How many different viruses are there on our planet? In the latest International Committee on Taxonomy of Viruses (ICTV) report, the list of named viruses has grown to 4404 species. What about unknown viruses? A study on estimating unknown viral diversity in Pteropus giganteus suggests that at least 320,000 different viruses infect mammals (5513 species). Following this method, there could be 100 million viruses in 1.7 million known species of animals, plants, insects and algae. When considering about viruses of bacteria, archaea, and other single-celled organisms, and viruses in less-studied biosphere (e.g. the ocean system), the number could be 1031. Just as the exploration of the Universe, scientists have never stopped taking efforts to further discover the viral universe and make a better life. On this issue’s cover, 3D-printed herpesvirus, adenovirus, poliovirus, hepatis B virus, and Zika virus (from left to right) are artistically presented in the vast space near the Leo constellation. 3D-printed viruses are courtesy of Dr. Ding Gao from the Core Facility of Wuhan Institute of Virology.
天然免疫是宿主抵抗病毒入侵的第一道防线。逃过宿主天然免疫系统的监视是流感病毒成功感染的前提之一。探讨流感病毒与宿主天然免疫（I型干扰素）信号通路中的关键分子的相互作用对于了解流感病毒的毒力及其致病性具有重要意义。本研究我们发现细胞中过表达miR-26a能显著抑制流感病毒的复制。但miR-26a并不直接靶向流感病毒基因组，而是在流感病毒感染过程中增强天然免疫信号通路及I型干扰素介导的靶基因表达，从而抑制流感病毒复制。利用荧光素酶报告基因筛选及Western Blot 等试验证实，miR-26a通过靶向I型干扰素信号通路的负调控因子USP3（泛素特异性蛋白酶）而维持I型干扰素的持续激活。然而，对宿主具有保护作用的miR-26a在流感病毒感染过程中却受到抑制。由此可见，下调miR-26a的表达是流感病毒抵抗天然免疫的一种新策略。我们的研究表明补充miR-26a可能是对抗流感病毒感染的潜在策略。
In summary,the present study demonstrates that the forces favoring intra-animal diversification can cause the emergence of variants that,benefiting of their diversity at the population level,are able to succeed and spread in an often highly homogeneous environment,and to be further selected later.