猪伪狂犬病病毒HNX株在免疫猪群中水平传播能力的研究

为研究猪伪狂犬病病毒(PRV)HNX株水平传播的能力及PRV活疫苗的保护效力,本研究通过以颈部肌肉接种PRV HNX株(2 m L 107 TCID50)的未免疫猪作为病毒的传染源,同居感染未免疫猪和Bartha-K61株活疫苗免疫猪,通过检测抗PRV的g B和g E蛋白抗体、中和抗体及干扰素水平等评估疫苗保护力,并利用荧光定量PCR方法检测同居感染猪排毒情况。结果显示Bartha-K61株活疫苗能够快速诱导免疫猪产生抗g B蛋白的抗体,但疫苗诱导产生的交叉保护中和抗体水平较低。同居感染期间,免疫猪和未免疫猪均出现典型的临床症状,体温明显升高。荧光定量PCR方法结果显示,疫苗免疫能够减少免疫猪排毒,但不能阻止排毒,也不能阻止野毒感染。本研究结果表明Bartha-K61株活疫苗阻止PRV HNX株水平传播的效力是有限的,有必要更换疫苗病毒株。同居感染期间,每组感染猪均表现敏感,表明PRV HNX株病毒具有较强的水平传播能力。     

伪狂犬病病毒Qihe547分离株主要保护性抗原基因序列的变异分析

2012年以来伪狂犬病(PR)在全国多省份暴发。为了解流行PR病毒(PRV)主要保护性抗原基因的变异情况,本研究从山东齐河地区经PRV Bartha-K61疫苗株免疫猪群中分离到一株PRV命名为Qihe547株,并采用PCR方法对该病毒分离株编码主要保护性抗原糖蛋白gB、gC和gD基因进行扩增及测序分析。结果显示,该病毒株与新近PRV分离株同属基因Ⅱ型。与Bartha株相比,Qihe547分离株在gB的优势抗原表位区(aa59~aa126)、gC膜外区(aa23~aa453)和gD主要抗原表位区,潜在的抗原位点及O-糖基化位点存在明显变异,推测这些变异可能影响Qihe547分离株的抗原性,利于病毒逃避宿主免疫反应,也可能是Bartha-K61疫苗诱导产生的中和抗体不能完全中和病毒的原因之一。本研究为PRV的有效防制及其疫苗研制提供了相关的数据。     

我国猪伪狂犬病变异株研究概况

伪狂犬病(Pseudorabies,PR)是由伪狂犬病病毒(Pseudorabies virus,PRV)引起的、严重危害养猪业的一种烈性传染病。在过去的几十年里,我国通过在猪群中广泛使用Bartha-K61株基因缺失弱毒疫苗,使PR得到了有效控制。但自2011年以来,在全国范围内,许多Bartha-K61疫苗免疫猪群出现了PR疫情。研究证实,该疫情是由PRV变异株引起的,与以往毒株相比,PRV变异株致病性明显增强,且Bartha-K61疫苗不能对猪只提供完全的免疫保护。目前针对PRV变异株的疫苗正在研制中,其中基因缺失活疫苗能够对当前流行的PRV变异株提供完全的免疫保护,这些疫苗大多处于转基因安全评价阶段。在诊断方法上,已经建立了能够有效区分Bartha-K61疫苗株、PRV经典强毒株和当前流行的变异株的三重荧光定量PCR方法。利用安全有效的基因缺失疫苗和配套的鉴别诊断技术,并结合有效的生物安全防控措施,对PR进行净化,是未来必由之路。本文对我国当前PR的流行病学、诊断方法、疫苗研制和防控策略等进行了简述和讨论。     

