The E2 glycoprotein of classical swine fever virus (CSFV) plays multiple roles in the viral life cycle. The chimeric live attenuated C strain with the E2 substitution of bovine viral diarrhea virus (BVDV) is a promising marker vaccine candidate. In this study, the recombinant chimeric CSFV/bE2 cDNA clone harboring heterologous E2 (bE2) of BVDV was constructed by genetic approaches. Recombinant infectious virus rCSFV/bE2 (P11) was recovered by 11 serial passages of transfected PK15 cells. Viral genome sequencing showed that a glutamic acid to glycine mutation (E260G) at position 260 of the bE2 was observed in rCSFV/bE2 P11. Alignment of amino acid sequences displayed that the glycine was one of three conserved residues in pestivirus E2. When the glutamic acid to glycine substitution (E260G) was introduced into chimeric CSFV/bE2 cDNA clone, the high-titer infectious rCSFV/bE2_E260G was rescued. The glycine to glutamic acid substitution at corresponding position in CSFV E2 resulted in significantly decreased rCSFV/E2_G259E production. We further identified that the conserved E2 residue G259 played a critical role in the release and binding activity of CSFV and that the E2 residues G259 and V111 modulated synergistically infectious virus production and replication.

经典猪瘟病毒 (CSFV) 的 E2 糖蛋白在病毒生命周期中发挥多种作用。具有牛病毒性腹泻病毒（BVDV）的E2替代的嵌合减毒活C株是有希望的标记疫苗候选物。在这项研究中，通过遗传方法构建了含有BVDV异源E2（bE2）的重组嵌合CSFV / bE2 cDNA克隆。通过转染的 PK15 细胞的 11 次连续传代回收重组感染病毒 rCSFV/bE2 (P11)。病毒基因组测序显示，在 rCSFV/bE2 P11 中观察到 bE2 第 260 位的谷氨酸到甘氨酸突变 (E260G)。氨基酸序列比对显示甘氨酸是瘟病毒中三个保守残基之一E2。当谷氨酸甘氨酸取代（E260G）被引入嵌合CSFV/bE2 cDNA克隆时，高效价感染性rCSFV/bE2 _E260G被挽救。CSFV E2 中相应位置的甘氨酸取代谷氨酸导致rCSFV/E2 _G259E产量显着降低。我们进一步确定了保守的 E2 残基 G259 在 CSFV 的释放和结合活性中起关键作用，并且 E2 残基 G259 和 V111 协同地调节感染性病毒的产生和复制。