Streptococcus pyogenes M55 protein (M55)

Streptococcus pyogenes M55 protein, encoded by the emm55 gene, is a major surface-expressed virulence factor and member of the M protein family. It plays a critical role in bacterial pathogenesis by facilitating immune evasion through the inhibition of opsonization and phagocytosis, as well as by binding to host complement proteins like C6 and C7. While historically associated with nephritogenic strains of Group A Streptococcus that cause acute glomerulonephritis, the protein itself is noted for being highly antigenic without being rheumatogenic. In modern biotechnology, Emm55 is utilized as the key component of DNA-based cancer immunotherapies, such as IFx-Hu2.0. In this context, the protein serves as an 'in situ' vaccine; when transfected into tumor cells, it induces the expression of a foreign bacterial antigen that 'primes' the host immune system. This process effectively bypasses tumor-induced immune tolerance, triggering a robust recruitment of T cells and a systemic anti-tumor response.

Other names

Emm55 proteinemm55-encoded proteinM protein type 55M55 surface proteinStreptococcus pyogenes serotype 55 M protein

Acts as an immunological priming agent by expressing a highly antigenic bacterial protein on the surface of tumor cells to overcome self-tolerance and recruit CD4+ and CD8+ T cells to the tumor microenvironment.