The clinical features and immune responses of asymptomatic individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have not been well described. We studied 37 ...asymptomatic individuals in the Wanzhou District who were diagnosed with RT-PCR-confirmed SARS-CoV-2 infections but without any relevant clinical symptoms in the preceding 14 d and during hospitalization. Asymptomatic individuals were admitted to the government-designated Wanzhou People's Hospital for centralized isolation in accordance with policy
. The median duration of viral shedding in the asymptomatic group was 19 d (interquartile range (IQR), 15-26 d). The asymptomatic group had a significantly longer duration of viral shedding than the symptomatic group (log-rank P = 0.028). The virus-specific IgG levels in the asymptomatic group (median S/CO, 3.4; IQR, 1.6-10.7) were significantly lower (P = 0.005) relative to the symptomatic group (median S/CO, 20.5; IQR, 5.8-38.2) in the acute phase. Of asymptomatic individuals, 93.3% (28/30) and 81.1% (30/37) had reduction in IgG and neutralizing antibody levels, respectively, during the early convalescent phase, as compared to 96.8% (30/31) and 62.2% (23/37) of symptomatic patients. Forty percent of asymptomatic individuals became seronegative and 12.9% of the symptomatic group became negative for IgG in the early convalescent phase. In addition, asymptomatic individuals exhibited lower levels of 18 pro- and anti-inflammatory cytokines. These data suggest that asymptomatic individuals had a weaker immune response to SARS-CoV-2 infection. The reduction in IgG and neutralizing antibody levels in the early convalescent phase might have implications for immunity strategy and serological surveys.
The effectiveness of control measures to contain coronavirus disease 2019 (COVID-19) in Wanzhou, China was assessed. Epidemiological data were analyzed for 183 confirmed COVID-19 cases and their ...close contacts from five generations of transmission of severe acute respiratory syndrome coronavirus 2 throughout the entire COVID-19 outbreak in Wanzhou. Approximately 67.2% and 32.8% of cases were symptomatic and asymptomatic, respectively. Asymptomatic and presymptomatic transmission accounted for 75.9% of the total recorded transmission. The reproductive number was 1.64 (95% confidence interval: 1.16-2.40) for G1-to-G2 transmission, decreasing to 0.31-0.39 in later generations, concomitant with implementation of rigorous control measures. Substantially higher infection risk was associated with contact within 5 d after the infectors had been infected, frequent contact and ≥8 h of contact duration. The spread of COVID-19 was effectively controlled in Wanzhou by breaking the transmission chain through social distancing, extensive contact tracing, mass testing and strict quarantine of close contacts.
We report acute antibody responses to SARS-CoV-2 in 285 patients with COVID-19. Within 19 days after symptom onset, 100% of patients tested positive for antiviral immunoglobulin-G (IgG). ...Seroconversion for IgG and IgM occurred simultaneously or sequentially. Both IgG and IgM titers plateaued within 6 days after seroconversion. Serological testing may be helpful for the diagnosis of suspected patients with negative RT-PCR results and for the identification of asymptomatic infections.
•A novel electrochemical immunosensor was developed for aflatoxin B1 detection.•The fabricated immunosensor was proved to be practical, simple and sensitive.•This method was successfully applied to ...detect AFB1 in corn powder.
A sensitive electrochemical immunosensor for aflatoxin B1 (AFB1) detection based on single-walled carbon nanotubes/chitosan was presented. The immunosensor was based on an indirect competitive binding to a fixed amount of anti-AFB1 between free AFB1 and AFB1-bovine serum albumin, which conjugate immobilized on covalently functionalized nanotubes/chitosan laid on the glass carbon electrode. Then, the anti-mouse immunoglobulin G secondary antibody labeled with alkaline phosphatase was bound to the electrode surface through reacting with primary antibody. Finally, alkaline phosphatase catalyzes the hydrolysis of the substrate α-naphthyl phosphate, which produced electrochemical signal. Compared with conventional methods, the established immunosensor was more sensitive and simple. Under optimal conditions, this method could quantitatively detect AFB1 from 0.01 to 100ngmL−1 with a detection limit of 3.5pgmL−1. Moreover, the immunosensor was successfully applied to assay AFB1 in corn powder, which showed good correlation with the results obtained from high performance liquid chromatography.
An ultrasensitive immunosensor for the direct detection of the illegally used livestock feed clebuterol (CLB) is described. It is based on the use of a glassy carbon electrode modified with an MoS
2
...-AuPt nanocomposite and on biotin-streptavidin interaction. The use of MoS
2
-AuPt accelerates electron transfer, and this leads to a sharp increase in the electrochemical signal for the electrochemical probe hydrogen peroxide. Differential pulse voltammetry was used to record the current signal at a peak potential of −0.18 V (vs SCE). Under optimal conditions, the electrode has a linear response in the 10 pg·mL
−1
to 100 ng·mL
−1
CLB concentration range and a 6.9 pg·mL
−1
detection limit (based on the 3σ criterium). This immunosensor is sensitive, highly specific and acceptably reproducible, and thus represents a valuable tool for the determination of CLB in pork.
Graphical abstract
Schematic of a voltammetric immunosensor for the determination of clenbuterol (CLB) based on the use of a nanocomposite prepared from molybdenum disulfide and a gold-platinum alloy (MoS
2
-AuPt), and making use of the biotin-streptavidin system.
