Fraction 1 capsular antigen (F1)

The Fraction 1 capsular antigen is a major virulence factor of Yersinia pestis, the bacterium responsible for bubonic, septicemic, and pneumonic plague [UniProt P0C1R7]. It is a proteinaceous capsule composed of polymerized Caf1 subunits that forms a protective layer around the bacterium, primarily expressed at 37 degrees Celsius to coincide with host entry [PubMed: 15273110]. Its primary biological role is to prevent phagocytosis by host macrophages and neutrophils, thereby facilitating the systemic spread of the pathogen [PubMed: 11113130]. Because of its high immunogenicity and essential role in pathogenesis, the F1 antigen is a central component of subunit vaccines, often paired with the V antigen in the rF1-V fusion protein [PubMed: 21640134]. Additionally, it serves as a critical diagnostic marker for the rapid detection of plague and a target for therapeutic monoclonal antibodies designed to neutralize the bacteria during infection [PubMed: 17606508]. Therapeutic challenges include the potential emergence of F1-negative strains which can still cause disease while evading F1-targeted immunity [PubMed: 8654447].

Other names

Fraction 1 antigenCaf1 proteinYersinia pestis F1 antigenCapsular antigen fraction 1

Induction of neutralizing antibodies (vaccines); Neutralization of bacterial virulence and enhancement of opsonophagocytosis (monoclonal antibodies).