抗性选育协同疫苗免疫对鸡羽囊马立克病毒载量的影响

为了研究马立克病(MD)火鸡疱疹病毒(HVT)疫苗接种和抗性选育对鸡马立克病毒(MDV-1)攻毒后羽囊中病毒载量的影响,选择普通霞烟鸡及其MD抗性品系,利用MDV-1攻毒后第7、14、21、28和35天(DPI)五次采集并分离的全部试验鸡的羽囊为材料,采用Real-time FQ-PCR技术对这些材料中meq基因进行绝对定量分析以确定其病毒载量,用来分析比较MDV-1在MD抗性/普通鸡及HVT疫苗免疫/HVT疫苗未免疫鸡体内的增殖情况。结果显示:1)从MD抗性对病毒载量的影响看,一方面,普通非免疫攻毒组(F组)的MDV-1含量于14、21DPI时显著(P0.05)高于MD抗性非免疫攻毒组(T组);另一方面,MD抗性免疫攻毒组(R组)的MDV-1含量总体上却和普通免疫攻毒组(G组)相当。2)从HVT疫苗免疫对病毒载量的影响看,一方面,MD抗性非免疫攻毒组(T组)的MDV-1含量于28DPI时显著(P0.05)高于MD抗性免疫攻毒组(R组);另一方面,普通非免疫攻毒组(F组)的MDV-1含量于14、21DPI时显著(P0.05)高于普通免疫攻毒组(G组)。3)从MD抗性协同HVT疫苗免疫对病毒载量的影响看,普通非免疫攻毒组(F组)的MDV-1含量于14(P0.05)、28(P0.01)、35(P0.05)DPI时显著高于MD抗性免疫攻毒组(R组)。结果表明,鸡MD抗性选育协同HVT疫苗接种可显著降低鸡羽囊的病毒载量,这将会降低MDV-1传播风险,并提高鸡的存活机会。     

鸡毒支原体感染病理模型复制

以鸡毒支原体(Mycoplasma gallisepticum,MG)S6标准菌株不同浓度接种16日龄雏鸡,5d后用鸡新城疫疫苗(I系)诱导发病,对以鸡新城疫为诱导因子的鸡毒支原体野外环境病理模型复制进行研究。结果表明:鸡毒支原体S6攻毒菌液浓度为109CCU/mL,攻毒后第5天,用鸡新城疫疫苗(I系)喷雾,5羽份/只,进行激发,可成功复制出鸡毒支原体感染病理模型。     

鸡传染性法氏囊病超强毒Gx与疫苗毒Gt在鸡体内的复制研究

本试验利用鸡传染性法氏囊病超强毒Gx及其致弱疫苗毒Gt为对象,研究超强毒与弱毒株在鸡体主要免疫器官内的复制情况,以探讨两类毒株表现不同生物特性的原因。分别利用鸡胚半数致死量和鸡胚成纤维细胞半数感染量对超强毒Gx和疫苗株Gt进行病毒滴度的测定;再利用荧光定量RT-PCR对两类毒株进行病毒量的校准。以相同量的病毒对2周龄SPF鸡进行攻毒。攻毒试验表明超强毒Gx能造成47.5%的死亡,法氏囊、脾脏、胸腺等免疫器官均严重损伤;而疫苗毒Gt无致死,且未能造成任何病理可见的损伤。病毒的体内复制情况表明超强毒相对于疫苗毒复制更为迅速,病毒载量更高。     