It is important to evaluate the durability of the protective immune response elicited by primary infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we systematically ...evaluated the SARS-CoV-2-specific memory B cell and T cell responses in healthy controls and individuals recovered from asymptomatic or symptomatic infection approximately 6 months prior. Comparatively low frequencies of memory B cells specific for the receptor-binding domain (RBD) of spike glycoprotein (S) persisted in the peripheral blood of individuals who recovered from infection (median 0.62%, interquartile range 0.48-0.69). The SARS-CoV-2 RBD-specific memory B cell response was detected in 2 of 13 individuals who recovered from asymptomatic infection and 10 of 20 individuals who recovered from symptomatic infection. T cell responses induced by S, membrane (M), and nucleocapsid (N) peptide libraries from SARS-CoV-2 were observed in individuals recovered from coronavirus disease 2019 (COVID-19), and cross-reactive T cell responses to SARS-CoV-2 were also detected in healthy controls.
Bilirubin is a biochemical substance with metabolic benefits. The objective of this research was to elucidate the association between serum bilirubin levels and metabolic alterations in different ...obesity phenotypes.
In total, 1,042 drug-naive participants were included in the study. Of them, 541 were obese patients and 501 were age-matched and sex-matched healthy control subjects. The obese patients were divided into metabolically healthy obesity (MHO) group and metabolically unhealthy obesity (MUHO) group according to the levels of fasting plasma glucose (FBG), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and blood pressure (BP). Clinical and biochemical parameters including total bilirubin (TBil), indirect bilirubin (IBil) and direct bilirubin (DBil) were measured. ANOVA or Kruskal-Wallis H test was used to test differences among the three groups. Pearson and Spearman correlations were used to analyze the relationships between two parameters. The relationships between bilirubin and other variables were analyzed using Multivariate regression analysis.
MHO group had favorable blood pressure, glucose and lipids profiles, along with increased TBil and DBil, and decreased high-sensitivity C-reactive protein (hsCRP) and homeostasis model assessment of insulin resistance (HOMA-IR) levels when compared to MUHO group (
< 0.05 for all). TBil and DBil were negatively correlated with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), fasting insulin (FINS), hsCRP and HOMA-IR, even after adjusted for age, gender and BMI (all
<0.01). Multivariate regression analysis demonstrated that HOMA-IR was independently correlated with TBil and DBIi levels (β = -0.400,
< 0.01).
MHO group harbors increased bilirubin level compared with MUHO group. HOMA-IR was independently correlated with TBil and DBIi levels.
The authors describe an electrochemical immunoassay for ultrasensitive direct determination of the carcinoembryonic antigen (CEA). A nanocomposite consisting of octahedral Cu2O nanocrystals covered ...with gold nanoparticles was utilized to modify a glassy carbon electrode which gives a strongly enhanced chronoamperometric signal for H
2
O
2
which is used as an electrochemical probe. The morphology and elemental composition of the the nanocomposite was studied by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. In addition, staphylococcal protein A was placed on the electrode for efficient capture of antibody to further enhance the sensitivity of the assay. Under optimal conditions and at a typical working voltage of −0.4 V (vs. Ag/AgCl), the response covers the 2 pg·mL
−1
to 20 ng·mL
−1
CEA concentration range with a 200 fg·mL
−1
lower detection limit. The method was successfully applied to the determination of CEA in (spiked) human serum.
Graphical abstract
Schematic of the fabrication of an electrochemical immunosensor for ultrasensitive detection the carcinoembryonic antigen. The sensor is based on the use of a glassy carbon electrode modified with an octahedral Cu
2
O-gold nanocomposite and staphylococcal protein A for signal amplification.
Background Ventilator-associated pneumonia (VAP) is a common and serious problem in intensive care units. However, limited literature has been reviewed to synthesize the findings about the incidence, ...case fatality rate, pathogen distribution, and drug resistance of neonatal VAP in China. Methods A search of electronic databases was undertaken to identify the incidence, case fatality rate, pathogen distribution, and drug resistance of neonatal VAP based on the inclusion and exclusion criteria. Meta-analysis was carried out using R3.0.2 software. Results A total of 16,587 participants were included in our final analysis. The incidence and case fatality rates were 42.8% and 16.4%, respectively. Gram-negative bacteria were detected in 77.6% of cultures, followed by gram-positive bacteria (18.8%) and fungi (3.7%). Gram-negative bacteria were sensitive to meropenem, imipenem, and ciprofloxacin, with resistance rates of 1.5%-25.0%, 4.9%-29.0%, and 8.5%-24.7%, respectively. Gram-positive bacteria have resistance rates as high as 72.7%-99.1% to penicillin, 62.6%-90.9% to erythromycin, and 80.3%-91.9% to oxacillin. Conclusions The incidence and case fatality rates of neonatal VAP are high in China. VAP was mainly caused by gram-negative bacteria that were resistant to most common antibiotics. The future study of drug-resistance mechanisms should be intensified, and effective measures of hospital infection control should be considered to prevent the outbreak of drug-resistant strains.
Peptidyl arginine deiminase, type VI (PADI6) is a member of the subcortical maternal complex (SCMC), which plays vital roles in mammalian embryogenesis. Most mutations in SCMC members have been ...reported to cause human embryonic arrest, and a total of 15 mutations in PADI6 have been shown to be responsible for early embryonic arrest according to previous studies. However, the genetic factors behind this phenotype remain to be understood in further detail. Here, we identified 13 novel mutations and 4 previously reported mutations of PADI6 in 14 patients who were diagnosed with abnormal embryonic development caused by early arrest, embryonic fragmentation, and recurrent implantation failure. Most of the mutations were predicted by in silico analysis to be deleterious or damaging to the function of PADI6. In addition, the total and East Asian population frequencies of the mutations were low or absent in the gnomAD database. Our study expands the mutational spectrum in PADI6 and will provide precise targets for genetic counseling in the future.
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