Table 1. Overview comparison of the gene drive systems explored in this manuscript.
Note that this table is for broad comparison purposes only and individual parameters (e.g. invasion thresholds) for systems grouped together (e.g. various 2-locus systems) will differ from one another. Equally, for a single system (e.g. unidirectional Wolbachia), characteristics will differ depending on the specifics of that system (e.g. fitness costs/maternal transmission rates and penetrance of cytoplasmic incompatibility).
| Wolbachia | Engineered UD | |||
|---|---|---|---|---|
| Bidirectional | Unidirectional | One-locus1 | Two-locus2 | |
| Status of modified vector | Non-GM | Non-GM | GM | GM |
| Intended outcome of drive deployment | Replacement | Replacement | Replacement/suppression (dependent on cargo gene) | Replacement/suppression (dependent on cargo gene) |
| Method of deployment | Requires bisex release | Requires bisex or female-only release | Requires bisex release (UDMEL can be established with male-only release) |
Can be established with male-only releases |
| Relative introduction allele frequency threshold (assuming equal fitness with existing wild population) | High (>0.5) | Low (>0) Current field strains estimated at ∼0.3 |
High (>0.5) | Low (<0.5) |
| Relative invasiveness | Low Assuming recipient non-target population has same Wolbachia infection as target population |
High Assuming recipient non-target population has no existing Wolbachia infection |
Low | High |
| Relative ‘drive-out’ ability | High Requires wild-type bisex release |
Low Requires wild-type bisex release |
High Requires wild-type bisex release (UDMEL can use single-sex female release) |
Low Can be achieved by releasing only wild-type, non-biting, males |
| Current development status | Proposed [32] | Field testing in A. aegypti | Laboratory proof-of-principle in D. melanogaster Laboratory development in Culex quinquefasciatus |
Laboratory proof-of-principle in D. melanogaster Laboratory development in A. aegypti |
Includes haploinsufficient, (1-locus) toxin-antidote (proposed but not yet developed), PTA overexpression, and (1-locus) UDMEL based systems.
Includes (2-locus) toxin-antidote (proposed but not yet developed), (2-locus UDMEL) and reciprocal chromosomal translocations based systems.
KEY: Drive outcome — goal of deploying drive. Either replacement of wild population with modified, less harmful population or suppression of wild population density. For engineered UD systems, outcome will depend on cargo gene tightly linked to other drive components. Bisex release: Release into the wild of individuals from both sexes, usually in roughly equal number. Introduction allele frequency threshold: The frequency the released modification must reach in the wild population before the drive will then begin to spread. Above this frequency, the drive conveys a population-level fitness advantage. Invasiveness: Propensity for a released drive to begin spreading in populations other than the one into which it was released. Note that these are relative invasiveness levels and all these systems are regarded as relatively non-invasive compared with other systems such as homing drives. Drive-out ability: The relative ease with which a population where the released modification has spread to fixation can be returned to its original non-modified state through the release of wild-type (non-modified) individuals. Note that this is the inverse of the introduction threshold/invasiveness of the system.