表达H7N9亚型禽流感病毒HA基因DNA疫苗对鸡免疫保护效力的研究

Protective efficacy of H7N9 DNA vaccine pVAH7 in SPF chickens

防控H7N9禽流感病毒(AIV)疫苗研制是必要的技术储备,本研究根据A/Anhui/1/2013(H7N9)株的HA基因进行了密码子优化和全基因合成,克隆于pVAX1中构建真核表达重组质粒pVAH7,将其作为DNA疫苗进行SPF鸡的免疫保护效力评价。采用60μg/羽剂量的pVAH7单次或加强免疫3周龄SPF鸡;首免7周后,以106EID50的A/Chicken/Shanghai/S1053/2013(H7N9)通过鼻腔接种途径攻毒。结果显示,pVAH7单次和加强免疫均可以有效诱导血凝抑制(HI)和中和(NT)抗体的产生。而且NT抗体水平与HI抗体水平呈正相关,并在免疫初期(3周)显著高于相对应的HI抗体水平;单次免疫组攻毒后第5 d在泄殖腔部位仍可以分离到病毒,加强免疫组鸡在攻毒后5 d则检测不到病毒,而对照组在感染后3 d^7 d均可分离到较高滴度的病毒。本研究结果表明,pVAH7能够对SPF鸡提供有效的保护作用,可以作为防制H7N9亚型禽流感的后备DNA疫苗。

The newly emerged H7N9 subtype avian influenza virus （AIV） poses a serious threat to human health. To construct and evaluate the candidate DNA vaccine against the virus, the codon-optimized HA gene of A/Anhui/1/2013 （H7N9） was synthesized and cloned into pVAX1 to construct the recombinant plasmid pVAH7 as DNA vaccine. Groups of 3-week-old SPF chickens were intramuscularly injected with the pVAH7 once or twice at dose of 60 μg/chicken, respectively, with unvaccinated chickens as control. All chickens were nasally challenged with 106 EID50 of the AIV A/Chicken/Shanghai/S1053/2013（H7N9） at 7 weeks post the initial vaccination. The results showed that HI and NT antibodies were higher in twice vaccinated chicken group than that in the single vaccinated group. In addition, the virus was isolated from some cloacal swabs of chickens in single vaccinated group at 5 days post challenge, but not from the chickens in twice vaccinated group, whereas virus shedding was detected in all chickens in the control group. Our results indicate that the pVAH7 is able to induce efficiently protection for chickens against the H7N9 virus challenge which could be applied potentially as a DNA vaccine.