超强马立克病病毒株的致病性研究

拟对一株超强马立克病病毒(MDV)SD2012-1株的致病性进行研究。将60只SPF鸡平均分成未免组、HVT免疫组和CVI988疫苗免疫组3组。于1日龄时对其进行马立克病(MD)疫苗免疫,于10日龄时进行SD2012-1攻毒;每天观察攻毒鸡临床症状,对病死鸡进行病理剖检和组织学观察;用PCR反应对感染鸡进行MDV跟踪监测。病理学研究结果显示:攻毒后第2周,试验鸡有轻微组织病变;攻毒后第6周,试验鸡有眼观病变,镜检有散在的肿瘤细胞团块;攻毒后第9周,试验鸡有明显的眼观肿瘤病变,镜检有大量肿瘤细胞聚集;SD2012-1可以突破CVI988疫苗免疫,引起高达30%的鸡发病。PCR跟踪监测结果显示:攻毒后第5天,未免组和HVT免疫组可检出MDV;攻毒后第10天,未免组和HVT免疫组阳性检出率均为100%,CVI988免疫组阳性检出率为30%;攻毒后第20天,3组试验鸡阳性检出率均为100%;用PCR检测病死鸡的肝、肾、肌胃、肠系膜、十二指肠、心和法氏囊样品的结果均为MDV阳性;攻毒300d后,健康存活鸡的羽髓PCR检测结果均为MDV阳性。结果表明,HVT疫苗对于SD2012-1株几乎无保护作用,超强马立克病病毒SD2012-1株能够长期在免疫鸡体内存在,突破免疫保护,引起发病,这对国内防控鸡马立克病提出了严峻挑战。     

MDV—gB重组病苗病毒诱导免疫的检测及保护性

用MDV-gB重组痘苗病毒RVV-gB、HVT冻干疫苗、痘苗病毒WR株分别按试验程序对细胞免疫及体液免疫检测试验中的1日龄SPF鸡进行免疫接种，并于15日龄时对试验各组鸡用GA株强毒攻击，经IFA抗体检测，及以PHA为有丝分裂原的淋巴细胞转化检测，结果表明，重组病毒和HVT冻干疫苗免疫鸡均获得了较高保护，体液免疫效果差异不显著；细胞免疫效果在攻毒有差异不显著，但攻毒后第2d开始，RVV-gB免疫组鸡的淋巴细胞转化率明显高于HVT冻干疫苗免疫组鸡。     

鸡传染性法氏囊病免疫复合物疫苗与活疫苗免疫鸡病毒载量和免疫效果的比较研究

为比较鸡传染性法氏囊病(IBD)免疫复合物疫苗与活疫苗免疫鸡法氏囊及外周血淋巴细胞(PBMC)中的病毒载量及免疫效果,本研究采用IBD免疫复合物疫苗和鸡传染性法氏囊病毒(IBDV)BX株活疫苗免疫1日龄SPF鸡,于免疫后7d、14d、21d、28d、35d、42d采用SYBRGreenI荧光定量PCR、ELISA方法及中和试验检测免疫鸡法氏囊和PBMC中IBDV载量和免疫鸡血清中IBDV抗体滴度,并攻毒,计算两种疫苗的保护率。结果显示,活疫苗免疫7d时IBDV在法氏囊和PBMC中的载量均比其它时间点的高,在14d时到达到最高,之后逐渐下降;两种疫苗刺激产生的IBDV抗体滴度随免疫时间的延长呈升高趋势;在免疫后7d攻毒两种疫苗的保护率均为0,其它时间的攻毒保护率均为100%。本研究结果表明,IBD免疫复合物疫苗与活疫苗免疫后病毒在鸡体内开始大量复制的时间并不相同,但免疫效果基本相同。本实验为IBD免疫复合物疫苗的研发提供实验依据。     

表达马立克氏病病毒CV1988／Rispens株糖蛋白B基因的重组鸡痘病毒疫苗的免疫保护研究

用鸡痘病毒载体表达马立克氏病病毒（MDV）糖蛋白B（gB)基因构建成重组鸡痘病毒（rF-PV)。以MDV GA或Md5和RBIB混合攻毒，在不同品种的鸡中评价rFPV-gB/R单价苗和与火鸡疱疹病毒（HVT）组成的二价苗的免疫保护效力。试验结果表明，MDV疫苗和FPV母源抗体阴性的SPF鸡和母源抗体阳性的商品鸡中，rFDV-gB/R均能提供免疫保护作用，且其中一种商品蛋鸡中rFPV-gB/R与HVT液氮苗或HVT冻干苗结合使用，均有显著的免疫协同保护作用。免疫学研究指出，rFPV-gB/R与常规疫苗一样，可显著地降低疫苗免疫攻毒鸡的病毒血症和羽囊排毒。     

