Gene transfer strategies: principles, state-of-the-art and the major barriers that need to be overcome 2

Published on August 5, 2014   30 min

Other Talks in the Category: Cell Biology

0:04
Next we list what could be the most relevant to discuss, toxicity concern when using gene transfer. Now most of the toxicity which we'll discuss first has to do with in vivo gene therapy. In which vector particles are directly administered to tissues. Because gene therapy usually entails the administration of large amounts of particles all together, like a bolus of particles, this is often a substantial dose acutely administered. It may trigger a number of acute short term responses. Particularly if the vector is a viral vector, for which the immune system, of course, has usually a good capacity to sense and respond. But also when using chemical or some sort of lipid complexes of DNA. Now some of these responses are usually dose-dependent, so they show the typical acute toxicity-dependent on the dosing of particles, and can be controlled by identifying a safe interval of doses, and the minimally effective and the maximally tolerated doses as in most pharmacology. Other responses on the other and may be not dose-dependent. They are acutely a type of allergic response to some components, and they may be more difficult to control. Most of the dose-dependent allergic responses as mentioned are triggered by innate cells recognizing the vector particle and releasing the inflammatory sequence. The key aspect of that recognition are Toll-like receptors present on the membrane, or in the endosome or immune cell, mostly innate immune cells, in the body. These are most often phagocytes in the tissues, in the spleen, in the liver. As mentioned they are very efficient at phagocytosis of the administered particle. And then the Toll-like receptor may recognize in the particle which is in the phagosome and partly degraded in the phagosome, RNA, ribosomal RNA, DNA-- which may have unmethylated CPG-like plasmid DNA-- triggering a strong innate immune reaction. Other sensors are cytosolic sensors, the RIG-I family. And I mentioned this when I was talking about uncoating before. In which DNA or RNA may be recognized in the cytosol as of foreign origin, because they for instance don't have again methylated CPG, or they don't have a 5' cap in the case of RNA. And trigger innate activation, interferon fear responses, and so on. Another type of toxicity may be driven by components of the vector particle itself, which may exert some tissue toxicity. For instance viral envelope, which fuses to cell membrane, can give rise to toxicity by fusing cells to each other. Especially when there is a lot of viral particle administered. So cells which are neighboring cells exposed to high vector dose may actually fuse to themselves. And this is called also fusion from without and may give rise then to toxicity and cell death. Lipids themselves, or in some cases viral proteins themselves, like replicase or integrase, may trigger toxicity into the cell.
Hide

Gene transfer strategies: principles, state-of-the-art and the major barriers that need to be overcome 2

Embed in course/own notes