Researchers Take 1st Step Toward Broad Strep B Vaccine
Four-protein combination used to combat the bacteria that threatens newborns
THURSDAY, June 30, 2005 (HealthDay News) -- Using genes from four different strains of group B streptococcus bacteria, researchers have developed what may be a universal vaccine for the germ that can cause life-threatening infections in newborn babies.
Because there are numerous strains of group B strep, the challenge for researchers had been to come up with a vaccine that could cover more than one strain. However, Italian and U.S. researchers worked their way around that problem by using different genes from different strains, and when the newly developed vaccine was given to adult female mice, it was able to protect their offspring against numerous strains of group B strep.
"Group B strep isn't a single species and that complicates the story quite a bit," explained Guido Grandi, vice president and head of biochemistry and molecular biology at Chiron Vaccines in Siena, Italy.
Results of the study appear in the July 1 issue of Science.
Group B strep is a common bacteria that may be present in as many as 40 percent of healthy women, according to background information in the study. While most pregnant women have no symptoms of infection, they can pass group B strep to their baby during delivery. In newborns, the bacteria can cause life-threatening infections, such as pneumonia, meningitis and blood infections.
"This is a very benign illness or infection for the mother and she may have no signs or symptoms, but it can be very dangerous, even fatal to newborns," said Dr. Karen Hopkins, a pediatrician at New York University Medical Center.
Current guidelines from the U.S. Centers for Disease Control and Prevention recommend routine testing of women between week 35 and 37 of pregnancy, and treating any woman who is found to have group B strep, according to Dr. Stanley M. Berry, corporate chairman of obstetrics and gynecology at William Beaumont Hospital in Royal Oak, Mich.
One problem with this method, however, is that group B strep doesn't always show up in tests.
"Group B is a wily beast. It appears and then disappears. A woman can have it at 30 weeks and then it can disappear at 35 and 37 weeks and reappear at the time of delivery," said Berry.
When group B streptococcus emerged in the 1970s, mortality was as high as 50 percent, according to Dr. Larry Madoff, an infectious disease specialist at Brigham and Women's Hospital and Harvard Medical School, both in Boston.
"That has declined to 10 percent in neonates [newborns], but even those who survive are often left with serious neurological [problems]," said Madoff, who added that because antibiotics are widely used to treat group B strep, doctors are concerned that the bacteria may become resistant to antibiotics.
That means, said Rino Rappuoli, chief scientific officer for Chiron Vaccines, that the "only way to eliminate the disease is through vaccination, and we do have the hope today to achieve that."
"We have technically solved the problem of making a vaccine," said Rappuoli.
To do that, the researchers analyzed the genome sequences of eight different strains of group B strep, and then tested 312 proteins as potential vaccines. Four proteins stood out, and were combined to make the new vaccine.
When used in combination, the researchers found that these proteins were highly effective in preventing infection from 12 different strains of group B strep in newborn mice. The vaccine's effectiveness ranged from 59 percent to 100 percent.
"At the end of the day, we identified four antigens, which when put together offered broad protection," said Grandi.
Rappuoli said the researchers haven't yet figured out what the next step will be, and noted that they'll have to work with the National Institutes of Health or the U.S. Food and Drug Administration before any human testing can be done. He said it would likely be at least six to 10 years before this vaccine could be commercially available.
He added that this study was also important because it validated the technique of using genomics for vaccine development. Rappuoli and his colleagues previously developed a meningitis vaccine using the same approach.
To learn more about group B strep, visit the CDC's Web site.