Influence of tissue differentiation on susceptibility to virus infection.

Abstract

SUMMARY The interaction of vaccinia virus with embryonic chick skin was studied in vitro using an organ culture technique. Skin explants were taken from chick embryos between 5½ to 6 days’ and 17 to 18 days’ incubation. Susceptibility of the epidermis of both the skin and the feather germ to vaccinia virus at these different stages remained unchanged; a generalized pattern of infection was observed with epidermal hyperplasia followed by necrosis. An exception to this behaviour pattern was seen in cultures from the 8½- to 9-day embryo where a ‘honeycomb’ type of infection occurred; the epidermis in the apical zone of the feather germ presented a characteristic appearance with neither hyperplastic reaction nor normal thickening. The dermis showed pronounced susceptibility to vaccinial infection in explants from 5½- to 6-day embryos, but became progressively and rapidly resistant at embryo ages between 7⅛ and 10 days. Dermal sensitivity was again marked in explants from 11- to 18-day embryos. The mesenchymal cells forming the mesodermal core of the feather germs were resistant to the pathogenic effect of the vaccinia virus in 6½- to 11-day explants; feather germ development was nevertheless modified. The dermal papilla, however, was grossly sensitive to viral infection from the time of its initial differentiation at 12 to 13 days’ incubation. The susceptibility of the cellular components of the skin to the viral infection appeared to be influenced by the inductive processes responsible for the differentiation of the normal skin. The pathogenic effect of vaccinia virus varied according to the stage of development of the embryonic skin.