Fig. 1 The diseases caused by nontypeable Haemophilus influenzae (NTHi) (Bakaletz LO & Novotny LA. 2018)
Fig. 2 Structure of commercially available Hib vaccine (Mettu R, et al. 2020)
Haemophilus influenzae, also called Pfeiffer's bacillus or Bacillus influenzae, is a small Gram-negative, nonmotile, coccobacillary, facultatively anaerobic pathogenic bacterium that belongs to the family Pasteurellaceae, genus Haemophilus. Encapsulated strains of Haemophilus influenzae are small coccobacilli with a size of 0.2-0.8 um. They are classified based on their distinct capsular antigens. Six types of encapsulated Haemophilus influenzae have been generally identified and are named as type a, b, c, d, e and f, as well as nonencapsulated or untypeable strains. These are found as both respiratory tract commensals and respiratory and invasive pathogens.
Haemophilus influenzae highly adapted to its human hosts and is widespread among the human population. It exists in the nasopharynx of about 75% of healthy children and adults. In some cases it can be found in the oral cavity. No other species was found to be a host of Haemophilus influenzae. Most strains of this bacterium are opportunistic pathogens. This means that they usually live in the hosts without any problems, but can cause diseases only when other factors create some opportunities, such as reduced immune function, viral infection and chronically inflamed tissues. The major diseases caused by untypeable strains are community-acquired pneumonia in adults, acute otitis media, acute sinusitis, and acute exacerbations of chronic bronchitis. And haemophilus influenzae type b (Hib) causes bacteremia, epiglottitis, pneumonia and acute bacterial meningitis in infants and children.
The polyribosyl ribitol phosphate (PRP) capsule of Hib allows evasion of mucosal immune responses or facilitates transmission between hosts by reducing desiccation, and also inhibits serum bactericidal activity and complement mediated phagocytosis. The induction of anti-PRP antibodies to protect those most at risk of Hib disease has been the goal of vaccine development. Hib conjugate vaccines consist of a length of PRP polysaccharide linked to a protein carrier, which are more immunogenic and show boosted responses characteristic of T-dependent memory. Hib conjugate vaccines induce protective humoral immune responses and also reduce circulating strains of Hib in the population by reducing nasopharyngeal carriage of Hib.
Creative Diagnostics now can provide various products of Haemophilus influenzae antigens, such as Haemophilus influenzae outer membrane protein, polyribosyl ribitol phosphate, etc. We provide high-quality products with cheaper price to support both research and industry applications.