由法氏囊病毒引起鸡的免疫抑制

1法氏囊 禽类法氏囊是雏鸡免疫系统的中枢免疫器官.它是鸟类特有的免疫器官,所以值得特别关注.许多研究已搞清了其生理学作用.雏鸡前3周是法氏囊快速发展时期,在这个时期法氏囊迅速增殖,3周龄后法氏囊就逐渐退化,研究表明,大约在12周龄,法氏囊就完全退化.     

Immunosuppression induced by infectious bursal disease virus.

Immunosuppression caused by infectious bursal disease virus (IBDV) is of major interest because of the widespread occurrence of the infection in commercial chickens. Infection with IBDV at an early age significantly compromises the humoral and local immune responses of chickens. The cellular immune response is also compromised by apparently to a lesser extent and for a short period. The immunosuppression seems to be a result of direct effect (lysis) of B cells or their precursors. Other mechanisms of immunosuppression have been suggested, notably the development of suppressor cells.     

Random cDNA probes to infectious bursal disease virus

Viruses from three commercially available modified-live infectious bursal disease virus vaccines were propagated in tissue culture. Following this, a series of 32P-labeled probes was generated using the entire RNA genome as template for formation of randomly primed cDNAs. These probes were tested against dot blots of the three vaccine strains, as well as the USDA standard challenge strain and one field-origin strain. Dot blots were made of both crude tissue extract and LiCl-precipitated RNA genome. All three probes detected the standard challenge and field strains. Although differences in probe binding could be quantified among the strains, cross-hybridization indicated considerable homology within genomic regions preferentially transcribed under the experimental conditions.     

传染性囊病病毒诱导细胞凋亡的初步观察

用１株ＩＢＤＶ强毒株感染易感小鸡，对病鸡法氏囊进行电镜观察及ＤＮＡ电泳分析，直接观察到病鸡法氏囊中Ｂ淋巴细胞凋亡的典型形态学特征和生化变化：染色质凝聚成团，集于核膜旁，胞膜与核膜出现凹陷，细胞拉长变形，最后细胞裂解成由膜包围着的小团，被网状细胞和巨噬细胞吞噬；感染ＩＢＤＶ２４～４８ｈ的法氏囊细胞总ＤＮＡ在电泳谱上呈梯状条带，而从正常的法氏囊提取的总ＤＮＡ在电泳谱上只有１条带。结果表明，ＩＢＤＶ感染小鸡之后，导致了法氏囊中Ｂ淋巴细胞的凋亡。作者据此推断，细胞凋亡是造成Ｂ淋巴细胞数量减少，从而导致小鸡免疫抑制的原因     

传染性法氏囊病病毒抗原表位分析--单克隆抗体的制备与鉴定

将传染性法氏囊病病毒(IBDV)分离毒株ZB和TA3的细胞培养物采用不连续蔗糖密度梯度离心的方法浓缩纯化病毒,免疫BALB/c小鼠,运用淋巴细胞杂交瘤技术将免疫鼠脾细胞与SP2/0骨髓瘤细胞融合,建立了6株分泌抗IBDV单克隆抗体(McAb)的杂交瘤细胞系1C1、1E6、2B2、2G8、3A2、3E2。间接ELISA测定,杂交瘤细胞培养上清液的抗体效价为102,诱生腹水的抗体效价为106～107。相加ELISA分析,这6株单克隆抗体对应不同的病毒抗原表位。中和试验结果表明,2G8对病毒有较强的中和能力,腹水的中和效价为105。用2B1和3E2配对建立的夹心ELISA可特异地检测IB DV。     

Prevention of avian lymphoid leukosis by induction of bursal atrophy with infectious bursal disease viruses.

Five groups of genetically susceptible chickens were inoculated at hatching with lymphoid leukosis virus; four of these were given infectious bursal viruses of varying virulence at 14 days of age and one group was not inoculated (control). All chickens in the control group developed evidence of lymphoid leukosis by 180 days. Two groups given relatively virulent bursal disease viruses, which destroyed bursal lymphoid cells, did not develop lymphoid leukosis. Treatment with avirulent vaccines had no visible effect on bursal morphology and did not significantly alter the incidence of lymphoid leukosis in two other groups, although the time of development was delayed. Results of our study show that viral-induced destruction of the bursa of Fabricius eliminates the development of lymphoid leukosis but that infection without bursal destruction has little effect on lymphoid leukosis.     

Baculovirus virions displaying infectious bursal disease virus VP2 protein protect chickens against infectious bursal disease virus infection

Infectious bursal disease (IBD) is an acute and contagious viral infection of young chickens caused by IBD virus (IBDV). The VP2 protein of IBDV is the only antigen for inducing neutralizing antibodies and protective immunity in the natural host. In the current study, we have succeeded in construction of one recombinant baculovirus BacSC-VP2 expressing His6-tagged VP2 with the baculovirus envelope protein gp64 transmembrane domain (TM) and cytoplasmic domain (CTD). The His6-tagged recombinant VP2 was expressed and anchored on the plasma membrane of Sf-9 cells, as examined by western blot and confocal microscopy. Immunogold electron microscopy demonstrated that the VP2 protein of IBDV was successfully displayed on the viral surface. Vaccination of chickens with the VP2-pseudotyped baculovirus vaccine (BacSC-VP2) elicited significantly higher levels of VP2-specific enzyme-linked immunosorbent assay antibodies and neutralizing antibodies than the control groups. IBDV-specific proliferation of lymphocytes was observed in chickens immunized with the recombinant BacSC-VP2. An in vivo challenge study of the recombinant baculovirus BacSC-VP2 showed effective protection against a very virulent (vv) IBDV infection in chickens. In addition, mortality and gross and histopathological findings in the bursa demonstrated the efficacy of the vaccine in reducing virulence of the disease. These results indicate that the recombinant baculovirus BacSC-VP2 can be a potential vaccine against IBDV infections.     

