Effect of pH and NaCl on Vero cell VRP titer

aPhosphate: 20 mM sodium phosphate buffer + 5.5% sucrose at designated pH used to titrate VRP packaged with indicated VEE GP coat.
bTris: 20 mM trishydroxymethylaminomethane + 5.5% sucrose at designated pH used to titrate VRP packaged with indicated VEE GP coat.
cInfectious unit (IU) titer determined on Vero cells.
dGenome equivalent (GE) titer determined by quantitative reverse transcription PCR.

a 磷酸钠缓冲液（sodium phosphate buffer）体系：配制含5.5%蔗糖的20 mM磷酸钠缓冲液，调节至指定pH值，用于滴定包裹有指定VEE GP包膜的VRP。
b 三羟甲基氨基甲烷（trishydroxymethylaminomethane，简称Tris）体系：配制含5.5%蔗糖的20 mM三羟甲基氨基甲烷缓冲液，调节至指定pH值，用于滴定包裹有指定VEE GP包膜的VRP。
c 感染性单位（Infectious Unit, IU）滴度：采用Vero细胞完成滴度测定。
d 基因组当量（Genome Equivalent, GE）滴度：通过定量逆转录PCR完成滴度测定。