表达MDV—gB基因的重组鸡痘病毒免疫效果观察

将马立克氏病病毒（MDV）gB基因插入鸡痘病毒中，构建了含有MDV－gB基因的重组鸡痘病毒（rFPV)，用rFPV、火鸡疱疹病毒（HVT）冻干疫苗、rFPV HVT二联疫苗分别免疫1日龄AA肉用雏鸡，8日龄攻毒后观察免疫保护效果。结果表明，3种疫苗均诱导了免疫应答，免疫保护率分别为69％、69％和85％。该重组病毒疫苗的免疫效果与HVT疫苗的免疫效果相当，二者联用具有免疫协同作用。     

表达马立克氏病病毒CVI988／Rispens株糖蛋白B基因的重组鸡痘病毒疫苗的免疫保护研究

用鸡痘病毒载体表达马立克氏病病毒（MDV）糖蛋白B（gB）基因构建成重组鸡痘病毒（rFPV）。以MDV　GA或Md5和RBIB混合攻毒，在不同品种的鸡中评价rFPV－gB／R单价苗和与火鸡疱疹病毒（HVT）组成的二价苗的免疫保护效力。试验结果表明，MDV疫苗和FPV母源抗体阴性的SPF鸡和母源抗体阳性的商品鸡中，rFDV－gB／R均能提供免疫保护作用，且其中一种商品蛋鸡中rFPV－gB／R与HVT液氮苗或HVT冻干苗结合使用，均有显著的免疫协同保护作用。免疫学研究指出，rFPV－gB／R与常规疫苗一样，可显著地降低疫苗免疫攻毒鸡的病毒血症和羽囊排毒。     

检测鸡球虫四价弱毒疫苗抗体应答的ELISA方法的建立及初步应用

本研究旨在建立检测鸡球虫四价弱毒疫苗(柔嫩艾美耳球虫、毒害艾美耳球虫、堆型艾美耳球虫、巨型艾美耳球虫)抗体应答的酶联免疫吸附试验(ELISA),并初步阐明鸡免疫四价弱毒疫苗及攻虫后的抗体应答。将300羽岭南黄鸡分为A(免疫攻虫组)、B(不免疫不攻虫组)、C(不免疫攻虫组)共3个组。A组雏鸡在4日龄时进行首免,11日龄时鸡开始二免,二免完成后(17日龄时)对A组及C组的鸡进行攻虫(28万个4种球虫的混合卵囊/羽),7 d后检查A、C两组鸡的存活率。在鸡二免和三免完成后,分别对A、B组进行采血,通过优化最佳抗原包被浓度、酶结合物工作浓度及最佳血清稀释度,建立了ELISA方法来检测鸡体对球虫四价弱毒疫苗的抗体应答情况。A组鸡血清抗体的平均D值为0.870和0.904,明显高于B组鸡的平均D值0.261和0.270,证明了鸡体免疫疫苗后可以刺激产生相应抗体。免疫鸡攻虫后的存活率和抗体应答的检测结果,都充分说明了此鸡球虫弱毒四价疫苗具有良好的免疫原性,所建立的ELISA方法为今后评价鸡球虫弱毒四价疫苗的免疫效力提供了有效手段。     

Protective efficacy of Marek's disease virus (MDV) CVI-988 CEF65 clone C against challenge infection with three very virulent MDV strains

