Foes to friends: do pathogens hold the key to gene therapy?

Imagine starting life with a disease where the chances of reaching a fifth birthday are unlikely, let alone making it to adulthood, and the only treatments available are palliative at best. This is the reality facing millions of individuals born with a rare genetic disease. Sometimes, due to a single DNA base change – out of a possible 3 billion – occurring in the wrong place. A simple spelling mistake! However, recent years have seen the first effective gene therapies being developed, based on supplementing patient cells with functional copies of the faulty genes, or using antisense oligonucleotides or small molecules to alter pre-mRNA processing. The challenges were how to deliver genes or alter gene expression in the diseased cells and how to do it safely, without negatively affecting other endogenous genes. The answers came in the form of viruses, small non-coding RNAs and bacterial proteins, which is somewhat ironic, because we are using infectious agents or mimetics of their products to help cure diseases. With old enemies turned allies, tool sets are now being assembled to tackle the most challenging of genetic diseases. This article explores some of those tool chests in further detail, using ataxia telangiectasia, spinal muscular atrophy and several other rare diseases to highlight progress and challenges.