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Microbiology

Towards a Streptococcus B Vaccine

Though the human body has a diversity of mechanisms for eliminating pathogens, it is never fully protected from infections. Patrick Trieu-Cuot's team at the Institut Pasteur,1 together with researchers from Portugal,2 have elucidated the mechanism by which Streptococcus agalactiae  or group B streptococcus–a particularly nasty germ–manages to overcome our defenses in certain circumstances.3 When infecting its host, the bacteria releases GAPDH (Glyceraldehyde3-Phosphate dehydrogenase), a normally cytoplasmic enzyme, into its environment. The researchers showed that GAPDH behaves in the host as a VIP, a virulence-associated immunomodulatory protein–i.e., a protein produced by a pathogen and that affects the host's immune system. By stimulating the production of interleukin IL-10, GAPDH suppresses inflammatory responses, thus favoring infection of the host by Streptococcus agalactiae.

Many people are healthy carriers of group B streptococcus, which becomes a major public health risk in the case of pregnancies. Indeed, about a quarter of pregnant women in developed countries are healthy carriers, thus exposing the baby to infection at birth. Most cases of newborn infections are due to mother-to-child transmission. Group B streptococcus is the most common cause of sepsis and meningitis in newborns, and a frequent cause of newborn pneumonia, causing up to 100 deaths a year in France. Even when the infection is successfully treated, half the infants suffer long-term neurological consequences, including speech, hearing, and vision problems, as well as mental retardation. Both treatment and prevention are based on the administration of antibiotics.

With GAPDH, a new potential target for vaccination has now been identified. No commercial vaccines are currently available against group B streptococcus, although vaccination would be a valuable tool and preferable to antibiotic treatment. As Patrick Trieu-Cuot points out, “vaccination could eliminate vaginal carriage in pregnant women, thereby preventing mother-to-child transmission.”

 

Alex Edelman

Notes :

1. Unité de biologie des bactéries pathogènes à gram-positif, (CNRS / Institut Pasteur).
2. ICBAS, Abel Salazar Biomedical Science Institute, and IBMC, Molecular and Cellular Biology Institute, Porto, Portugal.
3. P. Madureira et al., “Streptococcus agalactiae GAPDH is a virulence-associated immunomodulatory protein,” J. Immunology. 178:1379-87. 2007.

Contacts :

Patrick Trieu-Cuot, Institut Pasteur, Paris.
ptrieu@pasteur.fr


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