Comparative 50% protective dose (PD50) assays were performed using a plaque-purified preparation of Marek's disease virus (MDV) strain CVI-988 at the 65th chicken embryo fibroblast (CEF) passage level (MDV CVI-988 CEF65 clone C) and three commercial MD vaccines: herpesvirus of turkeys (HVT) FC126, MDV CVI-988 CEF35, and a bivalent vaccine composed of HVT FC126 and MDV SB-1. In addition, comparative PD50 assays were performed in groups of chickens with maternal antibody to each of the three vaccines. Three representatives of the newly emerged biovariant very virulent (vv) MDV strains-RB/1B, Tun, and Md5-were employed as challenge virus. The experiments made feasible the differentiation between virulent MDV and vvMDV strains, within serotype 1. Vaccination with CVI-988 clone C vaccine resulted in PD50 estimates of about 5 plaque-forming units (PFUs) against challenge infection with each of the three vvMDV strains. The PD50 estimate of CVI-988 clone C vaccine was 12-fold below the PD50 of HVT FC126. The protective synergism of bivalent vaccine, composed of HVT and SB-1, was confirmed by groups given the lowest vaccine doses. The bivalent vaccine, however, resulted in incomplete protection in groups given the highest vaccine doses. Homologous maternal antibodies to serotype 1 caused a fivefold increase in the PD50 estimate of CVI-988 clone C. Heterologous maternal antibodies against HVT did not interfere with efficacy of CVI-988 clone C vaccination. However, the combination of maternal antibodies against both HVT and SB-1 (serotypes 2 and 3) showed a strong adverse effect on CVI-988 clone C vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)     

鸡马立克氏病活疫苗免疫效力比较试验

用ＨＶＴ冻干苗、ＨＶＴ细胞结合苗、ＣＶＩ９８８细胞结合苗、ＳＢ１＋ＦＣ１２６双价活疫苗、３０１Ｂ／１＋ＦＣ１２６双价活疫苗和Ｚ４＋ＦＣ１２６双价活疫苗等６种鸡马立克氏病（ＭＤ）疫苗免疫ＳＰＦ白来航鸡或普通伊莎鸡，用鸡马立克氏病病毒（ＭＤＶ）强毒ＧＡ株、京－１血毒以及鸡马立克氏病超强毒ｖｖＭＤＶ－Ｍｄ５毒株分别攻击进行免疫效力比较试验。试验表明，ＭＤ单价苗的免疫效力强弱顺序依次是ＣＶＩ９８８、ＨＶＴ细胞结合苗和ＨＶＴ冻干苗，这３种ＭＤ单价苗均能给免疫鸡群提供有效的免疫保护力。ＳＢ１＋ＦＣ１２６、Ｚ４＋ＦＣ１２６和３０１Ｂ／１＋ＦＣ１２６等３种ＭＤ双价苗免疫效力显著高于ＭＤ单价苗，均能给免疫鸡群提供较强的免疫保护力，并能有效地抵抗ｖｖＭＤＶ－Ｍｄ５毒株的致瘤作用。Ｚ４＋ＦＣ１２６和３０１Ｂ／１＋ＦＣ１２６ＭＤ双价苗免疫效力无显著差异     

Effect of diluting Marek's disease vaccines on the outcomes of Marek's disease virus infection when challenged with highly virulent Marek's disease viruses

Dilution of Marek's disease (MD) vaccines is a common practice in the field to reduce the cost associated with vaccination. In this study we have evaluated the effect of diluting MD vaccines on the protection against MD, vaccine and challenge MD virus (MDV) kinetics, and body weight when challenged with strains Md5 (very virulent MDV) and 648A (very virulent plus MDV) by contact at day of age. The following four vaccination protocols were evaluated in meat-type chickens: turkey herpesvirus (HVT) at manufacturer-recommended full dose; HVT diluted 1:10; HVT + SB-1 at the manufacturer-recommended full dose; and HVT + SB-1 diluted 1:10 for HVT and 1:5 for SB-1. Vaccine was administered at hatch subcutaneously. One-day-old chickens were placed in floor pens and housed together with ten 15-day-old chickens that had been previously inoculated with 500 PFU of either Md5 or 648A MDV strains. Chickens were individually identified with wing bands, and for each chicken samples of feather pulp and blood were collected at 1, 3, and 8 wk posthatch. Body weights were recorded at 8 wk for every chicken. Viral DNA load of wild-type MDV, SB-1, and HVT were evaluated by real time-PCR. Our results showed that dilution of MD vaccines can lead to reduced MD protection, reduced relative body weights, reduced vaccine DNA during the first 3 wk, and increased MDV DNA load. The detrimental effect of vaccine dilution was more evident in females than in males and was more evident when the challenge virus was 648A. However, lower relative body weights and higher MDV DNA load could be detected in chickens challenged with strain Md5, even in the absence of obvious differences in protection.     

