Haemophilus influenzae type b polyribosylribitol phosphate capsular polysaccharide (PRP)

The Haemophilus influenzae type b (Hib) polyribosylribitol phosphate (PRP) capsular polysaccharide is the primary virulence factor of the Hib bacterium, which is a major cause of invasive infections like meningitis and pneumonia in children [3, 8]. This polysaccharide forms a protective capsule that enables the pathogen to evade the host's immune system by resisting phagocytosis and complement-mediated killing [3, 20]. In its pure form, PRP is a T-cell-independent antigen, which makes it poorly immunogenic in infants whose immune systems are not yet fully developed [20, 24]. To address this, modern Hib vaccines conjugate the PRP polysaccharide to carrier proteins, such as tetanus toxoid or CRM197, to recruit T-cell help and induce a robust IgG antibody response [4, 8, 19]. These vaccine-induced antibodies target the PRP capsule to facilitate the opsonization and clearance of the bacteria by the immune system [17]. Therapeutic and diagnostic efforts focus on this molecule due to its critical role in Hib pathogenesis and its status as the primary target for protective immunity [8, 10].

Other names

Polyribosylribitol phosphatePRPPolyribosyl-ribitol phosphateHaemophilus influenzae type b capsular polysaccharideHib PRPHib capsular polysaccharide

Vaccination with PRP-based conjugate vaccines induces the production of opsonophagocytic IgG antibodies that bind specifically to the PRP capsule, promoting bacterial clearance via the complement system and phagocytosis [8, 17, 20].