Characterization of pseudorabies virus glycoprotein B expressed by canine herpesvirus

A recombinant canine herpesvirus (CHV) which expressed glycoprotein B (gB) of pseudorabies virus (PrV) was constructed. The antigenicity of the PrV gB expressed by the recombinant CHV is similar to that of the native PrV. The expressed PrV gB was shown to be transported to the surface of infected cells as judged by an indirected immunofluorescence test. Antibodies raised in mice immunized with the recombinant CHV neutralized the infectivity of PrV in vitro. It is known that the authentic PrV gB exists as a glycoprotein complex, which consists of gBa, gBb and gBc. In MDCK cells, PrV gB expressed by the recombinant CHV was processed like authentic PrV gB, suggesting that the cleavage mechanism of PrV gB depends on a functional cleavage domain from PrV gB gene and protease from infected cells.     

猪伪狂犬病毒囊膜糖蛋白gB主要抗原表位区基因的克隆及原核表达

参照GenBank发表的猪伪狂犬病毒囊膜糖蛋白gB主要抗原表位的编码区基因序列,设计一对引物,通过PCR扩增后,将约为600bp的目的片段克隆到pGEM-T载体上,酶切后插入原核表达载体pET-32(a)的T7启动子下游,构建的重组质粒pET-gB经IPTG诱导,在大肠杆菌BL21(DE3)中获得了高效表达。SDS-PAGE结果显示,表达产物分子量约为42.4KDa,主要以包涵体形式存在。BandScan分析表明,表达量约占菌体蛋白的60.5%。利用His亲和层析方法得到了纯化的表达产物。Western blotting结果显示,重组蛋白能与阳性血清发生特异性反应,具有较好的抗原反应原性,可以作为检测用抗原。     

Bovine herpesvirus-1 (BHV-1) recombinant expressing pseudorabies virus (PrV) glycoproteins B and C induces type 1 immune response in BALB/c mice

Bovine herpesvirus 1 (BHV-1) attached poorly and penetrated into a mouse cell line, BALB 3T3/A31, but a recombinant BHV-1/TF7-6, which expresses pseudorabies virus (PrV) gB and gC genes, did attach and penetrated into cells more efficiently. In this study the gene green fluorescent protein (GFP) has been integrated into genome of BHV-1/TF7-6 and its parental line of BHV-1. When the mouse mesenteries were incubated in vitro and infected with BHV-1/TF7-6/GFP, strong fluorescence was observed while BHV-1/GFP infection hardly demonstrated fluorescence, suggesting that BHV-1 recombinant expressing PrV gB and gC can infect mouse tissue cells more efficiently than the parental BHV-1 does. When BALB/c mice were inoculated with purified BHV-1/TF7-6 or its parental BHV-1, the former induced lower level of anti-BHV-1 immunoglobulin G (IgG) than the latter did. When sub-classes of anti-BHV-1 IgG were analyzed, it was found that mice immunized with BHV-1/TF7-6 or the parental BHV-1 demonstrated the same level of IgG2a. Since anti-BHV-1 IgG1 level was lower in mice inoculated with BHV-1/TF7-6, the IgG2a:IgG1 ratio was higher in BHV-1/TF7-6 inoculated mice than in the parental BHV-1 inoculated ones. These results indicate that BHV-1/TF7-6 induces type 1 predominant immune to BALB/c mice.     

绿色荧光蛋白基因与猪瘟兔化弱毒疫苗株E2基因在杆状病毒中的融合表达

为了研究猪瘟病毒E2糖蛋白的立体结构及生物学特性，将增强型荧光蛋白基因（EGFP）和猪瘟兔化弱毒疫苗株（HCI.V）E2基因经PCR扩增后克隆至pBlueBacHis2A质粒，与杆状病毒DNA共转染后经PCR鉴定获得了含有EGFP和HCLVE2融合基因（GFPTE2）的重组杆状病毒rBACTE2-339，并将其感染sf9细胞后在荧光显微镜下观察到了亮绿色荧光．说明融合基因已初步表达。     

