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1.
The pathologic consequences of chicken anemia virus (CAV) oral inoculation in 4-wk-old broiler breeders of different major histocompatibility B complex (MHC) genotypes were evaluated. MHC B complex was determined by hemagglutination and sequence-based typing. Clinical signs, serology, gross lesions, histopathologic analysis, and CAV genome quantification were used to evaluate disease progression. Clinical disease was not apparent in the inoculated broilers throughout the experimental period. At 14 days postinoculation, antibodies against CAV were detected in 26.4% (29/110) of the inoculated birds. The distribution of percent positive was 34.6% (9/26) and 32.3% (10/31) of the chickens with B A9/A9 and B A9/A4 MHC genotypes, respectively, and seroconversion in six other genotypes was 19% (10/53). These differences among MHC genotypes for specific seroconversion rate were not statistically significant. CAV genomes were detected in the thymus of 87.7% (93/110) of the inoculated birds with no statistically significant differences between MHC genotypes. Mild thymic lymphocytolysis, lymphedema, and medullary hemorrhage were observed in the inoculated chickens. Histomorphometric analysis showed that cortical lymphocyte-to-parenchyma ratios did not differ between inoculated and uninoculated groups or among MHC genotypes. Similar findings have been reported previously in white-leghorn chickens of similar age, suggesting that broilers show a similar resistance to the effects of CAV infection at this age. The absence of significant clinical and pathological changes in the orally inoculated broilers at this age contrasts with CAV-associated thymus damage seen frequently in condemned commercial broilers at harvest. 相似文献
2.
Drén CN Kant A Van Roozelaar DJ Hartog L Noteborn MH Koch G 《Acta veterinaria Hungarica》2000,48(4):455-467
The pathogenesis of chicken infectious anaemia virus (CAV) infection was studied in 6-week-old and one-day-old SPF chickens inoculated intramuscularly with graded doses of Cux-1 strain (10(6)-10(2) TCID50/chicken). Viraemia, virus shedding, development of virus neutralizing (VN) antibodies and CAV distribution in the thymus were studied by virus isolation, polymerase chain reaction (PCR), immunocytochemistry (IP) and in situ hybridization until postinfection day (PID) 28. In 6-week-old chickens infected with high doses of CAV, viraemia and VN antibodies could be detected 4 PID and onward without virus shedding or contact transmission to sentinel birds. However, virus shedding and contact transmission were demonstrated in one-day-old infected chickens. In the 6-week-old groups infected with lower doses, VN antibodies developed by PID 14, transient viraemia and virus shedding were detected. The thymus cortex of all 1-day-old inoculated chickens stained with VP3-specific mAb. Cells with positive in situ hybridization signal were fewer and scattered throughout the thymus tissue of the one-day-old inoculated chickens as compared to IP-positive cells. These results suggest that early immune response induced by high doses of CAV in 6-week-old chickens curtails viral replication and prevents virus shedding. 相似文献
3.
鸡贫血病病毒感染雏鸡细胞周期的研究 总被引：1，自引：0，他引：1
用流式细胞仪对雏鸡感染鸡贫血病毒后不同时期胸腺和骨髓细胞的细胞周期进行了分析，结果显示感染鸡骨髓和胸腺发生了Ｇ１阻滞，这表明ＤＮＡ合成抑制，Ｇ２／Ｍ期细胞数量明显减少，这说明增殖性细胞在减少。本实验结果提示增殖性细胞减少是鸡传染性贫血病（ＣＩＡ）中胸腺淋巴细胞和骨髓造血细胞大量减少的重要原因之一，这为阐明ＣＡＶ的发病机理提供了新资料 相似文献
4.
The effects of a simultaneous and/or a subsequent coinfection with chicken anemia virus (CAV) isolate 10343 and fowl adenovirus (FAV) isolate 341 in specific-pathogen-free light chickens were evaluated. The simultaneous coinfection was conducted by the intramuscular route, whereas the subsequent coinfection trial considered FAVs administered orally. In trial 1, 20-day-old chickens simultaneously coinfected with CAV (10343) and FAV (341) intramuscularly (i.m.) showed 55% mortality and characteristic signs and lesions of inclusion body hepatitis/hydropericardium (IBH/HPS). In contrast, birds singly infected with FAV i.m. showed 10% mortality due to IBH/HPS. Trial 2 showed that birds receiving FAV 341 orally at day 7 post-CAV intramuscular infection (group A) developed a mild form of IBH/HPS with presence of inclusion bodies (INIBs) in 60% of the group and virus-neutralizing antibodies against FAV 341. Group B (FAV orally 14 days after CAV) showed significant decreased weight gain, nonspecific microscopic lesions in the liver, spleen, bursa, and thymus, and an antibody response against FAV 341. However, no INIBs could be detected in the hepatocytes of these chickens. Group C (FAV orally 35 days after CAV) showed nonspecific histopathologic changes in the liver and no antibody response to FAV. The oral single infection with FAV isolate 341 induced neither mortality nor macroscopic lesions of IBH/HPS in the birds. The present results corroborate previous reports on pathogenicity of Chilean FAV isolates, which suggest that synergism with other viruses or prior immunosuppression is necessary to produce IBH/HPS in chickens. These results also suggest that the susceptibility of chickens to FAV oral infection resulting in IBH/HPS varies throughout the course of CAV infection. 相似文献
5.
