A Vaccine of SARS-CoV-2 S Protein RBD Induces Protective Immunity.

The pandemic of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed great threat to the world in many aspects. There is an urgent requirement for an effective preventive vaccine. The receptor binding domain (RBD), located on the spike (S) gene, is responsible for binding to the angiotensin-converting enzyme 2 (ACE2) receptor of host cells. The RBD protein is an effective and safe antigen candidate. The six-helix bundle (6HB) "molecular clamp" is a novel thermally-stable trimerization domain derived from a human immunodeficiency virus (HIV) gp41 protein segment. We selected the baculovirus system to fuse and express the RBD protein and 6HB for imitating the natural trimeric structure of RBD, named RBD-6HB. Recombinant RBD-6HB was successfully obtained from the cell culture supernatant and purified to high homogeneity. The purity of the final protein preparation was more than 97%. The results showed that the protein was identified as a homogeneous polymer. Further studies showed that the RBD-6HB protein combined with AL/CpG adjuvant could stimulate animals to produce sustained high-level antibodies and establish an effective protective barrier to protect mice from challenges. Our findings highlight the importance of trimerized SARS-CoV-2 S protein RBD in designing SARS-CoV-2 vaccines and provide a rationale for developing a protective vaccine through the induction of antibodies against the RBD domain.

Immunogenicity and protective potential of chimeric virus-like particles containing SARS-CoV-2 spike and H5N1 matrix 1 proteins.

Coronavirus Disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has posed a constant threat to human beings and the world economy for more than two years. Vaccination is the first choice to control and prevent the pandemic. However, an effective SARS-CoV-2 vaccine against the virus infection is still needed. This study designed and prepared four kinds of virus-like particles (VLPs) using an insect expression system. Two constructs encoded wild-type SARS-CoV-2 spike (S) fused with or without H5N1 matrix 1 (M1) (S and SM). The other two constructs contained a codon-optimized spike gene and/or M1 gene (mS and mSM) based on protein expression, stability, and ADE avoidance. The results showed that the VLP-based vaccine could induce high SARS-CoV-2 specific antibodies in mice, including specific IgG, IgG1, and IgG2a. Moreover, the mSM group has the most robust ability to stimulate humoral immunity and cellular immunity than the other VLPs, suggesting the mSM is the best immunogen. Further studies showed that the mSM combined with Al/CpG adjuvant could stimulate animals to produce sustained high-level antibodies and establish an effective protective barrier to protect mice from challenges with mouse-adapted strain. The vaccine based on mSM and Al/CpG adjuvant is a promising candidate vaccine to prevent the COVID-19 pandemic.

Immunogenicity and protective potential of chimeric virus-like particles containing SARS-CoV-2 spike and H5N1 matrix 1 proteins

Coronavirus Disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has posed a constant threat to human beings and the world economy for more than two years. Vaccination is the first choice to control and prevent the pandemic. However, an effective SARS-CoV-2 vaccine against the virus infection is still needed. This study designed and prepared four kinds of virus-like particles (VLPs) using an insect expression system. Two constructs encoded wild-type SARS-CoV-2 spike (S) fused with or without H5N1 matrix 1 (M1) (S and SM). The other two constructs contained a codon-optimized spike gene and/or M1 gene (mS and mSM) based on protein expression, stability, and ADE avoidance. The results showed that the VLP-based vaccine could induce high SARS-CoV-2 specific antibodies in mice, including specific IgG, IgG1, and IgG2a. Moreover, the mSM group has the most robust ability to stimulate humoral immunity and cellular immunity than the other VLPs, suggesting the mSM is the best immunogen. Further studies showed that the mSM combined with Al/CpG adjuvant could stimulate animals to produce sustained high-level antibodies and establish an effective protective barrier to protect mice from challenges with mouse-adapted strain. The vaccine based on mSM and Al/CpG adjuvant is a promising candidate vaccine to prevent the COVID-19 pandemic.

One-Year Trajectory of Cognitive Changes in Older Survivors of COVID-19 in Wuhan, China: A Longitudinal Cohort Study.

