Real-time Fluorescence Quantitative RT-PCR Research Articles

Sensitivity, Specificity, Positive Rate and Consistency of Two Kits in SARS-CoV-2 Nucleic Acid Detection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was a highly transmissible and pathogenic coronavirus and it emerged in late 2019. SARS-CoV-2 had caused a pandemic of acute respiratory disease and its name was coronavirus disease 2019 (COVID-19). It threatened human health and public safety. This study would analyze and evaluate two different kinds of SARS-CoV-2 nucleic acid detection reagents which could provide value for accurate detection. 80 patients were randomly selected in the First Affiliated Hospital of Anhui Medical University in December 2022 and 80 oropharyngeal swabs were collected. Nucleic acid was extracted first, and then two real-time fluorescent quantitative RT-PCR nucleic acid amplification reagents were used to detect ORF1ab and N genes. Statistical software was used to compare and analyze the results. Among 80 patients, 57 were males and 23 were females with an age range of 5 - 90 years with an average age of 65.7 years. Most of the specimens were collected from Department of Infectious Diseases and Department of Respiratory and Critical care. Compared with regent Reference, the sensitivity of regent A and B was 88.3% and 93.3% and the specificity was 90.0% and 95.0%, respectively. The positive rates of the double target genes were 85.0% and 93.3%, the positive rates of ORF1ab gene were 86.7% and 95.0% and the positive rates of N gene were 88.3% and 96.7%, respectively. The Kappa values were all greater than 0.75, indicating high consistency. Between two nucleic acid detection reagents, reagent B had higher sensitivity and specificity. And the positive rate and consistency of reagent B were also higher than that of reagent A, with statistical significance. For weakly positive specimens with low viral load, it was recommended to use another reagent with higher sensitivity to retest and ensure the accuracy and repeatability of the results.

Effect of Neurokinin-1 Receptor Knockdown on the Expression of RANTES in Allergic Rhinitis.

Neurokinin-1 receptor (NK-1R) and normal T cell expressed and secreted (RANTES) have been shown to play important roles in allergic rhinitis (AR). However, whether the regulating effect of NK-1R in AR is achieved via RANTES remains unknown. In the present study, Sprague-Dawley rats were sensitized and challenged with ovalbumin to make AR models. During the challenge period, the rats were treated intranasally with NK-1R-specific small interfering RNA (siRNA) for NKR group, negative siRNA for NCS group, rats in NSAR group and NS group were given saline. The amount of nasal secretion and the numbers of nose rubs and sneezes were measured in each rat. The levels of NK-1R and RANTES in the nasal mucosal tissues were determined through real-time fluorescence quantitative RT-PCR and immunohistochemical staining. The numbers of eosinophils in the collected nasal lavage fluid (NLF) were counted, and the concentration of RANTES in NLF was determined by enzyme-linked immunosorbent assay. Compared with that in the NS group, the expression of NK-1R and RANTES was significantly higher in the nasal mucosa of NSAR and NCS group rats. The sneezing and nose rubbing counts and the amount of nasal secretions were increased significantly in the NSAR and NCS groups. Rats in the NKR group experienced greater relief from AR symptoms than rats in the NSAR and NCS groups. Furthermore, knockdown of NK-1R expression also significantly eliminated RANTES expression and eosinophil infiltration in the nasal mucosa of NKR group rats. For the first time, we show that intranasal treatment with NK-1R-specific siRNA can significantly decrease RANTES expression, AR-related symptoms, and eosinophil inflammation, suggesting that the regulating effect of NK-1R in the development of AR occurs via alteration of RANTES expression.

Soybean balanced the growth and defense in response to SMV infection under different light intensities.

Light is essential for the growth and defense of soybean. It is not clear how soybeans adjust their defenses to different light environments with different cropping patterns. The mechanism of soybean response to Soybean mosaic virus (SMV) infection under different light intensities was analyzed by RNA-seq sequencing method. Enrichment analysis illustrated that most defense-related genes were down-regulated in the dark and the shade, and up-regulated under hard light and normal light. Soybean can resist SMV infection mainly by activating salicylic acid signaling pathway. Light is essential for activating salicylic acid defense signaling pathways. With the increase of light intensity, the oxidative damage of soybean leaves was aggravated, which promoted the infection of virus. When light was insufficient, the growth of soybean was weak, and the plant-pathogen interaction pathway, MAPK pathway and hormone defense pathway in infected soybean was inhibited. Under hard light, some defense genes in infected soybean were down-regulated to reduce the degree of oxidative damage. The expression of differentially expressed genes was verified by real-time fluorescence quantitative RT-PCR. In order to adapt to the change of light intensity, soybean balanced allocation of resources between growth and defense through a series regulation of gene expression. The results of this study will provide a theoretical basis for the research of SMV resistance in intercropping soybean.

