In order to study whether there is a direct interaction between the key variant gene(AP-PV-YN-Mut)protein of atypical porcine pestivirus(APPV)Yunnan strain and the host protein signal sequence receptor subunit 4(SSR4),the physical and chemical properties,spatial structure and subcellular localization of SSR4 protein were analyzed and predicted using online software such as ProtParam,PredictProtein and TMHMM.The recombinant vectors pCMV-Tag4A-SSR4 and pET-GST-Mut were constructed for GST pull-down test in vitro.The recombinant vectors pBiFC-VN173-SSR4 and pBiFC-VC155-Mut were constructed and the bimolecular fluorescence comple-mentary test(BiFC)was performed in cells to verify whether there was direct interaction between APPV-YN-Mut and host protein SSR4 in vitro and in cells.The results showed that SSR4 protein was a hydrophobic stable protein with no transmembrane structure and signal peptide.The second-ary structure was mainly irregular curl,and the tertiary structure was stable,mainly located in the endoplasmic reticulum.GST pull-down and BiFC experiments showed that APPV-YN-Mut interac-ted directly with host protein SSR4 in vitro and in cells.

In order to study whether there is a direct interaction between the key variant gene(AP-PV-YN-Mut)protein of atypical porcine pestivirus(APPV)Yunnan strain and the host protein signal sequence receptor subunit 4(SSR4),the physical and chemical properties,spatial structure and subcellular localization of SSR4 protein were analyzed and predicted using online software such as ProtParam,PredictProtein and TMHMM.The recombinant vectors pCMV-Tag4A-SSR4 and pET-GST-Mut were constructed for GST pull-down test in vitro.The recombinant vectors pBiFC-VN173-SSR4 and pBiFC-VC155-Mut were constructed and the bimolecular fluorescence comple-mentary test(BiFC)was performed in cells to verify whether there was direct interaction between APPV-YN-Mut and host protein SSR4 in vitro and in cells.The results showed that SSR4 protein was a hydrophobic stable protein with no transmembrane structure and signal peptide.The second-ary structure was mainly irregular curl,and the tertiary structure was stable,mainly located in the endoplasmic reticulum.GST pull-down and BiFC experiments showed that APPV-YN-Mut interac-ted directly with host protein SSR4 in vitro and in cells.

Objective:To analyze the risk factors of bronchopulmonary dysplasia(BPD)in very preterm infants(VPI), and to provide scientific basis for the prevention and treatment of BPD in VPI.Methods:A prospective multicenter study was designed to collect the clinical data of VPI in department of neonatology of 28 hospitals in 7 regions from September 2019 to December 2020.According to the continuous oxygen dependence at 28 days after birth, VPI were divided into non BPD group and BPD group, and the risk factors of BPD in VPI were analyzed.Results:A total of 2 514 cases of VPI including 1 364 cases without BPD and 1 150 cases with BPD were enrolled.The incidence of BPD was 45.7%.The smaller the gestational age and weight, the higher the incidence of BPD( P<0.001). Compared with non BPD group, the average birth age, weight and cesarean section rate in BPD group were lower, and the incidence of male infants, small for gestational age and 5-minute apgar score≤7 were higher( P<0.01). In BPD group, the incidences of neonatal respiratory distress syndrome(NRDS), hemodynamically significant patent ductus arteriosus, retinopathy of prematurity, feeding intolerance, extrauterine growth restriction, grade Ⅲ~Ⅳ intracranial hemorrhage, anemia, early-onset and late-onset sepsis, nosocomial infection, parenteral nutrition-associated cholestasis were higher( P<0.05), the use of pulmonary surfactant(PS), postnatal hormone exposure, anemia and blood transfusion were also higher, and the time of invasive and non-invasive mechanical ventilation, oxygen use and total hospital stay were longer( P<0.001). The time of starting enteral nutrition, cumulative fasting days, days of reaching total enteral nutrition, days of continuous parenteral nutrition, days of reaching 110 kcal/(kg·d) total calorie, days of reaching 110 kcal/(kg·d) oral calorie were longer and the breastfeeding rate was lower in BPD group than those in non BPD group( P<0.001). The cumulative doses of amino acid and fat emulsion during the first week of hospitalization were higher in BPD group( P<0.001). Multivariate Logistic regression analysis showed that NRDS, invasive mechanical ventilation, age of reaching total enteral nutrition, anemia and blood transfusion were the independent risk factors for BPD in VPI, and older gestational age was the protective factor for BPD. Conclusion:Strengthening perinatal management, avoiding premature delivery and severe NRDS, shortening the time of invasive mechanical ventilation, paying attention to enteral nutrition management, reaching whole intestinal feeding as soon as possible, and strictly mastering the indications of blood transfusion are very important to reduce the incidence of BPD in VPI.