Biochemists Uncover M Protein Vulnerability That May Be Target for Anti-Group A Streptococcus Vaccine; Group A “Flesh-Eating” Strep Now Kills Over 500,000 Each Year

Biochemists at the University of California San Diego have uncovered patterns in the outer protein coat of group A Streptococcus that could finally lead to a vaccine against this highly infectious bacteria--responsible for more than 500,000 deaths a year, including toxic shock syndrome and necrotizing fasciitis or "flesh-eating disease." In a paper published online on September 5, 2016 in Nature Microbiology, the researchers reported that they had uncovered "hidden sequence patterns in the major surface protein and virulence factor" of group A Strep, called the M protein, that limit the body's immune response against these bacteria." The article is titled “Conserved Patterns Hidden within Group A Streptococcus M Protein Hypervariability Recognize Human C4b-Binding Protein.” “At present, there is no vaccine against group A Strep, and our discovery of hidden sequence patterns has offered up a novel way to devise such a vaccine," said Partho Ghosh, Ph.D., Chair of UC San Diego's Department of Chemistry and Biochemistry, who headed the team of researchers. Dr. Ghosh said that one of the biggest obstacles to the development of a vaccine against these bacteria is the "hyper-variability" of the M protein. Group A Streptococcus bacteria have a multitude of different strains, each of which displays a different protein on its surface. Because our immune systems must recognize these different proteins before launching an immune response with antibodies specific to the outer protein coat, the hyper-variability of the M proteins makes it difficult for our immune systems to attach antibodies specific to each of these proteins from different strains. "When we become infected with a particular strain of group A Strep, we generally mount an immune response against the particular M protein displayed by that strain," explains Dr. Ghosh.
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