Development of a reverse-transcription droplet digital PCR method for quantitative detection of Cucumber green mottle mosaic virus

Cucumber green mottle mosaic virus (CGMMV) is a re-emerging threat to the production of greenhouse cucumber and other Cucurbitaceae crops worldwide. This seed-borne virus can easily spread from a contaminated seed to seedlings and adjacent plants by mechanical contact between the foliage of diseased and healthy plants, causing extensive yield losses. An accurate method for detecting and quantifying this virus is urgently needed to ensure the safety of the global seed trade. Here, we report the development of a reverse-transcription droplet digital polymerase chain reaction (RT-ddPCR)-based method for specific and high-sensitive detection of CGMMV. By testing three primer–probe sets and optimizing reaction conditions, we showed that the newly developed RT-ddPCR method is highly specific and sensitive, with a detection limit of 1 fg/μL (0.39 copy/μL). The sensitivity of the RT-ddPCR method was compared with that of real-time fluorescence quantitative RT-PCR (RT-qPCR) using a series of plasmid dilutions and total RNAs extracted from infected cucumber seeds, and the detection limit of RT-ddPCR was 10 times higher than RT-qPCR with plasmid dilutions and 100 times higher than RT-qPCR for detecting CGMMV from infected cucumber seeds. The RT-ddPCR method was further assessed for detecting CGMMV from a total of 323 samples of Cucurbitaceae seeds, seedlings, and fruits as compared with the RT-qPCR method. We found that the infection rate of CGMMV on symptomatic fruits was as high as 100%, whereas infection rates were lower for seeds and lowest for seedlings. Notably, the results of two methods in detecting CGMMV from different cucurbit tissues showed the high consistency with Kappa value from 0.84 to 1.0, demonstrating that the newly developed RT-ddPCR method is highly reliable and practically useful for large-scale CGMMV detection and quantification.

Construction of Infectious cDNA Clone of Brassica Yellows Virus Isolated from Strawberry and Establishment of TaqMan RT-qPCR

The natural host range for brassica yellows virus (BrYV) is generally limited to Cruciferae. However, we found that BrYV can naturally infect strawberry. The full-length genome sequences of BrYV-MB (accession No. MZ666129) and BrYV-HY (accession No. ON060762) identified in strawberry from Yantai and Beijing, China, were obtained by high-throughput sequencing (HTS) combined with the RT-PCR and RACE techniques. The complete genome sequences of BrYV-MB and BrYV-HY are 5666 nt and contain six open reading frames (ORFs). The two isolates have the highest nucleotide (nt) sequence identity of 99.0%. The infectious cDNA clone of BrYV-HY was constructed through homologous recombination and used to agroinfiltrate Nicotiana benthamiana and Arabidopsis thaliana. The inoculated leaves of N. benthamiana showed necrotic symptoms after 4 days of inoculation (dpi), and the systematic leaves of A. thaliana exhibited purple symptoms at 14 dpi. To develop a rapid and high-sensitive method for the detection of BrYV, a TaqMan real-time fluorescence quantitative RT-PCR method (TaqMan RT-qPCR) was established. Under optimum reaction conditions, the sensitivity of the detection was as low as 100 fg and approximately 100-fold more sensitive than the conventional RT-PCR, so it can be used in large-scale testing.

RhEPO Upregulates the PPARγ Pathway in Long-term Cultured Primary Nerve Cells via PI3K/Akt to Delay Cell Senescence.

