The Investigation of Influenza and Related Viruses in the Electron Microscope, by a New Technique

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Abstract
Influenza and related viruses were studied by a new method in which virus is adsorbed on the membranes of laked fowl red cells for examination in the electron microscope. The numbers of virus particles adsorbed per unit area of red cell membrane were estimated from direct counts in micrographs of palladium-shadowed and unshadowed specimens. There was a definite saturation level of adsorption for each strain of virus, the value varying also according to the particular batch of cells and their age after storage at 0[degree]. For subsaturation conditions the number of particles adsorbed was proportional to the concn. of virus and the concn. of cells, and a function both of time of contact and temp. The relationships were complicated by the fact the elution began before adsorption was complete. The comparative data for the size and variation of these viruses were obtained from micrographs of prepns. directly adsorbed from infective allantoic fluid and thus not subjected to harsh methods of purification. The mean sizes (m[mu]) found for the dried virus were influenza A virus, 90 [plus or minus] 11.5; influenza B virus, 103 [plus or minus] 8; fowl-plague virus, 101 [plus or minus] 16; Newcastle disease virus, 193 + 28; and mumps virus, 179 [plus or minus] 28. The occurrence of long forms associated with influenza B virus was confirmed and filamentous structures were demonstrated for the first time in prepns. of a strain of fowl plague virus.