%0 Journal Article %A Ada, G. L. %A Perry, Beverley T. %A Abbot, A. %T Biological and Physical Properties of the Ryan Strain of Filamentous Influenza Virus %D 1958 %J Microbiology, %V 19 %N 1 %P 23-39 %@ 1465-2080 %R https://doi.org/10.1099/00221287-19-1-23 %I Microbiology Society, %X SUMMARY: An influenza A strain, Ryan, isolated in Melbourne in 1954 contains on a particle basis about 20% filaments. By using the electron microscope for particle counting, the efficiency as haemagglutinin of Ryan ‘long’ filaments (particles in which length: width ⩾ 6) was estimated to be about 6 times greater than that of spheres of PR 8 virus. Allantoic fluid preparations of Ryan virus have high values for the ratio (log) EID50:AD and estimates indicate that a maximum of 6 ‘long’ filaments are equivalent to one EID50, compared with 18 particles in the case of PR 8 virus or 14 particles in the case of a mutant strain of Ryan virus which exists almost exclusively as spheres. Compared with virus PR 8 spheres (16 particles: AD), spherical particles present in filamentous Ryan preparations have a low efficiency as haemagglutinin (29 to 38 particles:AD). These particles are formed before the ‘long’ filaments, and in fluids harvested 21 hr. after inoculation when the proportion of ‘long’ filaments is very low, about 9 spherical particles constitute 1 EID50. For the purpose of subsequent chemical examinations filaments were isolated and concentrated by a process involving specific adsorption to and elution from red cells, followed by 3 cycles of differential centrifugation. The ratio of filaments: spheres in such preparations is about 50:50. ‘Purified’ filaments weigh about 30 times as much as the spherical particles present and account for over 95 % of the total weight present in purified preparations. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-19-1-23