Previous studies have confirmed that both recombinant human erythropoietin (rhEPO) and peroxisome proliferator-activated receptors γ (PPARγ) activator pioglitazone can protect senescent nerve cells, and their mechanisms involve enhancing cell antioxidant capacity and reducing cell apoptosis. However, whether the PPARγ pathway is involved in the rhEPO anti-aging process in neuronal cells is still unclear. In this study, to explore the relationship between rhEPO and the PPARγ pathway at the cellular level, primary nerve cells cultured for 22days were used to simulate the natural aging process of nerve cells. Starting on the 11th day of culture, rhEPO, LY294002, and GW9662 were added for treatment. Immunochemical methods and SA-β-gal staining were used to observe the changes in cellular antioxidant capacity and the fraction of senescent cells. The results showed that PPARγ blockade retarded the effect of rhEPO on the cellular antioxidant capacity and altered the fraction of senescent cells. It was confirmed that PPARγ was involved in rhEPO's anti-aging process in neuronal cells. Real-time fluorescent quantitative RT-PCR, Western blotting, and immunofluorescence staining were used to observe the changes in PPARγ pathway-related factors in nerve cells after rhEPO treatment. The results showed that rhEPO significantly upregulated the expression of PPARγ coactivator-1α (PGC-1α), PPARγ, and nuclear PPARγ in cells but did not affect the level of phosphorylated PPARγ protein, confirming that rhEPO has the ability to upregulate the PPARγ pathway. PI3K/Akt and PPARγ pathway blockade experiments were used to explore the relationships among rhEPO, PI3K/Akt, and PPARγ. The results showed that after PPARγ blockade, rhEPO had no significant effect on the PI3K/Akt pathway-related factor p-Akt, while after PI3K/Akt blockade, rhEPO's effects on PPARγ-related factors (PGC-1α, PPARγ, and nuclear PPARγ) were significantly decreased. It is suggested that rhEPO delays the PI3K/Akt pathway in the process of neuronal senescence, which is located upstream of PPARγ regulation. In conclusion, this study confirmed that rhEPO can upregulate the expression of PGC-1α and PPARγ in cells and the level of PPARγ protein in the nucleus to enhance the antioxidant capacity of cells and delay the senescence of nerve cells through the PI3K/Akt pathway. These findings will provide ideas for finding new targets for neuroprotection research and will also provide a theoretical basis and experimental evidence for rhEPO anti-aging research in neural cells.

Establishment of an antigen-capture enzyme-linked immunosorbent assay for detecting avian reticuloendotheliosis virus

In this study, an antigen-capturing enzyme-linked immunosorbent assay (AC-ELISA) was established for the detection of avian reticuloendotheliosis virus (REV) using monoclonal and polyclonal antibodies against gp90. New Zealand white rabbits were immunized with recombinant REV-gp90 protein, and polyclonal antibodies were obtained after purification and used as the capture antibody. Mice monoclonal antibody 1A12D against REV-gp90 protein previously prepared in our laboratory was used as the detection antibody. The specificity of the AC-ELISA was confirmed with REV, avian leukosis virus subgroup J, Marek's disease virus serotype Ⅰ, avian hepatitis E virus and Fowl adenovirus serotype 4. The results showed that the AC-ELISA had specific binding reaction with REV, and did not react with other viruses. The detection limit of this assay was 195 TCID50 units of REV. Furthermore, commercial vaccine artificially contaminated with REV was detected by three methods: AC-ELISA, the TaqMan probe fluorescence real-time quantitative RT-PCR (RT-qPCR) and indirect immunofluorescence assay (IFA). The results showed that the positive coincidence rate of RT-qPCR and AC-ELISA was 90.63 %, and the positive coincidence rate of RT-qPCR and IFA was 96.88%, indicating that the AC-ELISA established in this study was effective and feasible. This method simplified the detection process for REV contamination in poultry attenuated vaccines, and provide necessary technical tools for high-throughput detection of REV.

EV71 was Detected by Real-Time Fluorescence Quantitative RT-PCR Combined with Hand-Foot-Mouth Disease Rhesus Monkey Model

In this study, a real-time fluorescence quantitative RT-PCR method was developed for the detection of enterovirus 71 (EV71) and the detection of EV71 viral load during the establishment of hand-foot-mouth disease (HFMD) model in rhesus monkeys. The model of hand-foot-mouth macaque was established by injecting newborn macaques infected with the virus venom, and the dynamic changes of virus content in blood samples from 0 to 14 days after infection were monitored by real-time quantitative RT-PCR. The linear range of the standard curve was between 103 and 108 copies/µL, and the PCR amplification rate was 99.37%. The results showed that the established method could detect a minimum of 102 copies of viral RNA, 100 times higher than the conventional RT-PCR method. It has the characteristics of strong specificity, high sensitivity and good stability. The results of blood sample analysis showed that the three groups of rhesus monkey models were successfully infected with EV71, and the copy number of virus proliferation was correlated with time and challenge dose. The results showed that real-time quantitative PCR could be used for quantitative detection of EV71 viral load.

