Virotherapy: Finding New Utility In Nature's Most Dangerous Killers

Virotherapy: Finding New Utility in Nature’s Most Dangerous Killers Using Viruses to Combat Cancer Andrew Taber and Alex Cheung For centuries, viruses have been one of the greatest threats to human survival and propagation, and it has been one of medicine’s greatest challenges to create vaccines and methods to stall the onset of these viral diseases. That being said, it should come as a surprise that viruses are now being used as one of medicine’s most promising new methods to attack the next prominent threat to humanity: cancer. B S J H istory of V irotherapy Since the 1800’s, there have been case studies in which it was reported that cancer regression coincided significantly with viral infections. Dramatic reduction in the white blood cell count of patients (usually signifying an improving condition) was observed when the patients were infected by such viruses as influenza and chicken pox. Doctors and scientists at the time concluded that viruses, in certain environments, could temporarily improve a patient’s condition, especially in young children with compromised immune systems. After many years of animal and clinical research, it was found that viral infection is indeed a very potent method to treat cancer. But, at this point scientists had to use the very blunt instrument of naturally occurring viruses in their trials, which often led to subject death. (Kelly and Russel 2007) The solution was to design the viruses and delivery systems using genetic engineering so that the immune system would let the viruses through and so that the viruses would target the desired cell type. The tools needed to achieve this goal, however, were not developed until relatively recently. Until then, science used a method called targeted evolution to encourage the propagation of mutations that would result in viruses attacking cancer cells.When recombinant DNA technology was developed, the effectiveness of virotherapy could be even more directly controlled. Today, virotherapy is showing significant effectiveness in treating many cancers and diseases in mice, and trials have even shown improvements in treating advanced melanoma in humans (Nutting 2005). These results are too significant to be ignored, and scientists are wasting no time in developing new viruses to fight other diseases. One of the ways to solve the problems of cell targeting is to add cancer-specific binding proteins to the virus. Each type of cell has an outer membrane that acts as a selective barrier between the cell and its surroundings. All membranes are coated with proteins that are used to identify a cell and its purpose in the body. One way of thinking of these proteins is as nametags, and scientists’ job is to engineer these proteins so that viruses “know” where “Virotherapy can succeed where past methods have failed.” 16 • B erkeley S cientific J ournal • I nfectious D isease • F all 2010 • V olume 14 • I ssue 1