DEPRESSION OF T-CELL EPITOPE GENERATION BY STABILIZING HEN LYSOZYME

Conformational stability of proteins is an important factor that deter mines their resistance/susceptibility to proteolytic digestion. Intrac ellular proteolysis is the key step in antigen presentation events for protein antigens; hence, it is likely that increasing protein stabili ty reduces the antigenicity of proteins, We prepared three hen egg whi te lysozyme derivatives possessing different stabilities by chemical m odification to clarify the relationship between conformational stabili ty and the antigenicity of the protein, One of the derivatives was con formationally unstabilized by removing one intramolecular disulfide bo nd, whereas the two others were stabilized by the addition of an intra molecular crosslink. The antigenicity of these derivatives was evaluat ed using hen egg white lysozyme-specific T-cell hybridoma cells and a B-lymphoma cell line, A20, as antigen-presenting cells. With an increa se in conformational stability, the T-cell response decreased. However , the reduction was not derived from the inefficiency of internalizati on to A20 cells nor the alteration of antigenicity by chemical modific ations. Moreover, from analyses of their susceptibility to proteolysis and the kinetics of presentation of the T-cell epitope, it was confir med that increasing protein stability led to the depression of T-cell epitope generation by increasing resistance to proteolysis. These resu lts have an important implication in devising a new strategy for manip ulating T-cell response by the stability of protein antigen.