There is currently no cure for the human immunodeficiency virus (HIV) which, without treatment, causes AIDS in humans. Antiretroviral therapy, which inhibits the virus from replicating within the body, can stop the illness progressing, but because the virus integrates its genome into the DNA of host cells, if treatment is interrupted the virus will start multiplying again. As such, antiretroviral therapy must be continued for life.
Now US researchers have shown that CRISPR/Cas9 can be used to delete SIV (a retrovirus similar to HIV, which infects non-human primates) genetic material from within the DNA of infected monkeys.
'This first proof-of-principal study on the rhesus macaque model indicates that this virus-vehicle-delivered-CRISPR system can reach many tissue sites of the body, and is able to effectively delete virus DNA in infected cells. This paves the way for applying the same technology to the human body, which could lead to a cure for HIV infection,' said Dr Binhua Ling, associate professor in virology at the Texas Biomedical Research Institute and a co-author of the research published in Nature Communications.
The researchers used CRISPR/Cas9-based genome editing, packaged inside a harmless virus vector to target specific sites where the retrovirus' genome was integrated into the macaque DNA. Three SIV-infected rhesus macaque monkeys each received a single injection of the treatment.
Three weeks later, Cas9 molecules were shown to have reached 'reservoir' tissues (where viruses like SIV and HIV can hide for years without being detected), such as bone marrow, lymph nodes, immune cells and the brain. Genetic analysis also showed that the proportion of viral DNA in blood and tissue samples was reduced.
'We hope to soon move our work into clinical studies in humans as well. People worldwide have been suffering with HIV for 40 years, and we are now very near to clinical research that could lead to a cure for HIV infection,' said Professor Kamel Khalili, professor in virology and neurology at Temple University in Philadelphia, Pennsylvania and a senior co-author of the study.
The researchers are now repeating the experiments for a longer period of time to understand if the CRISPR approach is safe and whether it is able to fully clear the SIV infection.