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

**Haemophilus influenzae type b capsular polysaccharide polyribosylribitol phosphate** (PRP) is a linear polymer composed of repeating units of ribose and ribitol connected by phosphate diester linkages[2][3]. The PRP capsule is the critical virulence factor of Hib, allowing the bacterium to evade host immune defenses and cause invasive diseases, especially in young children[1][4]. Vaccines based on PRP, often conjugated to a carrier protein, induce protective anti-PRP antibodies and have significantly reduced the incidence of Hib disease worldwide[5][7]. PRP does not have enzymatic or receptor-like functions but serves as a key surface antigen and therapeutic target for vaccination. Anti-PRP antibody titers can be used as immunological correlates of protection in clinical and epidemiological studies[5]. - The **PRP capsule** is the basis for Hib vaccine development and is directly targeted by conjugate vaccines, which are among the most effective means of preventing Hib infection[5][7]. - The **role of PRP** is non-enzymatic: as a structural, immune-evading polysaccharide on the bacterial outer surface[1][2]. - Polysaccharide-alone Hib vaccines are less effective in infants, prompting the use of protein-conjugated forms that stimulate robust, T cell-dependent immune responses[5]. PRP is not a human or animal protein target but a **bacterial macromolecule** with critical importance in immunology, vaccine development, and infectious disease prevention.

Other names

polyribosylribitol phosphateHib capsular polysaccharidePRP

Elicitation of protective antibody responses (by vaccines), Prevention of bacterial adhesion and invasion (by antibody binding to PRP capsule)