伪狂犬病病毒GD1406变异株的抗原性分析

为了解近年来广东省伪狂犬病病毒(PRV)变异情况,本研究从猪场收集Bartha-K61活疫苗免疫后的猪血清559份,经ELISA筛选出326份gB抗体阳性且gE抗体阴性的猪血清,进行中和试验,分析血清中的疫苗抗体对Bartha-K61株和临床分离到的PRV GD1406野毒株的中和能力。进一步应用小鼠进行交叉免疫保护性试验。结果显示,187份gB阳性且gE阴性的猪血清样品对Bartha-K61株和PRV GD1406野毒株的平均中和抗体滴度分别为1:57和1:13,并且免疫Bartha-K61株使小鼠免受PRV GD1406野毒株致死性攻击的保护率仅为20%,而免疫PRV GD1406野毒株使小鼠免受Bartha-K61株致死性攻击的保护率为100%,免疫灭活PRV GD1406野毒株使小鼠免受PRV GD1406野毒株致死性攻击的保护率为40%。根据试验结果推测,PRV GD1406野毒株与Batha-K61株之间存在抗原差异性,现用疫苗不能有效抵抗PRV变异株攻击。本研究结果将为PRV的防控提供实验依据,为研制PRV新疫苗提供新的思路。     

山东省部分地区猪伪狂犬病病毒分离株gC抗原基因的变异分析

为了解当前山东省猪伪狂犬病病毒(PRV)流行特点及病毒gC抗原基因的变异情况,本研究对2018年来自山东省不同地区的23份猪伪狂犬病疑似病料进行PRV的分离鉴定,并对分离株的gC抗原基因进行扩增及序列分析。结果表明,共分离到9株PRV;gC基因同源性比对结果显示,分离株与2012年之后国内PRV变异株的核苷酸及氨基酸序列的同源性均高于欧美毒株;遗传进化树及推导氨基酸序列分析结果显示,分离株与国内2012年后分离到的变异毒株同属于GenotypeⅡ;因此,推测目前山东省流行的PRV以变异毒株为主。9株分离株与Bartha-K61疫苗株相比,糖基化蛋白gC在潜在抗原位点和O-糖基化位点的重要位置(aa23～aa453)发生改变,这或许会影响分离株的抗原性,从而有助于其逃避宿主免疫防御,最终造成疫苗诱导产生的中和抗体不能有效地中和目前流行的变异PRV。本研究为变异PRV的防控及相关疫苗研制提供了一定的理论依据。     

猪伪狂犬病病毒变异株TK/gE/gI三基因缺失突变株在小鼠体内的免疫原性

应用PCR方法扩增了猪伪狂犬病病毒(PRV)NY株TK基因两侧序列,克隆至pUC-19载体,同时插入绿色荧光蛋白标记基因,构建转移质粒pUC-TKLRE,并与PRV变异株gE/gI双基因缺失突变株rPRV NY-gE~-/gI~-的基因组DNA共转染ST细胞,通过蚀斑纯化,获得表达荧光蛋白的PRV三基因缺失突变株。分别用PRV三基因缺失突变株、rPRV NY-gE~-/gI~-、PRV商品活疫苗Bartha-K61株、DMEM细胞培养液免疫6周龄雌性小鼠,2周后对小鼠进行第2次免疫,且首免后6周用PRV强毒NY株对小鼠进行攻毒试验。结果显示,成功拯救PRV三基因缺失突变株rPRV NY-gE~-/gI~-/TK~--EGFP~+,且对小鼠是安全的。间接ELISA试验和病毒中和试验证实rPRV NY-gE~-/gI~-/TK~--EGFP~+使小鼠机体产生了较高滴度的PRV特异性抗体,小鼠外周血T淋巴细胞亚群的测定证明,其诱导小鼠机体产生了细胞免疫应答。攻毒试验结果显示,rPRV NY-gE~-/gI~-/TK~--EGFP~+对PRV强毒NY株的攻击具有一定的抵抗力。本试验获得的PRV三基因缺失病毒rPRV NY-gE~-/gI~-/TK~--EGFP~+有望成为一种防控当前PR流行的疫苗株。     