Investigation of contamination of SARS-CoV-2 in imported frozen seafood from a foreign cargo ship and risk factors for infection in stevedores in Qingdao

Objective: To investigate the contamination status of SARS-CoV-2 in imported frozen seafood from a Russia cargo ship in Qingdao and to analyze the risk factors for infection in local stevedores. Methods: The method of "two-stage, full coverage and mixed sampling" was used to collect the seafood packaging samples for the nucleic acid detection of SARS-CoV-2 by real-time fluorescent quantitative RT-PCR. A unified questionnaire was designed to investigate 71 stevedores in two shifts through telephone interview. The stevedores were divided into two groups, with 23 in the shit with two infections was group A and 48 in the shift without infection was group B. Software Epi Info7.2 was used to identify the risk factors for SARS-CoV-2 infections in the stevedores. Results: In the frozen seafood from a Russia cargo ship, the total positive rate of SARS-CoV-2 nucleic acid in the frozen seafood was 11.53% (106/919). The positive rate of SARS-CoV-2 nucleic acid in the frozen seafood unloaded by group A (14.29%,70/490) was significantly higher than that in the frozen seafood unloaded by group B (8.39%,36/429)(χ2=7.79,P=0.01) and the viral loads detected in the frozen seafood unloaded by group A were higher than those detected in the frozen seafood unloaded by group B. The scores of personal protection and behaviors in the stevedores in group A were significantly lower than those in group B (P<0.05), and toilet use, smoking and improper hand washing before meals were the risk factors for the infection. Conclusions: The imported frozen seafood was contaminated by SARS-CoV-2 and the contamination distribution was uneven. Supervision and management of personal occupational protection and behaviors of workers engaged in imported frozen food transportation should be strengthened. It is suggested that a closed-loop monitoring and management system for the whole process of "fishing-transport- loading/unloading" should be established by marine fishery authority.

CRISPR/Cas9-mediated TEAD1 knockout induces phenotypic modulation of corpus cavernosum smooth muscle cells in diabetic rats with erectile dysfunction

To construct a corpus cavemosum smooth muscle cell (CCSMCs) line with TEAD1 knockout from diabetic rats with erectile dysfunction (ED) using CRISPR/Cas9 technology and explore the role of TEAD1 in phenotypic modulation of CCSMCs in diabetic rats with ED. Models of diabetic ED were established in male Sprague-Dawley rats by intraperitoneal injection of streptozotocin. CCSMCs from the rat models were primarily cultured and identified with immunofluorescence assay. Three sgRNAs (sgRNA-1, sgRNA-2 and sgRNA-3) were transfected via lentiviral vectors into 293T cells to prepare the sgRNA-Cas9 lentivirus. CCSMCs from diabetic rats with ED were infected by the lentivirus, and the cellular expression of TEAD1 protein was detected using Western blotting. In CCSMCs infected with the sgRNA-Cas9 lentivirus (CCSMCs-sgRNA-2), or the empty lentiviral vector (CCSMCs-sgRNA-NC) and the blank control cells (CCSMCs-CK), the expressions of cellular phenotypic markers SMMHC, calponin and PCNA at the mRNA and protein levels were detected using real-time fluorescence quantitative RT-PCR (qRT-PCR) and Western blotting, respectively. The primarily cultured CCSMCs from diabetic rats with ED showed a high α-SMA-positive rate of over 95%. The recombinant lentivirus of TEAD1-sgRNA was successfully packaged, and stable TEAD1-deficient CCSMC lines derived from diabetic rat with ED were obtained. Western blotting confirmed that the protein expression of TEAD1 in TEAD1-sgRNA-2 group was the lowest (P < 0.05), and this cell line was used in subsequent experiment. The results of qRT-PCR and Western blotting showed significantly up-regulated expressions of SMMHC and calponin (all P < 0.05) and down-regulated expression of PCNA (all P < 0.05) at both the mRNA and protein levels in TEAD1-deficient CCSMCs from diabetic rats with ED. We successfully constructed a stable CCSMCs line with CRISPR/Cas9-mediated TEAD1 knockout from diabetic rats with ED. TEAD1 gene knockout can induce phenotype transformation of the CCSMCs from diabetic rats with ED from the synthetic to the contractile type.

Surveillance of avian influenza virus in external environment in Jieyang, Guangdong, 2016-2020

