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Table I.
Some biological implications of the quasispecies nature of RNA viruses.
| 1. | Viral genomes are collections of mutant genomes termed mutant spectra or mutant clouds. Mutant clouds may include phenotypic variants adequate to respond to selective constraints (antibody- and cytotoxic T cell-escape mutants, inhibitor- or mutagen-resistant mutants; cell tropism and host-range mutants, etc.). The phenotypic repertoire of a viral quasispecies can contribute to viral persistence, pathogenesis and to the limited efficacy of treatments designed to limit viral replication. |
| 2. | Viral quasispecies can include memory genomes as minority components of their mutant spectra. Memory provides an adaptive advantage to viral populations. |
| 3. | Mutant spectra are not merely collections of mutant viruses acting independently. Positive interactions (of complementation) or negative interactions (of interference) can be established within mutant spectra. Thus viral quasispecies act as a unit of selection and cannot be accurately described by classical Wright-Fisher formulations of population genetics. |
| 4. | The understanding of quasispecies dynamics has helped defining protocols for preventive and therapeutic designs (vaccines to control viral quasispecies must be multivalent, antiviral agents must be sued in combination) and has impelled new antiviral strategies such as lethal mutagenesis (virus extinction by excess mutations). |