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

The Haemophilus influenzae type b polysaccharide–polyribosylribitol phosphate (PRP) is a linear high-molecular-weight polymer comprising repeating units of ribose and ribitol joined by phosphate diester linkages[1]. This molecule constitutes the capsule of Hib bacteria, allowing immune evasion, and is the primary antigen targeted by Hib vaccines. Purified PRP induces an antibody response, but is weakly immunogenic in young children unless conjugated to carrier proteins. Conjugate vaccines using PRP have dramatically reduced invasive Hib disease worldwide[1][2][3][4]. The structure and length of the PRP polysaccharide, as well as its conjugation to carrier proteins, are critical for vaccine immunogenicity. The minimal antigenic epitope recognized by protective antibodies consists of two repeating PRP units where ribose and ribitol are directly involved in binding[2]. Assays of anti-PRP antibody levels are standard biomarkers for evaluating immune protection.

Other names

Haemophilus influenzae type b polysaccharideHib capsular polysaccharidepolyribosyl ribitol phosphatePRP

Vaccines containing PRP induce anti-PRP antibodies, which facilitate opsonization and clearance of Hib[4]