Tongkamsai Suttitas, Lee Meng-Shiou, Cheng Ming-Chu, Chaung Hso-Chi, Tsai Yi-Lun, Lien Yi-Yang
Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan.
Faculty of Veterinary Medicine, Rajamangala University of Technology Tawan-ok, Chonburi 20110, Thailand.
Pathogens. 2019 Apr 12;8(2):48. doi: 10.3390/pathogens8020048.
Naturally acquired chicken anemia virus (CAV) infection in chickens frequently occurs from 3 weeks of age onward after maternally derived antibodies have decayed. The oral inoculation of older chickens with CAV was reported to have negative effects on cell-mediated immune function, and pathological changes were identified. To date, there has been no complete illustration of an immunological and persistent infection. To understand the pathogenesis of persistent CAV infection, an immunological study of CAV-infected 3-week-old specific pathogen-free (SPF) chickens was carried out by different routes of inoculation. The weight, packed cell volumes, and organ samples were obtained at 7, 14, 21, and 28 days postinfection (dpi). Here, we compared hematological, immunological, and sequential pathological evaluations and determined the CAV tissue distribution in different organs. Neither a reduction in weight gain nor anemia was detected in either the inoculated or the control group. The immune-pathological changes were investigated by evaluating the body and thymus weight ratio and specific antibody titer. Delayed recovery of the thymus corresponding to a low antibody response was detected in the orally inoculated group. This is different from what was found in chickens intramuscularly infected with the same dose of CAV. The CAV remaining in a wide range of tissues was examined by viral reisolation into cell culture. The absence of the virus in infected tissues was typically found in the intramuscularly inoculated group. These chickens were immediately induced for a protective antibody response. A few viruses replicating in the thymus were found 21 dpi due to the regression in the antibody titer in the orally inoculated group. Our findings support that a natural infection with CAV may lead to the gradual CAV viral replication in the thymus during inadequate antibody production. The results clearly confirmed that virus-specific antibodies were essential for viral clearance. Under CIA-risk circumstances, administration of the CAV vaccine is important for achieving a sufficient protective immune response.
自然感染鸡贫血病毒（CAV）在雏鸡中常见于3周龄后母源抗体衰减时。据报道，用CAV口服接种大龄鸡会对细胞介导的免疫功能产生负面影响，并发现了病理变化。迄今为止，尚未有关于免疫性和持续性感染的完整阐述。为了解持续性CAV感染的发病机制，通过不同接种途径对3周龄无特定病原体（SPF）的CAV感染鸡进行了免疫研究。在感染后第7、14、21和28天获取体重、血细胞压积和器官样本。在此，我们比较了血液学、免疫学和连续病理学评估，并确定了不同器官中CAV的组织分布。接种组和对照组均未检测到体重增加减少或贫血。通过评估体重与胸腺重量比和特异性抗体滴度来研究免疫病理变化。口服接种组检测到胸腺恢复延迟，对应抗体反应较低。这与相同剂量CAV肌肉注射感染的鸡的情况不同。通过将病毒重新分离到细胞培养中，检测了广泛组织中残留的CAV。肌肉注射接种组在感染组织中通常未发现病毒。这些鸡立即诱导产生保护性抗体反应。由于口服接种组抗体滴度下降，在感染后21天发现少数病毒在胸腺中复制。我们的研究结果支持，在抗体产生不足期间，CAV自然感染可能导致CAV病毒在胸腺中逐渐复制。结果清楚地证实，病毒特异性抗体对于病毒清除至关重要。在存在感染风险的情况下，接种CAV疫苗对于实现充分的保护性免疫反应很重要。
