C5a peptidase (ScpB) (ScpB)

C5a peptidase (ScpB) is a surface-anchored subtilisin-like serine protease expressed by Streptococcus agalactiae (Group B Streptococcus), a major pathogen responsible for neonatal sepsis, meningitis, and pneumonia (UniProt Q8E501). The enzyme plays a dual role in bacterial pathogenesis: it acts as a potent immune evasion factor by specifically cleaving and inactivating the human complement component C5a, thereby preventing the recruitment of neutrophils to the site of infection (Bohnsack et al., 1991). Additionally, ScpB functions as an adhesin and invasin, binding to extracellular matrix components like fibronectin to facilitate bacterial attachment and entry into host epithelial cells (Cheng et al., 2002). Because of its essential role in virulence and its high conservation across different serotypes, ScpB is a primary target for the development of universal vaccines against Group B Streptococcus (Uchiyama et al., 2023). Therapeutic strategies, such as the VAX-A1 vaccine candidate, aim to elicit opsonophagocytic antibodies that neutralize the peptidase's activity and enhance the clearance of the bacteria by the host immune system (McCabe et al., 2023). Research has shown that antibodies against ScpB can provide cross-protection against multiple streptococcal species due to the high sequence homology between ScpB and its Group A Streptococcus counterpart, ScpA (Uchiyama et al., 2023). Clinical development of ScpB-targeted therapies focuses on maternal immunization to provide passive immunity to neonates through placental antibody transfer (Pena et al., 2024).

Other names

SCPBC5a-aseStreptococcal C5a peptidaseC5a-inactivating proteaseGroup B streptococcal C5a peptidase

Vaccine-induced production of neutralizing and opsonizing antibodies that inhibit enzymatic activity and promote bacterial clearance.