The genetic aspects of influenza virus filamentous particle formation.

We analysed the genetic content of reassortants between parent viruses differing in their ability to form filaments. The results suggest that primarily HA, M, and NP genes are involved in the control of the filament forming ability. A lower buoyant density of the filamentous forms as compared to spherical particles allowed us to obtain a sufficiently pure population of filaments. A difference in the UV-inactivation kinetics between filaments and spherical virions suggests that the infectious filamentous forms are probably represented by multigenomic particles or partial heterozygotes.