Abstract
ALTHOUGH the presence of filamentary forms in preparations of influenza virus was first noted in 19461, the finding remained one of academic interest until the demonstration by Chu, Dawson and Elford in 19492 that recently isolated influenza A strains contain a high proportion of filaments. These forms have since been shown to possess many of the biological characteristics of spherical influenza virus particles3,4; but the question of the number of filaments needed to induce infection was not considered until recently. The main contribution in this direction has been the pioneer work of Donald and Isaacs5, who used quantitative counting techniques. They, however, did not claim any differences in the relative infectivity of virus filaments and spheres. Valentine and Isaacs6 have since suggested that, owing to the tendency of filaments to break up during adsorption on red cells, the actual counts of Donald and Isaacs5 are over-estimates of the number of filaments initially present, and hence there is an increased probability that filaments are infectious. In connexion with nucleic acid studies on filaments, we have used a strain of filamentary virus (Ryan) that has a mean ratio of 50 per cent egg infectivity dose/ agglutinating dose of the same order as that given by strains which exist almost exclusively as spheres. Using the counts of Donald and Isaacs5 together with our 50 per cent egg infectivity dose/agglutinating dose value, it can be calculated that, for this strain of virus, fewer filaments than spheres are necessary to induce infection in the embryonated egg.
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References
Mosley, V. M., and Wyckoff, R. W. G., Nature, 157, 263 (1946).
Chu, C. M., Dawson, I. M., and Elford, W. J., Lancet, i, 602 (1949).
Bang, F. B., and Isaacs, A., in “The Nature of Viruses”, Ciba Foundation Symposium, 249 (Churchill, London, 1956).
Burnet, F. M., and Lind, P. E., Arch. f. Virusforsch. (in the press).
Donald, H. B., and Isaacs, A., J. Gen. Microbiol., 11, 325 (1954).
Valentine, R. C., and Isaacs, A., J. Gen. Microbiol., 16, 195 (1957).
Ada, G. L., and Perry, B. T., Aust. J. Exp. Biol., 32, 453 (1954); J. Gen. Microbiol., 14, 623 (1956).
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ADA, G., PERRY, B. & EDNEY, M. Infectivity of Influenza Virus Filaments. Nature 180, 1134 (1957). https://doi.org/10.1038/1801134a0
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DOI: https://doi.org/10.1038/1801134a0
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