表达禽流感病毒H5HA、H7HA基因DNA疫苗的免疫原性研究

The immunogenicity of DNA vaccine co-expressing HA gene of H5 and H7 subtype AIV

为研究双顺反子DNA疫苗对禽流感病毒(AIV)的保护作用,将H5和H7亚型AIV的HA基因克隆到同一表达载体上,构建了双顺反子HA基因表达质粒pCI-H5HA-H7HA。以此质粒肌注免疫4周龄SPF鸡,首次免疫后3周加强免疫,同时设pCI-H5HA和pCI-H7HA联合免疫组及空白对照组,每周采血用微量血凝抑制法检测HI抗体。加强免疫后3周分别以100LD50的高致病力禽流感病毒(HPAIV)A/Goose/Guangdong/1/96(H5N1)和A/FPV/Rostock/34(H7N1)进行致死性攻击。结果显示各免疫组均可刺激鸡体产生H5、H7特异性抗体,pCI-H5HA-H7HA诱导产生的抗体对H5N1和H7N1的攻毒保护分别为50%和10%,而pCI-H5HA和pCI-H7HA联合免疫的攻毒保护均为70%。表明双顺反子质粒可诱导鸡产生较好或一定的保护,但免疫效果不够理想,推测与DNA的摄取及其体内表达有关,可望通过调整DNA疫苗的多种因素提高免疫效果。

The protective efficacy of a plasmid DNA that contains two AIV HA genes was evaluated in SPF chickens. Two AIV HA genes of H5 and H7 subtype were cloned into the same vector, thus a doublegene vector -pCI-H5HA-H7HA had been constructed successfully. And this plasmid was used to immunize 4-week age SPF chickens by intramuscular injection. For comparison, another group of SPF chickens were vaccinated with pCI-H5HA and pCI-H7HA jointly .The Haemagglutinin inhibition （HI） titer induced by DNA vaccine were tested weekly for 6 weeks and the protection ratio were calculated. The SPF chickens were challenged with H5N1 or H7N1 isolate of HPAIV at the sixth week after the immunization. And the result showed, 50 % and 10 % protection rate against H5N1 and H7N1 were obtained prospectively from pCI-H5HA-H7HA vaccinated groups, while 70 % of protection rate were obtained from the groups immunized with pCI-H5HA and pCI-H7HA jointly .The study suggested the possibility that the double-gene plasmid can induce protection more or less, but the titer is yet unsatisfactory, inferring that the ingestion ofD N A and its expression level may play an importantrole In order to improve the protective efficacy,the further study on varions influencing factor is still needed.