Switch-on Fluorescence Analysis of Protease Activity with the Assistance of a Nickel Ion-Nitrilotriacetic Acid-Conjugated Magnetic Nanoparticle.

Heterogeneous protease biosensors show high sensitivity and selectivity but usually require the immobilization of peptide substrates on a solid interface. Such methods exhibit the disadvantages of complex immobilization steps and low enzymatic efficiency induced by steric hindrance. In this work, we proposed an immobilization-free strategy for protease detection with high simplicity, sensitivity and selectivity. Specifically, a single-labeled peptide with oligohistidine-tag (His-tag) was designed as the protease substrate, which can be captured by a nickel ion-nitrilotriacetic acid (Ni-NTA)-conjugated magnetic nanoparticle (MNP) through the coordination interaction between His-tag and Ni-NTA. When the peptide was digested by protease in a homogeneous solution, the signal-labeled segment was released from the substrate. The unreacted peptide substrates could be removed by Ni-NTA-MNP, and the released segments remained in solution to emit strong fluorescence. The method was used to determine protease of caspase-3 with a low detection limit (4 pg/mL). By changing the peptide sequence and signal reporters, the proposal could be used to develop novel homogeneous biosensors for the detection of other proteases.

Neutralizing antibodies and cellular immune response after two doses of inactivated SARS-CoV-2 vaccine in China.

BACKGROUND: As of 2022, inactivated SARS-CoV-2 vaccines had been used in more than 91 countries. However, limited real world information was available on the immune responses of the inactivated SARS-CoV-2 vaccine. METHODS: We used SARS-CoV-2 pseudovirues to determine the neutralizing antibodies (NAbs) to wild type and several global variants and utilized enzyme-linked immunosorbent assay to investigate IFN-γ-secreting T-cell responses to SARS-CoV-2 among 240 vaccinated individuals after two doses of inactivated vaccine in China. RESULTS: A majority of the vaccinated (>90%) developed robust NAbs and T-cell responses to SARS-CoV-2 in the first two months after the second dose. After six months, only 37.0% and 44.0% of vaccinees had NAbs and T-cell immunity to SARS-CoV-2, respectively. Immune serum retained most of its neutralizing potency against the Alpha and Iota variants, but lost significant neutralizing potency against the Beta, Kappa, Delta, and Omicron variants. Only 40% of vaccine-sera retained low-level neutralization activities to Omicron, with a 14.7-fold decrease compared to the wild type. CONCLUSION: The inactivated SARS-CoV-2 vaccine stimulated robust NAbs and T-cell immune responses in the first two months after the second dose but the immune effect dropped rapidly, highlighing that a third dose or additional booster immunizations may be required to boost immunity against SARS-CoV-2.

Neutralizing Antibodies and Cellular Immune Responses Against SARS-CoV-2 Sustained One and a Half Years After Natural Infection.

Background: COVID-19 has caused more than 2.6 billion infections and several million deaths since its outbreak 2 years ago. We know very little about the long-term cellular immune responses and the kinetics of neutralizing antibodies (NAbs) to SARS-CoV-2 because it has emerged only recently in the human population. Methods: We collected blood samples from individuals who were from the first wave of the COVID-19 epidemic in Wuhan between December 30, 2019, and February 24, 2020. We analyzed NAbs to SARS-CoV-2 using pseudoviruses and IgG antibodies to SARS-CoV-2 spike (S) and nucleocapsid (N) protein using enzyme-linked immunosorbent assay in patients' sera and determined SARS-CoV-2-specific T-cell responses of patients with ELISpot assays. Results: We found that 91.9% (57/62) and 88.9% (40/45) of COVID-19 patients had NAbs against SARS-CoV-2 in a year (10-11 months) and one and a half years (17-18 months), respectively, after the onset of illness, indicating that NAbs against SARS-CoV-2 waned slowly and possibly persisted over a long period time. Over 80% of patients had IgG antibodies to SARS-CoV-2 S and N protein one and a half years after illness onset. Most patients also had robust memory T-cell responses against SARS-CoV-2 one and a half years after the illness. Among the patients, 95.6% (43/45) had an IFN-γ-secreting T-cell response and 93.8% (15/16) had an IL-2-secreting T-cell response. The T-cell responses to SARS-CoV-2 were positively correlated with antibodies (including neutralizing antibodies and IgG antibodies to S and N protein) in COVID-19 patients. Eighty percent (4/5) of neutralizing antibody-negative patients also had SARS-CoV-2-specific T-cell response. After long-term infection, protective immunity was independent of disease severity, sex, and age. Conclusions: We concluded that SARS-CoV-2 infection elicited a robust and persistent neutralizing antibody and memory T-cell response in COVID-19 patients, indicating that these sustained immune responses, among most SARS-CoV-2-infected people, may play a crucial role in protection against reinfection.

