Bankamp Bettina, Fontana Judith M, Bellini William J, Rota Paul A
Measles, Mumps, Rubella and Herpesvirus Laboratory Branch, Division of Viral Diseases, Centers for Disease Control and Prevention, MS C-22, 1600 Clifton Road, Atlanta, Georgia 30333, USA.
Virol J. 2008 Oct 27;5:129. doi: 10.1186/1743-422X-5-129.
Live, attenuated measles virus (MeV) vaccine strains were generated by adaptation to cell culture. The genetic basis for the attenuation of the vaccine strains is unknown. We previously reported that adaptation of a pathogenic, wild-type MeV to Vero cells or primary chicken embryo fibroblasts (CEFs) resulted in a loss of pathogenicity in rhesus macaques. The CEF-adapted virus (D-CEF) contained single amino acid changes in the C and matrix (M) proteins and two substitutions in the shared amino terminal domain of the phosphoprotein (P) and V protein. The Vero-adapted virus (D-VI) had a mutation in the cytoplasmic tail of the hemagglutinin (H) protein.
In vitro assays were used to test the functions of the wild-type and mutant proteins. The substitution in the C protein of D-CEF decreased its ability to inhibit mini-genome replication, while the wild-type and mutant M proteins inhibited replication to the same extent. The substitution in the cytoplasmic tail of the D-VI H protein resulted in reduced fusion in a quantitative fusion assay. Co-expression of M proteins with wild-type fusion and H proteins decreased fusion activity, but the mutation in the M protein of D-CEF did not affect this function. Both mutations in the P and V proteins of D-CEF reduced the ability of these proteins to inhibit type I and II interferon signaling.
Adaptation of a wild-type MeV to cell culture selected for genetic changes that caused measurable functional differences in viral proteins.
减毒活麻疹病毒（MeV）疫苗株是通过适应细胞培养而产生的。疫苗株减毒的遗传基础尚不清楚。我们之前报道过，致病性野生型MeV适应Vero细胞或原代鸡胚成纤维细胞（CEF）会导致恒河猴致病性丧失。适应CEF的病毒（D-CEF）在C蛋白和基质（M）蛋白中含有单个氨基酸变化，在磷蛋白（P）和V蛋白的共享氨基末端结构域中有两个替换。适应Vero的病毒（D-VI）在血凝素（H）蛋白的细胞质尾巴中有一个突变。
体外试验用于测试野生型和突变型蛋白的功能。D-CEF的C蛋白中的替换降低了其抑制微型基因组复制的能力，而野生型和突变型M蛋白对复制的抑制程度相同。D-VI H蛋白细胞质尾巴中的替换导致定量融合试验中的融合减少。M蛋白与野生型融合蛋白和H蛋白共表达会降低融合活性，但D-CEF的M蛋白中的突变不影响此功能。D-CEF的P蛋白和V蛋白中的两个突变均降低了这些蛋白抑制I型和II型干扰素信号传导的能力。
野生型MeV适应细胞培养选择了导致病毒蛋白出现可测量功能差异的基因变化。
