Objective:To realize prokaryotic expression, purification and identification of 2019-novel Coronavirus (2019-nCoV) nucleocapsid protein (NP), and apply it to the serological diagnosis.Methods:The synthetic 2019-nCoV NP gene was cloned into the prokaryotic expression vector pET28a to construct expression plasmid, and then purified by Ni-chelating affinity. SDS-polyacrylamide gel electrophoresis (SDS-PAGE), indirect enzyme-linked immunosorbent assay (ELISA), Western blot (WB), and immunochromatography were used to test the purified protein. Indirect ELISA reaction conditions were optimized for serum antibody detection.Results:The relative molecular mass of recombinant NP was about 50×10 3 after SDS-PAGE electrophoresis, which was consistent with the expectation. Indirect ELISA and WB results showed that it could specifically bind to the serum of patients infected with 2019-nCoV. The detection limit of NP was 0.2 ng/ml by immunochromatography. The sera from 32 patients infected with 2019-nCoV and the control sera were detected by indirect ELISA, and the results showed that they were clearly clustered. Conclusions:Prokaryotic expression of 2019-nCoV NP has good immunogenicity and can be used for the development of serological diagnostic reagents.

OBJECTIVE To analyze the risk factors contributing to piracetam-associated thrombocytopenia and develop a predictive model for risk prediction. METHODS The electronic medical record information of inpatients treated with piracetam was collected retrospectively from the First Affiliated Hospital of Guangxi Medical University from January 2021 to December 2023， including gender， age， underlying diseases， combined medication， and laboratory data， etc. Patients were divided into the occurrence group and the non-occurrence group according to whether thrombocytopenia occurred， and the differences in clinical data between the two groups were compared. The independent risk factors were determined through univariate/multivariate Logistic regression analysis. A nomogram was drawn to visually present the independent risk factors， and a risk prediction model was constructed. The predictive efficacy of the model was evaluated using the receiver operating characteristic （ROC） curve， Bootstrap internal validation and calibration curve. RESULTS A total of 224 patients were included， among which 196 cases were in the non- occurrence group and 28 cases in the occurrence group. The incidence of thrombocytopenia was 12.50%. The results of the univariate Logistic regression analysis showed that the proportion of patients using three or more combined antibiotics and the level of serum creatinine in the occurrence group were significantly higher than those in the non-occurrence group， while the level of hemoglobin was significantly lower （P＜0.05）. The results of the multivariate Logistic regression analysis revealed that the use of three or more combined antibiotics， low hemoglobin level and high serum creatinine level were independent risk factors for piracetam-associated thrombocytopenia （P＜0.05）. The constructed risk prediction model was LogitP＝ －1.114+1.256×three or more combined antibiotics－0.017×hemoglobin level+0.009×serum creatinine level. The AUC of the ROC curve of this model was 0.757， and the optimal cut-off value was 0.474； the AUC of the ROC curve of the Bootstrap internal validation was 0.733； the apparent curve and the bias-corrected curve were close to the ideal curve. CONCLUSIONS The use of three or more antibiotics， along with low hemoglobin level and high serum creatinine level， are identified as independent risk factors for piracetam-associated thrombocytopenia. The developed risk prediction model demonstrates good predictive value.