Group A Streptococcus (GAS)
infections are responsible for significant morbidity and mortality worldwide. The outlook for an effective global
vaccine is reduced because of significant antigenic variation among GAS strains worldwide. Other challenges in GAS
therapy include the lack of common access to
antibiotics in developing countries, as well as
allergy to and treatment failures with
penicillin and increasing
erythromycin resistance in the industrialized world. At the portal of entry, GAS binds to newly deposited extracellular matrix, which is rich in cellular
fibronectin isoforms with extra domain A (EDA, also termed EIIIA) via the surface adhesin, the streptococcal
collagen-like
protein 1 (Scl1). Recombinant Scl1 constructs, derived from diverse GAS strains, bind the EDA loop segment situated between the C and C' β-strands. Despite the sequence diversity in Scl1
proteins, multiple sequence alignments and secondary structure predictions of Scl1 variants, as well as crystallography and homology modeling studies, point to a conserved mechanism of Scl1-EDA binding. We propose that targeting this interaction may prevent the progression of
infection. A synthetic
cyclic peptide, derived from the EDA C-C' loop, binds to recombinant Scl1 with a micromolar dissociation constant. This review highlights the current concept of EDA binding to Scl1 and provides incentives to exploit this binding to treat GAS
infections and
wound colonization.