Objective To understand the dynamic distribution and epidemic characteristics of avian influenza virus in external environment in Jieyang, assess the risk of human infection with avian influenza, and we provide scientific basis for prevention and control of human avian influenza. Methods According to the random sampling method, relevant specimens were collected from poultry markets in 5 counties (county-level cities and districts) in Jieyang, 2016-2020. Real-time fluorescence quantitative RT-PCR method was used to detect the nucleic acid of influenza virus Type A. Positive specimens were then tested for the nucleic acid of H5N6, H7N9 and H9N2 subtypes of avian influenza virus. Results From 2016 to 2020, a total of 1 798 environmental samples were collected, of which 660 samples were positive for influenza A virus (FluA), with a positive rate of 36.71%. The positive rates of H5N6, H7N9 and H9N2 subtypes were 1.61%, 1.28% and 21.91%, respectively. The positive rate of avian influenza virus was higher in Puning county-level city (54.14%) and Huilai county (51.43%), and lowest in Jiexi county (4.84%). The highest positive rate of different types of samples (47.09%) was the washing of poultry sewage. Conclusion There are H5N6, H7N9, H9N2 and various subtypes of avian influenza virus contamination in external environment of poultry markets in Jieyang. The avian influenza virus has a wide epidemic area and there is a risk of human infection. It is necessary to continue to strengthen the real-time monitoring of avian influenza in external environment and the health supervision of urban and rural poultry market. 摘要：目的 了解揭阳市外环境禽流感病毒动态分布情况和流行特点, 评估人感染禽流感病毒的风险, 为人禽流 感防控提供科学依据。 方法 按随机抽样的方法, 对揭阳市2016—2020年5个县 (市、区)禽类市场进行相关标本采 集, 用实时荧光定量(RT-PCR)对标本进行流感病毒A型检测, 阳性标本再进行H5N6、H7N9、H9N2亚型禽流感病毒核 酸检测。 结果 揭阳市2016—2020年共采集外环境标本1 798份, 甲型流感病毒(FluA)阳性标本660份, 阳性率为 36.71%;其中H5N6、H7N9、H9N2亚型阳性率分别为1.61%、1.28%和21.91%。普宁市和惠来县的外环境禽流感病毒阳 性率较高, 分别为54.14%和51.43%。揭西县的外环境禽流感病毒阳性率最低, 为4.84%。不同类型标本检测阳性率最 高为清洗禽类污水(47.09%)。 结论 揭阳市禽类市场外环境中存在H5N6、H7N9、H9N2及多种亚型混合的禽流感病 毒污染, 禽流感病毒流行区域较广, 存在感染人的风险, 应继续加强外环境禽流感实时监测和城乡禽类市场卫生监管。

Study on therapeutic effect of Chaiyin Particles on combining disease with syndrome of human coronavirus pneumonia with pestilence attacking lung syndrome based on regulation of immune function

According to the classification of traditional Chinese medicine syndromes of coronavirus disease 2019 by the national competent authority, this study determined that human coronavirus 229 E(HCoV-229 E) was infected in a mouse model of cold and dampness syndrome, so as to build the human coronavirus pneumonia with pestilence attacking lung syndrome model. The model can simulate the traditional Chinese medicine treatment of common disease syndromes in Coronavirus Disease 2019 Diagnosis and Treatment Program(the sixth edition for trial). Specific steps were as follows. ABALB/c mouse model of cold and dampness syndrome was established, based on which, HCoV-229 E virus was infected; then the experiment was divided into normal control group, infection control group, cold-dampness control group, cold-dampness infection group(the model group), high-dose Chaiyin Particles group(8.8 g·kg~(-1)·d~(-1)), and low-dose Chaiyin Particles group(4.4 g·kg~(-1)·d~(-1)). On the day of infection, Chaiyin Particles was given for three consecutive days. Lung tissues were collected the day after the last dose, and the lung index and inhibition rate were calculated. The nucleic acid of lung tissue was extracted, and the HCoV-229 E virus load was detected by Real-time fluorescent quantitative RT-PCR. Blood leukocytes were separated, and the percentage of T and B lymphocytes was detected by flow cytometry. Lung tissue protein was extracted, and IL-6, IL-10, TNF-α and IFN-γ contents were detected by ELISA. High and low-dose Chaiyin Particles significantly reduced the lung index(P&lt;0.01) of mice of human coronavirus pneumonia with pestilence attacking the lung syndrome, and the inhibition rates were 61.02% and 55.45%, respectively. Compared with the model control group, high and low-dose Chaiyin Particles significantly increased cross blood CD4~+ T lymphocytes, CD8~+T lymphocytes and total B lymphocyte percentage(P&lt;0.05, P&lt;0.01), and reduced IL-10, TNF-α and IFN-γ levels in lungs(P&lt;0.01). In vitro results showed that TC_(50), TC_0, IC_(50) and TI of Chaiyin Particles were 4.46 mg·mL~(-1), 3.13 mg·mL~(-1), 1.12 mg·mL~(-1) and 4. The control group of in vitro culture cells had no HCoV-229 E virus nucleic acid expression. The expression of HCoV-229 E virus nucleic acid in the virus control group was 1.48×10~7 copies/mL, and Chaiyin Particles significantly reduced HCoV-229 E expression at doses of 3.13 and 1.56 mg·mL~(-1), and the expression of HCoV-229 E nucleic acid was 9.47×10~5 and 9.47×10~6 copies/mL, respectively. Chaiyin Particles has a better effect on the mouse model with human coronavirus pneumonia with pestilence attacking the lung syndrome, and could play a role by enhancing immunity, and reducing inflammatory factor expression.