Investigation of pseudorabies virus latency in nervous tissues of seropositive pigs exposed to field strain

The prevalence and quantity of latent pseudorabies virus (PrV) in nervous tissues of pigs exposed to field strain in Korea was investigated by nested and real-time PCR. Nervous tissues including trigeminal ganglion (TG), olfactory bulb (OB), and brain stem (BS) were collected from 94 seropositive pigs. PrV latent infection in nervous tissues was initially investigated by nested PCR targeting three glycoprotein genes (gB, gE, and gG). Based on the obtained result, latent infection was detected in 95.7% of screened animals. Furthermore, it was revealed that the examined tissues harbored different copy numbers of latent PrV genome ranging from <10(2.0) to 10(7.1) copies per microgram of genomic DNA in real-time PCR analysis. These results show that under normal conditions, levels of latent PrV in the nervous tissues of pigs can vary across a wide range. Therefore, the data presented here provides information regarding control of the endemic state of PrV in Korea.     

伪狂犬病病毒(PrV)糖蛋白gE基因在重组杆状病毒中的表达

应用ＰＣＲ方法扩增出１．８Ｋｂ的伪狂犬病毒糖蛋白ｇＥ基因,克隆到ｐＵＣ１１９中形成重组质粒ｐＲＺＥ。经测序鉴定后再将ｇＥ基因定向亚克隆到杆状病毒转移载体ｐＶＬ１３９２中,形成重组质粒ｐＶＬｇＥ。将ｐＶＬｇＥ与杆状病毒线性ＤＮＡ（ＢＡＣ－Ｎ－Ｂｌｕｅ ＤＮＡ）共转染Ｓｆ９昆虫细胞,经三轮蚀斑纯化,获得重组病毒ｒｐＶＬｇＥ。通过ＰＣＲ方法鉴定证明ｇＥ基因正确插入到杆状病毒基因组中,直接免疫荧光试验和Ｗｅｓｔｅｒｎ Ｂｌｏｔ结果表明ｇＥ基因在重组杆状病毒感染的Ｓｆ９昆虫细胞中获得高效表达。表达的ｇＥ蛋白将作为伪狂犬病强毒的ｇＥ基因缺失弱毒疫苗鉴别诊断ＥＬＩＳＡ方法的抗原,为进一步扑灭伪狂犬病发挥重要作用。     

传染性喉气管炎病毒王岗株糖蛋白gB基因在重组杆状病毒中的表达

将克隆到pUC119中的传染性喉气管炎病毒（ILTV）糖蛋白gB基因，通过EcoRI位点克隆至杆状态病毒转移载体pVL1393中，构建成重组杆状病毒转移载体rpVLgB，将rpVLgB转移载体质粒与杆状态病毒DNA（Bac-N-Blue DNA)共转染Sf9昆虫细胞，经3轮蚀斑纯化，获得重组病毒并命名为rpVL－ILTVgB。PCR方法鉴定证明gB基因正确插入到杆状病毒基因组中，直接免疫荧光试验和Dot－ELISA结果均表明gB基因在重组杆状病毒感染的Sf9昆虫细胞保获得表达，表达的gB蛋白将作为鸡传染性喉气管炎的亚单位疫苗和诊断抗原。     

Immunogenic properties of a bovine herpesvirus-1 (BHV-1) recombinant expressing major pseudorabies virus (PrV) glycoproteins in combination

A recombinant bovine herpesvirus type 1 (BHV-1), designated BHV-1/TF17-1, which expresses pseudorabies virus (PrV) glycoproteins gB, gC, gD, gE and gI in combination was constructed. To test the protective immunity, 10 mice were inoculated with BHV-1/TF17-1 and three weeks later 10 mice were intraperitoneally (i.p.) challenged with 20 LD50 virulent PrV (YS-81). BHV-1/TF17-1 protected all the mice from the PrV lethal challenge while all the control mice died in around 3 days. Mice vaccinated with BHV-1/TF17-1 acquired high PrV-neutralizing antibody titers and demonstrated strong delayed type hypersensitivity responses and moderate in vitro lymphocyte proliferative responses to PrV antigen. Since the major PrV glycoproteins were integrated into virions (probably into viral envelope), BHV-1/17-1 was neutralized with anti-PrV antiserum. However, the susceptibility of BHV-1/TF17-1 to anti-PrV antiserum is 2- to 4-fold lower than that of PrV vaccine lines. Our results demonstrated the possibility of BHV-1/17-1 as a vaccine to protect piglets from Audjesky's disease where maternal antibodies against PrV interfere attenuated live PrV vaccines.     

