Mengmei Deng
Student number: s4200951
Prac session: P5
The most commonly used treatment for HIV is known as anti-retroviral treatment (ART). This type of treatment shows effectiveness to a certain extent but is very high in cost and toxicity and is impractical to be taken every day for life. In order to solve these problems with ART, three groups of scientists endeavoured to find cure to HIV through the method of gene therapy.
The first group of scientists added a DNA-disrupting molecule, known as zinc fingers nucleases (ZFNs) which will zero in on and disrupt any chosen gene. In this case, the chosen gene is the CCR5 gene which codes for making the HIV door-handle protein. The CD4 cells, which are the cells attacked by HIV viruses, are then extracted from the patient’s blood and added with a harmless virus carrying the genes that code for the ZFNs. The altered CD4 cells produce ZFNs which sabotage the CCR5gene. The ZFNs and the harmless virus are then washed away and the modified cells are injected back to the patient’s body. The engineered cells replicate faster and live longer than the cells that are already infected with HIV, so that the modified cells will eventually become dominant CD4 cells and block HIV from getting into the cells. However, the problem with this method of gene therapy is that it raises the question of whether it is ethical to destroy a HIV patient’s existing immune cells, as the engineered cells won’t work if the existing immune cells are not eliminated.
The second group of scientists aimed to add the gene coding for ribozyme, an enzyme that disrupt HIV replication into the cell so that the HIV replication is inhibited once it gets inside the cell. The scientists extracted CD34 stem cells from the patients with a virus that carries a gene for a ribozyme. This enzyme will be expressed when the cells are injected back into the patients and the replication of HIV is stopped as the enzyme snips up the tat gene, the gene essential for the virus to replicate itself, in any HIV that enters the cell. However, the number of cells with the ribozyme disappeared rather than multiplying over a period of time and the therapy is not as effective as usual ART.
The third group of scientists combined the techniques of the first and second groups. These scientists used viruses to load patients’ blood cells with three genes to defend them from HIV: one prevents the HIV to get into the cell and the other two sabotage the HIV even if it does get into the cell. However, though this method had been applied to a few patients, the patients carried on their usual anti-retroviral treatment while the gene therapy was applied. Therefore, the effectiveness of this method has not yet been finally determined.
All of the three methods of gene therapy proposed by the scientists to cure HIV had its own problems. Though they all showed encouraging signs to the cure of HIV, it is still hard to determine whether gene therapy is the ultimate solution for the disease.
References:
“Gene therapy promises one-shot treatment for HIV” from http://www.newscientist.com/article/mg20126964.400-gene-therapy-promises-oneshot-treatment-for-hiv.html?full=true
“Gene therapy for HIV shows promise” from http://www.newscientist.com/article/dn16601-gene-therapy-for-hiv-shows
