Why Some People Are Immune to the Viruses Used in Gene Therapy

According to an article from ReliaWire, a sizable portion of the global population is likely to have an immunity to the inert viruses scientists use to administer gene therapy in patients with genetically-linked conditions.

Matt and James, brothers from the United Kingdom, both have hemophilia. When they heard about gene therapy clinical trials for their condition, they were both excited – Matt quickly signed up. However, he soon dropped out when he was informed that he was immune to the virus being used in the study.

About Hemophilia

Hemophilia is a rare medical condition that causes the blood to clot abnormally. Most cases of hemophilia are genetically linked, but as many as 30% of cases are not inherited. There are many different forms of hemophilia, but they are all related by their characteristic reduced clotting factor.

The causes of the disease differs between forms, but in all types of hemophilia, both minor and serious cuts take longer to clot and bleed for longer periods of time than in healthy individuals. People with hemophilia might also bruise easily, leaving large, deep bruises. Shocks to the head are of particular concern for people with hemophilia, because even light trauma could potentially cause bleeding into the brain.

Why Gene Therapy Might Not Work for Everyone

Gene therapy is an experimental field that uses genetic material to treat or prevent disease. It’s one of the fastest growing areas of medical research, and scientists from around the world are racing to find ways to use the human genetic code to fight against some of mankind’s most threatening health conditions.

Many of these therapies use modified, neutralized viruses that have been “deweaponized.” Viruses are some of the tiniest things we know of, and they are exceptionally good at penetrating the defenses of the human body. Scientist will edit a desired gene into many thousands of these viruses, which will be injected into a patient with a genetic condition. The viruses release their inert genetic code into the host along with the functioning copy of the artificially-placed target gene.

That’s how it’s supposed to work, anyway. Some people, however, have developed antibodies against the viruses mostly commonly used to deliver gene therapy. Across the globe, as much as 50% of people could be immune to the same AAV5 (that’s “adeno-associated virus 5”) virus that was being used in Matt’s clinical trial. For other commonly used viruses, such as AAV1 and AAV2, immunity rates could be even higher. Scientists lack a way to effectively test for immunity, so reliable estimates are difficult to come by.

Scientists believe other types of adeno-associated virus could have lower rates of immunity in the general population. Some researchers are engineering new forms of AAV in the lab that would be physically unrecognizable to immune antibodies. One way this approach might be used is by making many different “shapes” of virus, and testing to see which are the most effective at slipping through the immune system. This way, researchers hope to increase the number of people to whom this life-changing therapy can be made available.

Scientists are working on developing as many as 300 new gene therapies right now. Why do you think it’s so important to find alternative ways to administer these therapies? Share your thoughts with Patient Worthy!

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