The mechanism of natural resistance of the allantois to influenza infection

Eggs differ in their susceptibility to infection by influenza virus. This paper reports an investigation of the causes of this variation in suspended fragments of allantois-on-shell. The total yield of virus from an allantoic membrane is unrelated to the susceptibility of the membrane to infection by small inocula. It follows that relatively resistant eggs are resistant, not because a high proportion of their allantoic cells are uninfectible, but because their cells have a low average probability of being infected by any individual virus particle. This diminished likelihood of infection is not associated with a lowered uptake of virus or with less efficient liberation; the barrier to successful infection lies inside the cell. No heritable differences in infectivity could be detected in a population of virus particles studied.