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CMV: A virus in search of a vaccine

With the exception of the so-called cervical cancer vaccine, no shots have been approved specifically to prevent malignant tumors. But cervical cancer, which is caused by the sexually transmitted human papillomavirus (HPV), isn't the only tumor linked to a virus; another is cytomegalovirus (CMV), a usually harmless form of herpes that's the target of a possible therapeutic cancer vaccine for brain tumor patients.

As Scientific American reports this month, CMV has been found in the most common type of brain tumor, glioblastoma multiforme (GBM) — the cancer Massachusetts Democratic Sen. Edward Kennedy is battling. Duke University is recruiting 20 patients with these types of tumors for a combined phase 1/2 clinical trial (an early stage of testing that checks the safety and usefulness of a product) of an experimental vaccine treatment for these patients. It's also testing a similar version in another trial.

Duane Mitchell, the Duke University neuro-oncologist heading up the GBM vaccine treatment trials, is optimistic about them, telling Scientific American that creating a shot that goes after CMV "may be a radically new way to consider treating these tumors."

Pharma giant Novartis, meanwhile, is working on a CMV vaccine that would prevent infection with the virus. The company, headquartered in Basel, Switzerland, announced late last month that it expected to begin a phase 2 trial (which tests efficacy) of a preventive CMV vaccine this year. While CMV isn’t dangerous to most people, it infects 30,000 newborns in the U.S. annually, causing severe disability such as vision or hearing loss, seizures and cognitive problems in 8,000, according to the Centers for Disease Control and Prevention (CDC). It can also be deadly in people with weakened immune systems, such as AIDS patients.

Still, there are challenges. One researcher who tested a preventive CMV vaccine, University of Pennsylvania emeritus professor Stanley Plotkin, came up short when he found that it seemed to produce an immune response without actually preventing infection. "Is antibody sufficient, or do you need cellular immune responses? Or, are cellular immune responses sufficient and you don't need antibody? Those are unresolved issues," Plotkin told The Scientist in 2006, "that have somewhat hindered CMV vaccine development."

Image © iStockphoto/Douglas Allen

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