Effects of SARS-CoV-2 mutations on protein structures and intraviral protein-protein interactions.

Since 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 2019 (COVID-19) has infected 10 millions of people across the globe, and massive mutations in virus genome have occurred during the rapid spread of this novel coronavirus. Variance in protein sequence might lead to a change in protein structure and interaction, then further affect the viral physiological characteristics, which could bring tremendous influence on the pandemic. In this study, we investigated 20 nonsynonymous mutations in the SARS-CoV-2 genome in which incidence rates were all ≥ 1% as of September 1st, 2020, and then modeled and analyzed the mutant protein structures. The results showed that four types of mutations caused dramatic changes in protein structures (RMSD ≥ 5.0 Å), which were Q57H and G251V in open-reading frames 3a (ORF3a), S194L, and R203K/G204R in nucleocapsid (N). Next, we found that these mutations also affected the binding affinity of intraviral protein interactions. In addition, the hot spots within these docking mutant complexes were altered, among which the mutation Q57H was involved in both Orf3a-S and Orf3a-Orf8 protein interactions. Besides, these mutations were widely distributed all over the world, and their occurrences fluctuated as time went on. Notably, the incidences of R203K/G204R in N and Q57H in Orf3a were both over 50% in some countries. Overall, our findings suggest that SARS-CoV-2 mutations could change viral protein structure, binding affinity, and hot spots of the interface, thereby might have impacts on SARS-CoV-2 transmission, diagnosis, and treatment of COVID-19.

Development of a Nucleocapsid Protein-Based ELISA for Detection of Human IgM and IgG Antibodies to SARS-CoV-2.

SARS-CoV-2 is the etiologic agent of COVID-19, which has led to a dramatic loss of human life and presents an unprecedented challenge to public health worldwide. The gold standard assay for SARS-CoV-2 identification is real-time polymerase chain reaction; however, this assay depends on highly trained personnel and sophisticated equipment and may suffer from false results. Thus, a serological antibody test is a supplement to the diagnosis or screening of SARS-CoV-2. Here, we develop and evaluate the diagnostic performance of an IgM/IgG indirect ELISA method for antibodies against SARS-CoV-2 in COVID-19. The ELISA was constructed by coating with a recombinant nucleocapsid protein of SARS-CoV-2 on an enzyme immunoassay plate, and its sensitivity and specificity for clinical diagnosis of SARS-CoV-2 infection was assessed by detecting the SARS-CoV-2-specific IgM and IgG antibodies in COVID-19 patient's sera or healthy person's sera. The SARS-CoV-2 positive serum samples (n = 168) were collected from confirmed COVID-19 patients. A commercial nucleocapsid protein-based chemiluminescent immunoassay (CLIA) kit and a colloidal gold immunochromatography kit were compared with those of the ELISA assay. The specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of IgM were 100, 95.24, 100, and 91.84%, whereas those of IgG were 100, 97.02, 100, and 94.74%, respectively. We developed a highly sensitive and specific SARS-CoV-2 nucleocapsid protein-based ELISA method for the diagnosis and epidemiologic investigation of COVID-19 by SARS-CoV-2 IgM and IgG antibody detection.

Assessment of Knowledge, Attitude, and Practice Toward COVID-19 in China: An Online Cross-Sectional Survey.

To analyze the level of knowledge, attitude, and practice about COVID-19 among Chinese residents, noninterventional and anonymous survey was carried out with an online questionnaire. Among the survey respondents (n = 619), 59.9% were female, 61.1% were from 18 to 30 years of age, and 42.3% held an undergraduate's degree. The mean scores for each scale were as follows: perceived knowledge (36.3 ± 6.1), attitude (29.4 ± 4.7), practice (44.1 ± 4.8), total score (109.7 ± 13.2), barrier (0.2 ± 0.7), and cognition and behavior change score (8.5 ± 1.4). Perceived knowledge, attitude, practice, total score, and cognition and behavior changes were significantly and positively correlated, whereas barrier was negatively correlated with those scales (P < 0.001). Linear regressions revealed that those respondents who were medical professionals, civil servants, employees of state-owned enterprises and public institutions, and had relatively higher level of education were associated with a higher perceived knowledge score, attitude score, practice score, and total score. Higher mean cognition and behavior change score was associated with company employees (8.8 ± 1.3). More than half of the respondents (51.4%) were optimistic about the government's interventional measures. The respondents in China had good knowledge, positive attitude, and active practice toward COVID-19, yet, it is advisable to strengthen nationwide publicity and focus on the target undereducated population by means of We-Chat, microblog, website, and community workers for better control effect.

