Polyribosylribitol phosphate (of Haemophilus influenzae type b) (PRP)

Polyribosylribitol phosphate (PRP) is the capsular polysaccharide of Haemophilus influenzae type b (Hib), composed of a linear copolymer of repeating units of ribose and ribitol linked via phosphate diester bonds[1][2][5]. This capsule serves as the primary virulence factor of Hib, protecting the bacterium from phagocytosis and enabling invasive infections such as meningitis, pneumonia, and septicemia, particularly in young children[5][6]. PRP is highly immunogenic in adults but poorly immunogenic in infants unless it is chemically conjugated to a carrier protein, which transforms the response from T-independent to T-dependent and forms the basis of all modern Hib vaccines[5][6]. Measurement of anti-PRP antibody levels is used as a biomarker of immunity. Vaccines containing PRP conjugates have virtually eliminated invasive Hib disease in regions with high vaccine uptake.

Other names

PRP (polyribosylribitol phosphate)Haemophilus influenzae type b capsular polysaccharideHib polysaccharide capsule

Induction of antibodies against PRP; these antibodies bind to the polysaccharide on the bacterial capsule, promote complement activation (C3 binding), opsonization, and facilitate phagocytosis, leading to bacterial killing and protection against Hib infection[3][5] Infant vaccines use protein-polysaccharide conjugation to induce T-dependent, long-lasting antibody responses by recruiting T-helper cell support[5][6]