鸭源新城疫病毒强毒株感染对番鸭致病性和β-防御素基因表达的影响

Pathogenicity andβ-Defensin Gene Expression of a Duck Derived Virulent Strain of Newcastle Disease Virus in Muscovy Ducks

为了探讨鸭源新城疫病毒(NDV)感染对番鸭β-防御素(AvBD)基因表达的影响,本实验选取80只15日龄SPF番鸭,将其随机分为两组,每组40只。其中一组以滴鼻点眼方式接种107 EID50/0.2 mL的鸭源基因Ⅶ型NDVMd/CH/LGD/1/2005毒株;另一组以相同途径接种等量灭菌的磷酸盐缓冲液,作为对照组。攻毒后持续观察临床症状25 d。并在攻毒后36 h、72 h、7 d和25 d每组分别剖杀10只番鸭,采集5个免疫器官的样品,包括骨髓、脾脏、盲肠扁桃体、哈德氏腺和法氏囊,运用real-time RTPCR方法检测其中11种防御素基因表达量的变化差异。并在攻毒后36 h、72 h、7 d以及16 d、20 d和25 d每组各采集10只番鸭的血清,用血凝抑制试验(HI)检测新城疫病毒特异性抗体水平。结果表明:番鸭感染该鸭源NDV强毒株后出现新城疫病毒感染的典型临床症状,死亡率为7.5%;感染番鸭体内组织中AvBD1、AvBD2、AvBD5、AvBD10在广泛表达,且AvBD3、AvBD5、AvBD7在法氏囊内均有不同程度表达上调,番鸭感染该鸭源NDV强毒株后72 h开始抗体开始转阳,第7 d即达到高峰,之后16 d、20 d和25 d的抗体水平趋于平稳。以上结果表明,该鸭源NDV强毒株感染可在番鸭体内诱导产生抗病毒免疫应答反应。

In order to investigate the effect of duck-derived Newcastle disease virus(NDV)infection onβ-defensin(AvBD)gene expression,a total of eighty 15-day-old SPF Muscovy ducks were randomly divided into two groups.Forty ducks in one group were inoculated with 107 EID50/0.2mL of duck-derived genotype VII NDV Md/CH/LGD/1/2005 by intranasal eye drops and other forty ducks in another group were inoculated with the same amount of sterilized phosphate buffer by the same route as the control group.Clinical signs were observed for 25 days post infection.In order to examine the expression levels of 11 defensin genes,ten Muscovy ducks in each group were terminated at 36 h,72 h,7 d and 25 d post infection,and immune organs including bone marrow,spleens,cecal tonsils,Harderian glands and bursa of Fabricius were sampled and tested with real-time RT-PCR.In addition,serum samples were collected RTfrom ten Muscovy ducks at 36 h,72 h,7 d,and 16 d,20 d,25 d post infection,and antibody levels were measured by hemagglutination inhibition(HI).The results showed that Muscovy ducks infected with Md/CH/LGD/1/2005 developed typical clinical signs of Newcastle disease with a mortality rate of 7.5%.After infection with Md/CH/LGD/1/2005,AvBD1,2,5,and 10 were widely expressed in Muscovy ducks while AvBD3,5,and 7 were up-regulated in the bursa of Fabricius to varying degrees.The results also showed that the antibody response began to turn positive at 72 h post infection and reached the peak on the 7th day,and then kept stable at 16 d,20 d and 25 d.The above results indicated that infection with NDV strains duck origin induced antiviral immune response in Muscovy ducks.