Fig. 6: Filaments as a mechanism for viral persistence and adaptation.
From: Influenza A virus rapidly adapts particle shape to environmental pressures
a, IAV infections produce either more spherical or more filamentous populations independent of the input-virion shape and according to infection efficiency in each environment. b, Schematic of viral adaptation pathway showing if virion shape distributions were solely genetically encoded. A predominantly spherical strain infects an animal cell. Attenuation is permissive to filaments and selects for filamentous variants. Filaments persist, possibly adapting to overcome the attenuating pressure. In the absence of pressure, spheres have a fitness advantage and spherical variants are selected for. c, Model illustrating how dynamic virion shape distribution may promote viral persistence. A predominantly spherical population infects an animal cell. Attenuation induces filament production and any genetic variant has an equal probability of being enclosed in a filament, and thus population diversity is solely constrained by the extent of attenuation. These filaments persist under attenuating pressure, allowing further replicative cycles and possibly generating variants containing genetic changes that enable adaptation or immune evasion. Upon escaping attenuating pressure, the population immediately reverts to spheres without loss of genetic diversity.
