Gene Therapy and the HIV Virus by Brian Willman

What is Gene Therapy?

Gene therapy is the therapeutic delivery of nucleic acid polymers (DNA and RNA) into a patient's cells as a drug to treat disease. In the future, this technique may allow doctors to treat a disorder by inserting a gene into a patient’s cells instead of using drugs or surgery. Researchers are testing several approaches to gene therapy, including: replacing a mutated gene that causes disease with a healthy copy of the gene, inactivating, or “knocking out,” a mutated gene that is functioning improperly, and introducing a new gene into the body to help fight a disease.

Restriction Enzymes and Recombinant DNA

Restriction enzymes, also known as restriction endonucleases, are enzymes that cut a DNA molecule at a particular place. They are essential tools for recombinant DNA technology. The enzyme "scans" a DNA molecule, looking for a particular sequence, usually of four to six nucleotides. Once it finds this recognition sequence, it stops and cuts the strands. This is known as enzyme digestion. On double stranded DNA the recognition sequence is on both strands, but runs in opposite directions. This allows the enzyme to cut both strands. Sometimes the cut is blunt, sometimes the cut is uneven with dangling nucleotides on one of the two strands. This uneven cut is known as sticky ends.

Restriction Enzymes in Action

Most plasmids used for recombinant technology have recognition sequences for a number of restriction enzymes. Recombinant DNA is DNA that has been formed artificially by combining constituents from different organisms. This allows a scientist to choose from a number of places to cut the plasmid with a restriction enzyme. Ligation enzymes can then be used to sort of paste in new genomic sequences. These mutated, or recombined, plasmids can then be grown up in bacterial cells and used for a number of purposes, including the addition of genes to mammalian genomes.

Recombinant DNA

One Step Closer To Curing the HIV Virus

For the first time, researchers have used a gene-editing technique already used to produce cells resistant to HIV infection to target HIV-infected cells. They have managed to remove HIV genes completely from infected cells, as shown by reductions in the cells' overall rate of HIV production. In cells not already infected, the therapy has itself become part of their genome, producing cells that are resistant to infection for a prolonged period.

The therapy produced significant reductions in the ability of CD4 cells to be infected with HIV and to produce it. It produced positive results in a laboratory-generated CD4-cell analogue and in actual CD4 cells, both HIV-uninfected ones grown in the laboratory, and HIV-infected ones taken from four patients with HIV.

This gene-editing technique has so far only been used on cells in the laboratory dish, but this study takes us one step closer to a therapy that could be administered as an injection and work within the body.

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