Behaviour of influenza virus point-inoculated onto the mucous membrane of the chick tracheal explant.

Influenza virus was point-inoculated on to the chick tracheal mucous membrane cultivated on a solid medium (L-15 agar medium) with a platinum microloop (ca 0.03 microliter of inoculum). Following the rapid adsorption of the inoculated virus on the mucosal surface, the explant was infected with a high efficiency. The 50% minimal explant infectious doses (MEID50) of influenza A virus strains (A/PR8/34, A/Kumamoto/79 and A/Bangkok/79) were less than one pfu. Influenza B virus (B/Lee/40) was also adsorbed to the mucous membrane but this virus failed to infect the chick tracheal mucous membrane (MEID50 greater than 10(3.3) pfu). By point-inoculation of virus on to the large tracheal explant (2 X 12 mm), it was possible to trace the behaviour of the infecting virus on the tracheal mucous membrane. Thus, influenza virus A/Kumamoto/79 was shown to be infective at the point-inoculated site by overcoming mucociliary clearance. Thereafter, depending on virus production and the ciliary activity of the infected epithelial cells, the infection spread rapidly to the laryngeal side but more slowly to the bronchial side of the tracheal explant.