Genomic similarity and antibody-dependent enhancement of immune serum potentially affect the protective efficacy of commercial MLV vaccines against NADC30-like PRRSV

Porcine reproductive and respiratory syndrome(PRRS)is one of the most significant diseases affecting the pig industry worldwide.The PRRSV mutation rate is the highest among the RNA viruses.To date,NADC30-like PRRSV and highly pathogenic PRRSV(HP-PRRSV)are the dominant epidemic strains in China;however,commercial vaccines do not always provide sufficient cross-protection,and the reasons for insufficient protection are unclear.This study isolated a wild-type NADC30-like PRRSV,SX-YL1806,from Shaanxi Province.Vaccination challenge experiments in piglets showed that commercial modified live virus(MLV)vaccines provided good protection against HP-PRRSV.However,it could not provide sufficient protection against the novel strain SXYL1806.To explore the reasons for this phenomenon,we compared the genomic homology between the MLV strain and HP-PRRSV or NADC30-like PRRSV and found that the MLV strain had a lower genome similarity with NADC30-like PRRSV.Serum neutralization assay showed that MLV-immune serum slightly promoted the homologous HP-PRRSV replication and significantly promoted the heterologous NADC30-like PRRSV strain replication in vitro,suggesting that antibody-dependent enhancement(ADE)might also play a role in decreasing MLV protective efficacy.These findings expand our understanding of the potential factors affecting the protective effect of PRRSV MLV vaccines against the NADC30-like strains.

Identification of African swine fever virus MGF505-2R as a potent inhibitor of innate immunity in vitro

African swine fever(ASF)is etiologically an acute,highly contagious and hemorrhagic disease caused by African swine fever virus(ASFV).Due to its genetic variation and phenotypic diversity,until now,no efficient commercial vaccines or therapeutic options are available.The ASFV genome contains a conserved middle region and two flexible ends that code for five multigene families(MGFs),while the biological functions of the MGFs are not fully characterized.Here,ASFV MGF505-2R-deficient mutant ASFV-Δ2R was constructed based on a highly virulent genotype II field isolate ASFV CN/GS/2018 currently circulating in China.Transcriptomic profiling demonstrated that ASFV-Δ2R was capable of inducing a larger number of differentially expressed genes(DEGs)compared with ASFV CN/GS/2018.Hierarchical clustering of up-regulated DEGs revealed that ASFV-Δ2R induced the most dramatic expression of interferon-related genes and inflammatory and innate immune genes,as further validated by RT-qPCR.The GO and KEGG pathway analysis identified significantly enriched pathways involved in pathogen recognition and innate antiviral immunity.Conversely,pharmacological activation of those antiviral immune responses by exogenous cytokines,including type I/II IFNs,TNF-αand IL-1β,exerted combinatory effects and synergized in antiviral capacity against ASFV replication.Collectively,MGF505-2R is a newly identified inhibitor of innate immunity potentially implicated in immune evasion.

一种基于猪流行性腹泻病毒S1蛋白的单域抗体的阻断ELISA方法及其评价

文中旨在利用猪流行性腹泻病毒(Porcine epidemic diarrhea virus,PEDV)S1蛋白生物素化纳米抗体建立一种阻断酶联免疫吸附试验(Blocking enzyme-linked immunosorbent assay,bELISA)方法,用于检测猪体内PEDV抗体水平及疫苗免疫效果的评估。对PEDVS1蛋白的特异性单域抗体(Single-domain antibodies,sdAb)sdAb3基因进行扩增,并在3′端融合Avitag序列,构建至原核表达载体pET21b,进行sdAb3-Avitag蛋白诱导表达纯化。对纯化的sdAb3-Avitag融合蛋白进行生物素标记并鉴定其活性。以PEDV重组S1蛋白为抗原,通过对各反应条件进行摸索与优化,建立一种可靠灵敏的bELISA方法应用于血清样品检测,并与商品化试剂盒检测进行比价。成功构建重组载体pET21b-sdAb3-Avitag并诱导表达出sdAb3-Avitag蛋白。体外生物素标记的sdAb3(sdAb3-Biotin)具有良好的活性。所构建的bELISA方法中,最适参数为:S1蛋白的包被浓度200 ng/孔;血清稀释比例1︰2,血清孵育时间2 h;sdAb3-Biotin稀释比1︰8000,孵育时间30 min;酶标抗体稀释比例1︰5000,反应时间30 min。所建立的方法与猪传染性胃肠炎病毒、猪繁殖与呼吸综合征病毒等主要猪源病毒的阳性血清均无交叉反应,具有良好的特异性和重复性。利用建立的bELISA方法对临床54份猪血清样品进行检测,结果显示,该方法与商品化试剂盒检测结果具有92.56%的总体符合率。文中建立了一种省时可靠的bELISA方法,可用于PEDV的临床监测和疫苗免疫效果评估。

