Objective To prepare virus-like particles (VLPs) for yellow fever virus (YFV) using the pACYCDuet-1 single-plasmid dual expression system. Methods Gene fragments including NS1, NS5, and 5' untranslated region (UTR) and 3' UTR fragment of YFV were cloned into the expression plasmid pACYCDuet-1-MS2-TMpac (carrying MS2 coat protein gene) and transformed into E. coli BL21(DE3) for expression. VLPs were observed by TEM. After DNase I/RNase A digestion, RNA was extracted and transcribed into cDNA, which was subjected to fluorescence quantitative PCR detection. Results According to SN/T 3560-2013, double digestion and colony PCR of pACYCDuet-1-MS2-TMpac-YFV both produced expected bands. SDS-PAGE showed a target band at 25-35 kDa. RT-PCR amplified VLPs after enzyme digestion, and TEM revealed VLPs with clear edges and translucent interiors. Thus, the plasmid was successfully constructed, and the phage coat protein packaged YFV genes with nuclease resistance. Conclusion VLPs containing specific gene fragments of yellow fever virus have been successfully prepared. These nuclease-resistant VLPs can serve as safe and stable quality control materials to ensure the reliability of laboratory detection for YFV.

BackgroundGraduate students frequently face life events， many of which may adversely affect their mental well-being. However， the interaction between life events and the development of depression， anxiety， and somatic symptoms remains unclear. ObjectiveTo explore the relationship between life events and the development of depressive， anxiety and somatic symptoms in graduate students， thereby informing prevention strategies for these conditions. MethodsA sample of 6 722 newly enrolled graduate students at a comprehensive university in Southwest China from September to November 2018 was selected. The assessment was conducted using the Adolescent Self-rating Life Events Checklist （ASLEC）， the 7-item Generalized Anxiety Disorder scale-7 item （GAD-7）， the Patient Health Questionnaire Depression Scale-9 item （PHQ-9）， and the Patient Health Questionnaire-15 （PHQ-15）. Network analysis was implemented by using the bootnet and qgraph packages in the R software （version 4.2.3）， with centrality indices calculated to identify core and bridge symptoms within the network. ResultsThe study encompassed a total of 6 171 graduate students， representing 91.80% of the target population. The prevalence rates of anxiety， depressive， and somatic symptoms among graduate students were 12.59% （777/6 171）， 16.63% （1 026/6 171）， and 27.66% （1 707/6 171）， respectively. Network analysis revealed that 'academic stress' was the core symptom with the highest strength and expected influence （both values=1.207）， while 'feeling down， depressed， or hopeless' was the bridge symptom with the highest bridge strength and bridge expected influence （both values=0.454）. There was no significant difference in global network strength and edge weight between women and men （P>0.05）. ConclusionAcademic stress， emerging as the core symptom， assumes a dominant position within the symptom network and exhibits strong interactions with other negative affective states. There was no gender difference in the network structure.

Influenza vaccination is considered the most effective measure to prevent the occurrence and pandemic of influenza.Beijing has implemented free influenza vaccination policy to the elderly above 60 years old and students in middle and primary schools since 2007.To provide a more effective intervention and let influenza vaccination achieve its role of immune protection among the population,the influenza vaccination rate and its influencing factors,barriers and driving factors of free influenza vaccination for recipients in Beijing have been studied successively.This article aims to summarize previous findings,review social factors influencing the vaccination and introduce the experience and lesson learnt from Beijing.