Question

This week I would like you to discuss a topic that recalls some of what you learned in Lesson 2 and the topic of Biotechnology. In this Lesson, on Medical Technology, there is a significant connection with Lesson 2 and Viral Vectors, the use of a virus to impact or change the DNA of an organism. I first discovered this process in reading Dan Brown's recent novel, Inferno (2013) New York: Doubleday, which uses viral vectors as an important element in the book. You can learn more about Viral Vectors by going to Viral Vectors- What are Viral Vectors? Now for this week's discussion question. Scientists are constantly looking for new and successful methods to treat and cure cancer and the use of viral vectors has shown some success in the FDA's work, Developing gene therapy for cancers using viral vector. Of course this means changing, replacing, and removing some of the basic building block that makes us who we are. What do you think of this process? And if you had issues with how some biotechnology was used in Lesson 2, do you still feel the same way about this use?

Answer 1

ANSWER :-

1. Vector in other words can be considered as a carrier. In case of gene therapies, the vectors are used to carry the Therapeutic genes to the target tissue for mediating specific interactions.
2. Viruses can replicate inside host tissues and uses the host cell replication machinery to replicate inside the host or to integrated its genetic component in the host. This integration forms an integral part of an efficient genetic therapy for cancer.
3. Cancer is a condition which can occur due to a variety of factors. Although, targeting specific cells of tissues where cancer is present is a difficult task although vital vectors such as Retroviruses and Adenoviruses are specific for targeting tissues on the basis of exposing receptors on cell surface thereby initiating their recruitment.
4. In case of Retroviruses, the genetic material is a single-stranded RNA that when enters into the host cell gets converted to form the double stranded DNA under the influence of the enzyme Reverse transcriptase that is basically used to convert RNA back to the DNA.
5. In case of gene therapy, the gene of interest is inserted into the viral vector. Several manipulations are carried out in the vector. It is very important to reduce the virulence and hence the genes responsible for causing disease are being removed (depletion). In case of Retroviruses, the double stranded DNA formed after activity of reverse transcriptase leads to the formation of a Preintegration complex in the nucleus leading to the integration of the viral genome into the host's cell. This would lead to expression of the desired gene in the continually replicating cancer cell lines. It should be also taken into consideration that certain elements present in the viral vectors may be induce immunogenic effect which may affect expression of the therapeutic gene in the target tissue.
6. Adenoviruses are less specialized as the gene sequence of interest for therapy does not get integrated but remains exposed for a particular duration and at the same time may be associated with activation of certain other oncogenes that may trigger cancer formation.
7. So, in short, the potential of the viruses is used to trigger therapeutic response in case of cancer which satisfies and acts as a proper effective measure to elicit a desired response. Retroviruses can be used to insert around 4-10 kb of genes.

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