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RESISTANCE PHENOTYPES. “In the studies with HCV it was important to exclude that inhibitor resistance mutations had not been acquired as a consequence of fitness gain. This possibility was excluded not only by NGS but also by the multiplicity of infection (MOI)-independent kinetics of virus production in the presence of inhibitors, and the maintenance of the resistance phenotype in biological clones of the passaged populations." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

DRUG RESISTANCE. "One of the conclusions of these studies is that replicative fitness can be an independent predictor of the response of HCV to inhibitors used in therapy. It is known that viruses never exposed to inhibitors can nevertheless include in their mutant spectra mutations that confer resistance to the inhibitors." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

"FITNESS, defined as the overall capacity of a virus to produce infectious progeny has long been recognized as a critical parameter that reflects virus adaptation to a specific environment. Unperturbed replication of large viral populations in a constant environment results in fitness gain, adaptation, while repeated bottlenecks that result in accumulation of mutations result in fitness decrease, de-adaptation." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

UNIT OF SELECTION. "The evidence just summarized is consistent with the idea that viral quasispecies can act as a unit of selection, group selection, one of the features of complex systems in the sense that the properties of the “whole” cannot be directly inferred from the properties of the “individuals”. Viral quasispecies have approached virology to the growing field of biological complexity." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

GENES FROM LIVE VACCINES. "Importantly, the pathogenic consequences of recombination need to be carefully considered whenever multivalent live-attenuated vaccines are used. For example, recombination of poliovirus vaccine strains leads to the frequent recovery of recombinant pathogenic poliovirus; similarly, this is also observed for infectious bronchitis virus." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

MEMORY FITNESS ADVANTAGE. "This allows a viral population to respond more effectively to selective constraints that had already been experienced by the same virus lineage." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

HOST ECOSYSTEM. "It is thus possible to extend the concept of quasispecies to include viral strains that co-circulate and that, by coinfecting cells in the infected individuals, can recombine increasing the sequence space that the virus can explore in search for evolutionary innovation." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

MOLECULAR MEMORY. "There are additional observations that support the view that mutant spectra are true actors of evolutionary outcomes. Viral quasispecies can be endowed with a molecular memory consisting of minority genomes present at higher than basal frequency levels because the genomes had been dominant in a prior phase of evolution of the same lineage." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

GENES ACQUIRED FROM HOST. "In some viruses this new variation is achieved by borrowing genetic material from their hosts. For example, influenza A virus has been observed to recombine with cellular RNA, resulting in increased pathogenicity for the hybrid viruses." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn

EXTREME CASES. "Some extreme cases of complementation between variants generated during quasispecies evolution that can greatly alter viral population structure or function have been described." http://www.sciencedirect.com/science/article/pii/S0042682215001580 View in LinkedIn