Haemophilus influenzae type b capsular polysaccharide polyribosylribitol phosphate conjugated to tetanus toxoid (PRP-T)

Haemophilus influenzae type b capsular polysaccharide polyribosylribitol phosphate (PRP) conjugated to tetanus toxoid (PRP-T) is a vaccine component used to prevent invasive diseases caused by the Hib bacterium, such as meningitis and pneumonia [WHO, 2013]. The PRP capsule is the primary virulence factor of Hib, but as a pure polysaccharide, it is poorly immunogenic in children under two years of age due to its T-cell independent nature [CDC, 2022]. By chemically linking PRP to a tetanus toxoid protein carrier, the vaccine recruits T-cell help, transforming the immune response into a T-cell dependent process that induces high-affinity IgG antibodies and long-term immunological memory [PubMed, 2021]. This conjugate technology has been instrumental in reducing the global burden of Hib-related morbidity and mortality in the pediatric population [StatPearls, 2023]. PRP-T is typically administered as a primary series in infancy and is often found in combination vaccines such as ActHIB or Hiberix [FDA, 2019].

Other names

Hib-TTPRP-THaemophilus b conjugate vaccine (tetanus toxoid conjugate)Polyribosylribitol phosphate-tetanus toxoid conjugateActHIBHiberix

The PRP-T conjugate functions as an immunogen that induces a T-cell dependent immune response against Haemophilus influenzae type b (Hib). While the PRP polysaccharide alone is a T-cell independent antigen that fails to elicit memory or high-affinity antibodies in infants, its covalent conjugation to a tetanus toxoid protein carrier allows the complex to be processed by B-cells and presented to T-helper cells. This interaction triggers B-cell differentiation into plasma cells that secrete high-affinity IgG antibodies and the creation of memory B-cells, providing long-term protection against the Hib bacterium [StatPearls, 2023; CDC, 2022].