Load of challenge Marek's disease virus DNA in blood as a criterion for early diagnosis of Marek's disease tumors

Outbreaks of Marek's disease (MD) in vaccinated flocks still occur sporadically and lead to economic losses. Unfortunately, adequate methods to predict MD outbreaks are lacking. In the present study, we have evaluated whether high load of challenge MD virus (MDV) DNA in peripheral blood could aid in the early diagnosis of MD and in monitoring efficacy of vaccines against MD. One experiment was conducted to simulate field conditions by combining various vaccines (turkey herpesvirus [HVT] and HVT + MDV serotype 2 [SB1]) and challenge viruses (GA, Md5, and 648A). Vaccine efficacy among our experimental groups ranged from 13.3% to 94.2%. Each chicken was sampled three times during the length of the experiment (3, 5, and 15 wk postchallenge [wpc]), and gross lesions were evaluated in chickens that died and at termination of the experiment. DNA was extracted from whole blood and buffy coats from each sample, and the load of challenge MDV DNA and HVT DNA were quantified by real-time polymerase chain reaction. Chickens that developed MD by the end of the experiment had higher load of challenge MDV DNA (threshold cycle [Ct] glyceraldehyde-3-phosphate dehydrogenase [GAPDH]/Ct glycoprotein B [gB] ratios of 1.0, 1.04, and 1.05 at 3, 5, and 15 wpc, respectively) than those that did not develop MD (Ct GAPDH/Ct gB ratios of 0.7, 0.69, and 0.46 at 3, 5, and 15 wpc, respectively). However, load of HVT DNA in blood was not correlated with the development of tumors (Ct GAPDH/Ct HVT ratios from 0.04 to 0.10 in both groups). Vaccinated groups with >75% protection had statistically significant less challenge DNA virus (Ct GAPDH/Ct gB ratios of 0.76, 0.70, and 0.45 at 3, 5, and 15 wpc, respectively) than less protected groups (Ct GAPDH/Ct gB ratios of 0.92, 0.97, and 0.85 at 3, 5, and 15 wpc, respectively). No differences in the load of HVT DNA could be found between protected and nonprotected groups at any time point of the study (Ct GAPDH/Ct HVT from 0.05 to 0.09 in both groups). Our results showed that load of challenge MDV DNA but not load of HVT DNA in blood can be used as criterion for early diagnosis of MD.     

猪宿主蛋白G3BP1对猪圆环病毒2型在PK15细胞上复制的影响

猪宿主蛋白G3BP1在宿主抵抗病毒感染过程中起着重要作用,然而还未有相关报道G3BP1与猪圆环病毒2型(PCV2)感染过程中的联系。本文构建了G3BP1真核表达载体和干扰RNA,实现在PK15细胞上G3BP1的过表达及敲低。结果发现,PCV2感染细胞24 h后病毒复制出现显著差异,感染48 h相比于感染24 h病毒复制差异更显著,表明G3BP1能显著促进PCV2复制。过表达或敲低G3BP1后,用干扰素刺激DNA(ISD)刺激12 h, G3BP1能促进ISD诱导IFN-βmRNA的表达;感染PCV2 12 h后,G3BP1也能正调控IFN-βmRNA的转录。本文揭示了宿主蛋白G3BP1显著促进PCV2的复制,很可能是通过上调IFN-β表达引起的。     

Examination of the effect of a naturally occurring mutation in glycoprotein L on Marek's disease virus pathogenesis

