CRISPR-mediated excision of HTLV-1 reduces proviral loads in PBMCs from HAM/TSP patients

CRISPR technology is emerging as a promising therapeutic approach for eliminating chronic viral infections, such as herpesviruses and HIV. Here, for the first time, we demonstrate in vitro that CRISPR can be used to excise the HTLV-1 genome and reduce proviral loads in PBMCs from HAM/TSP (HTLV-1-associated myelopathy/tropical spastic paraparesis) patients. Single treatment with CRISPR-RNP (ribonucleoprotein) complexes composed of two gRNAs targeting the HTLV-1 env gene and 3'LTR sequences resulted in excision of a 2613 bp segment of the proviral genome, spanning tax and HBZ genes, without detectable off-target activity. Furthermore, CRISPR treatment led to over 50% reduction in proviral loads 5 days post-electroporation. Our data indicate that CRISPR-Cas9 gene editing can be used as a therapeutic strategy to eliminate HTLV-1 DNA from infected cells and may serve as a platform for curing HAM/TSP.