Analysis of the restriction to the growth of nonegg-adapted human influenza virus in eggs.

When nonegg-adapted human influenza virus, i.e., either the natural virus present in a clinical specimen or an isolate propagated exclusively in tissue culture cells, is first passaged in the allantoic cavity of embryonated hens' eggs, variants which have amino acid substitutions around the receptor binding site are selected. We have studied the biological basis for the restriction of MDCK cell-derived virus to growth in the egg by analyzing the relative binding activities of viruses derived from the same clinical specimen, one in MDCK cells and one in eggs, and have identified a difference between the interaction of egg- and cell-derived virus with the surface of allantoic cells. The majority population of MDCK cell-derived virus binds to but fails to be internalized by allantoic cells resulting in the selection of variants which have this ability.