高剂量高致病性猪繁殖与呼吸综合征病毒TJM-F92疫苗株对低剂量伪狂犬病毒Bartha-K61疫苗株的免疫干扰研究

为研究高剂量高致病性猪繁殖与呼吸综合征病毒(PRRSV)TJM-F92疫苗株对低剂量伪狂犬病毒(PRV)Bartha-K61疫苗株是否存在免疫干扰作用,本研究对其从体液免疫水平、免疫攻毒保护水平及病理学变化等方面进行评价。结果表明,二联免疫组抗体消长规律与低剂量PRV Bartha-K61株免疫对照组抗体消长规律相一致,二联免疫组中高剂量PRRSV TJM-F92株未抑制低剂量PRV Bartha-K61株抗体生成;二联免疫组与低剂量PRV Bartha-K61免疫对照组对PRV JL1株强毒攻击保护率均为5/5;免疫病理学研究结果表明,两组免疫组攻击PRV JL1株强毒后各组织器官病理变化轻微;二联免疫组与低剂量PRV Bartha-K61免疫对照组均可对PRV强毒攻击产生良好的保护效果。综上,高剂量PRRSV TJM-F92株对低剂量PRV Bartha-K61株无免疫干扰作用。     

PRV FB株gE/gI基因缺失株的构建及其灭活疫苗免疫保护效力评价

自2011年以来,新型伪狂犬病病毒(PRV)变异株在我国免疫猪场不断出现,导致目前商品化疫苗免疫效果不佳。为研究PRV FB株gE/gI基因缺失株疫苗防控新型PRV变异株感染的效果,本研究以PRV自然弱毒FB株作为亲本株,通过同源重组的方法构建了PRV g E/gI基因缺失株,将不同代次PRV FBΔgE/gI株与亲本PRV FB株分别接种BHK-21细胞,观察CPE和测定TCID50效价,分析缺失株的遗传稳定性,结果显示FBΔgE/gI株感染BHK-21细胞后产生与亲本株FB相似的CPE,且不同代FBΔgE/gI株的TCID50与亲本株相比均无明显变化。将FB株、FBΔgE/gI株、Bartha-K61株分别接种健康新西兰兔,比较三者的安全性,结果显示,接种BarthaK61株的家兔全部死亡(5/5),接种FB株的家兔死亡2只(2/5),而接种FBΔgE/gI株的家兔全部(5/5)健活,表明FBΔgE/gI株对新西兰兔的致病力较低,安全性更高。将FBΔgE/gI株分别与水相佐剂GEL02和两性佐剂ISA 206制成灭活疫苗免疫绵羊28 d后,采用ELISA法检测各组绵羊的gB和gE抗体,并且以PRV变异株FJ-2012攻毒,评估FBΔgE/gI株灭活疫苗对绵羊的保护效力,结果显示,接种GEL02和ISA 206为佐剂的FBΔgE/gI灭活疫苗绵羊在免疫后28 d,抗体均全部转阳;对照组绵羊在攻毒后6 d内全部死亡(5/5),以GEL02作为佐剂的灭活疫苗组绵羊死亡2只(2/5),而以ISA 206为佐剂的绵羊全部存活(5/5),保护率达到100%,表明以ISA 206作为佐剂的FBΔgE/gI株灭活疫苗能够完全保护绵羊抵御PRV变异株的攻击。本研究首次基于PRV自然弱毒FB株构建的FBΔgE/gI株,与Bartha-K61株相比具有更高的安全性,与佐剂ISA 206制成灭活疫苗免疫绵羊后能够完全抵抗新发变异PRV的攻击,具有完全保护作用。本研究为我国新发变异PRV疫苗的研发提供了新的参考依据。     

评估3种不同毒株的猪伪狂犬病活疫苗的免疫效果

猪伪狂犬病病毒变异株的流行对伪狂犬病的防控提出了严峻挑战,传统的疫苗对新流行毒株不能提供完全的保护。为评估3种不同毒株的活疫苗C株、HB2000株、Bartha-K61株的免疫效果,在某猪伪狂犬病gE抗体阴性猪场进行试验。结果显示,虽然3组疫苗1次和2次免疫后gB抗体阳性率达到100%,但是中和抗体的效价差异显著。从经典毒株HB-J和变异毒株CW的中和试验结果看,C株产生的平均中和抗体效价均为最高,显著高于HB2000株和Bartha-K61株,提示C株免疫效果优于HB2000株和Bartha-K61株,可以作为防控猪伪狂犬病的高效疫苗。     

