表达猪瘟病毒E2蛋白的重组腺病毒对猪的免疫效力评价

A RECOMBINANT ADENOVIRUS EXPRESSING THE E2 PROTEIN OF CLASSICAL SWINE FEVER VIRUS PROTECTS PIGS FROM LETHAL CHALLENGE

为了进一步验证含有猪瘟病毒E2基因的重组腺病毒(rAdV-E2)在猪体上的免疫效力,将rAdV-E2按108TCID50/头接种猪2次,同时用野生型腺病毒wtAdV作为阴性对照,当抗体上升到一定程度后用致死剂量的猪瘟强毒石门株进行攻击。结果表明,rAdV-E2免疫组(n=5)所有免疫猪在加强免疫后均产生了猪瘟特异性中和抗体,并于加强免疫后3w达到峰值,攻毒后所有猪只抗体迅速升高,除了一头猪短期体温升高外,未出现任何其它临床症状;而野生型腺病毒wtAdV免疫组(n=5)猪只在攻毒前一直没有检出特异性抗体,攻毒后全部出现典型的猪瘟临床症状和严重的病毒血症,剖检时可见典型猪瘟病理变化。这表明构建的猪瘟病毒E2基因重组腺病毒rAdV-E2免疫猪后产生了很好的免疫效果,有望成为具有开发价值的活载体疫苗。

Classical swine fever （CSF）, which is caused by classical swine fever virus （CSFV）, causes significant losses in pig industry in many Asian and European countries. The E2 glycoprotein of CSFV is the main target for neutralizing antibodies. We have evaluated previously the recombinant adenovirus （rAdV-E2） expressing the E2 glycoprotein of classical swine fever virus （CSFV） in rabbits. The results showed that the rabbits immunized with rAdV- E2 developed high- level CSFV - specific antibodies and were all free of the regular fever and the viral replication in the spleen upon challenge with C- strain, which were seen in the rabbits immunized with the parent adenovirus of rAdV - E2. This study was designed to evaluate further the efficacy of rAdV- E2 in pig. Pigs were immunized twice with 108 TCID50 of rAdV-E2 （n = 5） or control wtAdV （n = 5）, respectively, and challenged with virulent Shimen strain at 9 weeks of post boost following the booster immunization. The results indicated that pigs immunized with rAdV- E2 developed high titers of specific neutralizing antibodies against CSFV after the booster, and the antibody titers increased rapidly upon challenge. The immunized pigs showed no other clinical symptoms except short-term fever, whereas, the control pigs immunized with wtAdV produced no detectable antibody before challenge, and showed apparently clinical signs after challenge. All control animals developed extended viremia as detected by real- time RT- PCR. Severe pathologic lesions typical of CSFV infection were observed at necropsy. It is concluded that the recombinant adenovirus rAdV- E2 might be a vaccine candidate against CSFV.