It's a protein that's produced by other cells in the body and when it's enriched in a certain area it stimulates more production of red blood cells.

这种蛋白由体内的另一种细胞生成,而当其在某处富集时,就会刺激红细胞生成

耶鲁公开课 - 生物医学工程探索课程节选

You'd want to make sure that you separated the virus from all the other parts of cow skin so that your ultimate preparation was enriched in the virus and didn't contain quantities of other things that would be hazardous.

你要保证,你从所有的牛皮组织上分离出病毒,这样最终的制剂产品才会富集病毒,并且不会携带其它物质,这些物质可能带来危险

耶鲁公开课 - 生物医学工程探索课程节选