一株分离自免疫猪场的伪狂犬病病毒的鉴定与变异分析

为了明确河北某伪狂犬病疫苗免疫猪场的哺乳仔猪出现神经症状和死亡的病因,作者对发病仔猪进行研究时从脑组织中分离到1株病毒,通过PCR、免疫过氧化物酶单层试验(IPMA)、动物试验以及基因序列分析等试验,证明所分离的病毒为伪狂犬病病毒(PRV),命名为HBXT-2018株。皮下接种该病毒后24 h,家兔开始啃咬病毒接种部位皮肤,在44～68 h内全部死亡。抗PRV Bartha-K61株的血清对分离株的中和抗体效价低于1∶8,而抗PRV变异株血清的中和抗体效价为1∶58.9。与Bartha株比较,HBXT-2018株的gB和gC的核苷酸和氨基酸序列多处发生单个或连续几个碱基(或氨基酸)置换、插入和缺失突变,预测的gB和gC上的潜在抗原表位也发生了改变。基于gB、gC和TK的系统进化分析表明,HBXT-2018株与国内流行毒株尤其与2011年之后的流行毒株处于同一个进化分支,而与Bartha株及其他欧美毒株处于不同的进化分支。上述结果表明,分离的PRV HBXT-2018株为致病毒株,其与当前国内流行的PRV变异株具有相同的遗传特征,与Bartha株为代表的欧美流行株的遗传关系远。Bartha-K61株抗血清对分离株的中和作用不明显,提示gB与gC的突变可能与该毒株免疫逃逸、继而导致仔猪发病有关。     

Herpesvirus interference with virus-specific antibodies: bridging antibodies, internalizing antibodies, and hiding from antibodies

Herpesviruses have developed different tools to thwart efficient antibody-dependent neutralisation and lysis of virions and elimination of infected cells. This overview will briefly summarize different of these tools, including (i) viral Fc receptors and the resulting process of antibody bridging, (ii) internalization of individual viral proteins and clustered antibody-antigen complexes from the plasma membrane of infected cells, and (iii) directed egress of virus particles to sites of intimate cell-cell contact that are difficult to access for antibodies.     

Comparison of precipitin antibodies and virus-neutralizing antibodies to infectious bursal disease virus

Three hundred twenty-two serum samples from commercial pullets and multiplier breeders were analyzed for agar-gel precipitin (AGP) antibodies and virus-neutralizing (VN) antibodies to infectious bursal disease virus. Two hundred thirty-four of these sera were AGP-positive, and 88 were AGP-negative. The geometric mean of the reciprocal of the VN titers for the AGP-positive sera was 208.7, and 232 (99.1%) had a VN titer of 1:16 or greater. In contrast, the geometric mean of the reciprocal of the VN titers for the AGP-negative sera was 6.1, but 53 (60.2%) had a VN titer ranging from 1:4 to 1:256. When the AGP test was compared with the VN test, the sensitivity and specificity, respectively, of the AGP test were 81.5% and 100%.     

用PPA-ELISA测HCLV抗体和抑制法测HCLV

对早期建立的PPA-ELISA测猪瘟兔化弱毒(HCLV)抗体和PPA-ELISA抑制法测HCLV毒价的2种方法作总结性回顾。前者用于猪瘟的免疫监测,以抗体的分布曲线显示HCLV的免疫效果,出现低谷为免疫力不足,出现特异高峰则可能有强毒侵入;如群体保护率小于50%,表明免疫失败。后者主要用于细胞培养液小样的HCLV毒价测定,方法简单,一次能测多个样品。检测结果表明,在现用的疫苗中抑制价高的,完全有可能用16万或20万倍稀释通过兔体测毒。对此,建议将兔体半数反应量(RID50)标准提高至16万或20万倍稀释,一次通过,免疫剂量用400RID50,与国际接轨,达到早日消灭猪瘟的目标。     

Detection of antibodies against African swine fever virus using infected monolayers and monoclonal antibodies

Three monoclonal antibodies, specific for porcine IgG, IgM and IgA, were used to develop isotype-specific immunoperoxidase monolayer assays for the detection of antibodies against African swine fever virus. A mixture of anti-IgM and anti-IgG monoclonal antibodies was used in an assay designed for screening sera. This test was compared with a commercially available ELISA by using experimental sera and field sera obtained after an outbreak of African swine fever on two farms in the Netherlands in 1986. Although the ELISA was less sensitive than the immunoperoxidase monolayer assay on sera taken early after infection, the tests were equally useful for screening purposes. The isotype-specific assays gave epizootiological information about the stage of infection on the two farms.     

