Clostridioides difficile surface layer proteins (SLPs) and associated cell wall proteins (SLPs; SlpA (primary gene); HMW-SLP and LMW-SLP (protein isoforms))

Clostridioides difficile surface layer proteins (SLPs) are major bacterial surface antigens essential for pathogenesis and immune interaction in CDI. The primary SLP, SlpA, is encoded by a single gene (*slpA*) and undergoes post-translational cleavage to generate two distinct proteins: a conserved high-molecular-weight SLP (HMW-SLP) and a highly variable low-molecular-weight SLP (LMW-SLP), which form a superimposed heterodimeric crystalline lattice on the bacterial cell surface[1][3][5]. These proteins mediate critical host-pathogen interactions by promoting bacterial adhesion to intestinal epithelial cells and potently activating innate immune responses through toll-like receptor 4 signaling, leading to macrophage activation and production of pro-inflammatory cytokines[1][4]. The high sequence variability of LMW-SLP among different C. difficile strains enables immune evasion while the conserved HMW-SLP maintains structural integrity[1][2]. SLPs are emerging as promising therapeutic targets for CDI intervention through vaccine development, single-domain antibody therapies, and immunotherapeutic strategies, with animal studies demonstrating that anti-SLP antibodies effectively block bacterial adhesion and motility[1][5].

Other names

Surface layer proteinsS-layer proteinsSlpA (surface layer protein A precursor)High-molecular-weight surface layer protein (HMW-SLP; previously P47)Low-molecular-weight surface layer protein (LMW-SLP; previously P36)Cell wall proteins (Cwps): Cwp2, Cwp6, Cwp12, Cwp13, Cwp24, Cwp25, Cwp66, Cwp84, CwpVSurface antigens of C. difficile

TLR4-mediated signaling: SLPs activate TLR4 on host cell surfaces, initiating downstream signaling through nuclear factor-kappa beta (NF-κB) and interferon regulatory factor 3 (IRF3). Macrophage activation: Upregulate expression of cell-surface markers (TLR2, CD40, CD14, MHC class II) and enhance phagocytosis and migration. Adhesion blocking: Anti-SLP antibodies sterically block SLP-mediated binding to epithelial cells. Motility inhibition: Single-domain antibodies inhibit bacterial motility through LMW-SLP binding.