Host cell dependence of viral morphology

The morphology of influenza virions was found to depend on cellular determinants. Influenza viral filaments up to 30 mu m in length were observed to form at high levels on surfaces of various polarized epithelial cell types infected with the A/Udorn/72 virus. In contrast, virions produced by nonpolarized cell types infected with this virus were almost exclusively of spherical morphology. Disruption of the actin microfilament array by cytochalasin D treatment of polarized MDCK cells had a profound effect on viral morphology. Although virus Biters and release of spherical particles were not reduced in the presence of cytochalasin D, we observed a 15-fold reduction in the release of filamentous particles. In contrast, the ratio of filaments to spheres produced by infected MDCK cells was not altered by the microtubule-disrupting agent nocodazole. These observations indicate that the polarized cell phenotype and the Integrity of the actin microfilament network are important cellular determinants of the morphology of a filamentous influenza virus.