Keeping Siblings Together: Enterovirus Collective Dispersal through Extracellular Vesicles Involves Genetically Related Viral Particles

Viruses can disperse collectively using extracellular vesicles and other types of multi-virion structures. It has been hypothesized that, by increasing the cellular multiplicity of infection, this dispersal mode may favor cooperation among viral genomes. However, the spread of defective variants that function as social cheaters could also be promoted. To better understand the nature of virions present in vesicles, here we examine the genetic diversity harboured by vesicles of coxsackievirus B3 (CVB3), a model enterovirus. Our results confirm that CVB3 vesicles contain multiple infectious particles. However, we also find that virus variants coinfecting a cell typically allocate their progenies into different vesicles, precluding long-term interactions among them. Furthermore, Illumina sequencing indicates that dispersal through vesicles does not increase viral population genetic diversity appreciably. We conclude that vesicles enable the co-dispersal of groups of virions, but that these groups are highly related since they share the same parental genome. This should restrict the evolution of defective viruses, but also makes cooperation among different viral genetic variants unlikely. Our results are in line with a fundamental tenet of social evolution theory, according to which the evolution of cooperation typically requires that the interacting partners are genetically related. Overall design: Examination of genetic diversity accumulated after 20 serial transfers of coxsackievirus b3 at low multiplicity of infection selecting, in duplicate, vesicles (V), broken-vesicles (bV) and free viral particles (S) using Illumina Miseq sequencing. Genetic diversity of the founder was evaluated sequencing the viral population that was used to initiate the evolution.