Differences in sensitivity in haemagglutinin inhibition assays between A/equine/H3N8 viruses isolated in eggs and MDCK cells are linked to cleavage of the haemagglutinin molecule.

Two primary isolates of A/equine/H3N8 viruses were obtained in embryonated hens' eggs and in Madin-Darby canine kidney (MDCK) cells. Viruses isolated in MDCK cells were significantly more sensitive as antigens in haemagglutination inhibition (HI) tests. This sensitivity appeared to be primarily linked to the extent of cleavage of the haemagglutinin molecule.