Haemophilus influenzae type b polyribosylribitol phosphate polysaccharide (PRP (commonly used; stands for polyribosylribitol phosphate))

Haemophilus influenzae type b polyribosylribitol phosphate polysaccharide (PRP) is a linear, high-molecular-weight bacterial capsular polysaccharide composed of repeating units of ribose, ribitol, and phosphate. It forms the capsule on the surface of Hib bacteria and constitutes the principal virulence factor, enabling the bacterium to evade phagocytosis and causing invasive diseases in children and adults. PRP is the immunogenic component used in Hib vaccines, either as the native polysaccharide (now obsolete due to poor immunogenicity in young children) or more effectively as a conjugate vaccine in which PRP is covalently linked to a protein carrier. This conjugation transmits a T cell-dependent immune response, enabling protective antibody generation, immunologic memory, and long-lasting immunity that has dramatically reduced invasive Hib diseases worldwide.

Other names

Haemophilus influenzae type b capsular polysaccharidePRPHib capsular polysaccharide

Vaccines induce the production of antibodies against PRP, leading to bactericidal activity, complement fixation, and subsequent opsonization and phagocytosis of Hib bacteria Conjugate vaccines convert polysaccharide antigen into a T cell-dependent response by chemical conjugation to protein carriers, allowing for immunologic memory and long-lasting protection in infants and young children