Mahmood M S, Siddique M, Hussain I, Khan A, Mansoor M K
Department of Veterinary Microbiology, University of Agriculture, Faisalabad 38040, Pakistan.
Vaccine. 2006 May 29;24(22):4838-46. doi: 10.1016/j.vaccine.2006.03.016. Epub 2006 Mar 23.
In the present study the efficacy of recombinant plasmids DNA vaccine encoding VP2 gene of very virulent strain of infectious bursal disease virus (vvIBDV) isolated from Pakistan was investigated with or without coadministration of cytocine-phosphate-guanine oligodeoxynucleotide (CpG ODN) to protect the chickens against the disease. VP2 gene of vvIBDV was successfully amplified by reverse transcription-polymerase chain reaction (RT-PCR) and was cloned into eukaryotic expression plasmid vector, which consisted of human cytomegalovirus (HCMV) immediate early enhancer and promoter, adenopartite leader sequences and SV-40 polyadenylation signal, and this was designated as pRc-VP2. Seven-day-old maternal antibodies free chickens were intramuscularly injected with 500 microg of pRc-VP2 with or without CpG ODN twice at 1-week interval. At the age of 21 days the broiler chickens were challenged with 10(5) EID(50) of homologous strain of IBDV and observed for 14 days post-challenge. Immunization with pRc-VP2 plus CpG ODN conferred protection in 93% of the chickens as evidenced by the absence of clinical signs, atrophy of bursa of Fabricius (BF) and mortality followed by the group vaccinated with attenuated IBD vaccine and boosted with killed oil based IBDV vaccine, which conferred 90% protection. The protection of chickens injected with pRc-VP2 alone was 67% where as only 20% of the chickens in the negative control group were protected. However, enzyme-linked immunosorbent assay (ELISA) antibody titre in the group vaccinated with pRc-VP2 plus CpG ODN were significantly higher (P<0.05) than the group vaccinated with pRc-VP2 alone as well as the group vaccinated with commercial attenuated IBDV vaccine boosted with commercial oil adjuvanted killed IBDV vaccine. Responsiveness to a mitogenic lectin, phytoheamagglutinin-P was significantly reduced in group immunized with conventional vaccines (live boosted with killed) as compared to all the other groups (P<0.05). The results revealed that co-administration of recombinant plasmids with CpG ODN could protect chickens efficiently from IBDV challenge.
在本研究中，对编码从巴基斯坦分离的超强毒株传染性法氏囊病病毒（vvIBDV）VP2基因的重组质粒DNA疫苗，在单独使用或与胞嘧啶-磷酸-鸟嘌呤寡脱氧核苷酸（CpG ODN）共同使用时保护鸡抵抗该病的效果进行了研究。通过逆转录-聚合酶链反应（RT-PCR）成功扩增了vvIBDV的VP2基因，并将其克隆到真核表达质粒载体中，该载体由人巨细胞病毒（HCMV）立即早期增强子和启动子、腺病毒前导序列和SV-40聚腺苷酸化信号组成，将其命名为pRc-VP2。7日龄无母源抗体的鸡，肌肉注射500μg pRc-VP2，有或无CpG ODN，间隔1周注射两次。21日龄时，用10⁵EID₅₀的同源IBDV毒株攻击肉鸡，并在攻毒后观察14天。用pRc-VP2加CpG ODN免疫的鸡中，93%获得了保护，表现为无临床症状、法氏囊（BF）无萎缩且无死亡，随后接种弱毒IBD疫苗并用灭活油佐剂IBDV疫苗加强免疫的组保护率为90%。单独注射pRc-VP2的鸡的保护率为67%，而阴性对照组只有20%的鸡得到保护。然而，用pRc-VP2加CpG ODN免疫的组中的酶联免疫吸附测定（ELISA）抗体滴度显著高于单独用pRc-VP2免疫的组以及用商业弱毒IBDV疫苗并用商业油佐剂灭活IBDV疫苗加强免疫的组（P<0.05）。与所有其他组相比，用传统疫苗（活疫苗并用灭活疫苗加强免疫）免疫的组对促有丝分裂凝集素植物血凝素-P的反应性显著降低（P<0.05）。结果表明，重组质粒与CpG ODN共同使用可有效保护鸡免受IBDV攻击。