We recently reported a comparison of glycoprotein-encoding genes of different Marek's disease virus pathotypes (MDVs). One mutation found predominantly in very virulent (vv)+MDVs was a 12-bp (four-amino acid) deletion in the glycoprotein L (gL)-encoding gene in four of 23 MDV strains examined (three were vv+MDVs and one was a vvMDV). This mutation was noted in the gL of the TK (615K) strain, but not in the RL (615J) strain of MDV. These strains have identical mutations in the meq gene characteristic of vv+MDVs but can be distinguished by the mutation in the gL-encoding gene. The TK strain was originally isolated from vaccinated chickens and appeared to confer or enhance horizontal transmission of the vaccine virus, herpesvirus of turkeys (HVT). Because the molecular basis for increased virulence of MDV field strains is unknown, we hypothesized that one mechanism might be by coreplication of MDV-1 strains with HVT and that it could be mediated by the mutation of gL, an essential component of the glycoprotein H/L complex. In this study, we compared the pathogenicity of TK (615K) and RL (615J) strains of MDV in the presence and absence of simultaneous HVT coinfection. MDV infections were monitored at the levels of viremia (for both MDV-1 and HVT), clinical signs of MD, tumor incidence, and mortality in 1) inoculated chickens, 2) chickens exposed at 1 day of age, 3) chickens exposed at 2 wk of age, and 4) chickens exposed to both TK/HVT- and RL/HVT-infected chickens at 6 wk of age. We found high incidences of clinical MD signs in all inoculated treatment groups and all chickens exposed to TK and RL viruses, regardless of the presence of HVT. The median time to death of chickens exposed to TK1HVT-infected chickens, however, was lower than the other treatment groups for contact-exposed chickens. Although this difference was not considered to be statistically significant to a rigorously interpreted degree because of the removal of chickens for sampling from the test groups, these data suggest that replication of the TK strain and HVT, when coadministered, might incrementally affect the virulence of MDV-1 strains. The strict correlation of this enhancement of virulence with the mutation in gL, however, requires additional experiments with genetically identical MDV background strains.     

鸡肌内脂肪双向选择对脂肪性状及相关基因mRNA表达的影响

本试验旨在研究鸡肌内脂肪（IMF）双向选择对脂肪性状及相关基因mRNA表达的影响。试验采用北京油鸡肌内脂肪双向选育系和对照系雏鸡,饲养至56和120 d时,每个系分别屠宰30只母鸡,测定胸肌和腿肌IMF含量、腹脂重、腹脂率及LPL、H-FABP和A-FABP基因mRNA表达量,比较双选系各性状差异,分析IMF遗传选择效果。结果表明,上选系肌肉IMF含量和肉色亮度值（L^＊）显著大于下选系（P〈0.05）,胸肉终pH（pHu）显著低于下选系（P〈0.05）。LPL基因在120日龄上选系腹脂中的mRNA表达量显著高于下选系（P〈0.05）,下选系胸肌中H-FABP基因mRNA的表达显著高于上选系（P〈0.05）。结果表明IMF的双向选择是有效的,该双选系可以作为未来基因定位和基因互作效应研究的宝贵资源群体。     

Characterization of herpesvirus of turkeys. Replication using recombinant DNA

DNA has been isolated from herpesvirus of turkeys (HVT) virions and used to construct a partial gene library in pBR-322. The recombinants have been characterized and shown to contain HVT DNA inserts. A representative recombinant containing a 5.9-kilobase HindIII fragment was used as a probe to quantitate the yields of HVT DNA in vitro and to follow the kinetics of viral DNA replication. The data shown that in chicken fibroblasts, viral DNA synthesis initiates by about 12-14 hr postinfection and that the yield of progeny virus plateaus at 28-30 hr postinfection. Based upon quantitative hybridization to cloned DNA probes, we estimate that approximately 2000 HVT genomes are produced per infected cell in vitro; however, in vivo in persistently infected turkeys, the number of viral genomes was below the level of detection by Southern blotting.     

