April 11, 2007 / 9:13 AM / 12 years ago

Flu vaccine grown in caterpillar cells is safe

WASHINGTON (Reuters) - A flu vaccine grown in caterpillar cells instead of the usual risky and uncertain method based on chicken eggs is not only safe but effective in people, U.S. researchers reported on Tuesday.

A caterpillar moves on the blade of a leaf in the northeastern Indian city of Siliguri November 7, 2006. A flu vaccine grown in caterpillar cells instead of the usual risky and uncertain method based on chicken eggs is not only safe but effective in people, U.S. researchers reported on Tuesday. REUTERS/Rupak De Chowdhuri

They said their findings suggest a possible short-cut to making flu vaccines, focusing on a single protein in the flu virus.

Dr. John Treanor of the University of Rochester in New York, who led the study, believes the vaccine may be quicker and easier to make than current vaccines and might help create a bigger supply of vaccines to fight the common seasonal flu as well as a future pandemic.

“We currently don’t have enough vaccine in the United States to vaccinate everybody that we would like to vaccinate,” Treanor said in a telephone interview.

“Anything that we can do to increase the vaccine supply is useful.”

His team tested a vaccine called FluBl0k that is made by privately held Protein Sciences Corp. of Meriden, Connecticut.

It is grown in a batch of cells taken from the fall armyworm, a kind of caterpillar. “The company has actually taken those cells and further fooled around with them to make them better for making vaccines,” Treanor said.

Writing in the Journal of the American Medical Association, Treanor and colleagues said they tested the vaccine on 460 healthy people aged 18 to 49 during the 2004-2005 flu season.

One-third got a smaller dose of the vaccine, one-third received a larger dose, and one-third received a placebo shot with no vaccine.

Together, the two different doses of vaccine provided 86 percent protection, comparable to commercially available flu shots, Treanor said.


There were seven cases of flu in the group that got fake vaccines, two cases in the group that received the smaller dose, and no cases in the group that received the higher dose of vaccine.

Experts believe this so-called cell-culture method is the best way to improve the current method of making flu vaccines.

Now, flu vaccines are reformulated every year to match the three most common strains of circulating flu virus.

The virus must be taken from people, purified, and grown in fertilized chicken eggs. The process takes months and can easily go wrong.

Cell-culture methods can slice one or two months off the production process, Treanor said.

“Flu viruses can be temperamental, and it’s not always an easy matter to get the virus to grow as you want in eggs,” Treanor said.

If the next pandemic is caused by an avian flu virus such as H5N1, which kills chickens, relying on egg-based vaccines may not be a good idea.

The Protein Sciences vaccine is simpler than most current flu shots, which use pieces of the flu virus called hemagglutinin and neuraminidase.

FluBlOk, which has accelerated approval status from the U.S. Food and Drug Administration, targets only hemagglutinin.

“We got pretty good protection,” against flu, Treanor said.

Other companies are also working on cell-culture vaccines and each one is different and proprietary, Treanor said. Anyone who wanted to make the vaccines would have to obtain licenses from the companies that own and develop such technologies.

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