How does gene therapy work?

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          Now that we understand what a gene is and how it works we can take a look at what gene therapy is.  In the simplest terms gene therapy involves modifying a specific gene or group of genes to achieve a desired effect.  Often the desired effect is the treatment of a genetic disease.  There exists several ways of modifying a gene.  One can replace the gene altogether with a different gene to achieve a different phenotype.  You could turn a gene off by blocking its promoter.  You could over express the gene to enhance the existing effects of the gene.  Regardless of the exact approach each method shares the common goal of changing the expression of that particular gene in order to ultimately change the expression of a desired protein.

         
          There are several approaches taken to accomplish the methods discussed above.
          1)  The "new" gene can be incorporated into a retrovirus that has its virulence factors altered so there is little negative effect on the patient.  This method would have a high immune response against the virus which diminishes the effectiveness of the procedure.
          2)  The "new" gene can be incorporated into cells harvested from the patient's body.  The new gene becomes part of the cells through homologous recombination.  This method presents no immune response but is more invasive.
          3)  The "new" gene can be encapsulated in a lipid shell and delivered across the plasma membrane in that manner.  This is called a liposome.
          4)  There has also been recent research into developing a 47th chromosome that could be transferred into affected cells.  This chromosome would work alongside the existing 46 chromosomes and wouldn't affect their functioning.  It also has the ability to hold large amounts of DNA for multigenic diseases.

        Each method has its positives and its negatives.  Certain methods are better suited to certain cell types and gene sizes.  Since this is a relatively recent advance there hasn't been a single method stand out from the others as far as effectiveness and safety are concerned.

This page was created as part of the ISSI 470 class at Monmouth College.  All ideas are the property of the author.