表达鸡传染性法氏囊病病毒VP2基因的重组火鸡疱疹病毒的构建及生物学特性分析

鸡传染性法氏囊病（IBD）是一种严重危害养禽业的高度致死性和免疫抑制性传染病。为研制IBD重组火鸡疱疹病毒（HVT）活载体疫苗,本研究构建了表达鸡传染性法氏囊病病毒（IBDV）保护性抗原VP2基因的重组HVT并对其体外生物学特性进行了分析。通过RT-PCR扩增IBDV超强毒株VP2基因并克隆入pCI载体,获得重组真核表达质粒pCI-VP2。用限制性内切酶将携带CMV启动子的VP2基因表达框架切下,连接于入门质粒pENTR,构建获得重组入门质粒pENTR-VP2。将pENTR-VP2与HVT重组黏粒H3-Kan/ccdB进行LR重组反应,构建重组表达黏粒H3-VP2。用H3-VP2与其他4个相互重叠并覆盖HVT全基因组的黏粒共同转染鸡胚成纤维细胞（CEF）,拯救获得重组病毒rHVT-VP2。将重组病毒在CEF中连续传至20代后用PCR、间接免疫荧光试验和免疫印迹试验进行检测,并绘制重组病毒体外生长曲线,分析其体外复制特性。结果表明,重组病毒rHVT-VP2能够稳定表达VP2蛋白,rHVT-VP2在CEF中的复制能力与亲本病毒无明显差异。重组病毒rHVT-VP2免疫鸡后能够诱导产生IBDV中和抗体,并对IBDV强毒株攻击引起的死亡提供90%免疫保护。重组病毒rHVT-VP2的构建为研制IBD重组HVT活载体疫苗奠定了基础,对IBD的防控具有重要意义。     

The efficacy of recombinant fowlpox vaccine protection against Marek's disease: its dependence on chicken line and B haplotype

Earlier studies have shown that the B haplotype has a significant influence on the protective efficacy of vaccines against Marek's disease (MD) and that the level of protection varies dependent on the serotype of MD virus (MDV) used in the vaccine. To determine if the protective glycoprotein gene gB is a basis for this association, we compared recombinant fowlpox virus (rFPV) containing a single gB gene from three serotypes of MDV. The rFPV were used to vaccinate 15.B congenic lines. Nonvaccinated chickens from all three haplotypes had 84%-97% MD after challenge. The rFPV containing gB1 provides better protection than rFPV containing gB2 or gB3 in all three B genotypes. Moreover, the gB proteins were critical, since the B*21/*21 chickens had better protection than chickens with B*13/*13 or B*5/*5 using rFPV with gB1, gB2, or gB3. A newly described combined rFPV/gB1gEgIUL32 + HVT vaccine was analyzed in chickens of lines 15 x 7 (B*2/*15) and N (B*21/*21) challenged with two vv+ strains of MDV. There were line differences in protection by the vaccines and line N had better protection with the rFPV/gB1gEgIUL32 + HVT vaccines (92%-100%) following either MDV challenge, but protection was significantly lower in 15 X 7 chickens (35%) when compared with the vaccine CVI988/Rispens (94%) and 301B1 + HVT (65%). Another experiment used four lines of chickens receiving the new rFPV + HVT vaccine or CVI988/Rispens and challenge with 648A MDV. The CVI 988/Rispens generally provided better protection in lines P and 15 X 7 and in one replicate with line TK. The combined rFPV/gB1gEgIUL32 + HVT vaccines protected line N chickens (90%) better than did CVI988/Rispens (73%). These data indicate that rFPV + HVT vaccines may provide protection against MD that is equivalent to or superior to CVI988/ Rispens in some chicken strains. It is not clear whether the rFPV/gB1gEgIUL32 + HVT vaccine will offer high levels of protection to commercial strains, but this vaccine, when used in line N chickens, may be a useful model to study interactions between vaccines and chicken genotypes and may thereby improve future MD vaccines.