Protection against Pseudomonas aeruginosa lung infection in mice by recombinant OprF-pulsed dendritic cell immunization

Background

Porcine reproductive and respiratory syndrome (PRRS) has now been widely recognized as an economically important disease. The objective of this study was to compare the molecular and biological characteristics of porcine reproductive and respiratory syndrome virus (PRRSV) field isolates in China to those of the modified live virus (MLV) PRRS vaccine and its parent strain (ATCC VR2332).

Results

Five genes (GP2, GP3, GP4, GP5 and NSP2) of seven isolates of PRRSV from China, designated LS-4, HM-1, HQ-5, HQ-6, GC-2, GCH-3 and ST-7/2008, were sequenced and analyzed. Phylogenetic analyses based on the nucleotide sequence of the ORF2-5 and NSP2 showed that the seven Chinese isolates belonged to the same genetic subgroup and were related to the North American PRRSV genotype. Comparative analysis with the relevant sequences of another Chinese isolate (BJ-4) and North American (VR2332 and MLV) viruses revealed that these isolates have 80.8-92.9% homology with VR-2332, and 81.3-98.8% identity with MLV and 80.7-92.9% with BJ-4. All Nsp2 nonstructural protein of these seven isolates exhibited variations (a 29 amino acids deletion) in comparison with other North American PRRSV isolates. Therefore, these isolates were novel strain with unique amino acid composition. However, they all share more than 97% identity with other highly pathogenic Chinese PRRSV strains. Additionally, there are extensive amino acid (aa) mutations in the GP5 protein and the Nsp2 protein when compared with the previous isolates.

Conclusions

These results might be useful to study the genetic diversity of PRRSV in China and to track the infection sources as well as for vaccines development.     

Genetic diversity of the ORF5 gene of porcine reproductive and respiratory syndrome virus isolates in southwest China from 2007 to 2009

To gain insight into the molecular epidemiology and possible mechanisms of genetic variation of porcine reproductive and respiratory syndrome (PRRS) in Yunnan Province of China, the ORF5 gene of 32 PRRSV isolates from clinical samples collected from 2007 to 2009 were sequenced and analyzed. Nucleotide and amino acid analyses were carried out on 32 isolates and representative strains of the North American genotype, European genotype and two representative Chinese isolates. Results revealed that these isolates share 86.9-99.0% nucleotide and 87.5-98.0% amino acid identity with VR-2332 the prototypical North American PRRSV, 61.7-62.9% and 54.3-57.8% with Lelystad virus (LV) the representative strain of European genotype, 91.2-95.4% and 90.0-94.5% with CH-1a that was isolated in mainland China in 1996, 88.1-99.3% and 85.5-99.0% with JX-A1 the representative strain of High pathogenic PRRSV in China, and 86.2-99.8% and 85.5-100.0% between isolated strains of different years, respectively. Phylogenetic analysis revealed that all 32 PRRSV isolates belonged to the North American genotype and were further divided into two different subgenotypes. Subgenotype 1 comprised twenty two Yunnan isolates which divided into two branches. Subgenotype 2 comprised ten isolates which closely related to the RespPRRS vaccine and its parent strain VR-2332. The functional domains of GP5 such as the signal peptide, ectodomain, transmembrane regions and endodomain were identified and some motifs in GP5 with known functions, such as primary neutralizing epitope (PNE) and decoy epitope were also further analyzed. Our study shown the great genetic diversity of PRRSV in southwest China, rendering the guide for control and prevention of this disease.     

Genetic Variation of Chinese PRRSV Strains Based on ORF5 Sequence

Thirteen isolates of porcine reproductive and respiratory syndrome virus (PRRSV) from different provinces of China were studied and compared with several PRRSV isolates from other countries. Phylogenetic analysis shows that all Chinese isolates of PRRSV in this study belong to the American genotype, except for one strain, B13, which clustered as a European genotype. Sequence analysis revealed that PRRSV Chinese isolates of the American genotype were highly similar in the ORF5 sequence and could be classified into two subclades. One contains PRRSV isolates that are more closely related to the American vaccine strain MLV Resp and its parent strain VR-2332, and the other contains ones only distantly related to them. Within the Chinese isolates slight genetic variation occurred, and some strains may originate directly from the vaccine virus.     

