Resistance to Sigma Virus Infection in Drosophila

Abstract

Drosophila melanogaster is subject to infection by the sigma virus, either by virus carried in the fly gametes or by extracts from infected flies. Infected flies somehow become ‘CO₂-sensitive’ and thereafter are fatally poisoned if subjected to a dose of CO₂, which is merely anaesthetic to virus-free flies. Plus¹ showed that the time lag (incubation period) between a sigma injection and the onset of CO₂-sensitivity is a measure of the injected dose, and sigma extracts are now usually titred by using them as inocula and measuring the resultant incubation period in recipient adult flies.