Detection of antibodies to alphaviruses and discrimination between antibodies to eastern and western equine encephalitis viruses in rabbit sera using a recombinant antigen and virus-specific monoclonal antibodies

Three arthropod-borne alphaviruses, western equine encephalitis viruses (WEEV), eastern equine encephalitis viruses (EEEV) and Venezuelan equine encephalitis viruses are the aetiological agents of a sometimes severe encephalomyelitis in equines and humans in the New World. With regard to the different ecology and epidemiology of these viruses, a method applied in serological screening should be able to distinguish between them as well as other related members of the genus Alphavirus in the American continent. However, this has been hampered in the past by (a) the close antigenic relationship between alphaviruses in traditional serological assays, especially in the routinely used haemagglutination-inhibition, and (b) the need of biosafety level 3 facilities to grow the viral antigens. An epitope blocking assay using an EEEV glycoprotein E1-expressing recombinant Sindbis virus and virus-specific monoclonal antibodies (mAbs) binding to the E1 of EEEV (strain NJ/60) and the E1 of Sindbis virus was established using automated flow cytometry. The test was evaluated using sera of infected and vaccinated rabbits. A cut-off value of 30% inhibition for antigenic complex-specific seroconversion was found to be sufficient for the detection of the respective infection. By using three different mAbs in parallel, we were able to detect alphavirus genus-, EEEV- and WEEV-complex-specific serum antibodies. As this test is based on the inhibition of binding of virus-specific mAbs, sera of every origin other than mouse can be tested. Thus, this assay may prove useful in the serological screening of a variety of animal species during an outbreak investigation.     

ELISA detection of bovine viral diarrhoea virus specific antibodies using recombinant antigen and monoclonal antibodies

A panel of monoclonal antibodies was prepared by immunization of BALB/c mice with Moredun (BD) virus strains. These antibodies were characterized by immunofluorescence and seroneutralization against BD, BVD and hog cholera (HC) virus strains, and radioimmunoprecipitation of BVD-infected cells extracts. The MAbs reacting with the majority of the Pestivirus strains recognize the 80 kDa antigen of the BVD cytophathic strains. The 80 kDa antigen of the BVD/Osloss virus strain has been cloned and expressed in E. coli as a fusion protein with beta-galactosidase. The fusion protein has been purified from inclusion bodies and used successfully as an antigen for ELISA detection of BVDV specific antibodies in bovine sera. A competitive ELISA using MAbs is more specific than a direct assay. These results compare well with the ones obtained with antigen extracted from BVDV-infected cells.     

Detection of rinderpest antibodies

Rinderpest antibodies were detected by employing the fluorescent antibody test (FAT) and the immunoperoxidase test (IPT) and the results were compared with the counterimmuno electrophoresis test (CIE). FAT was found to be the most sensitive in detecting post-vaccinal antibodies followed by IPT and CIE tests.     

Induction and characterization of monoclonal anti-idiotypic antibodies reactive with idiotopes of canine parvovirus neutralizing monoclonal antibodies.

Monoclonal anti-idiotypic (anti-Id) antibodies (Ab2) were generated against idiotypes (Id) of canine parvovirus (CPV) specific monoclonal antibodies (MoAbs). The binding of most of these anti-Id antibodies to their corresponding Id could be inhibited by antigen, thus classifying these anti-Id antibodies as Ab2 gamma or Ab2 beta. By inhibiting experiments it was shown that these anti-Id antibodies did not recognize interspecies cross-reactive idiotopes, but recognized private idiotopes, uniquely associated with the Id of the anti-CPV MoAb used for immunization. This classifies these anti-Id antibodies as non-internal image Ab2 gamma. The potential use of these non-internal image anti-Id antibodies for the induction of antiviral antibodies in the CPV system is discussed.