B亚型禽偏肺病毒对SPF鸡的致病性

利用分离的1株B亚型禽偏肺病毒，采用静脉注射和点眼滴鼻两种途径接种SPF鸡，并在接种同时免疫新城疫弱毒疫苗。在攻毒后3、6、9、12、15d，每组随机抽取3只翅下采血，检测血液生化指标，利用血凝和血凝抑制试验检测新城疫HI抗体效价；利用流式细胞术分析外周血CD40／CD8比值，ELISA试剂盒测定血清中IL-2、IFN7的含量；同时观察静脉注射组和点眼滴鼻组鸡的临床症状、剖检病变和病理组织学变化。结果表明，攻毒后9～15d，静脉注射组和点眼滴鼻组外周血CD4＋/CD8＋比值和血清II-2、IFN-γ的含量均显著低于对照组（P〈0．05），而静脉注射组与点眼滴鼻组间无显著差异（P〉0．05）；静脉注射组和点眼滴鼻组的免疫器官指数低于对照组，但各组间差异不显著（P〉0．05）；各组间新城疫HI抗体水平无显著差异（P〉0．05）；血液生化指标仪谷丙转氨酶（ALT）和谷草转氨酶（AST）在攻毒后显著升高（P〈0．05），其他指标在各组间无显著差异（P〉0．05）；静脉注射组和点眼滴鼻组在感染后3～10d出现轻微临床症状；病理组织学检测结果显示，静脉注射组和点眼滴鼻组的呼吸道和肝脏病变最明显。综上所述，B亚型禽偏肺病毒感染SPF鸡后，在一段时间内抑制机体细胞免疫，导致免疫机能下降，并引起轻微的组织病变；B亚型禽偏肺病毒通过两种不同的攻毒途径对SPF鸡的致病性无显著差异。

Pathogenicity of avian metapneumovirus subtype B in SPF chickens

In this study,SPE chickens were inoculated intravenously or intraocular nasally with an isolate of avian metapneumovirus subtype B （aMPV/B）, meanwhile they were vaccinated with live attenuated Newcastle disease virus （NDV） vaccine. At 3,6,9, 12, 15 day post incubation, blood samples from three chickens in each group were randomly collected to obtain parameters in- eluding blood biochemical values, NDV antibody titres tested by haemagglutination inhibition, CD4＋ /CD8＋ ratio in peripheral blood by flow cytometry and serum IL 2,IFN-γ levels tested by El.ISA;clinical signs, postmortem and histopathologieal lesions were also recorded. The results showed that 9-15 d post incubation,CD4-/CD81 ratio in peripheral blood and serum II. 2,IFN-7 levels in intravenous infection with aMPV/B group and intraocular nasal infection with aMPV/B group were significantly lower than those of control group （P〉0.05）,and no significant differ ence was observed between intravenous infection and intraocular-nasal infection with aMPV/B group （P〉0. 05 ）;immune organ indexes showed infection groups had a lower level compared with control group; haemagglutination inhibition tests showed no significant difference in NI）V antibody titres was observed（P〉0. 05） ;blood biochemical values showed only ALT and AST ac tivities significantly increased after aMPV/B incubation （P〈0.05）;3 10 d post incubation,SPE chickens showed mild clinical symptoms in both infection group; and histological lesions were mainly observed in liver and respiratory tract. Taken all,aMPV/B infection could induce decreased immunocompetence and mild histological lesions in SPF chickens. In pathogenicity of aMPV/B, there is no significant difference via intravenous and intraocular-nasq,infectionin SPF chickens.