Immune memory in convalescent patients with asymptomatic or mild COVID-19.

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.

Effective control of SARS-CoV-2 transmission in Wanzhou, China.

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.

Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections.

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 policy1. 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.

Antibody responses to SARS-CoV-2 in patients with COVID-19.

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.

Electrochemical immunoassay for the carcinoembryonic antigen based on the use of a glassy carbon electrode modified with an octahedral Cu2O-gold nanocomposite and staphylococcal protein for signal amplification.

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 H2O2 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 Cu2O-gold nanocomposite and staphylococcal protein A for signal amplification.

A voltammetric immunosensor for clenbuterol based on the use of a MoS2-AuPt nanocomposite.

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 MoS2-AuPt nanocomposite and on biotin-streptavidin interaction. The use of MoS2-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 (MoS2-AuPt), and making use of the biotin-streptavidin system.

A novel electrochemical immunosensor for highly sensitive detection of aflatoxin B1 in corn using single-walled carbon nanotubes/chitosan.

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 100 ng mL(-1) with a detection limit of 3.5 pg mL(-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.

Bronchopulmonary infection of Lophomonas blattarum: a case and literature review.

Human infections with Lophomonas blattarum are rare. However, the majority of the infections occurred in China, 94.4% (136 cases) of all cases in the world. This infection is difficult to differentiate from other pulmonary infections with similar symptoms. Here we reported a case of L. blattarum infection confirmed by bronchoalveolar lavage fluid smear on the microscopic observations. The patient was a 21-year-old female college student. The previous case which occurred in Chongqing was 20 years ago. We briefly reviewed on this infection reported in the world during the recent 20 years. The epidemiological characteristics, possible diagnostic basis, and treatment of this disease is discussed in order to provide a better understanding of recognition, diagnosis, and treatment of L. blattarum infection.

Risk factors for ventilator-associated pneumonia in the neonatal intensive care unit: a meta-analysis of observational studies.

UNLABELLED: Ventilator-associated pneumonia (VAP) is a common and serious problem among mechanically ventilated patients in intensive care units (ICU), especially for the newborn. However, limited literatures have been reviewed to synthesize the finding of previous papers to investigate the risk factors for VAP although it has been a serious complication of mechanical ventilation (MV) with a high morbidity and mortality in the newborn. We performed this meta-analysis to extend previous knowledge for developing VAP prevention strategies by identifying the potential risk factors related to VAP in the neonatal intensive care unit (NICU). The relevant literatures published up to July 2013 were searched in the databases of PubMed, Cochrane Central Register of Controlled Trials, Embase, and Web of Science. Three reviewers screened those literatures and extracted data according to the inclusion and exclusion criteria independently. A total of eight studies including 370 cases and 1,071 controls were identified. Ten risk factors were found to be related to neonatal VAP which were listed as follows in order by odds ratios (ORs): length of stay in NICU (OR 23.45), reintubation (OR 9.18), enteral feeding (OR 5.59), mechanical ventilation (OR 4.04), transfusion (OR 3.32), low birth weight (OR 3.16), premature infants (OR 2.66), parenteral nutrition (OR 2.30), bronchopulmonary dysplasia (OR 2.21), and tracheal intubation (OR 1.12). CONCLUSION: We identified ten variables as independent risk factors for the development of VAP: length of stay in NICU, reintubation, enteral feeding, mechanical ventilation, transfusion, low birth weight, premature infants, parenteral nutrition, bronchopulmonary dysplasia, and tracheal intubation. Due to several limitations in the present study, further large and well-designed studies are needed to confirm the conclusion.

Effect of mesenteric lymph duct ligation on gene expression profiles of renal tissue in hemorrhagic shock rats with fluid resuscitation.

BACKGROUND: Acute kidney injury (AKI), a common pathological process following hemorrhagic shock, can lead to an internal milieu disorder, which is an important factor of multiple organ failure (MOF). It has been shown that the mesenteric lymph return plays a deleterious effect on MOF induced by hemorrhagic shock. In this study, we investigated the effects of mesenteric lymph duct ligation (MLDL) on gene expression profiles of renal tissue following hemorrhagic shock with fluid resuscitation. METHODS: After establishment of hemorrhagic shock model and fluid resuscitation in rats of shock and shock ligation groups, the MLDL was performed in shock ligation group, and only threading under the mesenteric lymph duct in the shock group. Then, the fixed position renal tissue was taken out for homogenate in two groups at 3 h after resuscitation, the total mRNA was extracted, reversely transcribed into cDNAs and marked with Cy3 and Cy5. The cDNAs were subjected for microarray scanning with 12,028 cDNA probes; the differentially expressed genes between two groups were analyzed. RESULTS: In the 5812 valid dates of rat genomes transcription, there were 34 known differentially expressed genes between the two groups, of which 11 genes were up-regulated whereas 23 genes were down-regulated by MLDL. These different expressed genes encoding protein function were mainly involved in signal transduction, transcription regulation, metabolism, transport, cell growth, cell cycle, cell adhesion, cell movement, cellular component, and biological process. CONCLUSIONS: The mechanism of MLDL alleviating the AKI aftershock might be associated with up- or down-regulation of the above gene expressions.

[Construction of biofilm formation related mutants in Vibrio parahaemolyticus].

