A new study aimed to aid the progression of HIV/AIDS gene therapy published in Nature Biotechnology has shown promising results. The study involved the genetic disruption of the CCR5 gene in mice, following this the mice were observed to have normal T cell counts and there were no further medical complications.
Researchers have known about the presence of the HIV ‘aiding’ gene CCR5 for many years. The CCR-5 gene encodes for a receptor protein of the same name found in a variety of immune cells which is thought to play a role in the inflammatory response to infection. In HIV-1 the virus binds to the CCR-5 receptor protein, facilitating the infection of the immune cell, enabling the spread of the disease. There is a naturally occurring null allele for CCR-5 protein which 1% of the Caucasian population are homozygous for. These individuals express resistance to the HIV-1 strain.
The study carried out at the University of South California, used genetically altered human stem cells for injection into mice. One group of mice was injected with CCR-5 disrupted stem cells whilst the others were given wild type stem cells. Following infection with HIV the control mice showed vast disruption of the immune system due to infection. However, the CCR-/- mice showed ‘significantly’ lower HIV levels and the human stem cells were found throughout the tissues of the body.
This is not the first time the CCR-5 receptor has been therapeutically targeted, pharmaceutical companies have been developing drugs to interrupt the interaction between viral HIV and CCR-5 for many years with varying success. Maraviroc (made by Pfizer) has recently been approved for treatment, whilst Alpaviroc (made by GSK) failed its clinical trials and Vicriviroc (made by Schering-Plough) is still being tested.
Whilst CCR-5 remains a good target for therapeutic intervention it is not likely to bring about a cure. The second main HIV strain, HIV-2, targets a different receptor CXCR-4, for which there has been no naturally occurring null allele yet found in the general population. The use of similar targeting techniques using a CXCR-4 knock out stem cell line could be promising for treatment of this strain. However, the fast mutation rate of both the HIV virus strains means that means that the window of no resistance may be limited.
In such a complex and challenging disease it is common that the slightest new discovery be heralded as the key scientific breakthrough. However, this new treatment does shown genuine promise and whilst not the vaccine or cure that is so desperately sought after it could prove to be a valuable weapon in humanities arsenal against the AIDs epidemic.