Haemophilus influenzae type b polyribosyl-ribitol-phosphate capsule antigen (Hib PRP)

The Haemophilus influenzae type b polyribosyl-ribitol-phosphate (PRP) capsule antigen is the primary virulence factor for the Hib bacterium, a major cause of invasive diseases such as meningitis and pneumonia in children [StatPearls, 2023]. This linear polymer consists of ribosyl-ribitol-phosphate units and functions by protecting the bacteria from phagocytosis and complement-mediated killing by the host immune system [PubMed, 2021]. As a T-cell independent antigen, pure PRP is poorly immunogenic in infants under two years of age; however, conjugation to carrier proteins like tetanus toxoid or diphtheria CRM197 transforms it into a T-cell dependent antigen [CDC, 2022]. This modification allows for the induction of high-affinity IgG antibodies and immunological memory, which are essential for long-term protection [WHO, 2013]. Therapeutic interventions primarily involve conjugate vaccines that target this capsule to elicit protective opsonophagocytic antibodies [FDA, 2021]. The widespread implementation of these vaccines has resulted in a significant global reduction in the incidence of Hib-related morbidity and mortality [NIH, 2020].

Other names

Polyribosyl-ribitol-phosphatePRPHib capsular polysaccharideHaemophilus influenzae type b antigenHib capsule

Vaccine-mediated induction of opsonophagocytic IgG antibodies against the PRP capsular polysaccharide to prevent bacterial invasion and promote clearance [CDC, 2022].