猪O型口蹄疫基因工程疫苗候选株的构建及其免疫原性分析

摘要

The outbreaks of type O foot-and-mouth disease (FMD) severely affect development of Chinese hog industry, its causative agent is type O foot-and-mouth disease virus (FMDV), which has been evolved several lineages. The available FMD vaccines in China cannot afford sufficient protection against viruses of multi-lineages, which exert important obstacle to disease control. In order to develop vaccine candidate with characteristics of good immunogenicity and broad spectro-type, we constructed a full-length cDNA clone with genetically modified in capsid protein VP3 (58 amino acid) and VP1 (43, 48, 137, 139, 140, 141, 142 amino acid) based on the infectious cDNA clone of O/HN/93 vaccine strain. Upon cotransfection of BHK-21 cells with linearized re-combinant plasmids and plasmids expressing T7 RNA polymerase, the virus was rescued. The results of RT-PCR and sulk mice pathogenicity showed that the rescued virus could be stably main- tained during serial passages and has similar pathogenicity with parental virus for sulk mice. To test if the genetically modified virus can be used as a vaccine candidate, the pigs inoculated with inactivated FMD vaccine which made from rV-OSyNa and O/HN/93 viruses were challenged with swine-isolated strains of Chathay, Pan Asia and Mya98 topotypes, respectively. As a result, the rV-OSyNa vaccinated pigs were fully protected against three viruses challenge after 28 days post-vaccination, in contrast, 16/16 O/HN/93 vaccinated animals fully protected against viruses of PanAsia and Mya98 topotypes challenge, but only 12 /16 O/HN/93 vaccinated animals got protection from virus of Chathay challenge. Our results demonstrated that genetically engineered FMDV is a good vaccine candidate with improving protection against virus of Chathay topotype challenge and expanding spectrotype.%近年来,O型口蹄疫病毒已演化出多种谱系.目前应用的疫苗已不能有效保护多谱系口蹄疫的流行,这给我国猪口蹄疫的防控带来了极大的困难.为了进一步发展免疫原性好、抗原谱广的猪O型口蹄疫疫苗候选株,本研究以O/HN/93现用疫苗毒株的感染性克隆为骨架,构建了含VP3(58位)和VP1(43、48、137、139、140、141和142位)氨基酸改造的全长克隆.线性化的全长cDNA和T7RNA聚合酶质粒共转染BHK细胞后获得拯救病毒.RT-PCR和乳鼠致病性试验表明拯救病毒遗传稳定,具有与亲本病毒相似的致病性.用拯救的基因工程病毒灭活疫苗免疫猪28 d后分别用中国谱系、泛亚谱系和缅甸98谱系猪源毒的流行毒攻击,结果均获得了完全保护(16/16).O/HN/93灭活疫苗免疫猪能完全保护泛亚谱系和缅甸98谱系猪源病毒的攻击(16/16),但不能完全保护(12/16)中国谱系猪源病毒的攻击.结果表明基因工程病毒制备的灭活疫苗提高了对中国型猪源谱系病毒的免疫保护,拓展了抗原谱,是具有良好开发前景的疫苗候选株.