IMX313 oligomerization domain (IMX313)

The IMX313 oligomerization domain is a 55-amino acid protein scaffold derived from the C-terminal domain of the chicken C4b-binding protein (C4bp) alpha chain (Spencer et al., 2012, PMID: 22438801). It is engineered to spontaneously form stable heptameric complexes, which allows for the multivalent display of fused antigens in vaccine formulations. This repetitive, high-density presentation mimics the surface of many pathogens, effectively promoting B-cell receptor cross-linking and enhancing antigen uptake and processing by dendritic cells (Ogilvie et al., 2015, PMID: 25713078). Consequently, IMX313-fused antigens elicit significantly stronger humoral and cellular immune responses compared to their monomeric counterparts. The use of a chicken-derived sequence, rather than human, is a strategic design choice intended to reduce the risk of inducing autoimmune responses against endogenous human C4bp. IMX313 has been successfully employed in several clinical-stage vaccine candidates, particularly for malaria, such as those targeting the TRAP and RH5 proteins (ClinicalTrials.gov: NCT01373606). While it is not a therapeutic target for drug inhibition, it serves as a potent molecular adjuvant and platform for modern vaccine development. Clinical studies have shown that IMX313 is well-tolerated and does not interfere with the safety profile of the primary antigens.

Other names

IMX313C4bp-based heptamerization domainC4b-binding protein alpha-chain oligomerization domain variantHeptameric protein scaffold

IMX313 acts as a molecular adjuvant by facilitating the self-assembly of fusion antigens into heptameric complexes, which enhances B-cell receptor cross-linking and improves the efficiency of antigen presentation to T-cells (Spencer et al., 2012; Ogilvie et al., 2015).