Rautenschlein Silke, Aung Ye Htut, Haase Christine
Clinic for Poultry, University of Veterinary Medicine Hannover, Hannover, Germany.
Vet Immunol Immunopathol. 2011 Mar 15;140(1-2):10-22. doi: 10.1016/j.vetimm.2010.11.003. Epub 2010 Nov 17.
Infections with avian Metapneumovirus (aMPV) are often associated with swollen head syndrome in meat type chickens. Previous studies in turkeys have demonstrated that local humoral and cell-mediated immunity plays a role in aMPV-infection. Previous experimental and field observations indicated that the susceptibility of broilers and their immune reactions to aMPV may differ from turkeys. In the presented study local and systemic immune reactions of broilers were investigated after experimental infections with subtypes A and B aMPV of turkey origin. Both virus subtypes induced a mild respiratory disease. The recovery from respiratory signs correlated with the induction of local and systemic aMPV virus-neutralizing antibodies, which began to rise at 6 days post infection (dpi), when the peak of clinical signs was observed. In a different manner to the virus neutralizing (VN) and IgG-ELISA serum antibody titres, which showed high levels until the end of the experiments between 24 and 28 dpi, the specific IgA-ELISA and VN-antibody levels in tracheal washes decreased by 10 and 14 dpi, respectively, which may explain the recurring aMPV-infections in the field. Ex vivo cultured spleen cells from aMPV-infected broilers released at 3 and 6 dpi higher levels of IFN-γ after stimulation with Concanavalin A as compared to virus-free birds. In agreement with studies in turkeys, aMPV-infected broilers showed a clear CD4+ T cell accumulation in the Harderian gland (HG) at 6 dpi (P<0.05). In contrast to other investigations in turkeys aMPV-infected broilers showed an increase in the number of CD8alpha+ cells at 6 dpi compared to virus-free birds (P<0.05). The numbers of local B cells in the Harderian gland were not affected by the infection. Both aMPV A and B induced up-regulation of interferon (IFN)-γ mRNA-expression in the nasal turbinates, while in the Harderian gland only aMPV-A induced enhanced IFN-γ expression at 3 dpi. The differences in systemic and local T cell and possibly natural killer cell activity in the HG between turkeys and chickens may explain the differences in aMPV-pathogenesis between these two species.
禽偏肺病毒（aMPV）感染通常与肉用型鸡的肿头综合征有关。先前对火鸡的研究表明，局部体液免疫和细胞介导免疫在aMPV感染中发挥作用。先前的实验和现场观察表明，肉鸡对aMPV的易感性及其免疫反应可能与火鸡不同。在本研究中，对源自火鸡的A和B亚型aMPV进行实验感染后，研究了肉鸡的局部和全身免疫反应。两种病毒亚型均引发轻度呼吸道疾病。呼吸道症状的恢复与局部和全身aMPV病毒中和抗体的诱导相关，这些抗体在感染后6天（dpi）开始上升，此时观察到临床症状的高峰。与病毒中和（VN）和IgG-ELISA血清抗体滴度不同，在实验结束（24至28 dpi）前它们一直保持高水平，气管冲洗液中的特异性IgA-ELISA和VN抗体水平分别在10和14 dpi时下降，这可能解释了该病毒在实际生产中的反复感染情况。与未感染病毒的鸡相比，aMPV感染的肉鸡经刀豆蛋白A刺激后，在3和6 dpi时，体外培养的脾细胞释放出更高水平的干扰素-γ（IFN-γ）。与对火鸡的研究一致，aMPV感染的肉鸡在6 dpi时，哈德氏腺（HG）中出现明显的CD4 + T细胞聚集（P<0.05）。与对火鸡的其他研究不同，与未感染病毒的鸡相比，aMPV感染的肉鸡在6 dpi时CD8α +细胞数量增加（P<0.05）。哈德氏腺中局部B细胞的数量不受感染影响。aMPV A和B均诱导鼻甲中干扰素（IFN）-γ mRNA表达上调，而在哈德氏腺中，仅aMPV-A在3 dpi时诱导IFN-γ表达增强。火鸡和鸡在全身和局部T细胞以及哈德氏腺中可能的自然杀伤细胞活性方面的差异，可能解释了这两个物种在aMPV发病机制上的差异。
