Covalent linkage to beta(2)-microglobulin enhances the MHC stability and antigenicity of suboptimal CTL epitopes

Many CTL epitopes of clinical importance, particularly those derived from t umor Ags, display relatively poor MHC binding affinity and stability. Becau se in vivo immunogenicity, and thus the efficacy of peptide-based vaccines, is thought to be determined by MHC/peptide complex stability, there is a n eed to develop a simple strategy for enhancing the binding of suboptimal ep itopes, Toward this goal, the ability to enhance suboptimal peptides throug h covalent linkage to beta(2)-microglobulin (beta(2)m) was explored. Two su boptimal variants of a high-affinity D-b-restricted influenza nucleoprotein peptide were covalently linked, via a polypeptide spacer, to the amino ter minus of human beta(2)m and the recombinant fusion proteins expressed in Es cherichia coli, When compared with their uncoupled counterparts, the beta(2 )m-linked epitopes display enhanced MHC stabilization and antigenicity. Thu s, tethering epitopes to beta(2)m provides a simple method for augmenting t he biological activity of suboptimal peptides and could be useful in the de sign of peptide-based vaccines or immunotherapeutics.