Characterization of emerging European-like porcine reproductive and respiratory syndrome virus isolates in the United States

European-like field isolates of porcine reproductive and respiratory syndrome virus (PRRSV) have recently emerged in North America. The full-length genomic sequence of an index isolate characterized in 1999, strain EuroPRRSV, served as the reference strain for further studies of the evolution and epidemiology of European-like isolates (type 1) in the United States. Strain EuroPRRSV shared 90.1 to 100% amino acid identity with the prototype European strain, Lelystad, within the structural and nonstructural open reading frames (ORFs) and 95.3% overall nucleotide identity. The 5' untranslated region and two nonstructural regions within ORF 1 were closely examined due to significant divergence from strain Lelystad. A 51-bp deletion in a region within ORF 1a, coding for nonstructural protein 2 (NSP2), was observed. Sequence analysis of the structural ORFs 2 to 7 of additional European-like isolates indicated that these isolates share 93% nucleotide identity with one another and 95 to 96% identity with the Lelystad strain but only 70% identity with the North American reference strain VR-2332. Phylogenetic analysis with published PRRSV ORF 3, 5, and 7 nucleotide sequences indicated that these newly emerging isolates form a clade with the Lelystad and United Kingdom PRRSV isolates. Detailed analysis of four of these isolates with a panel of 60 monoclonal antibodies directed against the structural proteins confirmed a recognition pattern that was more consistent with strain Lelystad than with other North American isolates.     

Emergence of fatal PRRSV variants: unparalleled outbreaks of atypical PRRS in China and molecular dissection of the unique hallmark

Porcine reproductive and respiratory syndrome (PRRS) is a severe viral disease in pigs, causing great economic losses worldwide each year. The causative agent of the disease, PRRS virus (PRRSV), is a member of the family Arteriviridae. Here we report our investigation of the unparalleled large-scale outbreaks of an originally unknown, but so-called "high fever" disease in China in 2006 with the essence of PRRS, which spread to more than 10 provinces (autonomous cities or regions) and affected over 2,000,000 pigs with about 400,000 fatal cases. Different from the typical PRRS, numerous adult sows were also infected by the "high fever" disease. This atypical PRRS pandemic was initially identified as a hog cholera-like disease manifesting neurological symptoms (e.g., shivering), high fever (40-42 degrees C), erythematous blanching rash, etc. Autopsies combined with immunological analyses clearly showed that multiple organs were infected by highly pathogenic PRRSVs with severe pathological changes observed. Whole-genome analysis of the isolated viruses revealed that these PRRSV isolates are grouped into Type II and are highly homologous to HB-1, a Chinese strain of PRRSV (96.5% nucleotide identity). More importantly, we observed a unique molecular hallmark in these viral isolates, namely a discontinuous deletion of 30 amino acids in nonstructural protein 2 (NSP2). Taken together, this is the first comprehensive report documenting the 2006 epidemic of atypical PRRS outbreak in China and identifying the 30 amino-acid deletion in NSP2, a novel determining factor for virulence which may be implicated in the high pathogenicity of PRRSV, and will stimulate further study by using the infectious cDNA clone technique.     

Molecular characterization of ORFs 2 to 7 of Korean porcine reproductive and respiratory syndrome virus (CA) and its protein expression by recombinant baculoviruses

To determine the characteristics of the Korean porcine reproductive and respiratory syndrome virus (PRRSV), CA, which was isolated from the serum of an infected pig in 2006, we investigated the nucleotide sequence and expression of the structural ORFs (ORFs 2 to 7) using the bApGOZA system. We found that the structural ORFs 2 to 7 of CA consisted of 3188 nucleotides that were the same as those formed from VR-2332. Comparison of the CA with the other strains revealed nucleotide sequence identity ranging from 89.8 to 99.5%. To better understand the genetic relationships between other strains, phylogenetic analyses were performed. The CA strain was closely related to the other North American genotype strains but formed a distinct branch with high bootstrap support. Additionally, expression levels of the PRRSV proteins in insect cells were strong or partially weak. The results of this study have implications for both the taxonomy of PRRSV and vaccine development.     

