How Does Gene Therapy Work?

Original Paragraph

Gene delivery is one of the biggest challenges to successful gene therapy. You can imagine it would be hard to actually inject these genes into the tiny cells, so a carrier, or a "vector," is used to accomplish this. Typically, viruses are used as the vectors.  The virus vector must be genetically altered to carry human DNA. These viruses are like those that cause the common cold, only they are "deactivated" so that they will not cause the patient to actually get the cold. In some cases, some cells are taken from the patient and the virus is exposed to the cells in the laboratory. The virus with the desired gene attached finds its way into the cells. These cells are allowed to grow in the laboratory, and are then given back to the patient by intravenous (IV) infusion or are injected into a body cavity (i.e. the lung) or a tumor. In other cases, the vector with the attached gene is directly inserted into the patient by intravenous infusion or is injected into a body cavity or a tumor.  Once the gene has reached the cell, it must go to the cell's nucleus and become integrated within the human genetic material. Then it needs to be "turned on," to produce the protein product encoded by the gene. For gene delivery to be successful, the protein that is produced must function properly.

Gene therapy is still experimental, so the means by which it is given may change as the technology develops. 

Key Ideas: 

- A carrier, also known as vector is used to inject genes into the tiny cells

- Viruses are used as the vectors, it is genetically altered to carry human DNA

- The virus with the desired gene attached finds its way into the cells

- Gene therapy is still experimental, so the means by which it is given may change as the technology develops

Source: 

"Gene Therapy: The Basics." Cancer Resources. N.p., n.d. Web. 16 Oct. 2014. <http://www.oncolink.org/treatment/article.cfm?c=15&id=323>.

Paraphrasing:

For gene therapy to become a revolutionary breakthrough for mankind, we must first invent a way for gene delivery. Researchers have discovered a particular method that utilizes carriers or "vectors" where the genes are kept and given to the patient's body. Certain viruses act as vectors, in which the virus is genetically engineered and its "bad" DNA is deactivated as to contain un-harmful human DNA. There are two ways for a virus vector to infect an infected cell. The first method is by exposing the virus to the cell outside the body. The cells of the patient are extracted and brought into a laboratory, where in it comes in contact with the virus vector. Once the new gene has infected the defective cells, it is returned back to the patient. In contrast, the second method is directly placing the virus vector into the patient's body. The gene will manage on its own to find the infected cell, where it will have to go to the cell's nucleus then become united within the human DNA. Once done, it needs to be activated, thus producing the needed protein. For the cell or vector to be inserted into the patient's body, doctors utilize intravenous infusion or injection into a body cavity or a tumor. Using this particular method for gene therapy might not be the only one, as gene therapy is still undergoing research, thus future developments will possibly invent other techniques. 

Figure 2: Using vectors to transfer new healthy genes to the cells in the body
http://ghr.nlm.nih.gov/handbook/therapy/procedures