Figure 8

Proposed mechanism of action of the Salmonella-delivered CRISPR/Cas9 system for the specific knockout of the MDV genes meq and ovo in experimental chickens. MDV enters chickens mostly via the respiratory epithelium and continues to infect macrophages, B cells, T cells, and other peripheral white blood cells. MDV particles circulate throughout the body, finally reaching feather follicles where they mature and are shed. To knock out the invading MDV genome, attenuated Salmonella delivers the CRISPR/Cas9 system to macrophages and tissues such as the lymph nodes, spleen, and liver, where cells are invaded and undergo random lysis by releasing the CRISPR/Cas9 plasmid. The expression of Cas9 may knock out the meq and pp38 genes, severely attenuating MDV. This may lead to reductions in viral activity and the ability to transform healthy tissues into cancerous ones.