Development of next-generation gene drive technologies for Anopheles population engineering

PROJECT SUMMARY
Malaria is currently the most impactful mosquito-borne disease worldwide, sickening 228 million people and
killing over 405,000 in 2018, 2/3 of which are young children — the most vulnerable demographic. Several
mosquito species of the Anopheles genus can act as vectors of the parasite causing malaria, and in recent
years their increasing resistance to pesticides is hampering current control methods and blunting our response
to eventual disease outbreaks. Globalization is further allowing both vectors and pathogens to move freely and
in certain situations to permanently establish themselves in new locations.
CRISPR-based gene drive technologies for mosquito population engineering are being developed as they
represent a new promising addition to our arsenal for fighting this disease. These technologies are
up-and-coming, yet few issues have come up during their development. Briefly, a gene drive system based on
CRISPR is composed of a Cas9 and a gRNA gene inserted in the mosquito genome at the location where the
gRNA targets it. The arrangement of this genetic cassette endowed it with self-replicating properties that allow
it to propagate to the same location on a wild-type chromosome. This property can be harnessed to spread
within a population a beneficial trait that would help reducing disease transmission (population modification), or
a deleterious trait to help reduce the mosquito population (suppression).
While this process is extremely accurate, it can result in the failure of self-propagating, and the generation of
small mutations at the targeted locus preventing further conversion by the gene drive. These “resistance
alleles” generated during the drive process have been identified as a major hindrance to field applications of
these tools. In addition, due to the deposition of active Cas9 and gRNA in the developing embryo, the mosquito
biology allows an extensive production of such resistance alleles when a gene drive is inherited from a female.
The long-term goal of this project is to develop powerful gene drive tools that can be used for the fast and
reliable engineering of wild Anopheles populations.
In order for these tools to be ready to have an impact on the malaria morbidity worldwide, the two issues
described above need to be overcome. To tackle these two problems, in the three Aims of the proposed
research, we will develop and optimize three parallel technologies in the fruit fly Drosophila melanogaster and
subsequently apply them to the major malaria vector Anopheles stephensi.

Grant Number: 5R01AI162911-05
NIH Institute/Center: NIH
Principal Investigator: ETHAN BIER