Several decades ago, gene therapy seemed to be on target to treat a disease by simply replacing a defective gene with a healthy one. A recent article republished in APNews from The Conversation, authored by Dr. Samira Kiani of Pittsburgh University, describes the initial goal as using gene therapy to treat genetically inherited disorders such as sickle cell anemia, hemophilia, and metabolic disorders.
However, many years later, scientists are still coping with several obstacles that prevent genes from delivering on that promise. One major obstacle involves the destruction of the gene and its transport vehicle by the immune system.
Also, the damage to the gene caused by the immune system often results in massive inflammation which can be life-threatening.
Controlling the Immune System
Although through the years scientists have been attempting to control the response of the immune system to the vehicle or to the gene by perfecting the technology, thus far they have been unsuccessful.
Steroids are often used to temper an immune response as they suppress the immune system. However, steroids have not proven effective, as they are hard to control and are responsible for several adverse events.
Dr. Kiani and her associate Dr. Ebrahimkhani, decided to use immune-suppressing agents that would enable them to make some headway in gene therapy and also have more control.
A Diagnosis of Pancreatic Cancer
Dr. Kiani explains that her interest in gene therapy began six years ago when she learned that her father had been diagnosed with pancreatic cancer, known to have an extremely low survival rate.
She believed that the only hope for her father would be found in gene therapy. However, the failure rate in gene therapy is high. Patients may develop an immunity from their own therapy or have a pre-existing immunity to the vehicle used to transport the gene. It is the aforementioned problems that have prevented wider use of the technology.
CRISPR, the “genetic surgeon”
Previously, the vehicles used to deliver genes to certain organs were harmless viruses. The genes produce a substance that replaces faulty, genetically inherited genes.
This process works for many genetic diseases but in others, the size of the faulty gene does not correspond with the replacement. Therefore, the process breaks down at this point.
A more common problem occurs when a harmless virus is caught by the immune system which immediately identifies it as a foreign pathogen. In response, the immune system produces antibodies. It mistakenly goes on the attack.
The Advent of CRISPR has changed that landscape through its gene-editing technology. When you think of CRISPR, picture a “genetic surgeon” using a scalpel. The surgeon identifies a defect and corrects it in targeted cells within the organism. CRISPR is able to correct several genes at one time.
An On-Off Switch
CRISPR can temporarily turn a gene off as well as return it to the “on” position. It can accomplish this without making a permanent change to DNA letters. The result is that researchers will be able to use CRISPR technology in the future to create a revolution in gene therapies.
This will solve one problem. But the immediate challenge is to create a vehicle that can evade an attack by the immune system and simply transport the virus safely into the body.
Dr. Kiani, a synthetic biologist, partnered with an associate, Dr. Ebrahimkhani. They used CRISPR to determine if it is possible to turn off the gene that blocks the gene therapy.
They researched the possibility of reducing gene activity to see if it would dull the immune response. Perhaps then the efficacy of the viruses would improve.
Myd88, A Key Immune System Gene
Myd88, one of the immune system’s critical genes, controls its response to viruses and bacteria. This includes the ordinary viruses used in gene therapy. Dr. Kiani and her partner injected CRISPR molecules into their lab animals. The target was Myd88. Their goal was to turn off the gene temporarily and find out if the injections lessened the number of antibodies that fought against their gene therapy viruses.
They were pleased that the injections worked and that their CRISPR treatment generated fewer antibodies against the virus. There was no doubt that their efforts prevented the immune response that had destroyed gene therapy viruses.
Less is More
The partners were curious to see if a second dose of the gene therapy would be doubly effective. If so, this would be contrary to the usual immune response.
Usually, when a second dose is administered to an immune system that has already had experience with a certain virus, antibodies remember the virus and destroy it prior to its arriving at the target.
This proved to be true with Dr. Kiani’s testing. In certain cases though, the gene therapy “effect” improved with the second dose in comparison to the first injection.
A series of experiments also proved that the Myd88 gene can be tweaked and fight off various types of inflammation. This can be useful in working with COVID-19 and sepsis.
The results of Dr. Kiani’s study, controlling Myd88 gene activity, has been published in Nature Cell Biology. The study shows how CRISPR technology can be used to program the immune system during gene therapies and various inflammatory responses.