高致病性猪繁殖与呼吸综合征活疫苗(HuN4-F112株)对类NADC30 PRRSV免疫保护效果的评价

Efficacy of vaccination with the attenuated highly pathogenic PRRSV Hu N4-F112 against NADC30-like PRRSV

类NADC30猪繁殖与呼吸综合征病毒(PRRSV)已成为我国PRRSV的主要流行株,为了评价当前商品化疫苗对类NADC30 PRRSV的免疫保护效果,本研究将12头6周龄仔猪随机分为3组,免疫组和攻毒对照组各5头、空白对照组2头,免疫组肌注高致病性猪繁殖与呼吸综合征活疫苗(HuN4-F112株)10^(5.0)TCID_(50)/头,免疫后21 d,免疫组和攻毒对照组每头各肌注2 mL和滴鼻2 mL类NADC30 PRRSV SD53-1603株(104.0TCID_(50)/mL)。攻毒后观察各组实验猪临床症状,可见攻毒对照组所有猪均发热,持续5 d9 d,免疫组仅2头猪发热1 d2 d。检测各组实验猪体重变化,结果显示,攻毒后免疫组和攻毒对照组体重增长均显著低于空白对照组(p<0.001),但攻毒14 d以后,免疫组体重增长显著高于攻毒对照组(p<0.05)。IDEXX ELISA测定各组猪血清中PRRSV的特异性抗体,结果显示免疫后14 d可以诱导免疫组仔猪产生良好的针对PRRSV的特异性抗体。利用荧光定量PCR测定血清和组织中的病毒载量,结果显示免疫组血清和组织中的病毒载量均极显著低于对照组(p<0.0001)。对PRRSV免疫后及攻毒后各组仔猪各脏器病理学观察,结果可见攻毒对照组与免疫组相比出现明显的剖检和组织病理学变化。以上结果表明,高致病性猪繁殖与呼吸综合征活疫苗(HuN4-F112株)对类NADC30 PRRSV可以提供一定的交叉保护,该研究为评价我国现有疫苗是否对类NADC30 PRRSV具有保护效果提供了参考依据。

NADC30-like PRRSV has become the major endemic strain in China. To evaluate the protective effect of the commercial vaccine against NADC30-like PRRSVs, twelve six-week-old PRRSV-negative piglets were randomly divided into three groups, immune group(n=5), challenge control group(n=5), and negative control group(n=2). The piglets in immune group were inoculated intramuscularly(2 mL, 105.0 TCID_(50)/mL) with vaccine of HP-PRRSV(HuN4-F112). At 21 day post-vaccination, the piglets in immune group and challenge control group were inoculated intramuscularly(2 m L, 104.0 TCID_(50)/mL) and intranasally(2 mL, 104.0 TCID_(50)/mL) with NADC30-like PRRSV strain SD53-1603. The results showed that all the piglets in challenge control group developed fever for 5 to 9 d, but only two piglets had fever for 2 d in immune group. All the piglets gained less body weight in immune and challenge group than the negative control piglets(p<0.001), but the body weight of piglets in immune group was significantly higher than that of challenge control group after 14 d post-challenge(p<0.05). The viral loads in tissues and serum of immune group were significantly lower than those of challenge control group(p<0.0001). In addition, the piglets in challenge control group displayed more severe pathological and histopathology changes than that of immune group. All the results suggest that the attenuated HuN4-F112 vaccine could provide cross-protection against NADC30-like PRRSV. This study provides a basis for evaluating whether the current vaccines in China have protective efficacy against NADC30-like PRRSV.