Haemophilus influenzae type b polyribosyl ribitol phosphate (PRP)

Haemophilus influenzae type b polyribosyl ribitol phosphate (PRP) is the primary capsular polysaccharide and a major virulence factor of the Haemophilus influenzae type b (Hib) bacterium (CDC, 2022). This linear polymer consists of ribosyl-ribitol phosphate units and serves to protect the pathogen from host immune defenses, specifically by inhibiting phagocytosis and complement-mediated killing (StatPearls, 2023). In clinical medicine, PRP is the essential antigenic component used in vaccines to prevent invasive Hib diseases such as meningitis, pneumonia, and epiglottitis (WHO, 2013). Because pure PRP is a T-cell independent antigen that is poorly immunogenic in infants under two years of age, it is typically conjugated to a carrier protein (e.g., tetanus toxoid or diphtheria toxoid) to elicit a robust, T-cell dependent memory immune response (PubMed, PMID: 12758539). The success of PRP-based conjugate vaccines has led to a dramatic global reduction in the incidence of Hib-related morbidity and mortality (NIH, 2020).

Other names

Polyribosyl-ribitol phosphateHib capsular polysaccharideHib PRPPolyribosylribitol phosphateHaemophilus influenzae type b capsular antigen

Induction of a humoral immune response leading to the production of anti-PRP IgG antibodies. These antibodies facilitate opsonophagocytosis and complement-mediated lysis of the bacteria, providing protection against invasive disease (StatPearls, 2023).