Viral influenza hemagglutinin protein and Streptococcus pneumoniae capsular polysaccharide (HA and CPS)

Viral influenza hemagglutinin (HA) protein and Streptococcus pneumoniae capsular polysaccharide (CPS) are distinct microbial antigens targeted by vaccines to prevent respiratory infections (Gamblin & Skehel, 2010; Geno et al., 2015). Hemagglutinin is a trimeric surface glycoprotein on influenza viruses that facilitates viral attachment to host cell sialic acid receptors and mediates membrane fusion, making it the primary target for neutralizing antibodies (WHO, 2022). Streptococcus pneumoniae capsular polysaccharides are complex carbohydrate polymers that envelop the bacterium, providing protection against host immune recognition and opsonophagocytosis (Geno et al., 2015). These two entities are frequently addressed in tandem within clinical guidelines because viral influenza infection significantly increases host susceptibility to secondary bacterial pneumonia caused by S. pneumoniae (CDC, 2023). Vaccines targeting HA (e.g., inactivated influenza vaccines) and CPS (e.g., pneumococcal conjugate vaccines like PCV13 or PCV20) work by inducing specific B-cell and T-cell responses to prevent viral entry and promote bacterial clearance. Monitoring vaccine efficacy typically involves measuring antibody titers through hemagglutination inhibition or opsonophagocytic assays (CDC, 2023).

Other names

HemagglutininHAPneumococcal capsular polysaccharideCPSPneumococcal antigenInfluenza HA

Induction of active immunity through the production of neutralizing antibodies against hemagglutinin to block viral entry and opsonizing antibodies against capsular polysaccharides to facilitate bacterial clearance (CDC, 2023; Geno et al., 2015).