中文摘要：

内部核糖体进入位点（IREs）是微RNA病毒起始蛋白合成的关键元件。为研究IRES元件在病毒致病过程中的作用，本研究以口蹄疫病毒（FMDV）为模型，在已建立的0型FMDVcDNA感染性克隆的基础上，利用融合PCR的方法以脑心肌炎病毒（EMCV）的IRES替换FMDV的IRES，构建并拯救出含有EMCVIRES的嵌合病毒（rFMDV-E IRES）。一步生长曲线结果显示rFMDV—E IRES无论是在鼠源BHK-21细胞还是在猪源IBRS-2细胞中的复制能力均与亲本病毒相近。另外，rFMDV-E IRES对乳鼠的致病力与亲本病毒也相同。以上研究结果表明，虽然EMCVIRES与FMDVIRES一级序列存在显著差异，但二者的置换并不影响FMDV的复制和毒力，该结果有助于加深IRES在微RNA病毒复制和致病性功能的认识。

英文摘要：

Internal ribosome entry site （IRES）, which is a cis-acting signal for facilitating translation initiation of the open reading frame of positive-strand RNA in a 5＇ （m7GpppN） cap-independent manner, is of great importance to Picornaviridae. By using overlapping PCR, a recombinant virus named as rFMDV-E IRES was generated based on FMDV O reverse genetic system, in which the cognate FMDV IRES was replaced with the counterpart of Encephalomyocarditis virus （EMCV）. This IRES-chimeric FMDV is highly stable after passages in BHK-21 cells. The growth kinetics analysis indicated that the chimera replicated as wild type FMDV in murine kidney-originated cells （BHK-21） and in porcine kidney-originated cells （IBRS-2）. Furthermore, the pathogenicity of rFMDV-Ew,~s was detected to be the same as wild type FMDV in sucking mice. These results show that the replacement of FMDV IRES by EMCV IRES has no effect on the biological characterization of FMDV in spite of IRES sequence differences. These data will help us to further understand effect of IRES on the replication and pathogenesis of Pircomariruses.