Group B Streptococcus alpha-like protein 1 (Alp1)

Group B Streptococcus alpha-like protein 1 (Alp1) is a surface-anchored virulence factor expressed by Streptococcus agalactiae, a major pathogen responsible for neonatal sepsis, meningitis, and pneumonia (PMID: 25216636). Alp1 belongs to the alpha-like protein (Alp) family, which is characterized by a conserved N-terminal domain and a variable number of tandem repeats that mediate interaction with host cells (PMID: 15659488). The N-terminal domain is particularly significant as it is highly immunogenic and serves as a critical target for protein-based vaccines, such as the GBS-NN fusion vaccine currently in clinical development (PMID: 21947714). By targeting this domain, vaccines aim to elicit opsonophagocytic antibodies that neutralize the bacteria's ability to adhere to and invade host tissues, thereby preventing systemic infection (ClinicalTrials.gov: NCT04596878). Alp1 is a key component in multi-antigen vaccine strategies designed to provide broad protection across various GBS serotypes and clonal complexes. Its role in pathogenesis involves facilitating the attachment of the bacteria to human epithelial cells, which is a prerequisite for colonization and subsequent invasive disease.

Other names

Alpha-like protein 1Alp1GBS Alp1Surface protein Alp1N-terminal domain of Alp1

Vaccine-induced production of opsonophagocytic antibodies that target the N-terminal domain to inhibit bacterial adhesion and facilitate immune-mediated clearance (PMID: 21947714).