A new vaccine may prevent dangerous infections in infants and their mothers. A vaccine against group B streptococcus (GBS)--which causes serious infections in nearly two of 1000 newborns and kills almost 10% of those infected--triggered production of antibodies against the bacterium in clinical trials.
Vaccines work by exposing the body to a decoy representing an infectious agent, so that when the real pathogen comes along the body will see a resemblance and mount an attack. The recognizable part of GBS is a complex sugar coating, which alone immunizes about 60% of people. To make a vaccine that can protect most of the rest, infectious-disease expert Dennis Kasper and his colleagues at Brigham and Women's Hospital in Boston used a relatively new technique to link the complex sugar to tetanus toxoid, a protein known to trigger a strong immune response.
The conjugate vaccine seems to do the trick, triggering protective antibody levels in 54 of 60 women tested, without serious side effects. The antibodies killed GBS in the test tube, and, at least in mice, were able to cross the placenta and immunize a fetus. After Kasper's researchers injected pregnant mice with antibodies from immunized women, the mice gave birth to pups immune to GBS. "The characteristics of the antibody were what we had hoped for,'' says Kasper, who with Carol Baker of Baylor College of Medicine in Houston detail the clinical trial in the latest issue of the Journal of Clinical Investigation.
The conjugate vaccine is the first shown to be both safe and effective, says Pamela McInnes, project officer for the Group B Streptococcal Initiative at the National Institute of Allergy and Infectious Diseases. More human trials are necessary, particularly to see if the vaccine is safe for pregnant women. McInnes says the vaccine also offers promise for decreasing the number of women of childbearing age who carry GBS--now estimated at 10% to 30%. Research can now proceed, she says, "with a more clinical focus and with real hope for prevention.''