Characterization of promoters integrated in the genome of bovine herpesvirus-1 (BHV-1).

Bovine herpesvirus-1 (BHV-1) has been used as a vector of live recombinant vaccines for cattle which express the genes of other pathogens. Because of the importance of the choice of the promoter which allows the efficient expression of the foreign genes in the BHV-1 vector, we compared the relative efficacy of various promoters integrated in the BHV-1 genome. The promoter sequences of the BHV-1 thymidine kinase (tk), gB, gC, SV40 early, and pseudorabies virus (PRV) immediate early (IE) genes were placed at the upstream of the open reading frame of the chloramphenycol acetyl transferase (CAT) gene and the promoter-CAT sequences were integrated into the tk gene of BHV-1 by homologous recombination. The promoter activity was assayed by measuring the CAT activity in the extracts of Madin Darby bovine kidney (MDBK) cells infected with the recombinant BHV-1. The PRV IE promoter was activated earlier and maintained at a higher level activity than the BHV-1 gB or gC promoters throughout the most of the growth phase of BHV-1. At the late phase, however, the activities of the BHV-1 gB and gC promoters reached the higher level. The BHV-1 tk promoter activity was low and the SV40 early promoter was hardly activated when integrated into the BHV-1 genome. promoter, recombinant BHV-1.     

Baculovirus-mediated gene expression in chicken primary cells

A recombinant baculovirus was constructed containing an expression cassette with a reporter gene, green fluorescent protein, directed by a constitutive mammalian promoter: a human cytomegalovirus immediate early promoter/enhancer (CMV-IE). High titer virus was prepared with ultracentrifugation. Efficient gene delivery and expression were observed in the virus-treated chicken primary culture, myoblast cells, and whole embryonic fibroblast cells. It was noticed that an addition of sodium butyrate (a selective histone deacetylase inhibitor) to viral transduction medium extremely enhanced the reporter-gene expression. However, there is no effect of presence of trichostatin A observed. To maximize the reporter-gene expression, the baculoviral infection condition was optimized with both cell types. Our approaches demonstrated that recombinant baculovirus could efficiently deliver its genome DNA into chicken primary cells and that CMV-IE, a mammalian-cell-active promoter, was functional in chicken primary cells and could direct a high level of gene expression. Clearly, the recombinant baculovirus provides an alternative means for foreign gene delivery into avian cells.     

Production of a baculovirus-derived gp50 protein and utilization in a competitive enzyme-linked immunosorbent assay for the serodiagnosis of pseudorabies virus.

The pseudorabies virus (PRV) gp50 envelope glycoprotein gene was cloned and expressed in a recombinant baculovirus. An anti-gp50 Mab (1842) recognized a protein of approximately 40 kDa in immunoblotting assays from infected insect cell lysates, while this product was not present in cells infected with wild-type baculovirus. The recombinant protein was purified by lectin affinity chromatography, utilizing lectins specific for O-linked oligosaccharides (Artocarpus integrifolia and Glycine max). Competitive (c) ELISAs, using either crude or lectin-purified antigen, were devised for the detection of antibodies to PRV in sera, and were capable of monitoring sero-conversion by day 14 post-infection. Furthermore, a specificity of 100% and sensitivity of 98% (crude lysate antigen) or 96% (lectin-purified antigen) was found for a panel of 80 swine sera, using the cELISA, as compared to a serum neutralization (SN) test. These studies demonstrated that recombinant PRV gp50 protein shows promise as a cELISA antigen, for serodetection of PRV.     

