The growth cycle of influenza viruses as studied in touch preparations of the allantoic layer of chick embryos. 3. The growth cycle of influenza A virus in allantoic cells as studied by immunofluorescence.

The growth cycle of Influenza A virus has been studied in touch preparations of infected allantoic layers of the chick embryo using the immunofluorescence technique. Eggs incubated for 11 days were inoculated with either of two comparative doses: (A) 10(9)ID50 (high multiplicity) and (B) 200 ID50 (low multiplicity). (A) After inoculation of 10(9)ID50 (multiplicity: 100ID50 to 3 cells) into the allantoic cavity, two closely associated cycles of infection were observed. (a) A single cycle of multiplication which occurred simultaneously in all cells (those in contact with the allantoic fluid) of the surface stratum of the allantoic layer and terminated with their degeneration followed by desquamation at around the 18-21st hour after inoculation. Consequently, the cells of the deep stratum, denuded of surface stratum, came into contact with the allantoic fluid, a fluid heavily infectious. This first infectious process is termed the major growth cycle. (b) Multiple cycles of infection which occurred in only about 1-5% of cells of the deep stratum of the allantoic layer, the other 95% of deep cells remaining constantly free from infection. This condition is referred to as the minor growth cycle and it lasted until death of the embryos occurred within a maximum of 6-7 days after inoculation.