In a recent PNAS publication by Buchman et al (2019), the authors report on the establishment and validation of transgenic Aedes aegypti containing a synthetic anti-ZIKV cassette, capable of conferring complete refractoriness to the virus.
Aided by piggyBac transposon-mediated insertion (Figure 1), they generated four lines of Ae. aegypti expressing a polycistronic miRNA-like cassette containing eight synthetic miRNAs under control of the Carboxypeptidase A promoter. The expressed miRNAs targetted three structural, and three non-structural genes in ZIKV, including NS5, a highly conserved gene among ZIKV strains (Figure 2). Small miRNA profiling of the transgenic lines identified efficient expression and processing of the miRNAs.
Challenge of the highest-expressing transgenic line with two divergent strains of ZIKV demonstrated complete ZIKV resistance for homozygous individuals and a strong reduction in heterozygous individuals.
Modeling of ZIKV infection in both Vero cells and in Stat-/- mice demonstrated a significant decrease in midgut and carcass infection, and also a decrease in prevalence in saliva.
The authors note that if the construct is linked to a gene drive system, it could be used to push the anti-ZIKV allele as homozygous through a population of Ae. aegypti, resulting in a population that is completely refractory to ZIKV.
Engineered resistance to Zika virus in transgenic Aedes aegypti expressing a polycistronic cluster of synthetic small RNAs Anna Buchman, Stephanie Gamez, Ming Li, Igor Antoshechkin, Hsing-Han Li, Hsin-Wei Wang, Chun-Hong Chen, Melissa J. Klein, Jean-Bernard Duchemin, Prasad N. Paradkar, Omar S. Akbari Proceedings of the National Academy of Sciences Feb 2019, 116 (9) 3656-3661; DOI: 10.1073/pnas.1810771116