Successful pseudorabies vaccination in maternally immune piglets using recombinant vaccinia virus vaccines

Three gilts were vaccinated with a NYVAC vaccinia recombinant expressing glycoprotein gD of pseudorabies virus (PRV) (NYVAC/gD). After farrowing, the piglets were allowed to nurse normally to obtain colostral immunity and then were divided into four groups, receiving NYVAC/gD, a NYVAC recombinant expressing glycoprotein gB of PRV (NYVAC/gB), an inactivated PRV vaccine (iPRV), or no vaccine. The piglets were vaccinated twice, three weeks apart beginning at approximately two weeks of age and later challenged with virulent PRV oronasally. Piglets that received NYVAC/gB or iPRV were the best protected based on lack of mortality, lower temperature responses, decreased weight loss and decreased viral shedding after challenge. These results indicate effective strategies for stimulating active immune response while still under the protection of maternal immunity.     

Characteristics of glycoprotein B of equine herpesvirus 1 expressed by a recombinant baculovirus.

A recombinant baculovirus (Bac-EgB) containing the complete open reading frame of equine herpesvirus 1 glycoprotein B (EHV-1 gB) expressed recombinant products of 107-133 kDa, 58-75 kDa and 53-57 kDa, corresponding to EHV-1 gB precursor, large and small subunits respectively. High molecular mass products (>200 kDa) in the Bac-EgB infected insect cells were consistent with oligomerisation of the recombinant EHV-1 gB products, and analysis with tunicamycin and endoglycosidases indicated that the baculovirus-expressed gB contained N-linked sugars with high mannose and hybrid chains. N-terminal amino acid sequence analysis of the gB forms revealed identical signal and endoproteolytic cleavage sites to those of gB in EHV-1 infected mammalian cells, and authenticity of processing and transport was supported by the presence of EHV-1 gB antigen at the surface of infected insect cells. Immunogold labelling and electron microscopy of recombinant baculovirus particles indicated that the recombinant gB was also present in baculovirus envelopes. Bac-EgB infected insect cells were able to induce low levels of complement dependent virus neutralising antibody, and have been shown to evoke protective immune responses in murine models of respiratory disease and abortion.     

伪狂犬病病毒gE/TK基因缺失突变株的构建

在伪狂犬病病毒转移载体pBdTK-Uni的多克隆位点中插入由SV40启动子控制下的IacZ基因表达盒,同时在右侧同源臂下游插入一个1.7kb的KpnI片段,构建成一个新的转移载体pUhi-LacZ.用该载体与Bartha-K61株基因组通过脂质体法共转染Vero细胞,经过10代蓝斑筛选纯化和PCR鉴定获得了一株稳定表达LacZ基因的伪狂犬病病毒gE/TK基因缺失突变株,命名为rPrV-LacZ.在不同的细胞(PK-15、IBRS-2、Vero和CEF)上,对该重组病毒与亲本病毒的增殖滴度和细胞病变进行比较,未见显著差异.结果表明转移载体pBdTK-Uni具有实用性,可用于构建伪狂犬病病毒基因工程活载体疫苗.     

牛疱疹病毒Ⅰ型gB、gE基因的克隆及其杆状病毒表达载体的构建

本试验用PCR方法扩增了牛疱疹病毒Ⅰ型(bovine herpesvirus-1,BHV-1)Bartha Nu/67株gB、gE基因片段,将其克隆到pGEM-T-easy载体。经转化、筛选、鉴定后将重组质粒经BamHⅠ和EcoRⅠ双酶切后,与经相同方法处理的杆状病毒转移载体pFastBacHTb连接,得到了重组质粒pFBHgB、pFBHgE。经酶切和测序鉴定后,将其转化入含穿梭载体Bacmid的感受态细胞DH10Bac,经抗性、蓝白斑筛选和PCR鉴定,得到了含gB、gE基因的重组穿梭载体。     