Our previous genetic characterization of chicken anemia virus (CAV) in commercial broiler chickens in Alabama revealed a previously undetected polymorphism: a glutamine codon at VP1 position 22, in 7 of the 14 sequences. The novel glutamine codon was always found in association with a VP1 "hypervariable region" identical to CAV field isolates that replicate poorly in culture. The complete genome of CAV73, representative of the sequences with the novel polymorphism, was generated from cloned polymerase chain reaction (PCR) fragments amplified directly from naturally infected tissues. CAV73 had been detected in 31-day-old broilers submitted for examination for reasons unrelated to anemia. After electroporation of the cloned genomes into MDCC-CU147 lymphoblastoid cells, the regenerated CAV caused the culture to fail within 9 days, and the medium contained 5 X 10(6) TCID50 CAV/ml. Use of MDCC-CU147 cells was essential, as identical electroporation of MDCC-MSB1 cells failed to generate CAV able to destroy the culture within 8 wk. Regenerated CAV73 produced anemia and severe lymphocytic depletion of the thymus when inoculated into susceptible 3-day-old chickens and was reisolated from these chickens. Furthermore, it replicated in low- and high-passage MDCC-MSB1 cells similarly to a low-passage CAV field isolate that contains a different VP 1 "hypervariable region." The regeneration of CAV from PCR products directly from naturally infected carcasses, as performed in this study, provides a tool for the evaluation of distinct genetic polymorphisms that may be detected in specimens where infective virions are no longer available. Our results also provide some insight into the differential susceptibility of cell lines for low-passage CAV field isolates. 相似文献
6.
鸡贫血病毒实验感染雏鸡胸腺与骨髓的超微结构观察 总被引：2，自引：1，他引：1
用鸡贫血病毒 Ｃｕｘ １ 毒株接种于 １ 日龄 Ｓ Ｐ Ｆ 雏鸡，在确认感染成功的基础上，对感染雏鸡胸腺和骨髓的超微结构进行了观察。电镜观察表明，感染鸡骨髓和胸腺细胞的形态变化具有较典型的凋亡特征，如细胞膜出泡、核染色质凝结边集、细胞核裂解、出现凋亡小体等，此外还见有可能由病毒粒子形成的环状物。本试验为证明鸡贫血病毒能引起细胞凋亡提供了依据。 相似文献
7.
Agustina Rimondi Silvina Pinto Valeria Olivera Marina Dibárbora Mariano Pérez-Filgueira María Isabel Craig Ariel Pereda 《Veterinary research》2014,45(1)
Infection of poultry with chicken anemia virus (CAV) is implicated in several field problems in broiler flocks due to the immunosuppression generated and, consequently, the increased susceptibility to secondary infections. Recently, we have reported an increased occurrence of clinical cases caused by CAV strains distantly related to those commonly used for vaccination. In order to understand the behavior of two Argentinean CAV strains (CAV-10 and CAV-18) in two-week-old chickens, an immune and histopathological study was performed. Neither mortality nor clinical signs were observed in the infected or control groups. Thymus lobes from chickens infected with both CAV viruses were smaller compared to the negative control group. At 14 days post-infection (dpi), only chickens inoculated with CAV-10 show a severe depletion of lymphocytes in the thymus cortex and in follicles from the bursa of Fabricius. Also thymopoiesis disorders, such as reduction in the percentage of total DP (CD4 + CD8α+) thymocytes and alteration in the percentages of DP subpopulations, were more important in animals inoculated with the CAV-10 than the CAV-18 strain. In addition, only animals infected with CAV-10 show a decrease in CD8αβ splenocytes. Altogether our results show that, although both Argentinean CAV strains produce subclinical infections in chickens causing immunosuppression at 14 dpi, they might differ in their in vivo pathogenicity. 相似文献
8.
