中文摘要：

将35头40日龄猪繁殖与呼吸综合征病毒(Porcine reproductive and respiratory syndrome virus,PRRSV)、猪瘟病毒(Classical swine fever virus,CSFV)、猪圆环病毒(Porcine circovirus type 2,PCV2)抗原及抗体均为阴性的健康仔猪,随机分成7组,每组5头,命名为XJ1~XJ7组。XJ1~XJ6组分别免疫PRRSV基因工程双标记疫苗rHN4-△25+NP49株,接种剂量分别为102TCID50/头、103TCID50/头、104TCID50/头、105TCID50/头、106TCID50/头和107TCID50/头,XJ7组为对照组,按1mL/头剂量接种DMEM。各试验组在免疫后28 d,用3×104.0TCID50/头剂量感染HP-PRRSV HuN4第5代强毒,疫苗免疫和攻毒后观察和检测各组试验猪的免疫效果。结果表明:攻毒前XJ2-XJ6组PRRSV ELISA抗体在免疫后14 d全部转为阳性,XJ1组在免疫后21 d转为阳性,但维持在较低水平;XJ2-XJ6组针对标记基因NP49的特异性抗体在免疫后28 d转阳性。攻毒后对照组全部发病,且死亡2头,XJ1有4头发病,XJ2-XJ6组无发病和死亡,本研究结果表明PRRSV基因工程双标记疫苗rHN4-△25+NP49株对仔猪提供免疫保护的最小免疫剂量为103TCID50/头。

英文摘要：

Thirty five 40-days old piglets without Porcine reproductive and respiratory syndrome virus (PRRSV), Porcine circovirus (PCV2) and Classical swine fever virus (CSFV) were selected and randomly divided into 7 groups (XJ1-XJ7). Each of piglets in groups XJ1-XJ6 was inoculated with 102TCID50 to 107TCID50 of HP-PRRS dual-marker vaccine rHN4-Δ25+NP49 strain, respectively. Group XJ7 served as infection control. On 28 day post immunization, all animal were infected with 3×104TCID50 HuN4-F5 strain. Fever and other clinical signs were recorded daily. Pigs in group XJ2-XJ6 developed high level of humoral response against PRRSV from day 14 post immunization while piglets in group XJ1 developed a low level PRRSV antibody response from day 21 post immunization. Four piglets in group XJ1 and 5 piglets in XJ7 had various disease manifestations, including persistently high fever and anorexia. Two piglets in group XJ7 died at days 5 and 20 post challenge. On the contrast, piglets in groups XJ2-XJ6 did not show any clinical signs post challenge. These results indicated that the minimum immunization dose of rHN4-Δ25+NP49 strain was 103TCID50, which conferred effective protection against HP-PRRSV.