猪繁殖与呼吸综合征病毒核衣壳蛋白基因的克隆与原核表达研究

采用RT—PCR方法自猪繁殖与呼吸综合征病毒基因组分离出核衣壳蛋白基因(ofr7),克隆到pMDl8—T载体构建成重组质粒pMDl8N并进行测序比较,结果表明,所克隆的核衣壳蛋白基因序列与PRRSV美洲型ATCCVR—2332株的同源性为100％,表明ofr7是PRRSV基因组内很保守的序列;将ofr7亚克隆到原核表达载体pGEX—KG,构建成重组质粒pGEX—KGN,用pGEX—KGN转化表达菌株BL21,经SDS—PAGE和Western-blot分析表明：克隆在谷胱苷肽转移酶(Glutathione S-transferase(GST)下游的核衣壳蛋白基因与GST获得了高效融合表达,表达的融合蛋白GST—N分子量约为41kDa,并且有免疫学反应活性;这为猪繁殖与呼吸综合征的血清学诊断方法的建立打下了基础。     

Genetic analysis of ORF5 porcine reproductive and respiratory syndrome virus isolated in Vietnam

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important swine pathogens because it is highly infectious and causes economic losses due to decreased pig productivity. In this study, the 603 bp complete major envelope protein encoding gene (ORF5) of 32 field PRRSV isolates from Vietnam collected during 2008–2012 were sequenced and analyzed. Multiple nucleotide (nt) and deduced amino acid (aa) alignments of ORF5 were performed on the 32 isolates: the representative strains (European and North American genotypes), Chinese strains available in GenBank and vaccine strains licensed for use in Vietnam. The results showed 94.8–100.0% nt identity and 94.0–100% aa similarity among the 32 isolates. These isolates shared similarities with the prototype of the North American PRRSV strain (VR‐2332; nt 87.8–89.3%, aa 87.5–90.0%), and Lelystat virus, the prototype of the European PRRSV strain (LV; nt 61.1–61.9%, aa 55.1‐57.0%). There was greater similarity with QN07 (nt 96.5‐98.5%, aa 96.0‐99.0%) from the 2007 PRRS outbreak in QuangNam Province, CH‐1a (nt 93.2–95.1%, 91.5–93.5%) isolated in China in 1995 and JXA1 (nt 96.5–98.6%, aa 95.0–98.0%), the highly pathogenic strain from China isolated in 2006. The Vietnamese isolates were more similar to JXA1‐R (nt 96.5–98.6%, aa 95.0–98.0%), the strain used in Chinese vaccines, than to Ingelvac MLV/BSL‐PS (nt 87.2–89.0%, aa 86.0–89.0%). Phylogenetic analysis showed that the 32 isolates were of the North American genotype and classified into sub‐lineage 8.7. This sub‐lineage contains highly pathogenic Chinese PRRSV strains. This study documents genetic variation in circulating PRRSV strains and could assist more effective use of PRRS vaccines in Vietnam.     

Generation of an infectious clone of VR-2332, a highly virulent North American-type isolate of porcine reproductive and respiratory syndrome virus

