Resurrecting the 1918 influenza virus

Genome analysis has shown that influenza viruses contain 8 pieces of RNA, and each one encodes one or more proteins. Tissue samples from a 1918 influenza virus preserved in Alaskan permafrost were recovered and the full viral genome sequenced by Taubenberger, et al. (2005). The nucleotide sequence of the eight RNA segments was obtained by the systematic use of random primers, reverse transcriptase, and PCR. Using the published sequences, eight cDNAs were constructed from synthetic oligonucleotides and the cDNAs cloned in a plasmid such that influenza virus genome RNA can be synthesized. These eight plasmids, together with four helper plasmids that express the three polymerase proteins and the nucleocapsid protein, were transfected into cells. Virus rescued from cloned DNA was released and used to infected mice.