Interference in the Chick Chorion

Summary: Experiments were carried out in an attempt to demonstrate in the chorionic cells of the chick chorio-allantoic membrane some of the interference phenomena with influenza viruses which are readily demonstrable in the allantoic cells. When a mixture of PR 8 and Lee viruses was inoculated on the chorion, no interference occurred; on the contrary, the soluble antigen titres for A and B antigen showed a highly significant positive correlation in individual eggs. Influenza virus, partially inactivated by heat or ultraviolet irradiation and shown to produce ‘auto-interference’ in the allantoic cells, showed no such effect when inoculated on the chorion; on the contrary, a phenomenon which may be similar to that described under the name ‘multiplicity reactivation’ was observed. Influenza virus completely inactivated by heat or by ultraviolet irradiation caused pronounced interference with the multiplication of large inocula of virus in the allantoic cavity; no interference was found when the same materials were inoculated on the chorion. However, there is some evidence to show that irradiated virus caused slight inhibition of the increase in infectivity which results when small doses of influenza virus are inoculated on the chorion.