HOST-CELL DEPENDENCE OF VIRAL MORPHOLOGY

The morphology of influenza virions was found to depend on cellular de terminants. Influenza viral filaments up to 30 mu m in length were obs erved to form at high levels on surfaces of various polarized epitheli al cell types infected with the A/Udorn/72 virus. In contrast, virions produced by nonpolarized cell types infected with this virus were alm ost exclusively of spherical morphology. Disruption of the actin micro filament array by cytochalasin D treatment of polarized MDCK cells had a profound effect on viral morphology. Although virus Biters and rele ase of spherical particles were not reduced in the presence of cytocha lasin 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 age nt nocodazole. These observations indicate that the polarized cell phe notype and the Integrity of the actin microfilament network are import ant cellular determinants of the morphology of a filamentous influenza virus.