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Virotherapy: the Best Defense is Offense.

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VIROTHERAPY: THE BEST DEFENSE IS OFFENSE ESP presented to Hermine Janjanian By Duyen Hau Nguyen 0230696 Vanier College 7th April 2004 Virotherapy: the Best Defense is Offense Viruses have been one of man's curses since the beginning of time, causing diseases from the common cold to AIDS or recently, the avian flu. Nevertheless, we may now be able to make them beneficial. Viruses are composed of DNA or RNA genes enclosed in a protein wrap called capsid. Viruses target cells, infect and destroy them by inserting their genes into the cell, and using its resources to replicates themselves. Moreover, each type of virus may infect a particular variety of cell because of the specificity in their capsid signal proteins that bind to specific suction-cuplike receptors. If we can genetically engineer a virus that targets cancer cells while leaving normal cells intact, this would be a possible alternative to traditional cancer treatments. ...read more.


They used adenovirus, a virus causing the common cold, to eliminate human tumors that were grafted into mice. The modern concept of virotherapy was thus developed. Some viruses like the one causing Newcastle disease naturally show a preference for certain types of tumor cells. However, other viruses like adenovirus must be genetically modified to target or to reproduce specifically within cancer cells. To insure that these engineered viruses target only the desired cells with no collateral damage, two main strategies have been developed. First, transductional targeting involves the modification of the capsid proteins by attaching adapter molecules or by directly modifying them so that they will only fit to the receptors of tumor cells. For example, the scientists engineering oncolytic adenovirus are trying to find an adapter molecule to attach to its outer coat proteins and make its viral signal unfit for receptors on regular cells. ...read more.


Further, chemotherapy is much more effective if we consider that chemotherapy will kill as much as one healthy cell for six cancerous cells1 whereas, according to Robert L. Martuza, director of the Cell Genesys centre, viruses only one kill one healthy cell for 1,000 or more cancerous cells. Virotherapy holds great promises as a novel treatment for cancer. Researchers, however, are unsure of the efficiency of these engineered viruses in the body. Methods to keep track of the virus' efficiency are being developed. The imaging strategies for instance involve inserting a tracer such as a fluorescent protein on the virus. The advantages of virotherapy include the ability to cause tumor destruction by numerous mechanisms. Nevertheless, this new technique may also present certain risks. Accordingly, to minimize risks, I think that the original virus should preferably cause only mild, well-known human symptoms such as the adenovirus. In addition, there should be some attempts in developing a secondary mechanism to prevent viral replication or to inactivate the virus. This will act as a back-up plan and minimize risks. ...read more.

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