伪狂犬病病毒Ea株gE基因的克隆、序列分析及其表达

对含伪狂犬病病毒（Pseudorabies Virus,PrV）Ea株gD基因部分编码序列，gI、gE和11k基因全序列、28k基因部分序列的质粒pSKB4.5进行亚克隆，构建了只含完整gE基因（长1.78kb）的重组质粒pSDM1.78 ，并采用双脱氧末终止法对全序列进行了分析，发现同国外标准毒株Rice株相比较，在核苷酸和氨基酸水平均存在一定程度的差异。进一步将gE基因克隆到高效真核表达载体pcNDA3.1 的Kpn1和BamH1位点之间，构建了gE基因的真核表达质粒pcDNA-gE。体外转染IBRS-2细胞，经间接免疫荧光法检测证实了gE基因在IBRS-2细胞中得到了表达，表达的蛋白具有生物学活性。     

Expression and Immunogenicity Analysis of Porcine Pseudorabies Virus gB Protein

In order to study the expression and immunogenicity of porcine pseudorabies virus (PRV) gB protein,the specific primers were designed with the template of PRV preserved in the laboratory, and the 612 bp conserved gene fragments were amplified and sequenced, then it was cloned into the expression vector pET-28a and transformed into E.coli BL21 (DE3), the target protein was obtained after induced expression and purification.Western blotting was performed to analyse its immunogenicity. The results showed that gB protein was 30 ku, which mainly expressed in the form of inclusion body, and the concentration of the protein was 106 μg/mL, with well reactogenicity. 13 PRV positive serum and 16 negative serum in the samples were detected using ELISA Kit on sale, using positive serum, the PRV antibody detection method was initially established with the PRV gB protein as antigen package.     

Experimental infection of European wild boars and domestic pigs with pseudorabies viruses with differing virulence

OBJECTIVE: To determine susceptibility of European wild boars (Sus scrofa) to infection with pseudorabies virus (PrV) and to characterize the virulence of a wildboar PrV isolate for wild and domestic pigs. ANIMALS: 18 wild boars and 16 domestic pigs. PROCEDURE: Three groups of 4 wild boars were inoculated with PrV Bartha, Kaplan, and a wild-boar isolate (BFW1) and housed with uninfected pigs. Two groups of domestic pigs (4 and 8 pigs/group, respectively) were inoculated with various doses of BFW1. Animals were observed daily for clinical signs, and samples were tested for PrV excretion and homologous antibodies. After reactivation of latent infection by induced immunosuppression, PrV was detected in tissues of necropsied animals, using cell culture and a polymerase chain reaction (PCR). RESULTS: Clinical signs depended on virulence of the PrV strain and dose of inoculum. Only infection with PrV Kaplan resulted in severe disease and death. Virus was isolated from nasal and genital swab specimens. Antibodies were first detected on day 7 after inoculation; a specific humoral immune response was delayed in BFW1-infected animals. Virus was isolated from various tissues of Kaplan-infected wild boars, whereas mainly viral DNA was detected in a few tissues of Bartha- and BFW1-infected animals, using PCR after immunosuppression. CONCLUSIONS AND CLINICAL RELEVANCE: European wild boars are susceptible to transmission of PrV infection from domestic pigs and vice-versa. The PrV isolate BFW1 is of low virulence and seems to be adapted to the wild boar population from which it was isolated.     

猪伪狂犬病病毒gB蛋白表达及免疫原性分析

本试验旨在研究猪伪狂犬病病毒（pseudorabies virus,PRV） gB蛋白的表达并分析其免疫原性,以PRV病毒液为模板,设计特异性引物,扩增大小为612 bp的保守片段并测序,将其克隆到表达载体pET-28a中,转化表达菌BL21（DE3）,经诱导表达、纯化得到目的蛋白,进行Western blotting分析验证并分析免疫原性。结果表明,表达的gB蛋白大小为30 ku,主要以包涵体形式存在,复性后浓度为106 μg/mL,且具有良好的反应原性。应用市售试剂盒检测到样品中含13份PRV阳性血清和16份阴性血清,利用检出的阳性血清,初步可建立以PRV gB蛋白为包被抗原的PRV抗体ELISA检测方法。