experienced with BA.2 infection or breakthrough infection potently inhibited BA.2 infection, but showed significantly reduced efficacy against XBB. Moreover, recently emerged XBB.1.5 subvariant also showed more significant resistance to the convalescent sera of BA.2- or BA.5-infected elderly. On the other hand, we found that the pan-CoV fusion inhibitors EK1 and EK1C4 can potently block either XBB-S- or XBB.1.5-S-mediated fusion process and viral entry. Moreover, EK1 fusion inhibitor showed potent synergism when combined with convalescent sera of BA.2- or BA.5-infected patients against XBB and XBB.1.5 infection, further indicating that EK1-based pan-CoV fusion inhibitors are promising candidates for development as clinical antiviral agents to combat the Omicron XBB subvariants.

Effect of chitooligosaccharide on the inhibition of SARS-CoV-2 main protease.

BACKGROUND: The main protease (Mpro) is a crucial target for severe acute respiratory syndrome coronavirus (SARS-CoV-2). Chitooligosaccharide (CS) has broad-spectrum antiviral activity and can effectively inhibit the activity of SARS-CoV. Here, based on the high homology between SARS-CoV-2 and SARS-CoV, this study explores the effect and mechanism of CS with various molecular weights on the activity of SARS-CoV-2 Mpro. METHODS: We used fluorescence resonance energy transfer (FRET), UV-Vis, synchronous fluorescence spectroscopy, circular dichroism (CD) spectroscopy and computational simulation to investigate the molecular interaction and the interaction mechanism between CS and SARS-CoV-2 Mpro. RESULTS: Four kinds of CS with different molecular weights significantly inhibited the activity of Mpro by combining the hydrogen bonding and the salt bridge interaction to form a stable complex. Glu166 appeared to be the key amino acid. Among them, chitosan showed the highest inhibition effect on Mpro enzyme activity and the greatest impact on the spatial structure of protein. Chitosan would be one of the most potential anti-viral compounds. CONCLUSION: This study provides the theoretical basis to develop targeted Mpro inhibitors for the screening and application of anti-novel coronavirus drugs.