Acinetobacter baumannii capsular polysaccharide (CPS)

Acinetobacter baumannii is a Gram-negative, opportunistic pathogen recognized by the World Health Organization as a critical priority due to its extensive multidrug resistance [1, 16]. The bacterial surface is enveloped by a dense layer of capsular polysaccharides (CPS), also known as K-antigens or O-antigen capsular carbohydrates, which are synthesized via the Wzy-dependent pathway [14, 16]. These carbohydrates are essential virulence factors that provide a physical barrier against host immune responses, effectively inhibiting complement-mediated killing and opsonophagocytosis by immune cells [8, 12]. Beyond immune evasion, the capsule plays a vital role in environmental persistence, protecting the bacterium from desiccation and aiding in biofilm formation on medical devices [9]. Because these polysaccharides are highly exposed and essential for pathogenicity, they are primary targets for novel therapeutic interventions, including monoclonal antibodies like MAb5 and BsAb C73, as well as experimental glycoconjugate vaccines [2, 5, 17]. A significant challenge in targeting these molecules is their extreme structural diversity, with over 200 distinct capsule types identified, which necessitates the use of multivalent vaccines or antibody cocktails to achieve broad clinical coverage [10, 16].

Other names

O-antigen capsular carbohydrateK-antigenAcinetobacter baumannii surface carbohydrateCapsular antigenK-locus polysaccharide

Enhancement of opsonophagocytosis and complement-mediated killing, and enzymatic degradation of the capsule layer.