The growth cycle of influenza viruses as studied in touch preparations of the allantoic layer of chick embryos. 2. The morphology of allantoic cells infected by influenza A virus.

The morphology of allantoic cells infected by influenza A virus was studied in touch preparations of the allantoic layer from 11-day embryos inoculated by the intra-allantoic route. Two comparative doses were used: 10(9) ID50 or large inocula (multiplicity: 100 ID50 to 3 cells) and 200 ID50 (multiplicity: 1 ID50 to 150,000 cells) or small inocula. The allantoic layer from 11-day eggs is an epithelium consisting of at least two strats: a superficial stratum and a deep one. Both with the large and the small inocula, a total and irreversible destruction of the superfifial stratum (cells having free facets in ocntact wit- allantoic fluid) was produced, while the profound one (a layer underlying the surface stratum, with cells normally not having any contact with the allantoic fluid) remained essentially intact. Three successive stages were observed. 1. Incubation period: The cells of both strata exhibited a normal appearance during the first 10 hours with the higher multiplicity, and for the first 15-17 hours with the lower multiplicity. 2. Necrotic period: The cells of the superficial stratum exhibited degenerative changes (the chromatin breaks up into numerous irregular and deeply stained fragments) followed by desquamation into the allantoic fluid within the next 10 hours (from 10th to 20-22th hour after inoculation) with the large, and the next 17 hours (from 15th-17th to 32nd-34th h.) with the small inocula. No morphological changes were observed with the profound cells. 3. Post-necrotic period: The profound stratum with cells of sound appearance, some of whoch showed giant nuclei (polyploid cells?) REMAINED UNTIL THE DEATH OF THE EMBRYos which occurred within a maximum of 6-7 days after inoculation. Occasionally, throughout this period, degenerated deep cells were found (about 1-5% in quantity) which, with the aid of immunofluorescence procedure, are believed to be related to a minor cycle of virus multiplication.