The First CRISPR-Based Therapeutic (SL_1.52) for African Swine Fever Is Effective in Swine.

African swine fever virus (ASFV) is a high-consequence pathogen that causes African swine fever (ASF), for which mortality rates can reach 90-100%, with death typically occurring within 14 days. ASF is currently a highly contagious pandemic disease responsible for extensive losses in pig production in multiple affected countries suffering from extended outbreaks. While a limited number of vaccines to prevent ASF are in use in south-east Asia, vaccines are not widely available, are only effective against highly homologous strains of ASFV, and must be used prior to an outbreak on a farm. Currently, there is no treatment for ASF and culling affected farms is the only response to outbreaks on farms to try and prevent spreading. CRISPR/Cas systems evolved as an adaptive immune response in bacteria and archaea that function by cleaving and disrupting the genomes of invading bacteriophage pathogens. CRISPR technology has since been leveraged into an array of endonuclease-based systems used for nucleic acid detection, targeting, genomic cleavage, and gene editing, making them particularly well-suited for development as sequence-specific therapeutic modalities. The programmability of CRISPR-based therapeutics offers a compelling new way to rapidly and specifically target pathogenic viral genomes simply by using different targeting guide RNAs (gRNA) as an adaptable antiviral modality. Here, we demonstrate for the first time a specific CRISPR/Cas9 multiplexed gRNA system that targets the African swine fever viral genome, resulting in sequence-specific cleavage, leading to the reduction in the viral load in infected animals, and subsequent recovery from an otherwise lethal dose of ASFV. Moreover, animals that recovered had protective immunity to subsequent homologous ASFV infection.