From plaques to pocks: carrying over bacteriophage assay techniques to the study of influenza and other animal viruses.

This article assesses the impact of the discovery of bacteriophages, which emerged from an investigation into a 1915 outbreak of bacillary dysentery in France, on influenza virus research. Specifically, it details the way in which the phages became a vehicle for importing certain assay techniques into the study of influenza and other viruses that cause infectious diseases in humans and other animals, thereby enabling the scaling up of vaccine production for these diseases. Very soon after his 1917 report of the discovery of bacteriophages, Felix d'Herelle developed an assay technique based on their ability to form countable plaques on solid media when incubated along with the dysentery bacteria. This basic technique was further refined by Macfarlane Burnet in the late 1920s. Still later, in the wake of a 1935 influenza outbreak in Australia, Burnet applied the principles of serial dilution and plaque counting, honed during his work on the phages, to develop a technique for cultivating influenza viruses in fertilised eggs and assaying them by counting the pocks induced on the chick embryo membranes. The ability to grow and assay these viruses proved crucial in developing the first successful vaccines against influenza. In the 1950s, bacteriophage assay techniques were once more carried over to the assaying of viruses on cultured cells by Renato Dulbecco and Marguerite Vogt. The importance of quantification in science, as well as the ability to apply the results of investigations in one area of biology to another, relatively unrelated field, is also discussed.