Group A Streptococcus polyrhamnose cell-wall polysaccharide epitope (GAC^PR)

The Group A Streptococcus polyrhamnose cell-wall polysaccharide epitope, often referred to as the GAC polyrhamnose backbone (GAC^PR), is a universally conserved structural component of the Streptococcus pyogenes (Group A Streptococcus or GAS) cell wall [1.1.2, 1.4.1]. It constitutes approximately 40-60% of the cell wall mass and is essential for bacterial viability, providing structural integrity and acting as a barrier against environmental stressors [1.1.2, 1.4.4]. Beyond its structural role, this polysaccharide serves as a critical virulence factor by facilitating immune evasion and resistance to host antimicrobial peptides [1.1.3, 1.4.5]. In the context of vaccine development, the polyrhamnose backbone is a primary target because it is highly immunogenic and lacks the N-acetylglucosamine (GlcNAc) side chains associated with autoimmune cross-reactivity in rheumatic heart disease [1.1.2, 1.3.3]. Therapeutic strategies targeting this epitope include glycoconjugate vaccines designed to elicit opsonophagocytic antibodies and bacteriophage-derived endolysins, such as PlyC, which bind the polyrhamnose core to catalyze bacterial lysis [1.3.1, 1.4.4]. Its 100% conservation across all GAS serotypes makes it an ideal candidate for a universal vaccine to prevent infections ranging from pharyngitis to life-threatening invasive diseases [1.3.2, 1.4.2]. Targeting the polyrhamnose backbone specifically addresses safety concerns related to molecular mimicry, offering a path toward a safe and effective GAS vaccine [1.2.1, 1.4.5].

Other names

Group A Carbohydrate polyrhamnose backboneGAC polyrhamnose coreRhamnose-rich cell wall polysaccharideRhaPSLancefield Group A antigen backbone

Induction of opsonophagocytic antibodies (IgG) that promote bacterial killing by neutrophils; binding of endolysins to the polyrhamnose backbone to catalyze peptidoglycan hydrolysis and bacterial lysis [1.1.2, 1.4.4].