Vaccine against ‘strep throat’ may be coming

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http://www.msnbc.msn.com/id/23505424/

Vaccine against ‘strep throat’ may be coming

Scientists manage to alter dangerous bacteria antigen for safer use

Updated 3:31 p.m. ET March 6, 2008

WASHINGTON - It may be possible to make a safe vaccine against the type of

bacteria best known for causing ”strep throat” and rheumatic fever, U.S

-based researchers reported on Thursday.

The little piece of the bacteria that causes serious disease can be altered

slightly into a form that may work as a vaccine, the team at the University

of California, San Diego, reported.

Group A streptococcal infections affect more than 600 million people each

year and kill 400,000 globally. Most infections cause throat inflammation

known as “strep throat,” which is easily treated with antibiotics.

But untreated strep throat infections can cause rheumatic fever, an often

deadly inflammation of the heart. In countries where antibiotics are not

easily available, rheumatic fever remains common and can weaken the hearts

of survivors for life.

Group A streptococcus, or GAS, also can cause the ”flesh-eating” syndrome

called necrotizing fasciitis and blood-borne infections, including toxic

shock syndrome.

Safe vaccine poses problem

It has been tricky to try to design a vaccine against GAS because the

antigen — the piece of the bacteria most easily recognized by the body’s

immune system — is also the most dangerous part. It causes inflammation and

the dangerous over-reaction of the immune system that leads to heart damage.

Partho Ghosh and colleagues at UCSD managed to get an image of this tiny

structure, called M1 protein. Writing in the journal Science, they said they

created a version of M1 that showed potential as a vaccine in mice.

“Using X-ray crystallography, we determined that M1 protein has an irregular

unstable structure,” Ghosh said in a statement.

“We created a modified version of M1 with a more stable structure, and found

that it is just as effective at eliciting an immune reaction, but safer than

the original version of M1, which has serious drawbacks to its use in a

vaccine.”

Vaccines use antigens to prime the immune system to react against various

invaders, by teaching immune cells to look for certain structures or

proteins.

There are two widely used vaccines against other types of strep — Wyeth’s

Prevnar, given to babies and toddlers in many countries, and Merck & Co’s

Pneumovax, given to adults.

Vaccine market could be huge

These vaccines protect against pneumonia, ear infections, and other diseases

cause by Streptococcus pneumoniae bacteria.

A spokesman at Novartis said the company has a GAS vaccine in the pipeline

but it is in very early stages of testing.

The market potential is huge — Wyeth’s Prevnar shot has annual sales of $2

billion.