Strep vaccine stirs antibody production

From San Francisco, at a meeting of the Infectious Diseases Society of America

An experimental vaccine against the microbe that causes strep throat can induce a potent immune response in adults, a U.S.–Canadian research team reports. The finding suggests that the vaccine is ready for large-scale testing in adults and children.

The vaccine targets group A streptococcus bacteria, which cause scarlet fever, rheumatic fever, and kidney damage as well as the throat infections that often circulate among school-age children. It also aims at the microbes—sometimes called flesh-eating bacteria—responsible for necrotizing fasciitis.

Researchers have identified more than 120 variations, or subtypes, of group A strep, and each subtype has a slightly different version of a surface molecule called the M protein. The new vaccine uses portions of the M protein found on 26 of these subtypes to spur a broad immune reaction. Those subtypes include all of those responsible for necrotizing fasciitis and rheumatic fever, which can result in permanent heart damage, and most of those that cause strep throat, says study coauthor Shelly A. McNeil, a physician at Dalhousie University in Halifax, Nova Scotia.

McNeil and her colleagues gave 70 healthy adults a series of three vaccinations over 6 months. Like most adults, the volunteers had come into contact with some natural group A strep microbes during their lifetimes and so already carried some antibodies to the bacterium. On average, the vaccinated volunteers boosted this antibody arsenal ninefold, McNeil says.

There is currently no vaccine against group A strep, says Peter E. Vink, a pediatrician with ID Biomedical Corp. of Bothell, Wash., the company that makes the experimental strep vaccine.