基于甲病毒复制子载体的猪瘟DNA疫苗的免疫效力评价

Alphavirus Replicon-vectored Plasmid DNA-based Vaccine Elicits Protective Immunity Against Classical Swine Fever Virus

此前已构建了基于SemlikiForest病毒(SemlikiForestvirus,SFV)复制子载体的表达猪瘟病毒(classicalswinefevervirus,CSFV)E2基因的新型猪瘟DNA疫苗pFV1CS-E2,通过动物试验证实,该疫苗以600μg/头的剂量免疫3次,免疫猪能抵抗致死剂量猪瘟强毒的攻击。为进一步评价该疫苗在较低的免疫剂量和较少的免疫次数情况下的免疫效力,将DNA疫苗pSFV1CS-E2和空载体pSFV1CS按100μg/头的剂量,接种猪只2次,然后用致死剂量的猪瘟强毒石门株进行攻击。结果表明,pSFV1CS-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,攻毒后所有猪只抗体迅速升高,除了短期体温升高外,未出现任何其它临床症状,部分猪出现短期轻微病毒血症,个别猪的部分脏器出现轻微病变;而空载体免疫组(n=3)猪只在攻毒前一直没有检出特异性抗体,攻毒后全都出现典型的猪瘟临床症状和严重的病毒血症,有2头猪分别于攻毒后第10和11d死亡,剖检时可见典型猪瘟病理变化。结果表明,基于甲病毒复制子载体的猪瘟DNA疫苗有望成为具有开发价值的猪瘟标记疫苗。

We have shown previously that a Semliki Forest virus （SFV） replicon vectored DNA vaccine （pSFV1CS-E2） expressing the E2 glycoprotein of classical swine fever virus （CSFV） conferred full protection for pigs immunized three times with 600μg of the vaccine. This study aims to evaluate the efficacy of the DNA vaccine with lower dosage and fewer inoculations. Pigs were immunized twice with 100μg pSFV1CS-E2 （ n = 5） or control plasmid pSFV1CS （ n = 3）, respectively. Pigs immunized with pSFV1CS-E2 developed high titers of specific neutralizing antibodies against CSFV after the booster, and the antibody titers increased rapidly upon challenge. The immunized animals showed no clinical symptoms except short-term fever and low-level viremia, whereas the control pigs immunized with the control plasmid produced no detectable antibody before challenge and showed obvious clinical signs following challenge, and 2 pigs died on 10 or 11 days post-challenge. All control animals developed extended viremia as detected by nested RT-PCR and real-time RT-PCR. Severe pathologic lesions typical of CSFV infection were observed at necropsy. We conclude that the alphavirus replicon-vectored DNA-based vaccine can be potential marker vaccine against CSFV.