为评价鸡传染性贫血病毒AV1550株的致病性,取1日龄、7日龄和14日龄SPF鸡分别经胸部肌肉注射不同病毒含量的病毒液,同时设置正常对照,隔离饲养观察21日。感染后14日采血测定红细胞压积,21日统计死亡率、体重变化以及胸腺、骨髓、法氏囊病变情况并测定1日龄SPF鸡感染后不同组织中的病毒载量。结果表明,1日龄SPF鸡感染AV1550株后,表现出精神沉郁、增重减缓、贫血等明显的临床症状,死亡率为53.9%;死亡鸡或观察期结束时存活鸡剖检,可见胸腺萎缩,骨髓变成淡黄色;不同剂量感染后14日,均能引起红细胞压积显著下降;21日时,胸腺病毒载量最高,可达106.7copies/mg 。7日龄SPF鸡感染后,出现增重减缓,高感染剂量（100000EID50）出现贫血,部分鸡出现胸腺萎缩和骨髓病变,但病变率低于30%。14日龄SPF鸡感染后,不引起明显临床症状。研究证实,CAV对SPF鸡的致病性具有明显的日龄依赖性,红细胞压积降低、骨髓病变、胸腺萎缩以及胸腺病毒载量测定可作为评价CAV致病的指标。 相似文献
9.
感染鸡贫血病毒雏鸡接种新城疫疫苗后免疫功能和免疫调节的变化 总被引：1，自引：1，他引：0
雏鸡1日龄感染鸡贫血病毒，8日龄接种Lasota疫苗，以未感染免疫雏鸡为对照，于免疫后7、14、28d检测血清免疫球蛋白IgG、IgM、IgA,在凝抑制抗体（HI）滴度；胸腺、法氏囊、脾脏T细胞、IgG^ 、IgM^ 、IgA^ ,抗体生成细胞数量及T、B细胞增殖反应；胸腺、脾脏细胞因子IL－2、IFN活性的变化。结果发现，感染CAV雏鸡Lasota疫苗免疫后，其血清IgG、IgM、IgA免疫球蛋白含量明显减少，HI抗体滴度降低；胸腺、法氏囊、脾脏T细胞、抗体生成细胞数量降低及T、B细胞增殖反应减弱，胸腺、脾脏IL－2及TNF诱生活性降低，表明其细胞免疫和体流免疫功能以及细胞因子免疫调节作用均未感染免疫雏鸡明显减弱。 相似文献
10.
Genetic characterization of chicken anemia virus from commercial broiler chickens in Alabama. 总被引：4，自引：0，他引：4
Chicken anemia virus (CAV) isolates show extremely limited genetic variability worldwide. We determined the nucleotide sequence of an 823-nucleotide portion of the 2.3-kb CAV genome found in 10 liver and/or spleen specimens of Alabama 29-to-49-day-old commercial broiler chickens exhibiting lymphocyte depletion of the thymus submitted to the state diagnostic laboratory because of problems unrelated to anemia. We determined the nucleotide sequence directly from DNA isolated from tissues, without isolation of virus in culture. This procedure enabled us to characterize CAV that might not have replicated in culture and avoided the potential for changes during passage. Results confirmed the limited genetic variability of CAV. All sequences were identical in 93% of nucleotide positions. The sequences encoded only two distinct VP1 hypervariable regions, and both had been found previously in other CAV isolates. A novel amino acid, glutamine, was found at VP1 position 22 in half the sequences, replacing the histidine residue encoded by most previously characterized CAV genomes. We were able to distinguish among CAV genomes with different codons at VP1 amino acid 22 and different hypervariable regions by restriction endonuclease analysis of polymerase chain reaction products. 相似文献
11.
