Recent gain-of-function studies in influenza A virus H5N1 strains revealed that as few as three-amino-acid changes in the hemagglutinin protein confer the capacity for viral transmission between ferrets. As transmission between ferrets is considered a surrogate indicator of transmissibility between humans, these studies raised concerns about the risks of gain-of-function influenza A virus research. Here we present an approach to strengthen the biosafety of gain-of-function influenza experiments. We exploit species-specific endogenous small RNAs to restrict influenza A virus tropism. In particular, we found that the microRNA miR-192 was expressed in primary human respiratory tract epithelial cells as well as in mouse lungs but absent from the ferret respiratory tract. Incorporation of miR-192 target sites into influenza A virus did not prevent influenza replication and transmissibility in ferrets, but did attenuate influenza pathogenicity in mice. This molecular biocontainment approach should be applicable beyond influenza A virus to minimize the risk of experiments involving other pathogenic viruses.
Bibliographical noteFunding Information:
This work was supported by the Center for Research on Influenza Pathogenesis, a National Institute of Allergy and Infectious Diseases–funded Center of Excellence in Influenza Research and Surveillance (HHSN266200700010C). B.R.T. is supported in part by the US Army Research Office under grant numbers W911NF-12-R-0012 and W911NF-08-1-0413 and the Burroughs Wellcome Fund. MDCK cells were kindly provided by P. Palese (Mount Sinai School of Medicine).