In March of this year at Temple University, scientists successfully edited HIV DNA out of the genome of human immune cells using the CRISPR/Cas9 gene editing method. The procedure simultaneously prevented virus replication and reinfection among the treated cells. CRISPR, which stands for "clustered regularly interspaced short palindromic repeats," are segments of prokaryotic (most often bacterial) DNA; they are made up of brief repetitions of DNA sequences followed by short segments of "spacer DNA," acquired from a virus that infects bacteria or a plasmid (small, circular, self-replicating strands of DNA that are independent from the cell's chromosomes). These "spacers", with the help of various additional proteins, recognize and excise exogenous and/or unwanted genetic material-in this case, the incorporated DNA of the HIV retrovirus. In this manner, the DNA of an organism can be cut at any desired location, and the cell acquires immunity to the unwanted sequence in the event of any future exposures. The CRISPR/Cas9 gene editing method essentially engineers and inserts a bacterial immune response into an animal cell.
The success of CRISPR/Cas9 in treating HIV in human cells is incredibly promising; while antiretroviral drugs can help control HIV infection, once patients stop taking them, the virus rapidly begins to replicate once again from copies of its DNA still present in patients' cells. "[These] findings are important on multiple levels," Dr. Kamel Khalili, director of the Comprehensive NeuroAIDS Center at Temple University, stated in an official press release. "They demonstrate the effectiveness of our gene editing system in eliminating HIV from the DNA of CD4 T-cells and, by introducing mutations into the viral genome, permanently inactivating its replication. Further, they show that the system can protect cells from reinfection and that the technology is safe for the cells, with no toxic effects."
Nevertheless, researchers face an uphill battle in implementing CRISPR/Cas9 in human test subjects. Delivering the required materials to the desired cells is still difficult; there remain numerous "off-target" effects, in which DNA is cut in places where it should remain intact; the experiment result may have a mixture of modified and unmodified cells, a phenomenon known as "genetic mosaicism." Other concerns are ethical in nature: there has not been enough research to establish the effects of CRISPR/Cas9 on subsequent generations. If a human has HIV DNA edited out of his or her genome and then goes on to have a child, what unknown consequences might arise in that child?
Regardless of the risks, CRISPR/Cas9 is expected to become progressively safer and more viable as a medical treatment; in the interim, the fight for the procedure's patent has already begun. The two main parties at the moment are the Broad Institute of MIT and Harvard and the University of California, the latter of which has alleged that all of the Broad Institute's CRISPR patents (approximately one dozen of them) were fraudulently obtained. The Broad Institute has denied the allegation, and the case is expected to drag well into the following year. Current pharmaceutical options for HIV focus on treatment, rather than a cure, spearheaded by biopharmaceutical companies such as Gilead Sciences
