Ⅰ型马立克氏病病毒不同致病型参考株与中国分离株pp24基因的克隆与序列分析

为了比较Ⅰ型马立克氏病病毒(MDV)的致病型与pp24基因的关系,将Ⅰ型MDV弱毒(mMDV)、强毒(vMDV)、超强毒(vvMDV)、特超强毒(vv MDV)等不同致病型的CVI988、GA、648A、RB1B、Md5和Md11等6个国际参考株,从中国河北、北京、广东和广西等地分离的7个中国分离株和1个中国疫苗毒814株的pp24基因分别做PCR扩增,并将其克隆到pMD-18载体中测序,与国外已发表的BC-1株进行序列比较.结果表明:Ⅰ型MDV的pp24基因非常保守,15个毒株中只出现5个碱基的随机变化,并引起相应的4个氨基酸改变,但与致病型无明显相关;pp24基因ORF的第81碱基出现差异,所有中国株为G,所有不同致病型国外参考株为C,但并未引起氨基酸改变,显示这一碱基差异只是作为MDV地域性分布的遗传标志,而与病毒分离的年代及致病型等因素无关.

Cloning and Sequencing of pp24 Genes of Different Pathotype Reference Strains and Chinese Field Strains of Marek's Disease Virus Type Ⅰ(MDV-Ⅰ)

To compare the relationship between pp24 genes and different pathotypes of Marek's disease viruses (MDV1),pp24 genes of different pathotype reference strains(mild MDV?virulent MDV?very virulent MDV?very virulent plus MDV) and Chinese field strains were amplified by polymerase chain reaction(PCR),and then cloned into pMD18-T separately for sequencing.The comparative analysis of the sequences indicated that the sequence of pp24 in different pathotypes of MDV is relatively conservative,only five nucleotide sites have changed randomly and caused corresponding four amino acid changes among 15 sequenced strains.There is an unique change at base #81 among the 15 sequenced strains(all Chinese field strains were G while all other different pathotype strains are C),but this mutation causes no amino acid change,so the diversity at the base #81 is only a regionally hereditary marker of MDV,not related to pathotypes of MDV.