A sensitive SYBR Green RT-qPCR method for grapevine virus E and its application for virus detection in different grapevine sample types

To develop a rapid and high-sensitivity method for detection of grapevine virus E (GVE), a SYBR Green based real-time fluorescence quantitative RT-PCR method (RT-qPCR) was established. This method could be used to detect GVE specifically, and the sensitivity was about 100 times greater than conventional RT-PCR. An excellent linear correlation (R2=0.997) and a high amplification efficiency (E=97.5%) were obtained from the standard curve of this method. Reproducibility tests revealed that the coefficients of variation in the intra- and inter-assay results were 0.31–1.03% and 0.82–2.62%, respectively, indicating a good reproducibility. The RT-qPCR method could be used to detect GVE in a wide range of grapevine sample types. The detection rates of RT-qPCR for nearly all sample types from different positions and seasons were higher than conventional RT-PCR. The detection rates in spring, summer, autumn and winter increased gradually. Samples in autumn and winter were best for detection, and the detection rates of most samples were 80–100%, which were 10 to 40% higher than conventional RT-PCR. In general, old petioles and branches were the best tissues for GVE detection. The detection rates of these samples in each season were all 100%, which were 20 to 40% higher than conventional RT-PCR. The second highest rates were in the old leaf, with detection rates for RT-qPCR of 80–100% in all seasons, which were 20 to 40% higher than conventional RT-PCR. GVE could be difficultly detected in young leaves by conventional RT-PCR, and the detection rates were only 0–50%, while by RT-qPCR the rates could increase to 0–80%. A total of 33 out of 363 samples (belonging to 68 cultivars) from 20 regions in China were detected to be positive by RT-qPCR (9.1%), which was more than twice the rate of the conventional RT-PCR (3.9%).

Investigation of a cluster epidemic of COVID-19 in Ningbo

Objective: To investigate a cluster epidemic of COVID-19 after a mass gathering activity in Ningbo of Zhejiang province and analyze the transmission chain and status of infection cases of different generations. Methods: The tracking of all the close contacts of the first COVID-19 case and epidemiological investigation were conducted on January 29, 2020 after a cluster epidemic of COVID-19 related with a Buddhism rally on January 19 (the 1.19 rally) in Ningbo occurred. The swabs of nose/throat of the cases and close contacts were collected and tested for nucleic acids by real-time fluorescence quantitative RT-PCR. Results: From January 26 to February 20, 2020, a total of 67 COVID-19 cases and 15 asymptomatic infection cases related with the 1.19 rally were reported in Ningbo. The initial case was the infection source who infected 29 second generation cases and 4 asymptomatic infection cases, in whom 23 second generation cases and 3 asymptomatic infection cases once took bus with the initial case, the attack rate was 33.82% (23/68) and the infection rate was 38.24% (26/68). The risks of suffering from COVID-19 and being infected were 28.91 times and 26.01 times higher in rally participants taking bus with initial case compared with those taking no bus with initial case. In this epidemic, 37 third+generation cases and 11 related asymptomatic infection cases occurred, the attack rate was 2.88% (37/1 283) and the infection rate was 4.76% (48/1 008). The main transmission routes included vehicle sharing and family transmission. Conclusion: It was a cluster epidemic of COVID-19 caused by a super spreader in a massive rally. The epidemic has been under effective control.

Investigation on a cluster epidemic of COVID-19 in a supermarket in Liaocheng, Shandong province

Objective: To explore clustered epidemic of COVID-19 in Liaocheng city and analyze infection status and chain of transmission of the cases. Methods: A joint investigation team of emergency response for COVID-19 epidemic by CDC professional workers of Liaocheng city and district at two levels on January 30, 2020. According to a indicator case from ZH supermarkets, close contacts and related subjects were tracked and screened on February 1, including ZH supermarket employees, family members having contact history with related cases during January 13-26, supermarket clients during January 16-30 and family members of related cases. an epidemiological investigation was carried on and their swab of nose/throat were collected and were sent to Liaocheng CDC laboratory, real-time fluorescence quantitative RT-PCR was used to detect nucleic acids of SARS-CoV-2. Results: a total of 8 437 people were screened during January 30 to February 9, 2020 (120 employees of supermarket, 93 family members, and 8224 clients of supermarket). The epidemic was caused by ZH cases and brought clustered cases in four families. A total 25 cases of SARS-CoV-2 infection, the total infection rate of subjects was 0.30% (25/8 437) with 22 confirmed cases (0.26%, 22/8 437) and 3 asymptomatic patients (0.04%, 3/8 437), asymptomatic patients accounted for 12.00% (3/25) of all infection cases. The infection rates of supermarket employees, family members of confirmed cases and supermarket clients were 9.17% (11/120), 12.90% (12/93) and 0.02% (2/8 224). Conclusions: This was a cluster epidemic caused by one imported case of COVID-19 in a supermarket of Liaocheng city. Prevention and control of cluster epidemic should be focused on chain of community transmission and family cluster cases. It must also be an attention for transmission risk of asymptomatic patients.

