Haemophilus influenzae type a capsular polysaccharide (Hia CPS)

The Haemophilus influenzae type a capsular polysaccharide (Hia CPS) is a critical virulence factor for the Hia bacterium, consisting of a repeating unit of [→4)-β-D-glucopyranosyl-(1→3)-D-ribitol-5-phosphate-(1→]. This polysaccharide capsule acts as a protective barrier that allows the pathogen to evade the host's innate immune system by resisting phagocytosis and complement-mediated lysis. While Haemophilus influenzae type b (Hib) was historically the primary cause of invasive disease, the success of Hib conjugate vaccines has led to the emergence of Hia as a significant cause of severe infections, including meningitis and pneumonia, particularly in indigenous populations. As a therapeutic target, the Hia CPS is utilized in the development of conjugate vaccines where the polysaccharide is chemically linked to a carrier protein to induce a T-cell dependent immune response. These vaccines aim to generate high-affinity IgG antibodies and immunological memory to provide long-term protection against invasive Hia disease.

Other names

Hia capsular polysaccharideSerotype a capsular polysaccharideHaemophilus influenzae serotype a polysaccharideHia antigen

Induction of polysaccharide-specific IgG antibodies that facilitate opsonophagocytosis and complement-mediated killing of the bacteria.