A: Gene therapies treat diseases using genetic tools.
They usually work by making lasting changes to your DNA — the genetic “cookbook” that provides instructions to make you. Vaccines, by contrast, deliver a short-lived signal (e.g. a burst of protein), then disappear. Vaccines and gene therapies both use customized genetic tools to achieve their goals.
Dr. Chana Davis of Fueled by Science joins us today to explain why you don’t have to worry about vaccines changing your DNA:
🧬 The idea for gene therapy has been around since the 1960s when we realized that many diseases were caused by mutations in single genes. In theory, we can cure these diseases by providing patients with a permanent healthy copy of that gene.
👩🏽🔬 This is easier said than done. You need to get the right genetic code into the right cells (eye, blood, muscles etc.) then into the inner vault of the cell where DNA “cookbook” lives, and do so in a way that is safe and long-lasting. Gene therapies often rely on modified viruses to accomplish this feat because they are experts at entering our cells, and can easily be altered to deliver the desired genetic code.
🌏 There are around twenty different gene therapies approved in at least one country (see links for review and FDA list). They treat a wide range of diseases including cancers and single-gene diseases of the blood, eye, and muscles. These therapies are the product of more than five decades of intense research and clinical trials – the first gene therapy entered human trials in the 1970s.
🙏 We owe a debt of gratitude to the patients who volunteered for early gene therapy trials, some of whom lost their lives before safer strategies were developed (read more in links).
👩🏽🍳 Gene therapies fall into two broad categories: In replacement gene therapy, modified viruses deliver a new, healthy DNA copy of a mutated gene; in “cell based” gene therapy, human cells are reprogrammed and deployed as soldiers to treat diseases like cancer. Many more gene therapies are in development, including novel strategies like gene editing that can directly fix mutations in your DNA cookbook.
🤸🏿♀️A recently approved gene therapy called Zolgensma is a great example of replacement gene therapy. This therapy helps people who suffer from spinal muscular atrophy (SMA) by providing a healthy version of a gene (SMN) that they need for proper muscle function. The healthy SMN gene is pasted inside a modified virus called an adeno-associated virus (AAV). Patients are injected with loads of modified viruses. These viruses bring the gene into the patient’s cells, where it travels to a special vault where the patient’s genes live (the nucleus). The new gene sits alongside the patient’s inherited genes and provides instructions for making the much-needed protein for years to come. It’s been remarkable to watch a little girl in my community develop in leaps and bounds after receiving this treatment.
🧪 Replacement gene therapies are either directly injected into the patient (in vivo) or used outside the body (ex vivo). In ex vivo gene therapy, the patient’s cells are removed from their body, treated with gene therapy, then put back into the body. This approach is often used for diseases involving blood cells, including some severe immunodeficiencies.
🛠️ Another type of gene therapy, called “cell-based” gene therapy, treats diseases by creating “killer” cells that are deployed as soldiers. They are made by using genetic engineering tools to permanently reprogram the DNA cookbook of certain immune cells. One example of this approach is Chimeric Antigen Receptor (CAR) T-Cell therapy that is being used to treat some cancers.
🧰 How are vaccines different from gene therapy? They both draw from the genetic toolkit, but use different tools to achieve different goals (see link for a sample catalogue!). Vaccines deliver a short signal (e.g. a burst of protein) that sparks a fire drill, then disappears.
🔬 Some COVID-19 vaccine developers reached for mRNA as their genetic tool of choice, because it disappears in a few days, and never goes near your DNA. Others turned to specialized viruses (e.g. chimpanzee adenovirus) designed to produce a short burst of protein then bid farewell.
‼️ While the scope and definition of gene therapy is constantly evolving, one thing is clear: you don’t have to worry about vaccines changing your DNA.