An estimated 35 million people have been infected with HIV-1, and while antiretroviral therapy (ART) has allowed the disease to be managed, current treatments are incapable of eliminating the virus or even stopping replication. Current ART treatments can only slow down replication of the virus to low levels.
Replication of the virus continues in certain immune cell types such as CD4+ cells, macrophages, and follicular dendritic cells and can hide in various other cells. ART does not block replication in these cellular reservoirs of the virus. As soon as ART stops, there is a rapid viral rebound. The failure to eradicate the virus means HIV-1 will persist, regardless of ART.
One potential solution is to disrupt the HIV genome using gene editing tools. While there are several tools that could potentially be used, each has its problems.
Extensive research is being conducted to find drugs and treatments that can eradicate the disease, with significant progress recently made by researchers in Japan. The team turned to the CRISPR-Cas9 gene editing tool to develop a potential functional cure for the disease.
The researchers – from Kobe University Graduate School of Medicine and Kobe University Graduate School of Health Sciences – have demonstrated that it is possible, in vitro, to stop the HIV-1 virus from replicating. Potentially, this treatment could be provided to patients in a one-time intervention to clear viral genomic persistence.
Using CRISPR-Cas9, the researchers successfully disrupted two regulatory HIV-1 genes called tat and rev. These genes are essential for replication of the virus and are highly conserved across different subtypes of HIV-1.
To use CRISPR-Cas9, the researchers had to develop guide RNAs that would allow specific gene edits to take place. The team developed three gRNAs for each of the two genes to guide the edits. The gRNAs and Cas9 enzyme were packaged in a lentiviral vector and introduced into cultured latently infected CD4+ T cells.
“Lentiviral delivery of CRISPR/Cas9 successfully reached the isolated proviral genome, cleaved regulatory genes, and significantly inhibited viral replication, even after latency reversal,” wrote the researchers. “The capability of lentiviral vectors to transduce non-dividing cells, including resting CD4+ T cells, and maintain stable, long-term Cas9 transgene expression supports their potential use in eradicating infected cells constituting the latent reservoir.”
While the researchers have demonstrated the effectiveness of the treatment in vitro, they have yet to translate their success to an in vivo treatment.
“In order to safely and effectively introduce the CRISPR-Cas9 system, the vectors must be improved,” said paper co-author Masanori Kameoka, Ph.D. “We hope this research will provide us with useful information in developing a treatment method that can completely cure HIV-1 infection.”
The research is detailed in the paper – CRISPR/Cas9 System Targeting Regulatory Genes of HIV-1 Inhibits Viral Replication in Infected T-Cell Cultures – recently published in Nature Scientific Reports.