Vertical induction of the inclusion body hepatitis/hydropericardium syndrome with fowl adenovirus and chicken anemia virus 总被引：2，自引：0，他引：2
The hypothesis that fowl adenovirus (FAV) and chicken anemia virus (CAV), transmitted vertically and simultaneously, induce the inclusion body hepatitis (IBH)/hydropericardium (HP) syndrome in progeny chickens was tested. Thus, 35-wk-old light brown layer breeders, showing absence of antibodies against FAV and variable titers against CAV, were intramuscularly singly infected with the FAV serotype 4 isolate 341 or dually infected with CAV (isolate 10343) and FAV. All hens (groups A [FAV alone], B [FAV + CAV], and C [noninfected]) were clinically healthy throughout the experimental period. Both infectious viruses FAV and CAV were isolated from progenies obtained as early as 5 days after infection of their breeders. Hematocrit, serum proteins, and aspartate-aminotransferase values showed a few statistical differences between the progeny groups. Most of these differences were detected in the progeny chickens of group B. However, almost all values met reference values for the species. The pathologic findings showed that progeny chickens obtained from both singly and dually infected breeders developed macroscopic and histopathologic changes of IBH/HP. The pathologic findings shown by progeny chickens of group A (FAV) were not expected because neither synergism nor prior immunodepression by CAV was concurrent. Chickens of group B (CAV + FAV) also developed IBH/HP. Although not many differences in the evaluated parameters between groups A and B were statistically significant, most pathologic findings of group B indicated a more severe manifestation of the disease. However, because FAV alone did reproduce the syndrome, the results shown by group B would not allow a definitive confirmation of the hypothesis that the association of FAV and CAV is necessary for the successful induction of the IBH/HP syndrome in chickens when transmitted vertically. 相似文献
12.
Haridy M Sasaki J Ikezawa M Okada K Goryo M 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2012,74(6):757-764
Subclinical infection of chicken anemia virus (CAV) at 4 to 6 weeks of age, after maternal antibodies have waned, is implicated in several field problems in broiler flocks. In order to understand the pathogenesis of subclinical infection with CAV, an immunopathological study of CAV-inoculated 4-week-old SPF chickens was performed. Sixty 4-week-old SPF chickens were equally divided into CAV and control groups. The CAV group was inoculated intramuscularly with the MSB1-TK5803 strain of CAV. Neither mortality nor anemia was detected in the CAV and control groups. In the CAV group, no signs were observed, except that some chickens were grossly smaller compared with the control group. Sporadic thymus lobes appeared to be reddening and atrophied. Within the first two weeks p.i. of CAV, there was a mild to moderate depletion of lymphocytes in the thymus cortex and spleen in some chickens. Moreover, lymphoid depletion of the bursa of Fabricius, proventriculus and cecal tonsils was observed. Hyperplastic lymphoid foci were observed in the liver, lungs, kidneys and heart at the 4th week p.i. of CAV. Immunohistochemically, a moderate lymphoid depletion of CD4(+)and CD8(+) T cells in the thymus cortex and spleen was observed in some chickens within two weeks p.i. of CAV. CAV inclusions and antigens were detected infrequently in the thymus cortex and spleen. It could be concluded that the immunosuppression in subclinical infection with CAV occurs as a result of reduction of cellular immunity. 相似文献
13.
S D Fitzgerald S J Kingwill S Briggs O Awolaja A Basile L Griffioen E A Potter C C Wu S P Taylor W M Reed 《Avian diseases》1999,43(3):476-483
The purpose of this series of experiments was to determine the effect of various types of immunosuppressive treatments (cyclophosphamide, infectious bursal disease virus [IBDV], chicken anemia virus [CAV], and combination infection with IBDV and CAV) on susceptibility of chickens to challenge with avian polyomavirus. In the first experiment, chickens were chemically bursectomized with intraperitoneal injections of cyclophosphamide; in the second study, chickens were orally inoculated with IBDV; in the third study, birds were intramuscularly inoculated with CAV; and in the final study, birds were inoculated with both IBDV and CAV. In all experiments, chickens were challenged with 10(4.7) tissue culture infective doses of polyomavirus intraperitoneally. Only chemically bursectomized chickens developed lesions similar to those found in the naturally occurring multisystemic fatal form of polyomavirus infection seen in psittacine nestlings, including hepatic necrosis and large pale intranuclear inclusions. 相似文献
14.
鸡贫血病毒VP1和VP2蛋白在家蚕中的联合表达 总被引：1，自引：0，他引：1
将鸡贫血病毒VP1和VP2基因分别克隆入转换载体pBacPAK8中，获得重组转移质粒pBac-vp1和pBac-vp2。以上两质粒分别与CvnⅠ酶切线性化的亲本病毒Bm-BacPAK6DNA共转染家蚕细胞，通过蓝白斑筛选，纯化得到重组病毒Bm-vp1和Bm-vp2。PCR分析表明Vp1和Vp2基因已整合进杆状病毒基因组中。将Bm-vp1和Bm-vp2共感染5龄家蚕，通过表达产物免疫SPF鸡产生的抗血清与CAV感染的MDCC－MSB1细胞的间接荧光抗体分析，证明表达产物能诱导鸡产生相应的抗体。该研究表明，表达VP1和VP2蛋白的重组家蚕杆状病毒（recombinant BmNPV）是很有前途的CAV亚单位疫苗的生产系统。 相似文献
15.