Importance: Determining the long-term impact of COVID-19 on cognition is important to inform immediate steps in COVID-19 research and health policy. Objective: To investigate the 1-year trajectory of cognitive changes in older COVID-19 survivors. Design, Setting, and Participants: This cohort study recruited 3233 COVID-19 survivors 60 years and older who were discharged from 3 COVID-19-designated hospitals in Wuhan, China, from February 10 to April 10, 2020. Their uninfected spouses (N = 466) were recruited as a control population. Participants with preinfection cognitive impairment, a concomitant neurological disorder, or a family history of dementia were excluded, as well as those with severe cardiac, hepatic, or kidney disease or any kind of tumor. Follow-up monitoring cognitive functioning and decline took place at 6 and 12 months. A total of 1438 COVID-19 survivors and 438 control individuals were included in the final follow-up. COVID-19 was categorized as severe or nonsevere following the American Thoracic Society guidelines. Main Outcomes and Measures: The main outcome was change in cognition 1 year after patient discharge. Cognitive changes during the first and second 6-month follow-up periods were assessed using the Informant Questionnaire on Cognitive Decline in the Elderly and the Telephone Interview of Cognitive Status-40, respectively. Based on the cognitive changes observed during the 2 periods, cognitive trajectories were classified into 4 categories: stable cognition, early-onset cognitive decline, late-onset cognitive decline, and progressive cognitive decline. Multinomial and conditional logistical regression models were used to identify factors associated with risk of cognitive decline. Results: Among the 3233 COVID-19 survivors and 1317 uninfected spouses screened, 1438 participants who were treated for COVID-19 (691 male [48.05%] and 747 female [51.95%]; median [IQR] age, 69 [66-74] years) and 438 uninfected control individuals (222 male [50.68%] and 216 female [49.32%]; median [IQR] age, 67 [66-74] years) completed the 12-month follow-up. The incidence of cognitive impairment in survivors 12 months after discharge was 12.45%. Individuals with severe cases had lower Telephone Interview of Cognitive Status-40 scores than those with nonsevere cases and control individuals at 12 months (median [IQR]: severe, 22.50 [16.00-28.00]; nonsevere, 30.00 [26.00-33.00]; control, 31.00 [26.00-33.00]). Severe COVID-19 was associated with a higher risk of early-onset cognitive decline (odds ratio [OR], 4.87; 95% CI, 3.30-7.20), late-onset cognitive decline (OR, 7.58; 95% CI, 3.58-16.03), and progressive cognitive decline (OR, 19.00; 95% CI, 9.14-39.51), while nonsevere COVID-19 was associated with a higher risk of early-onset cognitive decline (OR, 1.71; 95% CI, 1.30-2.27) when adjusting for age, sex, education level, body mass index, and comorbidities. Conclusions and Relevance: In this cohort study, COVID-19 survival was associated with an increase in risk of longitudinal cognitive decline, highlighting the importance of immediate measures to deal with this challenge.

A study of solid phase competition ELISA for detection of A-type foot-and-mouth disease virus antibody

In order to evaluate the immune levels of type A FMD vaccine, the monoclonal antibody (MAb) 3D9 of FMDV prepared in our lab was used as the capture antibody, and the HRP- labeled MAb 9A9 was used as the detection antibody. A solidphase competition ELISA method (SPCE) for the detection of antibody against FMDV serotype A based on monoclonal antibodies was developed and its conditions were optimized. The results showed that the optimal concentration of MAb 3D9 was 1.16 g/mL, the optimal dilution of A- type FMDV antigen was 1:5, and the optimal dilution of HRP- labeled MAb 9A9 was 1:5000. When the serum diluted at 1:32, the critical value of the assay was determined to be 35%. The method was used to detect positive serum of type A FMDV, type O FMDV, BCV, BRV, PRRSV, PCV and CSFV, respectively. The results showed that the solid phase competition ELISA method could specifically detect type A FMDV, but had no cross- reaction with other viruses. It showed that the method established in this study has strong specificity. The sensitivity test was performed on 3 positive sera samples by VNT (virus neutralization test). The sensitivity is 1:1 024, 1:256, 1:128, respectively, indicating the method has high sensitivity. Repeatability results showed the coefficient of variation of the intra-assay and inter-assay repeated tests were less than 10%, indicating that the repeatability is good. This method was used to detect 112 serum samples along with the liquid- phase blocking ELISA method (LPBE) and VNT and analyze the correlation. The results showed the correlation coefficient between the method established in this study and LPBE and VNT was 0.901 and 0.916, respectively. It indicated that this method had a good reliability and has a higher correlation with VNT. Using the SPCE and Korean Jeno A FMDV ELISA antibody detection diagnosis kitto detect 470 clinical samples (90 sheep serum samples, 170 cow serum samples and 210 pig serum samples). The results showed the overall coincidence rate between this method and Jeno kit is 90.3%, 91.8% and 89.0%, respectively, indicating that the detection result of this method is relatively accurate. This study laid a foundation for the establishment of a method for the detection of immunity level of type A foot-and-mouth disease vaccine.

Development of solid phase competition elisa for detection ofO-type foot-and-mouth disease virus antibodies based onmonoclonal antibody

In order to detect antibodies against foot-and-mouth disease virus (FMDV), the monoclonal antibody (MAb) 3D9was used as the capture antibody, and the HRP-labeled MAb 8E8 was used as the detection antibody. After several conditions wereoptimized, the critical value of the detection was established. A solid phase competition ELISA (SPCE) method for the detecting oftype O FMDV antibodies based on monoclonal antibodies. Specific, sensitive, and reproducible tests were performed on this method. The correlation between this method and the liquid phase blocking ELISA (LPBE) method and the virus neutralization test (VNT)was compared. The results showed that the optimal dilution of MAb 3D9 was 1:25 000, the optimal dilution of inactivated type OFMDV antigen was 1:3, and the optimal dilution of MAb 8E8 was 1:5 000. When the serum was diluted at 1:32, the cut-off value of the assay was determined to be 45%. The method was used to detect reference positive serum of type A FMDV, bovinecoronavirus, bovine rotavirus, porcine reproductive and respiratory syndrome virus, porcine circovirus 2, and classical swine fevervirus, respectively. The test results were all negative and no cross-reaction occurred. After testing, when the dilution of the positivestandard serum is 1:512, the method still has good sensitivity;the coefficient of variation of the intra-assay and inter-assay repeatedtests is less than 10%, indicating that the repeatability is better. The correlation between this method and VNT and LPBE was 0.923and 0.896, respectively. This study established a new method for the detection of domestic type O FMDV antibodies in China.