Targeting Conserved Sequences Circumvents the Evolution of Resistance in a Viral Gene Drive against Human Cytomegalovirus
Targeting Conserved Sequences Circumvents the Evolution of Resistance in a Viral Gene Drive against Human Cytomegalovirus
Tags: Arbovirus, Gene drive synthetic, Population modification/replacement, Replicator/site directed nucleaseM. Walter, R. Perrone, E. Verdin and F. Goodrum, Journal of Virology, 95:e00802-21. 2021.
Gene drives are genetic systems designed to efficiently spread a modification through a population. They have been designed almost exclusively in eukaryotic species, especially in insects. We recently developed a CRISPR-based gene drive system in herpesviruses that relies on similar mechanisms and could efficiently spread into a population of wild-type viruses. A common consequence of gene drives in insects is the appearance and selection of drive-resistant sequences that are no longer recognized by CRISPR-Cas9. In this study, we analyzed in cell culture experiments the evolution of resistance in a viral gene drive against human cytomegalovirus. We report that after an initial invasion of the wild-type population, a drive-resistant population is positively selected over time and outcompetes gene drive viruses. However, we show that targeting evolutionarily conserved sequences ensures that drive-resistant viruses acquire long-lasting mutations and are durably attenuated. As a consequence, and even though engineered viruses do not stably persist in the viral population, remaining viruses have a replication defect, leading to a long-term reduction of viral levels. This marks an important step toward developing effective gene drives in herpesviruses, especially for therapeutic applications.