Epidemiological characteristics of a case infected with avian influenza A (H5N6) virus associated with exposure to aerosol

Objective: To investigate the epidemiological and clinical characteristics of a case infected with avian influenza A (H5N6) virus associated with exposure to aerosol and provide evidence for the prevention and control of human infection with avian influenza virus. Methods: Epidemiological investigation was conducted to identify the history of exposure, infection route, and disease progression. Real-time fluorescent quantitative RT-PCR was used to test the samples collected from the case, close contacts, environment and poultry market. Results: The case had no history of exposure to live poultry and poultry market. But before the onset the case had a history of exposure to the live poultry placed in a car with doors and windows closed. The samples collected from the case's lower respiratory tract and the remaining frozen chicken meat were all influenza A (H5N6) virus positive. Conclusions: The source of infection was the live poultry, and the infection route might be the exposure to aerosol in a car with doors and windows closed, where the poultry were temporarily stored. It is necessary to promote centralized poultry slaughtering, cold chain distribution and fresh poultry sale, as well as strengthen health education and establish the concept of consuming fresh poultry.

Detection and management of an imported case of Chikungunya fever in Henan

ObjectiveTo understand the epidemiological and etiological characteristics of an imported Chikungunya fever case occurred in Huixian county of Henan province in August 2019 and provide evidence for the prevention and control of the further spread. MethodsThe serum samples of the case, person with co-exposure and contacts as well as mosquito samples were detected with real-time fluorescence quantitative RT-PCR and the virus isolation was conducted, E1 gene of the isolate was sequenced and analyzed by Clustal X and MEGA 7.0. Epidemiological investigation was conducted, and prevention and control measures were taken according to related technical guidelines. ResultsThe serum sample of the case was positive for nucleic acid of Chikungunya virus. The virus isolate (GenBank No. MN432879) belonged to ECSA genotype of Chikungunya virus. In E1 section, the isolate shared 100% nucleotide/amino acid homology of MN432879 with an imported strain (GenBank No. MG912993) in Zhejiang in 2017, and shared 99.4% nucleotide homology and 99.8% amino acid homology with an imported strain (GenBank No. MG925665) isolated in Henan. There was one case with co-exposure and three contacts, all of them showed no clinical manifestations of Chikungunya fever. The breteau index of the epidemic point declined from 9.5 in the first surveillance to 3.2 in the third surveillance and remained at a low level. Mosquito samples were negative for nucleic acid of Chikungunya virus. ConclusionThe imported Chikungunya fever case in Huixian county of Henan was caused by ECSA genotype Chikungunya virus, no further spread occurred in this area.

Protective Effect of Salvianolic Acid B on Intestinal Ischemia-reperfusion Injury in Rats

Objective To investigate the protective effect of salvianolic acid B(SAB)on the intestinal tract of rats after intestinal ischemia-reperfusion injury(IIRI). Methods Forty-eight healthy male SD rats were equally randomized into IIRI group,SAB+IIRI group,sham control group,and SAB+sham control group. The malonyldialdehyde(MDA)level and superoxide dismutase(SOD)activity in the ileum were measured in each group according to the kit instructions,the transcription levels of inflammatory factors in the ileum of rats were detected by real-time fluorescence quantitative RT-PCR,the secretion level of inflammatory factors was detected by ELISA,and the effects of intestinal ischemia-reperfusion on intestinal permeability and histological lesions were measured by histopathology. Results The MDA level in IIRI group was significantly higher than those in negative control group(P=0.005)and SAB+IIRI group(P=0.012). SOD activity of IIRI group was significantly lower than those of negative control group(P=0.006)and SAB+IIRI group(P=0.017). The optical densities of tumor necrosis factor-α(TNF-α)(P=0.003,P=0.009),interleukin(IL)-1β(P=0.026,P=0.005),IL-6(P=0.015,P=0.003),and nuclear factor kappa-B(NF-κB)(P=0.007,P=0.015)in IIRI group were significantly higher than those in sham control group and SAB+IIRI group. The TNF-α(P=0.002,P=0.006),IL-1β(P=0.002,P=0.006),IL-6(P=0.008,P=0.002),and NF-κB(P=0.026,P=0.005)levels in IIRI group were significantly higher than those in sham control group and SAB+IIRI group. The inulin level in IIRI group was significantly lower than that in negative control group(P=0.015)and significantly higher than that in SAB+IIRI group(P=0.011). The dextran level in IIRI group was significantly lower than those in sham control group(P=0.011)and SAB+IIRI group(P=0.012). The dextran gel level in IIRI group was significantly higher than those in sham control group(P=0.031)and SAB+IIRI group(P=0.020). SAB pretreatment remarkably improved the edema,necrosis,and villus stripping of the intestinal mucosa in the ileum of rats. The Chiu score was significantly higher in SAB+sham control group than in sham control group(P=0.001)and was significantly lower in SAB+IIRI group than in IIRI group(P=0.001). Conclusion SAB pretreatment can alleviate IIRI in rat models,and this protective effect may be achieved by alleviating oxidative stress and inflammation in the intestinal tract.

