Streptococcus agalactiae capsular polysaccharide serotype IV (GBS CPS IV) (GBS CPS IV)

The Streptococcus agalactiae capsular polysaccharide serotype IV is a complex carbohydrate structure located on the outermost surface of Group B Streptococcus (GBS) [Cieslewicz et al., 2005, Infect. Immun.]. It plays a fundamental role in bacterial pathogenesis by acting as a protective barrier against host immune defenses, specifically by inhibiting C3 deposition and subsequent opsonophagocytosis [Edwards et al., 2019, Principles and Practice of Infectious Diseases]. The biochemical structure of the serotype IV polysaccharide is characterized by a branched pentasaccharide repeating unit that includes a terminal sialic acid residue, which is crucial for its anti-phagocytic properties [Carboni et al., 2017, Carbohydrate Research]. Historically less common, serotype IV has seen a significant increase in clinical prevalence over the last decade, contributing to invasive diseases such as neonatal sepsis, meningitis, and infections in pregnant women and older adults [Madrid et al., 2017, Clin. Infect. Dis.]. Because it is a primary target for protective antibodies, it is included as a key component in several multivalent conjugate vaccines currently in clinical trials, such as Pfizer's hexavalent GBS6 vaccine [Absalon et al., 2021, Vaccine]. These vaccines function by inducing high titers of serotype-specific IgG that facilitate the clearance of the bacteria through the recruitment of the complement system and phagocytic cells [Baker et al., 2014, J. Infect. Dis.]. The emergence of this serotype highlights the need for broad-spectrum GBS vaccines that cover multiple capsular types to ensure comprehensive protection across different geographic regions [Bianchi-Jassir et al., 2020, Vaccine]. Targeting this polysaccharide is a validated strategy for preventing GBS-related morbidity and mortality in vulnerable populations [Kobayashi et al., 2021, JAMA Network Open].

Other names

Group B Streptococcus capsular polysaccharide serotype IVGBS type IV CPSS. agalactiae type IV CPSGBS serotype IV capsular polysaccharideType IV GBS CPS

Induction of serotype-specific opsonophagocytic antibodies that facilitate complement-mediated killing and phagocytosis of the bacteria.