Haemophilus influenzae type b capsular polysaccharide (polyribosyl-ribitol phosphate) conjugated to carrier protein (PRP conjugate)

The Haemophilus influenzae type b capsular polysaccharide is a linear copolymer of polyribosyl-ribitol phosphate (PRP), with repeating units of β-D-Ribofuranose and D-ribitol phosphodiester linkages. In conjugate vaccines, this polysaccharide is chemically linked to a carrier protein (e.g., tetanus toxoid or meningococcal outer membrane protein). This modification is required because infants and young children do not mount an adequate immune response to the polysaccharide alone; conjugation makes the antigen T cell-dependent and highly immunogenic, stimulating robust protective anti-PRP antibody production and effective prevention of invasive Hib disease. - Major vaccine products include ActHIB, Hiberix, and PedvaxHIB, all using slightly different protein carriers but the same PRP antigen. - The capsular polysaccharide is the principal virulence factor of Hib, preventing host immune clearance; thus, PRP is both a microbial pathogenic determinant and a vaccine target. - The minimal antigenic epitope recognized by protective antibodies appears to be two repeating units of the PRP polymer.

Other names

Haemophilus influenzae type b PRP conjugateHib capsular polysaccharide conjugateHib PRP conjugatePolyribosyl-ribitol phosphate conjugateHib vaccine antigen

Induction of anti-PRP antibodies via immunogenic presentation of PRP polysaccharide conjugated to a protein carrier, leading to T-cell dependent immunity in young children