PAF-AH and PLA2 activity of Leptospira interrogans LA_2144 gene product

Objective To analyze the enzymatic activity of Leptospira interrogans (L.interrogans) LA_2144 gene product to hydrolyze platelet activating factor acetylhydrolase (PAF-AH) and phosphatidase A2 (PLA2). Methods Bioinformatic softwares were used to predict transmembrane regions, signal peptides and domains of the LA_2144 gene of L. interrogans strain Lai. A prokaryotic expression system for signal peptide-free LA_2144 gene was established. The expressed target recombinant protein rLep2144 was extracted by Ni-NTA affinity chromatography and then renatured. Spectrometry was used to detect the activity of rLep2144 to hydrolyze PAF-AH substrate 2-thio PAF and the Km and Kcat values as well as the activity to hydrolyze PLA2 substrate arachidonoyl 2-thio PC. Real-time fluorescence quantitative RT-PCR and Western blot were performed to detect the transcription, protein expression and secretion of LA_2144 gene during infection of human and mouse vascular endothelial cells (HUVEC and EOMA) with L. interrogans. Results L. interrogans LA_2144 gene contained a signal peptide and a domain belonging to SGNH hydrolase superfamily, but no transmembrane regions. The established prokaryotic expression system for signal peptide-free LA_2144 gene could efficiently express rLep2144. The extracted rLep2144 was shown as a single protein fragment in separation gel and then successfully renatured. rLep2144 had a stronger PAF-AH activity with the Km and Kcat values of 688.235 μmol/L and 0.976/s, but its PLA2 activity was relatively weak. Expression of the LA_2144 gene at mRNA and protein levels in HUVEC and EOMA was rapidly increased after the cells were infected with L. interrogans (P<0.05) and the secretion of LA_2144 gene product could be detected. Conclusions L. interrogans LA_2144 gene product had a stronger PAF-AH and a certain PLA2 activity, which might involve in the hemorrhage and inflammatory response in leptospirosis. Key words: Leptospira interrogans; LA_2144 gene; PAF-AH; PLA2; Enzymatic activity

Relationship between hs-CRP and the etiology of children with hand-foot-and-mouth disease

Objective To explore the relationship between hs-CRP and the etiology of children with hand-foot-and-mouth disease(HFMD). Methods A total of 1 156 laboratory-confirmed children diagnosed with HFMD by pathogenic detection(detection methods include EV71-CA16 IgM antibody detection and universal real-time fluorescent quantitative RT-PCR detection of enterovirus nucleic acid EV71/CA16/EV) in the Children′s Hospital of Hangzhou were involved in the research from September 2014 to July 2016.The hs-CRP levels in the early days(≤5 days) were recorded, and all data were analyzed with SPSS16.0. Results Of all the 1 156 cases, there were 642 cases with hs-CRP level more than 10mg/dL, of whom 37 cases were infected by EV71(5.8%), 552 cases were infected by EV(86.0%), 53 cases were infected by CA16(8.2%). In 514 cases with hs-CRP level less than 10mg/dL, of whom 298 cases were infected by EV71(58.0%), 152 cases were infected by EV(29.6%), 64 cases were infected by CA16(12.4%). Of cases with hs-CRP>10mg/dL, EV universal type got a significantly higher rate, with statistically significant difference(P<0.05). Of cases with hs-CRP<10mg/dL, EV71 got a significantly higher rate, with statistically significant difference(P<0.05). Conclusion The higher the hs-CRP level of the HFMD, the higher infection rate of EV.The lower the hs-CRP level of the HFMD, the higher infection rate of EV71. Key words: Enterovirus infections; Fluorescent antibody technique; Virulence factors; C-reactive protein; Hand-foot-and-mouth disease; Etiology detection