Funding for this research was provided by:
Program for National Natural Science Foundation of China (81702052)
Received: 11 March 2020
Accepted: 21 April 2020
First Online: 8 May 2020
Ethics approval and consent to participate
: The protocol of the present study has been approved by the Ethics Committees of the Institute of Pathogen Biology, Chinese Academy of Medical Sciences (IDs: IPB-2015-5 and IPB-2016-8). All participants have signed the written informed consent.
: Not applicable.
: The authors declare that they have no competing interests. L. G promises that he had no communication with other editors about this article, and would strictly abide by the rules of this journal and not participate in the review PROCESS.