Because these viruses abortively infect human and most mammalian cells yet still effectively present encoded foreign genes to the host immune system.

因为这类病毒不能感染人和大多数哺乳动物细胞，却可以有效地将外源基因编码的蛋白递呈给宿主免疫系统。

As a part of the urban public transport system, Beijing metro is designed and constructed abortively with the standard of modernization and the idea of international metropolis.

作为城市公共交通系统组成部分的北京地铁，正在以现代化的标准为实现国际化大都市的设想进行精心规划、设计和施工。