鸡传染性法氏囊病病毒的快速检测

随着 IBDV变异株的出现 ,发病鸡常不产生法氏囊的肉眼病变 ,由于传染性和非传染性因素亦可引起淋巴细胞减少和法氏囊坏死 ,所以 ,采取组织病理学方法诊断 IBDV感染并不完全可靠。由于主动性抗体应答需要一定的时间及大多数雏鸡都带有母源抗体 ,因此血清学早期诊断也不完全可靠。该试验采用本所研究的 IBD快速试纸与经典的琼扩试验 ,在对 IBDV的检测效果上进行了详细的比较 ,介绍如下。1　材料与方法1 .1　 IBD快速检测试纸　由河南省农业科学院生物技术研究所制备提供。1 .2　试验鸡　 1日龄试验鸡 30 0只由河南农业大学试验鸡场提…     

The role of T cells in protection by an inactivated infectious bursal disease virus vaccine

The current belief is that the humoral immune response plays the principal role in defense against virulent infectious bursal disease virus (IBDV). In this study we used a model, in which chickens were compromised in functional T cells by neonatal thymectomy and Cyclosporin A (TxCsA) treatment, to demonstrate the role of T cells in protective immunity against IBDV. We demonstrated that T cells were necessary to achieve full protection against virulent IBDV. When T cell compromised TxCsA-treated chickens were vaccinated with an inactivated IBDV (iIBDV) vaccine, 91% were not protected against IBDV challenge in comparison to T cell-intact chickens, which had a protection rate of 91%. The iIBDV vaccine induced virus neutralizing (VN) and ELISA antibodies, respectively, in 65 and 5% of TxCsA-treated, and in 100 and 58% of T cell-intact birds. These observations provide evidence that the stimulation of T helper cells is needed for the production of protective antibody levels in iIBDV-vaccinated chickens. Passive administration of VN anti-IBDV antibodies inducing a circulating antibody level of log(2)8 in chickens revealed that the levels of antibodies that protected T cell-intact chickens against virulent IBDV challenge were not protective for TxCsA chickens. These results indicated that antibody alone was not adequate in inducing protection against IBDV in chickens and that T cell-involvement was critical for protection. We propose that the inability of iIBDV to protect TxCsA chickens was due to compromised T cell immunity, functional T helper cells and most likely also cytotoxic T cells are needed in iIBDV vaccine protection.     

黄芩苷体外抗传染性法氏囊病病毒作用

为探讨黄芩苷体外抗传染性法氏囊病病毒(IBDV)感染鸡胚成纤维细胞系(DF1)作用机制,以DF1细胞为宿主细胞,利巴韦林为阳性对照药物,从黄芩苷对IBDV的直接灭活作用、阻滞作用、抑制吸附、穿入及其复制5个方面探讨黄芩苷抗IBDV机理。结果显示,黄芩苷的CC50为(206.48±12.74)mg/L,EC50为(46.76±3.15)mg/L,选择指数SI为4.415,在无毒质量浓度范围内其对IBDV的最高抑制率为72.02%;在阻滞试验和复制抑制试验中最高抑制率分别达到60.85%和68.11%;在病毒吸附、穿入抑制和直接灭活试验中抑制率很低,表明黄芩苷不能阻断IBDV对DF1细胞的吸附、穿入和直接灭活。结果表明,黄芩苷在体外可有效抑制IBDV对DF1细胞的感染,其抗病毒机制可能是干扰病毒的复制和阻滞,提示黄芩苷可作为预防及治疗传染性法氏囊病病毒的药物。     

Very virulent infectious bursal disease virus in southeastern Europe

Clinical outbreaks of severe acute infectious burial disease (IBD) were recorded since the mid- and late 1990s in several countries in the southeastern part of Europe. Epidemiologic data showed that both infectious bursal disease virus (IBDV)-vaccinated and IBDV-nonvaccinated chickens were affected with acute IBD and mortality up to 50% independent of the IBDV vaccination status of the appropriate parent flocks. For investigation of the causative agent of acute IBD, the variable region of VP2 was amplified, cloned, and sequenced. Nucleotide sequence analysis of polymerase chain reaction fragments showed several silent nucleotide exchanges in comparison with the sequence of the very virulent (vv) IBDV strain UK661. Also, restriction enzyme cleavage sites proposed specific for vvIBDV were present in all investigated strains. On the basis of clinical signs in affected flocks, recorded epidemiologic data, and sequence analysis, it is very likely the IBD-causing strains were of the vv phenotype.     

Susceptibility of ducks and duck-origin cell cultures to infectious bursal disease virus

Specific-pathogen-free (SPF) ducks that were 1, 3, 4, 7, 10, 30, and 180 days old were inoculated experimentally orally or nasally with infectious bursal disease virus (IBDV). Attempts to induce clinical disease in ducks with strain J1 or FK-78 of IBDV were unsuccessful. Virus-recovery attempts from organ and intestinal contents were also unsuccessful. No significant gross or histopathological lesions were found in liver, spleen, kidney, heart, or bursa of Fabricius of 1- and 3-day-old ducks at 4 or 7 days postinoculation. The ratios of bursa weight to body weight of 1-, 10-, and 30-day-old inoculated and control ducks revealed no difference at 21 days postinoculation. The ducks responded serologically, however, by developing both virus-neutralizing and agar-gel-precipitin antibodies. Virus multiplied in embryonated duck eggs and duck embryo fibroblast cells but not in duck kidney cells.     

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%.