A full-length cDNA clone of the prototypical North American porcine reproductive and respiratory syndrome virus (PRRSV) isolate VR-2332 was assembled in the plasmid vector pOK(12). To rescue infectious virus, capped RNA was transcribed in vitro from the pOK(12) clone and transfected into BHK-21C cells. The supernatant from transfected monolayers were serially passaged on Marc-145 cells and porcine pulmonary alveolar macrophages. Infectious PRRSV was recovered on Marc-145 cells as well as porcine pulmonary macrophages; thus, the cloned virus exhibited the same cell tropism as the parental VR-2332 strain. However, the cloned virus was clearly distinguishable from the parental VR-2332 strain by an engineered marker, a BstZ17I restriction site. The full-length cDNA clone had 11 nucleotide changes, 2 of which affected coding, compared to the parental VR-2332 strain. Additionally, the transcribed RNA had an extra G at the 5' end. To examine whether these changes influenced viral replication, we examined the growth kinetics of the cloned virus in vitro. In Marc-145 cells, the growth kinetics of the cloned virus reflected those of the parental isolate, even though the titers of the cloned virus were consistently slightly lower. In experimentally infected 5.5-week-old pigs, the cloned virus produced blue discoloration of the ears, a classical clinical symptom of PRRSV. Also, the seroconversion kinetics of pigs infected with the cloned virus and VR-2332 were very similar. Hence, virus derived from the full-length cDNA clone appeared to recapitulate the biological properties of the highly virulent parental VR-2332 strain. This is the first report of an infectious cDNA clone based on American-type PRRSV. The availability of this cDNA clone will allow examination of the molecular mechanisms behind PRRSV virulence and attenuation, which might in turn allow the production of second-generation, genetically engineered PRRSV vaccines.     

我国猪繁殖与呼吸综合征病毒NT0901分离株分子特征

猪繁殖与呼吸综合征病毒(PRRSV)是目前引起国内外养猪业严重经济损失的重要病原之一,病毒基因和毒力变异较大。PRRSV NT0801株分离自我国发病猪群,毒力较强,但NSP2基因不存在高致病性PRRSV 30个氨基酸的缺失。为了进一步阐明该分离株的分子特征,本研究对该毒株全基因序列进行了测定和分析,结果该毒株基因组全长15 439 bp,其中包含29 nt Poly(A)。与高致病性PRRSV毒株JXA1比较,核酸序列同源性为96.7%,推导的GP3和GP5氨基酸序列同源性分别为97.2%和98.5%,但NSP2基因无30个氨基酸的缺失;与传统型毒株ch-1a比较,推导的GP3和GP5氨基酸序列同源性分别为92.9%和91.5%;基因进化树分析结果显示其介于高致病性和传统PRRSV毒株之间。与其它不同毒力PRRSV分离株基因序列比较,未发现明显重组信号。不同毒力毒株氨基酸残基比对分析结果显示,15个位点潜在毒力相关氨基酸残基中,该毒株有9个与高致病性PRRSV毒株一致,3个与高致病性PRRSV毒株不同,但与传统型和JXA1疫苗株相同,1个位点只与JXA1疫苗株相同,2个与其它毒株都不相同。表明该分离株与高致病性PRRSV密切相关,PRRSV流行毒株变异与基因突变有关,从而为该病毒毒力基因定位研究奠定了基础。     

我国两个不同地区猪繁殖和呼吸综合征病毒分离株ORF5基因序列比例

猪繁殖和呼吸综合征病毒(porcine reproductive and respiratory syndrome virus,PRRSV)为动脉炎病毒科成员之一,可引起感染母猪流产、死胎及断奶仔猪呼吸困难和死亡.该病毒呈球形,有囊膜,大小45nm～83nm,基因组为单股RNA,大小约15kb,有8个阅读框(ORF),分别编码2种非结构蛋白和6种结构蛋白,其中ORF5编码病毒糖基化膜蛋白(GP5)[1,2].GP5蛋白为该病毒主要结构蛋白之一,含有病毒线性中和抗原表位.该蛋白可诱导感染细胞发生细胞凋亡[3,4].目前,PRRSV有欧洲型和美州型两个血清型,其结构蛋白基因同源性为54%～70%[5,6].不同美洲型PRRSV野毒株基因也有一定差异.由ORF5基因推导的氨基酸序列有4个相对保守区,但其N端和C端氨基酸残基可变性较大.由该基因构建的重组质粒具有良好免疫原性[7,8].尽管一些欧美国家已普遍使用Resp PRRS弱毒疫苗,但该病仍时有发生[9,10].我国于1996年亦已证实存在该病,并有不断蔓延趋势,已造成我国养猪业严重经济损失.     

