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.
AdaG. L.,
PerryB. T.1956; Influenza virus nucleic acid: relationship between biological characteristics of the virus particle and properties of the nucleic acid. J. gen. Microbiol 14:623
BangF. B.,
IsaacsA.1957; Morphological aspects of virus cell relationship in influenza, mumps and Newcastle (myxovirus). The Nature of Viruses p. 249 Ciba Foundation Symposium London: Churchill;
BurnetF. M.,
LindP. E.1957; Studies on filamentary forms of influenza virus with special reference to the use of dark-ground-microscopy. Arch. Virusforsch 7:413
BurnetF. M.,
McCreaJ. F.,
StoneJ. D.1946; Modification of human red cells by virus action. 1. The receptor gradient for virus action in human red cells. Brit. J. exp. Path 27:228
HorsfallF. L.1954; On the reproduction of influenza virus. Quantitative studies with procedures which enumerate infective and haemagglutinating virus particles. J. exp. Med 100:135
MorganC.,
RoseH. M.,
MooreD. H.1956; Structure and development of viruses observed in the electron microscope. III. Influenza virus. J. exp. Med 104:171