Replication of influenza A viruses in an avian macrophage cell

The virulent avian influenza virus A/Ty/Ont/7732/66 (H5N9) (Ty/Ont) causes severe destruction of the lymphoid cells in infected birds. Previous studies have suggested that viral infection of macrophages may be involved. However, Ty/Ont failed to replicate produc-tively in primary cultures of chicken macrophages. Therefore, in an effort to develop an in vitro system for our studies, we examined the susceptibility of an avian macrophage c ll line, HD 11, to Ty/Ont. We found that Ty/Ont replicated in the HD11 ceils to high titres, as measured by haemagglutination (HA) assays and infectivity ields. To determine whether this property was unique to Ty/Ont, we also examined the replica-tion of influenza viruses representative of all 13 HA subtypes and an attenuated variant of Ty/Ont. All o