Complete genome sequence of two novel Chinese virulent porcine reproductive and respiratory syndrome virus variants

A highly pathogenic strain of porcine reproductive and respiratory syndrome virus (PRRSV), characterized by a discontinuous 30-amino-acid deletion in its Nsp2-coding region, has been emerging in China since 2006. Here, we report the complete genomic sequence of two novel Chinese virulent PRRSV variants with additional NSP2-gene deletions, which will help us understand the molecular and evolutionary characteristics of PRRSV in Asia.     

Clinical and biochemical indexes from 2019-nCoV infected patients linked to viral loads and lung injury

The outbreak of the 2019-nCoV infection began in December 2019 in Wuhan,Hubei province,and rapidly spread to many provinces in China as well as other countries.Here we report the epidemiological,clinical,laboratory,and radiological characteristics,as well as potential biomarkers for predicting disease severity in 2019-nCoV-infected patients in Shenzhen,China.All 12 cases of the 2019-nCoV-infected patients developed pneumonia and half of them developed acute respiratory distress syndrome (ARDS).The most common laboratory abnormalities were hypoalbuminemia,lymphopenia,decreased percentage of lymphocytes (LYM) and neutrophils (NEU),elevated C-reactive protein (CRP) and lactate dehydrogenase (LDH),and decreased CD8 count.The viral load of 2019-nCoV detected from patient respiratory tracts was positively linked to lung disease severity.ALB,LYM,LYM (%),LDH,NEU (%),and CRP were highly correlated to the acute lung injury.Age,viral load,lung injury score,and blood biochemistry indexes,albumin (ALB),CRP,LDH,LYM (%),LYM,and NEU (%),may be predictors of disease severity.Moreover,the AngiotensinⅡlevel in the plasma sample from 2019-nCoV infected patients was markedly elevated and linearly associated to viral load and lung injury.Our results suggest a number of potential diagnosis biomarkers and angiotensin receptor blocker (ARB) drugs for potential repurposing treatment of 2019-nCoV infection.     

Signal Peptide Cleavage from GP5 of PRRSV: A Minor Fraction of Molecules Retains the Decoy Epitope,a Presumed Molecular Cause for Viral Persistence

Porcine reproductive and respiratory syndrome virus (PRRSV) is the major pathogen in the pig industry. Variability of the antigens and persistence are the biggest challenges for successful control and elimination of the disease. GP5, the major glycoprotein of PRRSV, is considered an important target of neutralizing antibodies, which however appear only late in infection. This was attributed to the presence of a “decoy epitope” located near a hypervariable region of GP5. This region also harbors the predicted signal peptide cleavage sites and (dependent on the virus strain) a variable number of potential N-glycosylation sites. Molecular processing of GP5 has not been addressed experimentally so far: whether and where the signal peptide is cleaved and (as a consequence) whether the “decoy epitope” is present in virus particles. We show that the signal peptide of GP5 from the American type 2 reference strain VR-2332 is cleaved, both during in vitro translation in the presence of microsomes and in transfected cells. This was found to be independent of neighboring glycosylation sites and occurred in a variety of porcine cells for GP5 sequences derived from various type 2 strains. The exact signal peptide cleavage site was elucidated by mass spectrometry of virus-derived and recombinant GP5. The results revealed that the signal peptide of GP5 is cleaved at two sites. As a result, a mixture of GP5 proteins exists in virus particles, some of which still contain the “decoy epitope” sequence. Heterogeneity was also observed for the use of glycosylation sites in the hypervariable region. Lastly, GP5 mutants were engineered where one of the signal peptide cleavage sites was blocked. Wildtype GP5 exhibited exactly the same SDS-PAGE mobility as the mutant that is cleavable at site 2 only. This indicates that the overwhelming majority of all GP5 molecules does not contain the “decoy epitope”.     

