Yersinia pestis envelope antigen fraction 1 (F1 antigen)

The Yersinia pestis envelope antigen fraction 1, commonly referred to as the F1 antigen, is a major capsular protein expressed on the surface of the bacterium responsible for the plague. It is encoded by the caf1 gene located on the pFra (pMT1) plasmid and is specifically upregulated when the bacteria are within a mammalian host at 37°C (UniProt: P0C1R7). The F1 antigen assembles into a large, gel-like capsule via a chaperone-usher pathway, which provides critical antiphagocytic properties that allow the pathogen to evade the host's innate immune system, particularly by inhibiting uptake by macrophages and neutrophils (PubMed: 15273412). Due to its high immunogenicity and essential role in virulence, the F1 antigen is a primary component of recombinant subunit vaccines, such as the rF1-V vaccine, and serves as the target for rapid diagnostic assays (PubMed: 22434297). However, the emergence of naturally occurring or engineered F1-negative virulent strains remains a significant therapeutic challenge, as these strains can bypass F1-targeted immunity (PubMed: 11448603).

Other names

Capsular antigen F1Caf1 proteinFraction 1 capsular antigenProtein Caf1Yersinia pestis F1 capsular protein

Induction of protective humoral immunity through neutralizing antibodies that facilitate opsonophagocytosis and prevent bacterial colonization.