基于CRISPR/Cas9技术的高通量筛选平台:发掘病毒复制相关宿主分子的新途径

病毒作为严格的细胞内寄生生物,需要多种宿主蛋白辅助其完成生命周期。寻找与病毒复制相关的宿主因子并揭示其作用机制,将有助于阐明病毒的感染机制,为疫病的防治提供新靶标。与RNA干扰技术相比,近年来兴起的CRISPR/Cas9技术能更特异、高效、准确地实现基因组编辑,因而在功能基因研究中得到更广泛应用。而基于CRISPR/Cas9系统的宿主全基因组sgRNA文库高通量筛选技术平台,可快速发现参与病毒侵入、复制等生物学过程的关键宿主因子,通过明确病毒-宿主分子相互作用进而揭示病毒的生命周期,为分子病毒学和免疫学提供了强大的研究工具。本文主要总结了基于CRISPR/Cas9技术的高通量筛选平台的具体筛选流程,归纳和讨论了该平台在筛选调控病毒复制相关宿主因子中的应用现状和发展前景。

Host metabolism dysregulation and cell tropism identification in human airway and alveolar organoids upon SARS-CoV-2 infection

The coronavirus disease 2019(COVID-19)pandemic is caused by infection with the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),which is spread primary via respiratory droplets and infects the lungs.Currently widely used cell lines and animals are unable to accurately mimic human physiological conditions because of the abnormal status of cell lines(transformed or cancer cells)and species differences between animals and humans.Organoids are stem cell-derived selforganized three-dimensional culture in vitro and model the physiological conditions of natural organs.Here we showed that SARS-CoV-2 infected and extensively replicated in human embryonic stem cells(hESCs)-derived lung organoids,including airway and alveolar organoids which covered the complete infection and spread route for SARS-CoV-2 within lungs.The infected ceils were ciliated,club,and alveolar type 2(AT2)cells,which were sequentially located from the proximal to the distal airway and terminal alveoli,respectively.Additionally,RNA-seq revealed early cell response to virus infection including an unexpected downregulation of the metabolic processes,especially lipid metabolism,in addition to the well-known upregulation of immune response.Further,Remdesivir and a human neutralizing antibody potently inhibited SARS-CoV-2 replication in lung organoids.Therefore,human lung organoids can serve as a pathophysiological model to investigate the underlying mechanism of SARS-CoV-2 infection and to discover and test therapeutic drugs for COVID-19.

Environmental surveillance of SARS-CoV-2 RNA in wastewater systems and related environments in Wuhan:April to May of 2020

Wastewater-based epidemiology(WBE)has emerged as an effective environmental surveillance tool in monitoring fecal-oral pathogen infections within a community.Congruently,SARS-Co V-2,the etiologic agent of COVID-19,has been demonstrated to infect the gastrointestinal tissues,and be shed in feces.In the present study,SARS-Co V-2 RNA was concentrated from wastewater,sludge,surface water,ground water,sediment,and soil samples of municipal and hospital wastewater systems and related environments in Wuhan during the COVID-19 middle and low risk periods,and the viral RNA copies quantified using reverse transcription quantitative polymerase chain reaction(RT-q PCR).From the findings of this study,during the middle risk period,one influent sample and three secondary effluents collected from waste water treatment plant 2,as well as two samples from Jinyintan Hospital wastewater system influent were SARS-Co V-2 RNA positive.One sludge sample collected from Guanggu Branch of Tongji Hospital,which was obtained during the low risk period,was also positive for SARS-Co V-2 RNA.These study findings demonstrate the significance of WBE in continuous surveillance of SARS-Co V-2 at the community level,even when the COVID-19 prevalence is low.Overall,this study can be used as an important reference for contingency management of wastewater treatment plants and COVID-19 prevention and control departments of Wuhan.

SARS-CoV-2 Does Not Replicate in Aedes Mosquito Cells nor Present in Field-Caught Mosquitoes from Wuhan

Dear Editor,Severe acute respiratory syndrome coronavirus 2(SARSCoV-2), the etiologic agent of COVID-19, is an enveloped,positive-sense single-stranded RNA virus that first discovered in December 2019 from a seafood market in Wuhan, China(Zhou et al. 2020).