Gene Therapy
Gene Therapy

Gene Therapy: Definition, 11 Vectors, and Why It Is Important

Modern biotechnology utilizes human skills in manipulating living things in order to be used to produce the desired goods. Modern biotechnology uses genetic engineering organisms through treatments that change the determinant of life’s ability, namely changing the gene order that determines the specific nature of an organism, so that the conversion process can take place more efficiently and effectively.

Advances in biotechnology, inseparable from the role of microbes. Because the microbial genetic material is simple, so it is easy to manipulate to be inserted into other genes. In addition, because microbial genetic material can act as vectors (plasmids) that can move a gene from the organism chromosome to another organism gene, such as gene therapy.

Gene Therapy Definition

Gene therapy is a medical action that involves the use of genes to treat or prevent diseases.

Genes play an important role in a person’s health. Therefore, research on how to modify or replace faulty genes with healthy genes to treat diseases has been conducted for many years.

Since August 2017, the United States Food and Drug Administration (FDA) has approved three types of gene therapies developed from research.
Two of these gene therapies involve the use of cells in the body to destroy cancer cells. While the third type of gene therapy aims to treat diseases caused by certain genetic mutations.

Before it is rolled out to the public, its level of safety and effectiveness in human gene therapy needs to be tested. Through this test, the therapeutic benefits can certainly outs of the risk. Until now, the United States provided gene therapy as part of clinical trials.

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Gene therapy vectors

Gene therapy uses DNA fragments to repair damaged or defective genes – ex vivo or in vivo, using viral vectors. Some studies using adenovirus vectors (AD) and herpes simplex (HSV) get increased expression of BCL2 and HSP72, thus preventing neuron cell death due to apoptosis. Other researchers get reduced neuron cell necrosis due to ischemia, after transfection the interleukin receptor antagonist gene.


All viruses bind to their hosts and introduce their genetic material into the host cell as part of the replication cycle. This genetic material contains basic ‘instructions’ on how to produce more copies of this virus, hijacking the body’s normal production machine to serve the needs of the virus. The host cell will carry out this instruction and produce an additional copy of the virus, which causes more and more cells to become infected.

Some types of viruses physically insert their genes into the host’s genome (a feature that determines retroviruses, a family of viruses that include HIV, is that the virus will introduce reverse transcriptase enzymes into the host and thus use RNA as a “clue”).


The genetic material in retroviruses is in the form of RNA molecules, while the genetic material from their hosts is in the form of DNA. When a retrovirus infects the host cell, it introduces the RNA together with several enzymes, namely reverse transcriptase and integrase, into the cell. These RNA molecules from retroviruses must produce DNA copies of RNA molecules before they can be integrated into the host cell’s genetic material.

The process of producing DNA copies of RNA molecules is called reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. Once this DNA copy is produced and free in the nucleus of the host cell, it must be inserted into the host cell’s genome.


Adenoviruses are viruses that carry genetic material in the form of double-stranded DNA. They cause respiratory, intestinal, and eye infections in humans (especially the common cold). When this virus infects the host cell, they introduce their DNA molecules into the host.

The genetic material of adenoviruses is not inserted (temporarily) into the host cell of the genetic material. DNA molecules are left free inside the nucleus of the host cell, and the clue in this extra is that DNA molecules are transcribed just like any other gene.

Adeno-associated virus

Adeno-associated virus, from the Parvovirus family, a small virus with a single-strand DNA genome. Wild AAV types can include genetic material on specific sites on chromosome 19 with almost 100% certainty. But the recombinant AAV, which contains no viruses only genes and gene therapy, does not integrate into the genome.

In contrast, the recombinant viral genome fuses at its ends through ITR (inverted terminal repeats) recombination to form circular, episomal forms that are thought to be the main cause of long-term gene expression.

Envelope protein Pseudotyping of viral vectors

The viral vectors described above have a natural host cell population that they infect most efficiently. Retroviruses have limited the range of natural host cells, and although adenoviruses and Adeno-associated viruses can infect relatively broader cells efficiently, some cell types are refractory to infection by these viruses as well.

Non-viral methods

Non-viral methods are now a particular advantage over viral methods, with the production of simple large-scale and low immunogenicity hosts of which only two. Previously, low levels of transfection and gene expression held non-viral methods at a disadvantage, but recent advances in vector technology produced molecules and techniques with transfection efficiency similar to viruses.

Naked DNA

This is the simplest method of non-viral transfection. Conducted clinical trials of intramuscular injection of naked plasmid DNA have occurred with some success, but the expression has been very low compared to other methods of transfection. In addition to trials with plasmids, there has been a trial with naked PCR products, which have greater similarities or success.


The use of synthetic oligonucleotides in gene therapy is to disable the genes involved in the disease process. One strategy uses antisense specific to the target gene to interfere with the transcription of damaged genes. Others use small molecules of RNA called siRNA to signal cells to break down specific sequences unique in mRNA transcription of faulty genes, disrupting incorrect mRNA translation, and due to gene expression.

Lipoplexes and polyplexes

To improve the delivery of new DNA into cells, DNA must be protected from damage and entry into the cell must be facilitated. To this end new molecule, lipoplexes and polyplexes, have been created that have the ability to protect DNA from unwanted damage during the transfection process. Plasmid DNA can be covered with fat in organized structures such as micelles or liposomes.

Hybrid method

Since each gene transfer method has its drawbacks, there are several hybrid developed methods that combine two or more techniques. Virosomes are one example; they combine liposomes with inactive HIV or influenza viruses.

It has been shown to have more efficiency in the transfer of epithelial cell respiratory genes than viruses or liposomal methods alone. Other methods involve mixing other viral vectors with cationic lipids or hybridizing viruses.


A dendrimer is a highly macromolecule branch with a rounded shape. Surface particles can be functioned in many ways and many of the resulting building properties are determined by their surface. In particular, it is possible to build a cationic dendrimer, i.e. One with a positive surface charge. When in the presence of genetic material such as DNA or RNA.

Why gene therapy is important?

In short, gene therapy is to insert DNA into cells as a medicine, to improve the effects of mutated genes in the body, working directly and with precision to correct mutations and further treat diseases. Also known as human gene transfer, gene therapy is very different from other treatments available because its purpose is to cure genetic defects, while altering the source of the disease, doing more than just treating it.

Another very promising hope in this field of study is the difference between the two classifications of gene therapy – Somatic gene therapy and germline gene therapy.

If in somatic gene therapy, DNA is integrated into cells, such as bone marrow but not into reproductive cells, germline gene therapy inserts DNA into the reproductive cells, therefore it has the ability to modify the genome, altering which can be passed down to the child from the patient in the future.

Thus, germline gene therapy can potentially help permanently eliminate certain hereditary diseases. While this sounds very promising, it is important to note that the technology is still in its experimental stages and due to inadequate knowledge regarding risks and ethical reasons, Germline gene therapy is still a very sensitive topic and in most countries it is currently prohibited from using it in humans.

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Gene Therapy: Definition, 11 Vectors, and Why It Is Important

Post in | Last updated: January 20th, 2021 |