Multiplicity Reactivation in Gamma Irradiated Influenza Viruses

MULTIPLICITY reactivation was first demonstrated in 1947 by Luria¹, in bacteriophages irradiated by ultraviolet light. In 1951, Henle and Liu² showed the same phenomenon in influenza viruses irradiated with ultraviolet light and grown in chick embryos. Their results were confirmed by Barry³ in 1961. In the same year Polley⁴, investigating the sterilizing potentialities of ionizing radiations, found that viral infectivity could be destroyed completely by high doses of cobalt-60 gamma rays while viral haemagglutinin (HA) appeared more resistant. In these experiments, the loss of infectivity was a perfectly exponential function of the radiation dose, and no evidence of multiplicity reactivation was observed.