Day-old, straight-run broiler chickens were procured from a hatchery located in the Pacific Northwest. The chickens were subdivided individually into nine groups of 20 chickens. The chickens were tagged, housed in isolation chambers on wire, fed commercial broiler feed, and given water ad libitum. Three isolates of Campylobacter jejuni of poultry origin and one of human origin were tested in this study. Various C. jejuni cultures were inoculated into 9-day-old chickens by crop gavage. Four groups of 20 chickens were inoculated at a dose level of 0.5 ml of 1 x 10(2) colony-forming units (CFU)/ml. The other four groups were inoculated with 0.5 ml of 1 X 10(4) CFU/ml. One group of 20 chickens was kept as an uninoculated control group. Four randomly selected chickens from each of the inoculated and uninoculated groups were necropsied at 5, 12, and 19 days postinoculation (DPI). The C. jejuni was cultured and enumerated from a composite of the upper and midintestine and the cecum. Body weights of all chicken groups at 7 days of age and at 5, 12, and 19 DPI were measured and statistically analyzed. No significant differences were present in the mean body weights (MBWs) of 7-day-old, 5 DPI, and 12 DPI male and female broiler chickens inoculated with C. jejuni at both dose levels compared with uninoculated controls. Differences in MBWs of the male and female broilers at 19 DPI were observed in some of the groups. Results of the C. jejuni culture enumeration mean (CEM) of composite intestine samples at 5 DPI from all inoculated chicken groups, irrespective of the dose level, ranged from (2.5 +/- 5.0) x 10(2) to (2.8 +/- 4.8) x 10(5) CFU/g (mean +/- SD). Results of cecum C. jejuni CEM at 5 DPI inoculated at both dose levels ranged from (2.5 +/- 5.0) x 10(6) to (1 +/- 0.0) x 10(7) CFU/g in all treatment groups irrespective of the dose level. CEM results from the composite intestine samples at 12 and 19 DPI increased by 1 log unit, or sometimes more. Results of cecum C. jejuni CEM at 5 DPI inoculated at both dose levels ranged from (2.5 +/- 5.0) x 10(6) to (1 +/- 0.0) x 10(7) CFU/g in all treatment groups irrespective of the dose level. Increases of 2-5 log units in C. jejuni CEM was present in chicken groups inoculated with 1 X 10(2) CFU of C. jejuni, and a 2- to 3-log increase was present in groups inoculated with a higher dose level of C. jejuni at 12 DPI. The results of C. jejuni CEM from cecal samples at 19 DPI were similar to chicken groups at 12 DPI. Campylobacterjejuni was not isolated from the uninoculated control chickens at 5, 12, and 19 DPI. Clinical signs of illness or gross pathologic lesions were not present in any of the chicken groups during this study. No lesions were present on histopathologic evaluations in C. jejuni-inoculated chickens or uninoculated control chickens. 相似文献
16.
鸡体内减毒鼠伤寒沙门氏菌的繁殖和免疫反应 总被引：2，自引：1，他引：1
初步研究了cya和crp双基因突变减毒鼠伤寒沙门氏菌(Salmonella typhimurium)在鸡体内的繁殖和免疫反应。1、4或7日龄肉鸡分别经口感染10^8或10^9CFU减毒S．typhimurium X4550，接种后3—4周鸡体内特异性细胞和体液免疫达到最高峰。4日龄口服10^9CFu组免疫效果最佳，但1日龄高剂量组表现增重降低及免疫抑制。28日龄每鸡口服攻击10^10CFU强毒S．typhimurium 50333，各免疫组保护率为100％。同时免疫鸡还能全部或部分阻止沙门氏菌在肝脏和脾脏的繁殖。接种后病毒S．typhimurium在泄殖腔的检出时间为4周左右。 相似文献
17.