Safety and Efficacy of Ixekizumab and Antiviral Treatment for Patients with COVID-19: A structured summary of a study protocol for a Pilot Randomized Controlled Trial.

OBJECTIVES: A severe epidemic of COVID-19 has broken out in China and has become a major global public health event. We focus on the Acute Respiratory Distress Syndrome (ARDS)-like changes and overactivation of Th17 cells (these produce cytokines) in patients with COVID-19. We aim to explore the safety and efficacy of ixekizumab (an injectable drug for the treatment of autoimmune diseases) to prevent organ injury caused by the immune response to COVID-19. Ixekizumab is a human monoclonal antibody that binds to interleukin-17A and inhibits the release of pro-inflammatory cytokines and chemokines. TRIAL DESIGN: The experiment is divided into two stages. In the first stage, the open trial, 3 patients with COVID-19 are treated with ixekizumab, and the safety and efficacy are observed for 7 days. In the second stage, 40 patients with COVID-19 are randomly divided into two groups at 1:1 for 14 days. This is a two-center, open-label, randomized controlled pilot trial with 2-arm parallel group design (1:1 ratio). PARTICIPANTS: Patients with COVID-19 aged 18-75 with increased Interleukin (IL)-6 levels will be enrolled, but patients with severe infections requiring intensive care will be excluded. The trial will be undertaken in two centers. The first stage is carried out in Xiangya Hospital of Central South University, and the second stage is carried out simultaneously in the Third Xiangya Hospital of Central South University. INTERVENTION AND COMPARATOR: In the first stage, three subjects are given ixekizumab ("Taltz") (80 mg/ml, 160 mg as a single hypodermic injection) and antiviral therapy (α-interferon (administer 5 million U by aerosol inhalation twice daily), lopinavir/ritonavir (administer 100mg by mouth twice daily, for the course of therapy no more than 10 days), chloroquine (administer 500mg by mouth twice daily, for the course of therapy no more than 10 days), ribavirin (administer 500mg by intravenous injection two to three times a day, for the course of therapy no more than 10 days), or arbidol (administer 200mg by mouth three times a day, for the course of therapy no more than 10 days), but not more than 3 types). The treatment course of the first stage is 7 days. In the second stage, 40 randomized patients will receive the following treatments--Group 1: ixekizumab (80 mg/ml, 160 mg as a single hypodermic injection) with antiviral therapy (the same scheme as in the first stage); Group 2: antiviral therapy alone (the same scheme as in the first stage). The length of the second treatment course is 14 days. MAIN OUTCOMES: The primary outcome is a change in pulmonary CT severity score (an imaging tool for assessing COVID-19, which scores on the basis of all abnormal areas involved). Pulmonary CT severity score is assessed on the 7th day, 14th day, or at discharge. RANDOMISATION: In the second stage, 40 patients with COVID-19 are randomly divided into two groups at 1:1 for 14 days. The eLite random system of Nanjing Medical University is used for randomization. BLINDING (MASKING): The main efficacy indicator, the CT results, will be evaluated by the third-party blinded and independent research team. NUMBERS TO BE RANDOMISED (SAMPLE SIZE): In the second stage, 40 patients with COVID-19 are randomly divided into two groups at 1:1 for 14 days. TRIAL STATUS: Trial registration number is ChiCTR2000030703 (version 1.7 as of March 19, 2020). The recruitment is ongoing, and the date recruitment was initiated in June 2020. The anticipated date of the end of data collection is June 2021. TRIAL REGISTRATION: The name of the trial register is the Chinese Clinical Trial Registry. The trial registration number is ChiCTR2000030703 ( http://www.chictr.org.cn/ ). The date of trial registration is 10 March 2020. FULL PROTOCOL: The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest of expediting the dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol. The study protocol has been reported in accordance with the Standard Protocol Items: Recommendations for Clinical Interventional Trials (SPIRIT) guidelines (Additional file 2).