Attenuation of wild-type human influenza A virus by acquisition of the PA polymerase and matrix protein genes of influenza A/Ann Arbor/6/60 cold-adapted donor virus.M H Snyder, Mary Lou Clements, D De Borde, Hunein F. Maassab, Brian R. MurphyJournal of clinical microbiology1985Wild-type influenza A viruses can be attenuated for humans by the acquisition of genes from the A/Ann Arbor/6/60 cold-adapted (ca) donor virus. Six-gene reassortants, that is, viruses containing the… (More)