猪生殖和呼吸综合征病毒B13株ORF7基因的克隆及在杆状病毒系统中的表达

利用单管RT－PCR方法扩增猪生殖和呼吸综合征病毒（PRRSV）分离株B13株包括ORF7基因的片段,并对其序列进行了测定,结果PRRSV分离株B13ORF7基因长度为384bp,编码128个氨基酸组成的15kD蛋白。与已发表的PRRSV LV株、VR－2332株进行同源性比较,发现核苷酸同源性分别为99.2%、59.4%;氨基酸同源性分别为98.4%、54.7%。。表明PRRSV分离株B13在基因结构上可能与LV株同属于欧洲亚群。同时构建了重组转移载体质粒pAcGHLT-B-ORF7,且该重组转移载体质粒与线性化苜蓿丫纹夜蛾核型多角体病毒（AcMNPV-SVI^-G)基因组DNA（baculo gold linearized baculovirus DNA）共转染草地夜蛾（Spodoptcra frugiperda,Sf9）细胞,得到重组病毒AcMNPV-OCC^--GST-6xHis-ORF7。在感染了重组病毒的Sf9细胞中检测到分子量为46kD的ORF7基因的GST融合蛋白表达产物,能被猪抗PRRSVB13株多克隆血清所特异识别。此结果为PRRS新型诊断抗原的研制奠定了基础。     

不同PRRSV毒株间ORF1a基因密码子偏爱性差异分析

运用CodonW、ClustalX、TreeView软件及EMBOSS（,rIleEuropean MolecularBiologyOpenSoftwareSuite）、CIMMiner在线分析软件对选取的29株PRRSVORFla基因进行密码子偏爱性聚类分析．CAI、CBI、Fop、Nc、GC3s和GC含量、基因长度等相关性分析显示PRRSV各毒株编码的ORFla基因密码子偏爱性各有差异,其中Lelystadvirus、LV4-2．1、VR-2332、RespPRRSMIV与国内分离的高致病性PRRSV变异株之间差异较大．密码子使用概率聚类分析表明CC．1、NVSL．97．7895、CH—1a、RespPRRSMLV、LV4．2．1、Lelystadvirus与高致病性PRRSV变异株距离较远．而国内分离株相互间的聚类距离则较接近。此结果与基于氨基酸序列比对构建的系统进化树图谱基本一致．由此可见．PRRSV病毒ORF1a基因密码子使用偏爱性的差别与病毒的遗传多样性密切相关．     

套式RT-PCR检测猪繁殖和呼吸综合征病毒的研究

参照ATCC VR-2332株及LV株保守区段设计了3条引物,以此建立了检测猪繁殖和呼吸综合征病毒的套式RT-PCR方法。利用其分别对ATCC VR-2332株、LV株及B13株进行套式RT-PCR,结果从3个不同地区分离的毒株中均能特异性的扩增出相应的片段,大小分别约为430bp(预期片段为430bp)、410bp(预期片段为413bp)及410bp(预期片段为413bP),而3个非PRRSV的病毒(猪瘟病毒、细小病毒及伪狂犬病毒)均未扩增出相应的片段。其敏感性可达到10^-2TCI     

Analysis of molecular variation in porcine reproductive and respiratory syndrome virus in China between 2007 and 2012

In the present study, 89 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in China during 2007 to 2012 were randomly selected from the GenBank genetic sequence database. Evolutionary characteristics of these isolates were analyzed based on the sequences of non-structural protein 2 (Nsp2) and glycoprotein 5 (GP5). The genetic variations of the isolates were also compared with six representative strains. The results showed that a high degree of genetic diversity exists among the PRRSV population in China. Highly pathogenic PRRSV isolates, with a discontinuous deletion of a 30 amino acid residue in the Nsp2 region, remained the most dominant virus throughout 2007–2012 in China. Owing to the extensive use of representative vaccine strains, natural recombination events occurred between strains. Three isolates — HH08, DY, and YN-2011 — were more closely related to vaccine strains than the other isolates. Both YN-2011 and DY were the evolutionary products of recombination events between strains SP and CH-1R. The results of the present study provide useful information for the epidemiology of PRRSV as well as for vaccine development.