Haemophilus influenzae type b capsular polysaccharide-specific B-cell receptor (Hib BCR)

The Haemophilus influenzae type b (Hib) capsular polysaccharide-specific B-cell receptor (BCR) is a membrane-bound immunoglobulin that specifically recognizes polyribosylribitol phosphate (PRP), the primary virulence factor of Hib (CDC, 2022). In the context of vaccination, this receptor is the primary target for Hib conjugate vaccines, which link the PRP carbohydrate to a carrier protein such as tetanus toxoid or CRM197 (WHO, 2013). Because pure polysaccharides are T-cell independent antigens that fail to induce immunological memory in young children, the BCR-mediated uptake of the conjugate is essential for recruiting T-cell help (Pollard et al., 2009). Upon binding the conjugate, the B cell internalizes the complex, processes the carrier protein, and presents peptides via MHC class II to CD4+ T-helper cells. This interaction triggers isotype switching, high-affinity antibody production, and the establishment of long-lived memory B cells (Kelly et al., 2004). Consequently, this target is central to the prevention of invasive Hib infections, including bacterial meningitis, pneumonia, and epiglottitis.

Other names

Hib PRP-specific BCRPolyribosylribitol phosphate-specific B-cell receptorAnti-PRP B-cell receptorHaemophilus influenzae type b BCR

The target facilitates the recognition and receptor-mediated endocytosis of Hib capsular polysaccharide (PRP) antigens. When PRP is conjugated to a carrier protein, the BCR binds the PRP component, leading to the internalization of the entire conjugate complex. The B cell then processes the carrier protein and presents its peptides via MHC class II to CD4+ T-helper cells. This interaction provides the necessary co-stimulatory signals (e.g., CD40-CD40L) and cytokines to induce B-cell differentiation into plasma cells and memory B cells, resulting in a robust, T-cell dependent immune response (Pollard et al., 2009).