Coinfection of specific-pathogen-free chickens with Marek's disease virus (MDV) and chicken infectious anemia virus: effect of MDV pathotype 总被引：3，自引：0，他引：3
Both Marek's disease virus (MDV) and chicken infectious anemia virus (CIAV) infections are prevalent in chickens throughout the world. In the past decade, MDV strains with increased virulence (very virulent plus MDV pathotype [vv+MDV]) have been isolated. The purpose of this experiment was to determine the effects of coinfection of chickens with CIAV and a vv+MDV isolate. Specific-pathogen-free chickens were inoculated at 1 day posthatch with RB1B (very virulent MDV pathotype [vvMDV]) only, 584A (vv+MDV) only, CIAV only, RB1B + CIAV, 584A + CIAV, or nothing. Samples of spleen, thymus, and bursa of Fabricius were collected at 4, 7, 10, and 13 days postinoculation (DPI). Thymic and bursal atrophy at 13 DPI and final mortality at 30 DPI were significantly greater in chickens inoculated with 584A with or without added CIAV, or with RB1B plus CIAV, compared with birds inoculated with RB1B alone. Both amounts of virus reisolated and levels of virus detected by quantitative-competitive polymerase chain reaction were greater at 4 DPI in 584A inoculates compared with RB1B inoculates. To monitor the early cytolytic infection, northern analysis was done with a probe for the MDV immediate early gene ICP4 (infected cell protein 4). In the absence of CIAV, ICP4 expression was more apparent in chickens inoculated with 584A than in those inoculated with RB1B. CIAV coinfection increased ICP4 expression in the spleens of chickens infected with RB1B. These results indicated that inoculation of chickens with the 584A isolate caused a more robust early cytolytic infection compared with inoculation with RB1B alone and support the classification of 584A as a vv+MDV strain. Coinfection with CIAV exacerbated vvMDV strain RB1B infection. The extent of this exacerbation was less evident when birds were coinfected with 584A and CIAV. 相似文献
18.
19.
根据鸡传染性贫血病病毒(chicken infectious anemia virus,CAV)基因组保守区域设计1对特异性引物和探针,通过优化反应条件,建立了一种快速检测CAV的TaqMan实时荧光定量PCR方法,同时验证其特异性、灵敏性和重复性.本试验建立的TaqMan实时荧光定量PCR方法灵敏度可达1.8×101拷贝/μL,远高于常规PCR方法;并与禽类其他病毒性疾病无交叉反应,具有高特异性.用分离的病毒人工感染1日龄SPF雏鸡,14日龄剖检,对感染鸡体内各器官的病毒分布及载量进行检测,结果表明,在脑、心脏、肝脏、脾脏、肺脏、肾脏、胸腺、法氏囊和血清中均可检测到病毒,肝脏、胸腺病毒载量明显高于其他组织.本研究建立的TaqMan实时荧光定量PCR方法特异性强、灵敏度高、重复性好,可同时检测大量临床样品,适用于CAV的诊断与流行病学分析. 相似文献
20.
Protective immunity against infectious bursal disease virus in chickens in the absence of virus-specific antibodies 总被引：1，自引：0，他引：1
The role of cell-mediated immunity (CMI) in pathogenesis of infectious bursal disease virus (IBDV) was investigated. One-day-old specific pathogen-free chickens were treated with 3mg of cyclophosphamide (Cy) per chicken for 4 consecutive days and, 3 weeks later, infected with the IBDV-IM strain. Chickens were examined for: (a) mitogenic response of splenocytes to ConA, as an indicator of T-cell functions in vitro, (b) antibody against IBDV by ELISA, (c) IBDV genome in various tissues by RT-PCR and (d) immunological memory. At the time of IBDV infection, Cy-treated chickens had depleted bursal tissue (an avian primary B-cell lymphoid organ), severely compromised antibody-producing ability, but normal T-cell response to ConA. In primary infection, no detectable antibody against IBDV antigen in Cy-treated, IBDV-infected chickens was observed up to 28 days post-infection (PI), while IBDV genome was detected by RT-PCR in spleen, thymus, liver and blood until 10 days PI. Like intact control chickens infected with IBDV, Cy-treated, IBDV-infected chickens suppressed splenocytes responses to ConA from 5 to 10 days PI, suggesting that intact control as well as Cy-treated chickens responded similarly to IBDV infection in the early phase. Following re-infection with IBDV, no detectable secondary antibody response to IBDV as well as IBDV genome in tissues were observed in Cy-treated chickens, while intact control chickens developed vigorous secondary antibody response. Similar to intact control chickens infected with IBDV, Cy-treated chickens after second infection with IBDV did not suppress splenocyte response to ConA. These results suggested that in the absence of detectable anti-IBDV antibodies, protection of Cy-treated chickens from IBDV infection may occur via immunological memory mediated by CMI. We concluded that under normal conditions, IBDV induces a protective antibody response, however, in the absence of antibody, CMI alone is adequate in protecting birds against virulent IBDV. 相似文献