Polyribosylribitol phosphate-tetanus toxoid glycoconjugate (PRP-TT) (PRP-TT)

Polyribosylribitol phosphate-tetanus toxoid (PRP-TT) glycoconjugate is a vaccine component designed to prevent invasive diseases caused by Haemophilus influenzae type b (Hib) (CDC, 2022). PRP is the primary capsular polysaccharide and virulence factor of Hib; however, as a pure polysaccharide, it is poorly immunogenic in infants due to its T-cell independent nature (WHO, 2013). By chemically conjugating PRP to a tetanus toxoid carrier protein, the vaccine induces a robust T-cell dependent immune response characterized by high-affinity IgG production and the formation of memory B cells (PubMed, PMID: 12758308). This approach has been highly successful in reducing the global incidence of Hib-related meningitis, pneumonia, and epiglottitis in pediatric populations (StatPearls, 2023). The conjugate is the active immunogenic ingredient in several widely used commercial vaccines, such as ActHIB and Hiberix (FDA, 2023). It functions by enabling the host immune system to recognize and neutralize the Hib bacteria before they can cause systemic infection.

Other names

PRP-THib-TTHaemophilus influenzae type b conjugate vaccineActHIBHiberixPolyribosyl-ribitol phosphate-tetanus toxoid

The conjugate vaccine works by chemically linking the PRP polysaccharide (a T-independent antigen) to a tetanus toxoid protein carrier, thereby converting it into a T-dependent antigen. This allows the immune system to recruit T-helper cells, which stimulate B-cells to undergo isotype switching and affinity maturation, resulting in high-affinity IgG antibodies and long-term immunological memory against the Hib capsule.