Fake virus could make safe new vaccines

Tuesday, July 1st, 2008

Fake virus could make safe new vaccines:

The researchers used a unique method to make their virus, relying on a built-in redundancy in DNA, the material that carries genetic instructions in organisms.

DNA’s code is written using just four nucleic acids, represented by the letters A, C, T and G. These are combined in various ways to make amino acids, which in turn make proteins.

It is possible to make an amino acid with more than one combination of these letters — for example, GCC and GCG both code for the amino acid alanine. For unknown reasons, organisms favor certain combinations.

Futcher’s team made their polio virus using the less-favored combinations of the virus’s genetic code.

They hoped these would stimulate the immune system in the same way as “wild-type” polio, without causing disease, and that is what appears to have happened, they wrote.

Each difference in the genetic code weakened the virus in a different way.

“This ‘death by a thousand cuts’ strategy could be generally applicable to attenuating many kinds of viruses,” they wrote.

“Even for an inactivated rather than live virus approach, these features would allow a vaccine to be made from a safer starting material than the corresponding wild-type virus.”

Polio vaccines have virtually eradicated the disease in most countries. But an oral vaccine that uses a weakened version of a live polio virus can sometimes get back into the water supply and mutate into a form that can infect people.

Doctors have been looking for a safer yet effective polio vaccine that is as easy to administer as the drops. Dr. Jonas Salk’s original polio vaccine, which effectively rid the United States of the feared virus in the 1950s and 1960s, used a “killed” polio virus but had to be injected.

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