OBJECTIVE: To construct the mutants of biofilm related genes in Vibrio parahaemolyticus and confirm the mutants. METHODS: The homologous upstream and downstream flanking fragments of target gene were amplified by using PCR, and the fusion homologous fragment was amplified by using the two flanking fragments as template. Then the fusion homologous fragment was digested by restriction enzyme and cloned into suicide plasmid pDS132. The recombinant plasmid was transferred into Vibrio parahaemolyticus RIMD 2210633 through conjugation. The mutants were screened and identified by PCR and the phenotype of one mutant was analyzed in order to verify that the mutants were constructed successfully. RESULTS: Six recombinant plasmids carrying the fusion homologous fragments of genes vbfR, crp, hns, swrZ, swrT and cpsR respectively were constructed and identified by PCR. The amplification products of 1190, 1128, 1136, 953, 1242 and 1112 bp were obtained respectively. The six mutants (ΔvbfR, Δcrp, Δhns, ΔswrZ, ΔswrT and ΔcpsR) were constructed using recombinant plasmids. Verified by PCR, the size of amplification products of mutants (1190, 1128, 1136, 953, 1242 and 1112 bp respectively) was less (610, 739, 421, 542, 427 and 1367 bp respectively) than the corresponding positive control. Meanwhile, none of the products was amplified using the primers locating on the target gene. One mutant Δhns was selected to test the ability of biofilm formation. The result showed that the ability of biofilm formation of mutant Δhns was increased compared with the wild type. CONCLUSION: Six mutants of biofilm related genes in Vibrio parahaemolyticus were constructed and tested by molecular and phenotype experiment to confirm that the mutants were constructed successfully.

[Distribution of the of nosocomial infection pathogens among general hospital in China: a Meta analysis].

OBJECTIVE: To provide basic and direction for nosocomial infection prevention and control through evaluation the distribution of nosocomial infection pathogens and understand current situation of pathogens among general hospital in China. METHODS: Articles were searched and collected from CBM, CNKI,VIP database and Wanfang database published between creating database to March. 2013 about investigation of nosocomial infection. Those literatures were screened and extracted according to the inclusion and exclusion criteria by two reviewers independently. The analysis of pathogens distribution was performed by using comprehensive Meta analysis software and stratified by factor as year, hospital level and region of the study. The distribution rate of different pathogens were merged according to statistical tests for the heterogeneity test. RESULTS: The 345 trials were included. The results show 1)the pooled distribution rates of common pathogens in 1987-2000 were as follows:18.6% (95% CI:13.7%-24.9%), 18.1% (95% CI:15.4%-21.0%), 14.8% (95% CI: 12.2%-17.9%), 5.2% (95%CI:4.1%-6.6%) for Fungus, Staphylococcus, Pseudomonas, and Klebsiella respectively;the pooled rates of common pathogens in 2001-2012 were as follows:17.6% (95% CI: 16.4%-18.8%), 15.0% (95% CI:14.2%-15.8%), 13.9% (95% CI:13.1%-14.7%), 10.4% (95% CI: 9.9%-11.0%)for Fungus, Staphylococcus, Pseudomonas, and Klebsiella respectively. 2)The pooled distribution rates of pathogens in second and below grade hospital were 3.2% (95%CI:0.3%-29.9%), 4.7% (95% CI:3.4%-6.3%), 7.2% (95% CI:1.7%-26.1%)for Mycoplasma, Shigella and Alkaligenes respectively;the pooled distribution rates of pathogens in third grade hospital were 1.1% (95% CI: 0.1%-15.4%), 1.8% (95%CI:0.6%-5.1%), 4.3% (95%CI:2.3%-8.0%)for Mycoplasma, Shigella and Alkaligenes respectively. 3)The pooled rate of Mycoplasma for Yangtze River Economic Area was 14.3% (95%CI:2.0%-58.1%)and for Southwest Economic Area was 0.3% (95%CI:0.1%-1.1%). The pooled rate of Corynebacterium for Yangtze River Economic Area was 0.4% (95%CI:0.1%-1.4%)and for Southeast Economic Area was 9.5% (95% CI:2.4%-31.1%). The pooled rate of Haemophilus for Northern Economic Area was 0.5% (95%CI:0.2%-0.9%)and for Southeast Economic Area was 9.2% (95% CI:7.3%-11.6%). The pooled rate of Salmonella for Yangtze River Economic Area was 6.3% (95% CI:4.6%-8.6% ) and for Southeast Economic Area was 0.4% (95% CI:0.1%-3.0% ). CONCLUSION: The common nosocomial infection pathogens were Fungus, Staphylococcus, Pseudomonas and Escherichia among general hospitals in China. A remarkable note is that Klebsiella was increased significantly in recent years and becomes one of the most common pathogens. There were differences in the distribution rate of nosocomial infection pathogens among general hospitals between levels and regions in China.

Use of rich BHI medium instead of synthetic TMH medium for gene regulation study in Yersinia pestis.

OBJECTIVE: This study is to verify the use of rich BHI medium to substitute synthetic media for gene regulation studies in Yersinia pestis. METHODS: The transcriptional regulation of rovA by PhoP or via temperature upshift, and that of pla by CRP were investigated when Y. pestis was cultured in BHI. After cultivation under 26 °C, and with temperature shifting from 26 to 37 °C, the wild-type (WT) strain or its phoP or crp null mutant (ΔphoP or Δcrp, respectively) was subject to RNA isolation, and then the promoter activity of rovA or pla in the above strains was detected by the primer extension assay. The rovA promoter-proximal region was cloned into the pRW50 containing a promoterless lacZ gene. The recombinant LacZ reporter plasmid was transformed into WT and ΔphoP to measure the promoter activity of rovA in these two strains with the ß-Galactosidase enzyme assay system. RESULTS: When Y. pestis was cultured in BHI, the transcription of rovA was inhibited by PhoP and upon temperature upshift while that of pla was stimulated by CRP. CONCLUSION: The rich BHI medium without the need for modification to be introduced into the relevant stimulating conditions (which are essential to triggering relevant gene regulatory cascades), can be used in lieu of synthetic TMH media to cultivate Y. pestis for gene regulation studies.