Streptococcus pyogenes M protein (type 55) (Emm55)

Emm55 is a specific type of M protein, a major virulence factor found on the surface of Streptococcus pyogenes (Group A Streptococcus) (UniProt Q99XV0). In the context of oncology, Tumor cells expressing Emm55 protein refers to an experimental model where human cancer cells are genetically engineered to express this bacterial protein on their surface (MacDiarmid et al., Cancer Cell, 2007). This system is primarily used as a proof-of-concept for testing targeted drug delivery platforms, most notably the EnGeneIC Dream Vector (EDV) technology (MacDiarmid et al., Nature Biotechnology, 2009). In these models, bispecific antibodies are designed with one arm targeting the delivery vehicle (such as the O-antigen of a minicell) and the other arm targeting the Emm55 protein on the tumor cell. This allows for the precise delivery of cytotoxic drugs, such as doxorubicin, or gene-silencing agents like siRNA directly to the engineered cells. While Emm55 is not a naturally occurring human tumor antigen and is not used as a target in clinical practice, it has served as a vital tool in demonstrating the versatility and specificity of antibody-guided delivery systems in preclinical research.

Other names

M55 proteinGroup A streptococcal M protein type 55emm55 gene productM protein serotype 55

Targeted delivery of cytotoxic or genetic cargo via bispecific antibody-mediated binding to cells expressing the Emm55 protein.